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Vibrotactile subjective magnitude as a function of hand preference
.Ve”ropsychologra. Vd. ?I. No. 4. pp. 38>395, Pnntcd in Great Britain.
VIBROTACTILE
,983
0018-3932 83~s3.00+0.00 c 1983 Pergamon Press Ltd.
SUBJECTIVE MAGNITUDE OF HAND PREFERENCE*
AS A FUNCTION
RONALD T. VERRILLO Institute
for Sensory Research, Syracuse University, Syracuse, NY 13210. U.S.A. (Accepted
15 November 1982)
Abstract-The vibrotactile subjective magnitudes of test stimuli were determined by a psychophysical matching technique as a function of the time interval between conditioning and test stimuli in right-, left-, and ambi-handed subjects. Ipsilateral stimulation on either hand produced equal amounts ofenhancement of subjective magnitude in all subjects. Contralateral stimulation produced suppression, followed by enhancement in right- and left-handers, but produced no effect in ambihanders. The results suggest that the bilateral neural connections of ambi-handers is different from those of right- and left-handers.
INTRODUCTION THE EXPERIMENTS reported
here deal specifically with a relationship between self-reported hand preference and a task involving the sensation magnitude of vibrotactile stimuli. The implications that the results have for possible neural mechanisms associated with hand preference will be discussed. The preference for using one hand over the other for performing unimanual tasks has provided us with an extensive, rich, often-misleading and, until recently, predominently nonscientific body of literature [ 11,211. Attempts to measure it can be traced to biblical times and the consequences of hand preference along a multitude of behavioral, social, sensory, motor, perceptual, and even moral dimensions has been a matter of interest for thousands of years [ 111. Hand preference, which implies choice, should not be confused with manual proficiency, which involves performance. Although they are often confused, both of these measurable quantities have been linked, with varying degrees of success, to the notions of cerebral dominance and the specialization of function within the cortical hemispheres [S, and 23 for recent reviews]. The sensory phenomenon of enhancement, observed in the present experiments, was first described for the auditory sense [32-341. Enhancement refers to an increase in the subjective magnitude of a stimulus when it is preceded or followed by another stimulus at a short time interval. Suppression refers to a decrease of subjective magnitude under the same conditions. Enhancement and suppression of vibrotactile sensation have been investigated for both ipsi- and contralateral stimulus conditions [ 10,26,27] for both single- and multiplesite stimulation [ 10,271 and for forward and backward modes of stimulus presentation [29]. The effect of handedness was never considered in the previous experiments.
*This research was supported by grant NS 09940 from the National Institutes of Health, Department of Health and Human Services. 383
381
RO>.ALD T
XIETHODS
I’ERRILLO
AND PROCEDURES
The subjects here all patd volunteers +~ntversity students and persons from the communr:y There here s:x subjects tn each group. three male and three female. The three groups ivere defined by predomm~nt hand preference. rtght (R.H.). left (L.H.). or ambt (;\.H.j. Hand preferencevvas determined by a I?-item questtonnaireselected from a Il3-Item questtonnatre pubhshed by RA~ZRO~VS~I, K.AL\T and NERES [Xl. Only Items wtth reltabthty and validity indices above 0.90 were selected (.-\ppendix .A). In a survey of test items used in hand-preference questtonnaires by six investigators. PORK and COREY [21] reported that the first 1I items shown in ?-\ppsndix .A had a test-retest concordance of 92-lW”,, (mean=Yj.9”,,) for periods of trme up to I yr, The concordance between self report and actual behavior for these items ranged betueen 91 and lOO”,, (mean =96.6”.,). iltem 12 uas not mcluded in therr survey. I The items asked hand preference (right. left, or both1 on an assortment oiuntmanual tasks and were scored R= - I. L= - 1. B=O. Based on thtr sconng system. sub_jects classrfied as right-handed scored - ! I to - 13.those vvho were clawtied as left-handed scored -8 to - 12. and those classtried as ambt-handed scored - 3 to T -1. These designations are within the score definitions assigned by HFRRO~ [I21 whose 90 subjects were classrfied as righthanded. -8 to T 12; left-handed, -7 to - 12: and ambt-handed. -6 to r7 The apparatus consisted of the approprtate equtpmsnt to generate. ttme. and control the amplitude of stnusordal uaveforms. The signals uere delivered to Goodmans 390A and 103r\ vtbrators. u hich were used to sttmulaie the thenar emtnence and the dtstal pad of the middle finger of one hand during the control experiment. In the contralateral experiments, the vibrators were used to stimulate the hands separately. The intensity of vtbration was controlled by the subject during the matching phase of the experiment by two foot-operated switches. operating a precision dtgital attenuator. Intensity was increased by 1.0 dB at the right foot and decreased by 1.0 dB at the left foot. Smusotdal vibratory stimuli were delivered to the thenar cmtnence ofone or both hands. In a control experiment the stimulr were deltvered sequenttally to the thenar eminence and the dista! pad of the middle finpe: of the same hand. r\ 2.3-cm’ circular contactor was used at the thenar and 1.3 cm’ at the finger. Surface vtbrations on the skin Lvere confined to the tmmedtate region of the contactor by a rtgtd surround, placed at a drstance of 1 mm concentrrc to the contactor. Before each session the contactor was adjusted so that it pressed 0.3 mm beyond contact urth th? surface of the sktn. Amplitude of vibratron was measured by a caltbrated, precision accelerometer mounted directly on the moving element of the vibrator. ,411 measurements are expressed in dB. re 1.0 gm peak displacement. Sttmuli were 20 msec tn duratton. measured at the half-power points. and had 2.F msec rise-fall ttmes measured hetwecn the 10 and 90”,, points of Gaussian envelopes. The power spectrum of the 25 Hz stimulus consisted oia main lobe centered at 25 Hz with addttional small lobes at higher frequencies. The highest frequency associated with the main lohe was given by the carrier frequency plus 40 Hz. and the peak of the highest secondary lobe was 38 dB down from the lobe at 25 Hz. Well over 99”,, of the total energy of the stimulus was confined to frequencies making up the main lobe [see 9. Fig. 21. The vibrator assembly and the subject were located in a booth which provided adequate isolation from sound in the laboratory and from building vtbrations. Sounds emmattng from the vibrator were masked by narrow-band noise centered at the vibration frequency and delivered through ctrcumaural earphones. The subject’s detection threshold was measured at the start ofeach session. and the intensity of the test stimulus was set at a sensation level of IO dB (Fig. I). The intensity of the conditioning stimuius was then adjusted until the subject reported an intensity match to the test stimulus. The intensity ofthe conditioning stimulus was then ratsed an additional 10 dB above this subjective match. The procedure for measuring enhancement and suppresston first requires the subject to match the sensation magnitude of the matching stimulus to that of the test stimulus in the absence of the conditioning sttmulus (Fig. 1.
TEST
MATCHING
T$T
MAri”lNG
CONTROL MATCH
CONDITIONING MATCH , EXPERIMENTAL
+-At
_t______
750
MSEC
~1
FK;. 1. Sttmulus paradigm used to measure the sffzcts ofsuppresston and enhancement. AlI bursts of sinusoids are 20 msec in duratron vcith 75 msec rise-fall times. Enhancement and suppression are measured as a functron ofthe time Interval (A0 between the conditionins and test stimuli. See text for a full explanation.
VIBROTACTILE SLBJECTI~F M~cislnD~
As A FL-SUCTION OF H-\SD PREFERESCE
335
Control &latch). Followmg the control match, the subject matches the sensation magnitude 31 the matchmg stimulus to that of the test sttmulus in the presence of the conditioning stimulus (Fig. 1, Expertmental MatchI. The time interval between the onsets of the condtttoning and test stimult (Jr) was varied over the range of t&500 msec. and the matching stimulus followed the test sttmulus by 750 msec. The sttmulus sequence Has presented every 3.0 sec. hfter completing the expertmental matches. the control match was repeated and the results of the pre- and post-controi matches were averaged to compensate for adaptation during :he session. The subjects Nere instructed to use a bracketing procedure in all matches. On a single trtal they made several adjustments to the upper and lower limtts of the ma:ch and then adjusted the mtensity iterattvely toward thecenter of this zone of uncertainty. All of the SubJects were carefully instructed and trained for several sessions to match the subjective magnitude of vibrotactile bursts separated by various time Intervals prior to the sesstons in which data were collected. The subjects made three matches for each experimental condition, with a randomized presentation of AI’S within each expertmental session. The order of presentation of other variables was counterbalanced either over blocks of trials ~ithtn a session or over sessions. The effects of the presence of the conditioning stimulus upon the sensation magnitude of the tes: stimulus (enhancement or suppression) was expressed as the difference in dB between the experimental matches involving conditioning, test. and matching stimuli and the average of pre- and post-test control matches in which the conditioning stimulus was absent (Fig. I). This difference, the change in intensity level in dB. is plotted as a function of At. The data points on the graph represent mean values of the subjects in each group. The standard error of the mean (s.e.) will be reported as a measure of variability. Because of the number of data points in each graph, the range (R) and mean (R) of the standard errors will be given for each group in the text and in Table 1. The frequencies of the bursts were either 3OtX3W300 Hz, 2>25-25 Hz, or 25-300-300 Hz. These frequencies were chosen such that maximal excitation would be delivered selectively to the Pacinian corpuscle mechanoreceptots (300 Hz) and the non-Pa&an mechanoreceptors (2s Hz), and to stimulate both receptor channels within the same brief period of time (2s30&300 Hz). (The reader is referred to 8.9, 12. 13 and 14 for detailed discussions of the duplex model ofmechanoreception and the effects ofenhancement and suppression nithin the context of the model.) The experiments performed are listed below: (1) Control 1: The frequency of all three bursts set at 300 Hz, presented to the thenar eminence of the right hand and of the left hand. (2) Control ?: The conditioning stimulus presented to the tinger pad of the mtddie finger, and the test and matching stimuli to the thenar eminence of the same hand. The frequency of all stimuli was 300 Hz. Both hands were tested. (3) Contralateral 1: The conditioning stimulus presented to the thenar eminence of the left hand, and the conditioning and matching stimuli presented to the thenar eminence of the right hand. The frequency of all stimuli was 300 Hz. (4) Contralateral 2: Same as Contralateral 1. but wtth the order of presentation to the t*o hands reserved. (5) Contralateral 3: Same as Contralateral 1, but with the frequency of the three bursts set at 25 Hz. (6) Contralateral 4: Same as Contralateral 1, but wtth the frequency oftheconditioning stimulus set at 25 HZ. and of the test and matching stimuli set at 300 Hz. The order of performing the experiments was counterbalanced among subjects.
RESULTS The results of the contralateral experiments show that a conditioning vibrotactile stimulus delivered to one hand can influence the sensation magnitude of a subsequent (test) stimulus delivered to a homologous site on the other hand in both right- and left-handers. However, no such effect is measurable in ambi-handers. The effect is essentially the same in right-, left-, and ambi-handers for both the Pacinian and non-Pacinian mechanoreceptor systems, and there are no cross-channel effects in any of the three groups. The data shown in Fig. 2 are the results of Control experiment 1 performed to determine if an experiment performed ipsilaterally with all three bursts delivered to the same hand, either the right or left, would show a difference between the three groups. The results were virtually the same for all groups. All subjects showed the characteristic enhancement curve in which the presence of the conditioning stimulus produces an enhancement of the perceived intensity of the test stimulus amounting to about 6.0 dB at At = 75 msec. The effect decreases as At is increased up to 400 msec and beyond where the enhancement effect reduces to nil. The s.e. values of the three groups for data collected from the right hand (Fig. 2A) are: R.H., R=O.ll-0.35, n=O.25; L.H., R=0.09-0.37, M=O.23; A.H., R=0.18-0.42, R=0.28. The
386
RONALD T. VERRILLO
RIGHT
8
0
HAND
.
RIGHT-
o
LEFT-
HANDED
HANDED
x
AMBI-
HANDED
300-300-300
A
2-
B
I-
O
I 0
I
1 100 TIME
I
I 200
I
INTERVAL
I 300
(
I
I 400
IN
500
MSEC
FIG. 2. The effect of the conditioning stimulus upon the perceived intensity of the plotted as a change in intensity level in dB as a function of the time interval in msec conditioning and test stimuli. Results are shown for the right (A) and left (B) thenar right- (e), left- (0). and ambi- ( x ) handed individuals. The frequency of all three stimuli within the range of maximal sensitivity of the Pacinian system.
test stimulus bertceen the eminences of was 300 HI
s.e. values from the left hand (Fig. 2B) are: R.H., R=0.12-0.34, R =0.25; L.H., R=0.08-0.21, I%=O.12; A.H., R=0.08-0.31, ti=O.19 (Table 1). These curves are comparable to previous results in vibration [9, 26, 291 and in audition [33, 34). The data indicate with reasonable certainty that the enhancement effect does not operate differentially as a function of hand preference. The experiment was not repeated using 25-25-25 Hz since it has been shown that the curves for either a high or a low frequency are essentially the same using this experimental paradigm [9, 261. When the conditioning stimulus is presented to one site on the skin’s surface and the test and matching stimuli are presented to another site, either ipsilaterally [27] or contralaterally [lo], the effect of the conditioning stimulus upon the test stimulus changes character dramatically from the one-site condition. At short At’s (O-100 msec), the effect is a marked suppression of the perceived magnitude of the test stimulus, followed at longer Ar’s by an enhancement effect that reaches a maximum at 150 msec and then decreases inversely with At to nil beyond 300 msec. Figure 3 shows these effects in Control experiment 2 in which the conditioning stimulus was presented to the finger pad of the middle finger of the right hand, and the test and matching stimuli were presented to the thenar eminence of the same hand. The data of right- and left-handers were so similar they have been combined. The figure illustrates that both suppression and enhancement are measurable and the results are virtually the same regardless of the hand preference of the subjects, and that ambi-handers do not differ from right- and left-handers.
VIBROTACTILE
SUBJECTIVE
NAGNITUDE
Table Group Fig. 2
AS A FLNCTIOl’
1. Standard
errors
Hand
R.H.
A.H.
1lean
Range
R L R L R L
L.H.
OF H.AND PREFERESCE
0.1 l-O.35 0.12-0.34 0.09-0.37 0.08-0.2 1 0.18-0.42 0.08-0.3 1
0.25 0.25 0.23 0.12 0.25 0.19
Fig. 4
R.H. L.H. A.H.
0.10-1.91
0.53
0.060.86
0.44
Fig. 5
R.H. L.H. A.H.
0.10-0.83 o.ofSo.27 0.1 l-0.54
0.3 1 0.18 0.32
Fig. 6
R.H. L.H. A.H.
0.15-0.75 0.08-0.33 0.03-0.37
0.36 0.13 0.17
Fig. 7
R.H. L.H. A.H.
0.07-0.36 0.04-0.32 0.13-0.32
0.16 0.17 0.21
300-300-
5
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Z
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m
0
I
loo
I
I 200
TIME
1
RIGHT8 LEFT-HANDED AMBI -HANDED
I 300
INTERVAL
I
I 400
I
I 500
IN MSEC
FIG. 3. The effect of the conditioning stimulus presented to the finger pad of the middle finger upon the perceived intensity of the test stimulus presented to the thenar eminence of the same hand. The frequency of all three stimuli was 300 Hz. At time intervals less than 50 msec the conditioning stimulus has a pronounced suppressive effect on the perceived magnitude of the test stimulus. Beyond 50 msec enhancement reaches a peak at 150 msec before decreasing to nil at 400 msec. The results are the same for right-, left- (whose data have been combined) and ambi-handed individuals.
387
ROSALD T. VERRILLO
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,
ICO TIME
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IN
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400 MSEC
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/
500
FK,. 4 Suppression and enhancement effect:. mczzured v, hen the conditioning st~mulur u 3s presented to the thenar eminence of the left hand and the test and matching stimuli were presented to the right thenar eminence. All three stimuli were set at 300 Hz. Although reduced in magnitude, the effect in right- (0) snd Icft- (C,) handed individuals is a close parallel to the ipsilatrral results shown in Fi,q. 3. The results given by ambi-handed indlriduals show neither suppression nor enhancement effects.
The results shown in Fig. 4 are from Contralateral experiment 1 in which the conditioning stimulus was presented to the left hand, and the test and matching stimuli were presented to the right hand. The frequency of the three bursts was 300 Hz. The right- (a) and left- (0) handed subjects showed the effect of suppression followed by enhancement diminishing to nil beyond At = 300 msec, as shown by GESCHEIDER and VERRILLO [lo]. The responses of the ambi-handed subjects (Fig. 4, ( x )), however, showed virtually no effect of either suppression or enhancement across the body. The s.e. values of the combined R.H. and L.H. groups are: R=O.10-1.91, .a =O.S3; and for the A.H. group: R=0.06-0.86, M=0.44 (Table 1). The absence of any contralateral effects was first noted in two subjects vvho were participating in a previous study on contralateral effects [lo] in which handedness was not being considered. When asked about their hand preference, one designated himself as ambihanded and the other considered herself left-handed. The father of the ambi-handed subject confirmed that the subject showed no hand preference in infancy and early childhood. but developed different hand preferences for different tasks as he matured. The female subject revealed that her mother and an aunt wereambi-handed in their everyday behavior and both considered themselves to be “ambidextrous”. Subsequently, both subjects scored as ambihanded on the questionnaire, which led to a search for ambi- and left-banders and the present experiments. 2 in which the conditions and Figure 5 shows the results of Contralateral experiment frequencies (300-30&300 Hz) were the same as those for Fig. 4, except that the conditioning stimulus was presented to the right hand and the test and matching stimuli were presented to the left hand. The results are essentially .the same. The right- and left-handers gave very similar results to each other and to the results shown in Fig. 4, and the ambi-handers again
VIBROT.ACTILE
SCBJECTWE
MAGSITUDE
/
r
A.5 A FL?;CTlOS
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s
0
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OF H.*SD
PREFERESCE
389
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4:
3-
2
-l ld > w J
2-
a
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mx
x
xx c_,_ v, z -2f z -3-
x ”
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CONTRALATERAL 300-300-300 R L L
z
.
= - -4w
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-6-7-
0 x
HANDEDNESS RIGHT
.
LEFT
o
AMBl
x
8
11
0
11
11 100 TIME
5
1
200 300 INTERVAL
’
IN
1 400 MSEC
!
I
,
500
FIG. 5. Same as Fig. 4, but with the conditioning stimulus presented to the right hand and the test and matching stimuli presented to the left hand. The effects of hand preference are close to those shown in
Fig. 4.
showed virtually no suppression or enhancement effects, Change of intensity levels in the ambi group were all within t I .O dB of the control match. The s.e. values of the three groups are: R.H., R=0.1&0.83, m~O.31; L.H., R=0.060.27, ti10.18; A.H., R=O.ll-0.54, M =0.32 (Table 1). The data shown in Fig. 6 (Contralateral 3) were obtained under the same experimental conditions as those of Fig. 4, except that the frequency used for all three stimulus bursts was 25 Hz. Again, the right- and left-handed subjects produced results similar to each other and similar to those shown in Figs 4 and 5. The ambi-handed subjects again showed neither suppression nor enhancement effects, all of the change of intensity levels being within $1.0 dB of the control match. The s.e. values of the three groups are: R. H., R =0.1X).75, M=0.36; L.H., R=0.08-0.33, R=0.13; A.H., R=0.03-0.37, ~1=0.17 (Table 1). In the final experiment (Contralateral 4) the frequency of the conditioning stimulus was set at 25 Hz and that of the test and matching stimuli at 300 Hz. These frequencies were chosen to selectively stimulate the Pacinian (300 Hz) and non-Pacinian (25 Hz) mechanoreceptor systems. The results shown in Fig. 7 would indicate that in all three groups neither suppression nor enhancement takes place across the mechanoreceptor channels when the stimuli are presented contralaterally. This result confirms earlier results showing no crosschannel interactions in one-site [26] and in ipsilateral two-site [27] experiments. The s.e. valuesofthethreegroupsare: R.H.,R=0.07-0.36,~1=0.16;L.H., R=0.04-0.32, I%=O.17; A.H., R=0.13-0.32, R=0.21 (Table 1).
DISCUSSION When conditioning and test stimuli were presented results were the same regardless of hand preference.
to the same hand, right or left, the The effect, when both stimuli were
RONALD T. VERRILLO
390
4m = z _I
30
2-
Y ’ w -IO.
x=xx
z -,v, = -2w + f -3 -
0
x
+
. 0
‘0 x
L
0
0
Q-6I U
n
R
R
HANDEDNESS
-4-
w z -5-
8 x
CONTRALATERAL 25-25-25
. .
5
’
l
RIGHT
.
LEFT
o
AMBI
x
0
-7
I
I
I
I
100 TIME
0
I
I
I
I
200 300 INTERVAL IN
I
I
II
500
400 MSEC
FIG. 6. Same as Fig. 4, but with all three stimttli set at a frequency of25 Hz. At this frequency the nonPacinian receptor systems are preferentially activated. The effects of hand preference are close to those shown in FIG. 4.
I
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-= -I -4
HANDEDNESS
II
0
I
11 100 TIME
11
RIGHT
.
LEFT
o
AMEI
x
11
300 200 INTERVAL
1 IN
400 MSEC
’
1 500
’
I
’
I
FIG. 7. The effect of the conditioning stimulus upon the perceived intensity of the test stimulus when the frequency of the conditioning stimulus (25 Hz) is within the region of maximal sensitivity of non-
Pacinian receptor systems, and the frequency of the test and matching stimuli (300 Hz) is within the region of maximal sensitivity of the Pacinianereceptor system. No effects were measurable in this cross-channel condition and hand preference did not have an effect upon the results.
VIBROTACTILE
SUBJECTIVE
MAGNITUDE
AS A FUWZllON
OF HA?“D PREFERENCE
391
presented to the same site (Control l), was an enhancement of the subjective intensity of the test stimulus at short interstimulus intervals. The effect diminished as the interstimulus interval was increased. When conditioning and test stimuli were presented to different sites on the same hand (Control 2), there were again no differences as a function of handedness. The effect was first suppression, followed by enhancement, and finally no effect with increasing values of the interstimulus interval. When the conditioning and test stimuli were presented to homologous contralateral sites (Contralateral 1,2, 3), the conditioning stimulus influenced the perceived magnitude of the test stimulus delivered to the opposite hand in both right- and left-handers. The results were similar to the ipsilateral, two-site experiment. However, the effect was not measurable in the ambi-handed, whose responses showed a lack of sensory influence laterally across the body. The findings will be discussed from several points of view. First, they will be considered as purely psychophysical results, descriptive of the performance of human beings in a task involving the judgment of vibrotactile sensations. Second, the psychophysical results will be viewed as clues that may provide some insights into the organization of the cerebral hemispheres with regard to tactile stimuli. The fact that a sensory stimulus can have an effect on the sensation magnitude produced by a second stimulus that occurs simultaneously or follows it closely in time has been well established within the auditory [2, 7, 14, 33, 343 and vibrotactile systems [9, 10, 25-281. Depending upon specific combinations of spatial, temporal, and intensive stimulus parameters, the interaction may produce an increase or a decrease in sensation. The phenomena reported here include both of these sensory effects. The results confirm previous findings that when two vibrotactile stimuli are presented at short time intervals (< 500 msec) to a single site, the subjective intensity of the second is increased (enhancement) by the presence of the first, and that the change is inversely related to the time interval separating the two stimuli. The magnitude and course of the enhancement effect of two stimuli presented to the same site on the same hand are not effected by the hand preference of the subject, nor by the hand to which the stimuli are presented (Control 1). It also has been shown in previous work that the effect persists with age [25]. Whatever the underlying neural mechanism for the phenomenon, it apparently does not differ in persons with different hand preferences, including right-, left-, and ambi-handers. To our knowledge, only one attempt has been made to explain the enhancement effect. ELMASIAN, GALAMBOS and BERNHEIM [5] recently postulated a factor they called mergence, in which the overlap in time and space of events within the brain causes the test stimulus to take on the perceived characteristics of the conditioning stimulus. Judgmental errors, due to a related factor they call difJiculry, interferes with the accurate perception of the test stimulus. This hypothesis is mentioned because, although there is little in the way ofconcrete evidence for it, it is the only one that has been offered in the literature. It is also demonstrated here that when two brief vibrotactile stimuli are presented in close temporal proximity, but at different ipsilateral sites (Control 2), suppression of the second by the first occurs at very short time intervals (< 100 msec). This phase of the sensory effect is followed by enhancement which reaches a maximum at 150 msec and then reduces to nil at time intervals beyond 300 msec. As in the case of the single-site experiment, hand preference appears to have no effect on the course or magnitude of these effects. The results discussed above for the one- and two-site, ipsilateral conditions are shown here only for stimulation within the Pacinian mechanoreceptor system. The conditioning, test,
392
ROS.%LD T
VERRILLO
and matching stimuli were all set at a frequency (300 Hz) to which the Pacinian corpuscle is maximally sensitive. Previous research has shown the same result in these experiments when a frequency (25 Hz) is selected that selectively stimulates the non-Pacinian system at threshold amplitudes [26. 273, suggestin, 0 that enhancement is measurable within either system. However, when the frequencies of the conditioning and test stimuli are selected so that they stimulate different systems, the enhancement effect disappears [36.27]. and both suppression and enhancement are reduced to nil when the stimuli are presented contralaterally [lo]. The results of the current experiments confirm previous findings of no effects in a cross-channel condition (Contralateral 4) and demonstrate that there is no effect of hand preference on the results. The only experimental condition in which a clear-cut difference appears that is dependent on hand preference is when the conditioning stimulus is presented to one hand and the test and matching stimuli to the other hand (Contralateral 1. 2 3). In this condition the results given by right- and left-handers are the same. At short time intervals, starting at At=0 msec, the conditioning stimulus produces a marked suppression of the subjective intensity of the test stimulus, which diminishes until At= 100 msec. At this time interval, enhancement begins to occur, reaching a maximum at At= 150 msec before it diminishes to nil at about Ar = 300 msec. Neither suppression nor enhancement, however, are observed in the data of the ambi-handed subjects. The results in all groups remained consistent regardless of which hand received the conditioning stimulus and which the test and matching stimuli. The result was also the same for stimulation within either the Pacinian (300 Hz) or the nonPacinian (25 Hz) system. The results of the contralateral experiments clearly indicate in right- and left-handed subjects that a conditioning stimulus delivered to one hand can infuence the sensation magnitude on the other hand of a stimulus following closely in time. In the ambi-handed group, however. the results of the contralateral experiments were strikingly different. The conditioning stimulus appeared to have no effect on the sensation magnitude of the test stimulus delivered contralaterally. The results obtained from right- and left-handed subjects imply that neural event.< occurring on one side of the body cross contralaterally and affect neural events occurring within corresponding areas of the other side. In the case of the ambi-handed subjects. the sensory events experienced on one hand appear to be independent of simulation delivered to the other hand. By implication, this suggests that the mechanism by which neural activity on one side is able to affect events in the contralateral hemisphere is lacking or severely limited in ambi-handed individuals. There is evidence that cortical cells receiving specific input from Pacinian and nonPacinian mechanoreceptors may be localized within specific cortical areas [lg, 193. and that the destination of fibers from the different types of mechanoreceptors is correlated with the cytoarchitecture of somatosensory areas I and II [3. 6, 131. It is also generally accepted that the enhancement effect is most probably the result of neural processing at higher levels of the central nervous system [S, 73. Enhancement within the auditory system could not be detected electrophysioiogically at the level of the auditory nerve of cat [I], and no effects of auditory enhancement were detected by EEG recordings in man at the level of the brainstem [Z]. A problem remains as to where in the somatosensory pathways the sensory information coming from one side of the body gains access to the sensory information available at the cortical level of the opposite side. Although the opportunity for the crossover of fibers exists at the level of the reticular formation [20] and the posterior group of thalamic nuclei [20], it
vIBROT&CTILESL'BJECTICZMAGSITIJDE AS A FL~CTION OF HASD PREFERESCE
393
is generally accepted that the major portion of somatosensory fibers cross either by decussating at the level of the spinal cord or at the level of the nuclei gracilis and cuneatus in the medulla [4, 17). Direct connection between somatosensory areas of the cortex is made via the corpus callosum, with SI projecting to both SI and SII of the opposite side, and SII projecting almost exclusively to its contralateral counterpart [ 15,16]. JOMS and PO~L-ELL, however, found no commissural connections from distal limb regions, thus supporting an earlier opinion [31] that other mechanisms must account for bilateral connections. Although it would be convenient as well as simple to ascribe the results of the current experiments to a difference in commissural connections between single- and ambi-handers, the available anatomical data does not allow this simple interpretation of the results. Bilateral connections within somatosensory systems are complex, The evidence presented in this paper would imply that the integrity of function for localized cortical areas associated with specific cutaneous mechanoreceptors is preserved across the body. Furthermore, it is reasonable to hypothesize that there is a difference in bilateral connections between individuals who have a strong right- or left-handed orientation and those who may be characterized as ambi-handed. It is not possible, however, at this time to specify the locus of that difference.
REFERENCES I. BAUER, J. W. and GLAMBOS, R. Evoked 2. 3. 4.
5. 6. 7. X. 9. 10.
I I. 12. 13. 14. 15. 16. 17.
potentials in cat auditory nerves: Suppression by prior tonal stimulation. Percept. Psychophys. 17, 43-47. 1975. BAUER, J. W., ELMMIAN. R. and GALAMBOS, R. Loudness enhancement in man: I. Brainstem evoked response correlates. J. acoust. Sot. Am. 57, 165-171, 1975. BENNEIT, R. E., FERRINCTON, D. G. and ROWE, M. Tactile neuron classes within second somatosensory area (SII) of cat cerebral cortex. J. Neurophysiol. 43, 292-309, 1980. BROWN, A. G. Ascending and long spinal pathways: Dorsal columns, spinocenical tract and spinothalamic tract. In Handbook of Sensory Physiology. Vol. II: Somatosensory Svstem, A. IGGO (Editor), pp. 315-338. Springer-Verlag, New York, 1973. ELMASIAN, R., GALAMBOS, R. and BERNHEIM,A.. Jr. Loudness enhancement and decrement in four paradigms. J. ucoust. Sot. Am. 67, 601-607, 1980. FERRINGTON. D. G. and ROWE, M. Differential contributions to coding of cutaneous vibratory information by cortical somatosensory areas I and II. J. Neurophysiol. 43, 310-33 I, 1980. GALAMBOS, R., BAUER. J.. PICTON, T., SQUARES, K. and SQUIRES, N. Loudness enhancement following contralateral stimulation. J. ucoust. Sot. Am. 52, 1127-I 130, 1972. GAZZANIGA, M. and LE Dovx, J. E. The Integrated Mind. Plenum Press, New York, 197% GEXHEIDER, G. A., VERRILLO. R. T.. CAPRARO, A. J. and HILMER,R. D. Enhancement ofvibrotactile sensation magnitude and predictions from the duplex model of mechanoreception. Sensory Processes 1, 187-203. 1977. GESCHEIDER. G. A. and VERRILLO. R. T. Contralateral enhancement and suppression of vibrotactile sensation. Percept. Psychophys. (in press). HARRIS, L. J. Left-handedness: Early theories, facts and fancies. In Neurops.~cholo,g)- of Left-Handedness, J. HERRON (Editor), pp. 3-78. Academic Press, New York, 19SO. HERRON, J. Two hands, two brains, two sexes. In Neuropsycholog,v oflefi-Handedness. J. HERRON (Editor). pp. 233-260. Academic Press, New York. 1980. HYV~INEN, J. and PORANES, A. Receptive field integration and submodality convergence in the hand area of the post-central gyrus of the adult monkey. J. Physiol. 283, 539-556. 1978. IRWIN, R. J. and ZWISLOCKI, J. J. Loudness effects in pairs of tone bursts. Percept. Psychophps. 10, 189-192, 1971. JOhT.3, E. G. and POWELL, T. P. S. The commissural connections of the somatic sensory cortex in the cat. J. Anat.. Land. 103, 433455. 1968. Jon. E. G. and POWELL, T. P. S. Connections of the somatic sensory cortex of the rhesus monkey. II. Contralateral cortical connections. Brain 92, 717-730. 1969. MARTIN, J. H. Somatic sensory system II: Anatomical substrates for somatic sensation. In Principles of Neuroscience, E. R. KANDEL and J. H. SCHWARTZ (Editors), pp. 170-183. Elsevier/North Holland. New York, 1951.
393
ROSALD T VERRILLO
18. PAUL. R. L.. GOODMAN. H. and .MERZENICH. Xl. Alterations in mechanoreceptor Input to Brodmann‘s areas I and 3 of the postcentral hand area of .tfacaca mukrrn after nene section and regeneration. Brain Res. 39, 1-19, 1972. PAL.L. R. L.. MERZENICH. 1M. and GOODMAN. H. Representation of slowly and rapidly adapting mechanoreceptors of the hand in Brodmann’s areas 3 and 1 of .Ifacaca nurk~~a. Brain 36, X9-249. 1972. POMPEIANO, 0. Reticular formation. In Handbook of Semor_v Ph.vsiology. Vol. II: Somaiosensory .S.vsrem. A. IGCO (Editor). pp. 38 I-455. Springer-Verlag. New York. 1973 PORAC. C. and COREN. S. Lareral Preferences and Human Behmior. Springer-Verlag. New York. 198 I. RACZKOWSKI, D., KALAT. J. W. and NEBES. R. Reliability and validity ofsome handedness questionnaire times. Neurophysiologia 12, 43-47, 1974. SPRISGER, S. P. and DEUTSCH. G. Lef Brain, Righr Brain. Freeman. San Francisco. CA, 1991. VERRILLO. R. T. A duplex mechanism of mechanoreception. In The Skin Sertses, D. R. KEMHALO (Editor), pp. 139-159. C. C. Thomas, Springfield, IL, 1968. VERRILLO. R. T. Effects of aging on the suprathreshold responses to vibration. Percept. Ps~choph~s. (in press). VERRILLO. R. T. and GESCHEIDER, G. A. Enhancement and summation in the perception of two successive vibrotactile stimuli. Percept. Psychophys. 18, 128-136. 1975. VERRILLO. R. T. and GFXHEIDER. G. A. Effect of double ipsilateral stimulation on vibrotactile sensation magnitude. Sensor) Processes 1, 127-137, 1976. VERRILLO. R. T. and GESCHEIDER, G. A. Psychophysical measurements of enhancement, suppression, and surface gradient effects in vibrotaction. In Sensory Frtncrions of Ihe Skin o,fHumnns. D. R. KENSHALO (Editor), pp. 153-182. Plenum Press. New York, 1979. 29. VERRILLO, R. T. and GEXHEIDER, G. A. Backward enhancement and suppression of vibrotactile sensation. Sens0r.v Processes 3, 249-160. 1979. in somatosensory area I in primates. J. 30. WERMR, G. and WHITSEL, B. L. Topology of the body representation Neurophysiol. 31, 856-869, 1968. 31. WOOLSEY.C. M. and WANG, G. H. Somatic sensory areas I and 11 of the somatic cortex of the rabbit. Fed. Proc. Fed. .4m. Sow. e.rp. Biol. 4, 79, 1945. and summation in pairs of short sound bursts. J. 32. ZWISLOCKI, J. J. and KETKAR. I. Loudness enhancement arousr. Sot. ilm. 51, 140(A), 1972. and summation tn 33. ZWISLOCKI, J. J., KETKAR, I.. CANNON. M. W. and NODAR, R. H. Loudness enhancement pairs of short sound bursts. Percept. Psychophys. 16, 91-95. 1974. ofa tone burst by a preceding tone burst. Perceppl. 31. ZWISLOCKI, J. J. and SOKOLICH, G. On loudnessenhancement Psr’chophys. 16, 87-90. 1974.
APPENDIX
A
Date
Name
This is a survey to discover which hand you use in the following manual tasks. Circle L if you perform the task with your left hand; circle R ifyou perform the task with your right hand; circle B if you perform the task equally well with both hands. Assume that your hands are empty (except as indicated) before attempting each task. If you have no experience with a given task, do not mark a preference. With which hand do vou: 1. draw’? 2. write’? 3 remove the top card of a deck of cards (i.e. dealing)? 4: throw a baseball to hit a target’? 5. use a hammer’! 6. use a toothbrush’! 7. use a screwdriver? 8. use an eraser on paper’.’ 9. use a tennis racket? 10. use scissors’! Il. stir a liquid or semi-solid? 12. on which shoulder do you rest a bat before swinging?
L L L L L L L L L L L L
R R R R R R R R R R R R
B B B B B B B B B B B B
VIBROTACTILE
SLwECTlVE
btACNITuDE
AS A FUNCTION
OF HASD
PREFERENCE
L'amolitude subiective 4e stimuli-tests vibrotactil's a et6 GtcrminPe nar une technique d'aooariwent osych+ohysiwp en fonction rln J'+qt~rvalle 40 terms entre fun stimulus conditionnant et le stimulus-tnst. Chew 4-s wiets L'aoolication 4~s 4wx stimuli sur droitiers. oauchers et anbidrxtres. l'uv ou l'autre win a orovoqu$ une auvwntation IS= l'amolitt~dn Flthiecsuiets. L'anolication 411 stimnlils conditinnnant d tive chw tous les une main et du test d l'autr~ main a nrovorr116 uw sunnrpssioq sllivip d'auqmentation chez les droitiers et les qauchers mais oas chw 1~s 'es r6sultatf suqn$rPnt 17~9 les covwxions wrvn~~scs bilatialbidextres. rales sont diffirentes chez let amhidextres et chew 1~s droitiprs ou chez les qauchers.
Zusammenfassung:
Mit
einer
St;irke Funktion und
psychophysischen
der
Wahrnehmung
des
Zeitintervalls
Teststimuli
bei
ambitextrischen lationen der
jeder
einer war. bei
den.
rief
war
Van
die
bei
RechtsDie
bilateralen denen
eine
von
van
linksh
bei
einer
und
Linkshandern,
Nervenverbindungen Rechts-
und
Versuchsfijhrte
Verstarkung
legen
und Stimu-
Empfindung allen
Stimulierung
Ergebnisse
die
eine
konditfionierenden
gleichstarke
Kontralaterale
Ambidextern.
wurde als
Gleichseitipe
Vibrationsschwelle
UnterdrUckung,
dal3 die sich
Hand
hervor.
und
zwischen
rechtshandigen.
Personen"rersucht.
subjektiven
personen
Zuordnunostechnik fiir Vibrationsreize
die van
Linkshandern
zu
gefolgt aber
Annahme
nicht nahe.
Ambidextern unterschei-
395
VIBROTACTILE
,983
0018-3932 83~s3.00+0.00 c 1983 Pergamon Press Ltd.
SUBJECTIVE MAGNITUDE OF HAND PREFERENCE*
AS A FUNCTION
RONALD T. VERRILLO Institute
for Sensory Research, Syracuse University, Syracuse, NY 13210. U.S.A. (Accepted
15 November 1982)
Abstract-The vibrotactile subjective magnitudes of test stimuli were determined by a psychophysical matching technique as a function of the time interval between conditioning and test stimuli in right-, left-, and ambi-handed subjects. Ipsilateral stimulation on either hand produced equal amounts ofenhancement of subjective magnitude in all subjects. Contralateral stimulation produced suppression, followed by enhancement in right- and left-handers, but produced no effect in ambihanders. The results suggest that the bilateral neural connections of ambi-handers is different from those of right- and left-handers.
INTRODUCTION THE EXPERIMENTS reported
here deal specifically with a relationship between self-reported hand preference and a task involving the sensation magnitude of vibrotactile stimuli. The implications that the results have for possible neural mechanisms associated with hand preference will be discussed. The preference for using one hand over the other for performing unimanual tasks has provided us with an extensive, rich, often-misleading and, until recently, predominently nonscientific body of literature [ 11,211. Attempts to measure it can be traced to biblical times and the consequences of hand preference along a multitude of behavioral, social, sensory, motor, perceptual, and even moral dimensions has been a matter of interest for thousands of years [ 111. Hand preference, which implies choice, should not be confused with manual proficiency, which involves performance. Although they are often confused, both of these measurable quantities have been linked, with varying degrees of success, to the notions of cerebral dominance and the specialization of function within the cortical hemispheres [S, and 23 for recent reviews]. The sensory phenomenon of enhancement, observed in the present experiments, was first described for the auditory sense [32-341. Enhancement refers to an increase in the subjective magnitude of a stimulus when it is preceded or followed by another stimulus at a short time interval. Suppression refers to a decrease of subjective magnitude under the same conditions. Enhancement and suppression of vibrotactile sensation have been investigated for both ipsi- and contralateral stimulus conditions [ 10,26,27] for both single- and multiplesite stimulation [ 10,271 and for forward and backward modes of stimulus presentation [29]. The effect of handedness was never considered in the previous experiments.
*This research was supported by grant NS 09940 from the National Institutes of Health, Department of Health and Human Services. 383
381
RO>.ALD T
XIETHODS
I’ERRILLO
AND PROCEDURES
The subjects here all patd volunteers +~ntversity students and persons from the communr:y There here s:x subjects tn each group. three male and three female. The three groups ivere defined by predomm~nt hand preference. rtght (R.H.). left (L.H.). or ambt (;\.H.j. Hand preferencevvas determined by a I?-item questtonnaireselected from a Il3-Item questtonnatre pubhshed by RA~ZRO~VS~I, K.AL\T and NERES [Xl. Only Items wtth reltabthty and validity indices above 0.90 were selected (.-\ppendix .A). In a survey of test items used in hand-preference questtonnaires by six investigators. PORK and COREY [21] reported that the first 1I items shown in ?-\ppsndix .A had a test-retest concordance of 92-lW”,, (mean=Yj.9”,,) for periods of trme up to I yr, The concordance between self report and actual behavior for these items ranged betueen 91 and lOO”,, (mean =96.6”.,). iltem 12 uas not mcluded in therr survey. I The items asked hand preference (right. left, or both1 on an assortment oiuntmanual tasks and were scored R= - I. L= - 1. B=O. Based on thtr sconng system. sub_jects classrfied as right-handed scored - ! I to - 13.those vvho were clawtied as left-handed scored -8 to - 12. and those classtried as ambt-handed scored - 3 to T -1. These designations are within the score definitions assigned by HFRRO~ [I21 whose 90 subjects were classrfied as righthanded. -8 to T 12; left-handed, -7 to - 12: and ambt-handed. -6 to r7 The apparatus consisted of the approprtate equtpmsnt to generate. ttme. and control the amplitude of stnusordal uaveforms. The signals uere delivered to Goodmans 390A and 103r\ vtbrators. u hich were used to sttmulaie the thenar emtnence and the dtstal pad of the middle finger of one hand during the control experiment. In the contralateral experiments, the vibrators were used to stimulate the hands separately. The intensity of vtbration was controlled by the subject during the matching phase of the experiment by two foot-operated switches. operating a precision dtgital attenuator. Intensity was increased by 1.0 dB at the right foot and decreased by 1.0 dB at the left foot. Smusotdal vibratory stimuli were delivered to the thenar cmtnence ofone or both hands. In a control experiment the stimulr were deltvered sequenttally to the thenar eminence and the dista! pad of the middle finpe: of the same hand. r\ 2.3-cm’ circular contactor was used at the thenar and 1.3 cm’ at the finger. Surface vtbrations on the skin Lvere confined to the tmmedtate region of the contactor by a rtgtd surround, placed at a drstance of 1 mm concentrrc to the contactor. Before each session the contactor was adjusted so that it pressed 0.3 mm beyond contact urth th? surface of the sktn. Amplitude of vibratron was measured by a caltbrated, precision accelerometer mounted directly on the moving element of the vibrator. ,411 measurements are expressed in dB. re 1.0 gm peak displacement. Sttmuli were 20 msec tn duratton. measured at the half-power points. and had 2.F msec rise-fall ttmes measured hetwecn the 10 and 90”,, points of Gaussian envelopes. The power spectrum of the 25 Hz stimulus consisted oia main lobe centered at 25 Hz with addttional small lobes at higher frequencies. The highest frequency associated with the main lohe was given by the carrier frequency plus 40 Hz. and the peak of the highest secondary lobe was 38 dB down from the lobe at 25 Hz. Well over 99”,, of the total energy of the stimulus was confined to frequencies making up the main lobe [see 9. Fig. 21. The vibrator assembly and the subject were located in a booth which provided adequate isolation from sound in the laboratory and from building vtbrations. Sounds emmattng from the vibrator were masked by narrow-band noise centered at the vibration frequency and delivered through ctrcumaural earphones. The subject’s detection threshold was measured at the start ofeach session. and the intensity of the test stimulus was set at a sensation level of IO dB (Fig. I). The intensity of the conditioning stimuius was then adjusted until the subject reported an intensity match to the test stimulus. The intensity ofthe conditioning stimulus was then ratsed an additional 10 dB above this subjective match. The procedure for measuring enhancement and suppresston first requires the subject to match the sensation magnitude of the matching stimulus to that of the test stimulus in the absence of the conditioning sttmulus (Fig. 1.
TEST
MATCHING
T$T
MAri”lNG
CONTROL MATCH
CONDITIONING MATCH , EXPERIMENTAL
+-At
_t______
750
MSEC
~1
FK;. 1. Sttmulus paradigm used to measure the sffzcts ofsuppresston and enhancement. AlI bursts of sinusoids are 20 msec in duratron vcith 75 msec rise-fall times. Enhancement and suppression are measured as a functron ofthe time Interval (A0 between the conditionins and test stimuli. See text for a full explanation.
VIBROTACTILE SLBJECTI~F M~cislnD~
As A FL-SUCTION OF H-\SD PREFERESCE
335
Control &latch). Followmg the control match, the subject matches the sensation magnitude 31 the matchmg stimulus to that of the test sttmulus in the presence of the conditioning stimulus (Fig. 1, Expertmental MatchI. The time interval between the onsets of the condtttoning and test stimult (Jr) was varied over the range of t&500 msec. and the matching stimulus followed the test sttmulus by 750 msec. The sttmulus sequence Has presented every 3.0 sec. hfter completing the expertmental matches. the control match was repeated and the results of the pre- and post-controi matches were averaged to compensate for adaptation during :he session. The subjects Nere instructed to use a bracketing procedure in all matches. On a single trtal they made several adjustments to the upper and lower limtts of the ma:ch and then adjusted the mtensity iterattvely toward thecenter of this zone of uncertainty. All of the SubJects were carefully instructed and trained for several sessions to match the subjective magnitude of vibrotactile bursts separated by various time Intervals prior to the sesstons in which data were collected. The subjects made three matches for each experimental condition, with a randomized presentation of AI’S within each expertmental session. The order of presentation of other variables was counterbalanced either over blocks of trials ~ithtn a session or over sessions. The effects of the presence of the conditioning stimulus upon the sensation magnitude of the tes: stimulus (enhancement or suppression) was expressed as the difference in dB between the experimental matches involving conditioning, test. and matching stimuli and the average of pre- and post-test control matches in which the conditioning stimulus was absent (Fig. I). This difference, the change in intensity level in dB. is plotted as a function of At. The data points on the graph represent mean values of the subjects in each group. The standard error of the mean (s.e.) will be reported as a measure of variability. Because of the number of data points in each graph, the range (R) and mean (R) of the standard errors will be given for each group in the text and in Table 1. The frequencies of the bursts were either 3OtX3W300 Hz, 2>25-25 Hz, or 25-300-300 Hz. These frequencies were chosen such that maximal excitation would be delivered selectively to the Pacinian corpuscle mechanoreceptots (300 Hz) and the non-Pa&an mechanoreceptors (2s Hz), and to stimulate both receptor channels within the same brief period of time (2s30&300 Hz). (The reader is referred to 8.9, 12. 13 and 14 for detailed discussions of the duplex model ofmechanoreception and the effects ofenhancement and suppression nithin the context of the model.) The experiments performed are listed below: (1) Control 1: The frequency of all three bursts set at 300 Hz, presented to the thenar eminence of the right hand and of the left hand. (2) Control ?: The conditioning stimulus presented to the tinger pad of the mtddie finger, and the test and matching stimuli to the thenar eminence of the same hand. The frequency of all stimuli was 300 Hz. Both hands were tested. (3) Contralateral 1: The conditioning stimulus presented to the thenar eminence of the left hand, and the conditioning and matching stimuli presented to the thenar eminence of the right hand. The frequency of all stimuli was 300 Hz. (4) Contralateral 2: Same as Contralateral 1. but wtth the order of presentation to the t*o hands reserved. (5) Contralateral 3: Same as Contralateral 1, but with the frequency of the three bursts set at 25 Hz. (6) Contralateral 4: Same as Contralateral 1, but wtth the frequency oftheconditioning stimulus set at 25 HZ. and of the test and matching stimuli set at 300 Hz. The order of performing the experiments was counterbalanced among subjects.
RESULTS The results of the contralateral experiments show that a conditioning vibrotactile stimulus delivered to one hand can influence the sensation magnitude of a subsequent (test) stimulus delivered to a homologous site on the other hand in both right- and left-handers. However, no such effect is measurable in ambi-handers. The effect is essentially the same in right-, left-, and ambi-handers for both the Pacinian and non-Pacinian mechanoreceptor systems, and there are no cross-channel effects in any of the three groups. The data shown in Fig. 2 are the results of Control experiment 1 performed to determine if an experiment performed ipsilaterally with all three bursts delivered to the same hand, either the right or left, would show a difference between the three groups. The results were virtually the same for all groups. All subjects showed the characteristic enhancement curve in which the presence of the conditioning stimulus produces an enhancement of the perceived intensity of the test stimulus amounting to about 6.0 dB at At = 75 msec. The effect decreases as At is increased up to 400 msec and beyond where the enhancement effect reduces to nil. The s.e. values of the three groups for data collected from the right hand (Fig. 2A) are: R.H., R=O.ll-0.35, n=O.25; L.H., R=0.09-0.37, M=O.23; A.H., R=0.18-0.42, R=0.28. The
386
RONALD T. VERRILLO
RIGHT
8
0
HAND
.
RIGHT-
o
LEFT-
HANDED
HANDED
x
AMBI-
HANDED
300-300-300
A
2-
B
I-
O
I 0
I
1 100 TIME
I
I 200
I
INTERVAL
I 300
(
I
I 400
IN
500
MSEC
FIG. 2. The effect of the conditioning stimulus upon the perceived intensity of the plotted as a change in intensity level in dB as a function of the time interval in msec conditioning and test stimuli. Results are shown for the right (A) and left (B) thenar right- (e), left- (0). and ambi- ( x ) handed individuals. The frequency of all three stimuli within the range of maximal sensitivity of the Pacinian system.
test stimulus bertceen the eminences of was 300 HI
s.e. values from the left hand (Fig. 2B) are: R.H., R=0.12-0.34, R =0.25; L.H., R=0.08-0.21, I%=O.12; A.H., R=0.08-0.31, ti=O.19 (Table 1). These curves are comparable to previous results in vibration [9, 26, 291 and in audition [33, 34). The data indicate with reasonable certainty that the enhancement effect does not operate differentially as a function of hand preference. The experiment was not repeated using 25-25-25 Hz since it has been shown that the curves for either a high or a low frequency are essentially the same using this experimental paradigm [9, 261. When the conditioning stimulus is presented to one site on the skin’s surface and the test and matching stimuli are presented to another site, either ipsilaterally [27] or contralaterally [lo], the effect of the conditioning stimulus upon the test stimulus changes character dramatically from the one-site condition. At short At’s (O-100 msec), the effect is a marked suppression of the perceived magnitude of the test stimulus, followed at longer Ar’s by an enhancement effect that reaches a maximum at 150 msec and then decreases inversely with At to nil beyond 300 msec. Figure 3 shows these effects in Control experiment 2 in which the conditioning stimulus was presented to the finger pad of the middle finger of the right hand, and the test and matching stimuli were presented to the thenar eminence of the same hand. The data of right- and left-handers were so similar they have been combined. The figure illustrates that both suppression and enhancement are measurable and the results are virtually the same regardless of the hand preference of the subjects, and that ambi-handers do not differ from right- and left-handers.
VIBROTACTILE
SUBJECTIVE
NAGNITUDE
Table Group Fig. 2
AS A FLNCTIOl’
1. Standard
errors
Hand
R.H.
A.H.
1lean
Range
R L R L R L
L.H.
OF H.AND PREFERESCE
0.1 l-O.35 0.12-0.34 0.09-0.37 0.08-0.2 1 0.18-0.42 0.08-0.3 1
0.25 0.25 0.23 0.12 0.25 0.19
Fig. 4
R.H. L.H. A.H.
0.10-1.91
0.53
0.060.86
0.44
Fig. 5
R.H. L.H. A.H.
0.10-0.83 o.ofSo.27 0.1 l-0.54
0.3 1 0.18 0.32
Fig. 6
R.H. L.H. A.H.
0.15-0.75 0.08-0.33 0.03-0.37
0.36 0.13 0.17
Fig. 7
R.H. L.H. A.H.
0.07-0.36 0.04-0.32 0.13-0.32
0.16 0.17 0.21
300-300-
5
3DDHz
0
m TI
0
z
8 8 0
0
I tn
w-5 i3
-
RIGHT HAND FINGER THENAR
Z
d
0
i:
l
-10
m
0
I
loo
I
I 200
TIME
1
RIGHT8 LEFT-HANDED AMBI -HANDED
I 300
INTERVAL
I
I 400
I
I 500
IN MSEC
FIG. 3. The effect of the conditioning stimulus presented to the finger pad of the middle finger upon the perceived intensity of the test stimulus presented to the thenar eminence of the same hand. The frequency of all three stimuli was 300 Hz. At time intervals less than 50 msec the conditioning stimulus has a pronounced suppressive effect on the perceived magnitude of the test stimulus. Beyond 50 msec enhancement reaches a peak at 150 msec before decreasing to nil at 400 msec. The results are the same for right-, left- (whose data have been combined) and ambi-handed individuals.
387
ROSALD T. VERRILLO
I
I
I
1
1
I
4m 7J z -1 w > it: > + -
3$
2-
C
‘r:
x
xx*
x
15
1
*
: x
2
-_
a
Q
O
I-
‘-I
z -2w !i- -3f
.
CONTRALATERAL 300300300 L R R
0 .
-4-
HANDEDNESS
si
w y$ -5-
RIGHT
.a
LEFT
o
a 1 -6-
AMBI
x
”
-7-
g I
0
,I,,,
,
ICO TIME
200 300 INTERVAL
,
IN
(
400 MSEC
,
,
/
500
FK,. 4 Suppression and enhancement effect:. mczzured v, hen the conditioning st~mulur u 3s presented to the thenar eminence of the left hand and the test and matching stimuli were presented to the right thenar eminence. All three stimuli were set at 300 Hz. Although reduced in magnitude, the effect in right- (0) snd Icft- (C,) handed individuals is a close parallel to the ipsilatrral results shown in Fi,q. 3. The results given by ambi-handed indlriduals show neither suppression nor enhancement effects.
The results shown in Fig. 4 are from Contralateral experiment 1 in which the conditioning stimulus was presented to the left hand, and the test and matching stimuli were presented to the right hand. The frequency of the three bursts was 300 Hz. The right- (a) and left- (0) handed subjects showed the effect of suppression followed by enhancement diminishing to nil beyond At = 300 msec, as shown by GESCHEIDER and VERRILLO [lo]. The responses of the ambi-handed subjects (Fig. 4, ( x )), however, showed virtually no effect of either suppression or enhancement across the body. The s.e. values of the combined R.H. and L.H. groups are: R=O.10-1.91, .a =O.S3; and for the A.H. group: R=0.06-0.86, M=0.44 (Table 1). The absence of any contralateral effects was first noted in two subjects vvho were participating in a previous study on contralateral effects [lo] in which handedness was not being considered. When asked about their hand preference, one designated himself as ambihanded and the other considered herself left-handed. The father of the ambi-handed subject confirmed that the subject showed no hand preference in infancy and early childhood. but developed different hand preferences for different tasks as he matured. The female subject revealed that her mother and an aunt wereambi-handed in their everyday behavior and both considered themselves to be “ambidextrous”. Subsequently, both subjects scored as ambihanded on the questionnaire, which led to a search for ambi- and left-banders and the present experiments. 2 in which the conditions and Figure 5 shows the results of Contralateral experiment frequencies (300-30&300 Hz) were the same as those for Fig. 4, except that the conditioning stimulus was presented to the right hand and the test and matching stimuli were presented to the left hand. The results are essentially .the same. The right- and left-handers gave very similar results to each other and to the results shown in Fig. 4, and the ambi-handers again
VIBROT.ACTILE
SCBJECTWE
MAGSITUDE
/
r
A.5 A FL?;CTlOS
I
I
s
0
I
OF H.*SD
PREFERESCE
389
i
4:
3-
2
-l ld > w J
2-
a
I0.
mx
x
xx c_,_ v, z -2f z -3-
x ”
0
x
x
CONTRALATERAL 300-300-300 R L L
z
.
= - -4w
. 0
‘:
-5-
0
a I u
-6-7-
0 x
HANDEDNESS RIGHT
.
LEFT
o
AMBl
x
8
11
0
11
11 100 TIME
5
1
200 300 INTERVAL
’
IN
1 400 MSEC
!
I
,
500
FIG. 5. Same as Fig. 4, but with the conditioning stimulus presented to the right hand and the test and matching stimuli presented to the left hand. The effects of hand preference are close to those shown in
Fig. 4.
showed virtually no suppression or enhancement effects, Change of intensity levels in the ambi group were all within t I .O dB of the control match. The s.e. values of the three groups are: R.H., R=0.1&0.83, m~O.31; L.H., R=0.060.27, ti10.18; A.H., R=O.ll-0.54, M =0.32 (Table 1). The data shown in Fig. 6 (Contralateral 3) were obtained under the same experimental conditions as those of Fig. 4, except that the frequency used for all three stimulus bursts was 25 Hz. Again, the right- and left-handed subjects produced results similar to each other and similar to those shown in Figs 4 and 5. The ambi-handed subjects again showed neither suppression nor enhancement effects, all of the change of intensity levels being within $1.0 dB of the control match. The s.e. values of the three groups are: R. H., R =0.1X).75, M=0.36; L.H., R=0.08-0.33, R=0.13; A.H., R=0.03-0.37, ~1=0.17 (Table 1). In the final experiment (Contralateral 4) the frequency of the conditioning stimulus was set at 25 Hz and that of the test and matching stimuli at 300 Hz. These frequencies were chosen to selectively stimulate the Pacinian (300 Hz) and non-Pacinian (25 Hz) mechanoreceptor systems. The results shown in Fig. 7 would indicate that in all three groups neither suppression nor enhancement takes place across the mechanoreceptor channels when the stimuli are presented contralaterally. This result confirms earlier results showing no crosschannel interactions in one-site [26] and in ipsilateral two-site [27] experiments. The s.e. valuesofthethreegroupsare: R.H.,R=0.07-0.36,~1=0.16;L.H., R=0.04-0.32, I%=O.17; A.H., R=0.13-0.32, R=0.21 (Table 1).
DISCUSSION When conditioning and test stimuli were presented results were the same regardless of hand preference.
to the same hand, right or left, the The effect, when both stimuli were
RONALD T. VERRILLO
390
4m = z _I
30
2-
Y ’ w -IO.
x=xx
z -,v, = -2w + f -3 -
0
x
+
. 0
‘0 x
L
0
0
Q-6I U
n
R
R
HANDEDNESS
-4-
w z -5-
8 x
CONTRALATERAL 25-25-25
. .
5
’
l
RIGHT
.
LEFT
o
AMBI
x
0
-7
I
I
I
I
100 TIME
0
I
I
I
I
200 300 INTERVAL IN
I
I
II
500
400 MSEC
FIG. 6. Same as Fig. 4, but with all three stimttli set at a frequency of25 Hz. At this frequency the nonPacinian receptor systems are preferentially activated. The effects of hand preference are close to those shown in FIG. 4.
I
w >
w
‘-
-lo
L - _,_
:,$Lg&“., .
I’
I
s!
Q
‘I’
I
x
0
g
x
v)
= -2 w Iz -3
CONTRALATERAL 25-300-300 L R R
-= -I -4
HANDEDNESS
II
0
I
11 100 TIME
11
RIGHT
.
LEFT
o
AMEI
x
11
300 200 INTERVAL
1 IN
400 MSEC
’
1 500
’
I
’
I
FIG. 7. The effect of the conditioning stimulus upon the perceived intensity of the test stimulus when the frequency of the conditioning stimulus (25 Hz) is within the region of maximal sensitivity of non-
Pacinian receptor systems, and the frequency of the test and matching stimuli (300 Hz) is within the region of maximal sensitivity of the Pacinianereceptor system. No effects were measurable in this cross-channel condition and hand preference did not have an effect upon the results.
VIBROTACTILE
SUBJECTIVE
MAGNITUDE
AS A FUWZllON
OF HA?“D PREFERENCE
391
presented to the same site (Control l), was an enhancement of the subjective intensity of the test stimulus at short interstimulus intervals. The effect diminished as the interstimulus interval was increased. When conditioning and test stimuli were presented to different sites on the same hand (Control 2), there were again no differences as a function of handedness. The effect was first suppression, followed by enhancement, and finally no effect with increasing values of the interstimulus interval. When the conditioning and test stimuli were presented to homologous contralateral sites (Contralateral 1,2, 3), the conditioning stimulus influenced the perceived magnitude of the test stimulus delivered to the opposite hand in both right- and left-handers. The results were similar to the ipsilateral, two-site experiment. However, the effect was not measurable in the ambi-handed, whose responses showed a lack of sensory influence laterally across the body. The findings will be discussed from several points of view. First, they will be considered as purely psychophysical results, descriptive of the performance of human beings in a task involving the judgment of vibrotactile sensations. Second, the psychophysical results will be viewed as clues that may provide some insights into the organization of the cerebral hemispheres with regard to tactile stimuli. The fact that a sensory stimulus can have an effect on the sensation magnitude produced by a second stimulus that occurs simultaneously or follows it closely in time has been well established within the auditory [2, 7, 14, 33, 343 and vibrotactile systems [9, 10, 25-281. Depending upon specific combinations of spatial, temporal, and intensive stimulus parameters, the interaction may produce an increase or a decrease in sensation. The phenomena reported here include both of these sensory effects. The results confirm previous findings that when two vibrotactile stimuli are presented at short time intervals (< 500 msec) to a single site, the subjective intensity of the second is increased (enhancement) by the presence of the first, and that the change is inversely related to the time interval separating the two stimuli. The magnitude and course of the enhancement effect of two stimuli presented to the same site on the same hand are not effected by the hand preference of the subject, nor by the hand to which the stimuli are presented (Control 1). It also has been shown in previous work that the effect persists with age [25]. Whatever the underlying neural mechanism for the phenomenon, it apparently does not differ in persons with different hand preferences, including right-, left-, and ambi-handers. To our knowledge, only one attempt has been made to explain the enhancement effect. ELMASIAN, GALAMBOS and BERNHEIM [5] recently postulated a factor they called mergence, in which the overlap in time and space of events within the brain causes the test stimulus to take on the perceived characteristics of the conditioning stimulus. Judgmental errors, due to a related factor they call difJiculry, interferes with the accurate perception of the test stimulus. This hypothesis is mentioned because, although there is little in the way ofconcrete evidence for it, it is the only one that has been offered in the literature. It is also demonstrated here that when two brief vibrotactile stimuli are presented in close temporal proximity, but at different ipsilateral sites (Control 2), suppression of the second by the first occurs at very short time intervals (< 100 msec). This phase of the sensory effect is followed by enhancement which reaches a maximum at 150 msec and then reduces to nil at time intervals beyond 300 msec. As in the case of the single-site experiment, hand preference appears to have no effect on the course or magnitude of these effects. The results discussed above for the one- and two-site, ipsilateral conditions are shown here only for stimulation within the Pacinian mechanoreceptor system. The conditioning, test,
392
ROS.%LD T
VERRILLO
and matching stimuli were all set at a frequency (300 Hz) to which the Pacinian corpuscle is maximally sensitive. Previous research has shown the same result in these experiments when a frequency (25 Hz) is selected that selectively stimulates the non-Pacinian system at threshold amplitudes [26. 273, suggestin, 0 that enhancement is measurable within either system. However, when the frequencies of the conditioning and test stimuli are selected so that they stimulate different systems, the enhancement effect disappears [36.27]. and both suppression and enhancement are reduced to nil when the stimuli are presented contralaterally [lo]. The results of the current experiments confirm previous findings of no effects in a cross-channel condition (Contralateral 4) and demonstrate that there is no effect of hand preference on the results. The only experimental condition in which a clear-cut difference appears that is dependent on hand preference is when the conditioning stimulus is presented to one hand and the test and matching stimuli to the other hand (Contralateral 1. 2 3). In this condition the results given by right- and left-handers are the same. At short time intervals, starting at At=0 msec, the conditioning stimulus produces a marked suppression of the subjective intensity of the test stimulus, which diminishes until At= 100 msec. At this time interval, enhancement begins to occur, reaching a maximum at At= 150 msec before it diminishes to nil at about Ar = 300 msec. Neither suppression nor enhancement, however, are observed in the data of the ambi-handed subjects. The results in all groups remained consistent regardless of which hand received the conditioning stimulus and which the test and matching stimuli. The result was also the same for stimulation within either the Pacinian (300 Hz) or the nonPacinian (25 Hz) system. The results of the contralateral experiments clearly indicate in right- and left-handed subjects that a conditioning stimulus delivered to one hand can infuence the sensation magnitude on the other hand of a stimulus following closely in time. In the ambi-handed group, however. the results of the contralateral experiments were strikingly different. The conditioning stimulus appeared to have no effect on the sensation magnitude of the test stimulus delivered contralaterally. The results obtained from right- and left-handed subjects imply that neural event.< occurring on one side of the body cross contralaterally and affect neural events occurring within corresponding areas of the other side. In the case of the ambi-handed subjects. the sensory events experienced on one hand appear to be independent of simulation delivered to the other hand. By implication, this suggests that the mechanism by which neural activity on one side is able to affect events in the contralateral hemisphere is lacking or severely limited in ambi-handed individuals. There is evidence that cortical cells receiving specific input from Pacinian and nonPacinian mechanoreceptors may be localized within specific cortical areas [lg, 193. and that the destination of fibers from the different types of mechanoreceptors is correlated with the cytoarchitecture of somatosensory areas I and II [3. 6, 131. It is also generally accepted that the enhancement effect is most probably the result of neural processing at higher levels of the central nervous system [S, 73. Enhancement within the auditory system could not be detected electrophysioiogically at the level of the auditory nerve of cat [I], and no effects of auditory enhancement were detected by EEG recordings in man at the level of the brainstem [Z]. A problem remains as to where in the somatosensory pathways the sensory information coming from one side of the body gains access to the sensory information available at the cortical level of the opposite side. Although the opportunity for the crossover of fibers exists at the level of the reticular formation [20] and the posterior group of thalamic nuclei [20], it
vIBROT&CTILESL'BJECTICZMAGSITIJDE AS A FL~CTION OF HASD PREFERESCE
393
is generally accepted that the major portion of somatosensory fibers cross either by decussating at the level of the spinal cord or at the level of the nuclei gracilis and cuneatus in the medulla [4, 17). Direct connection between somatosensory areas of the cortex is made via the corpus callosum, with SI projecting to both SI and SII of the opposite side, and SII projecting almost exclusively to its contralateral counterpart [ 15,16]. JOMS and PO~L-ELL, however, found no commissural connections from distal limb regions, thus supporting an earlier opinion [31] that other mechanisms must account for bilateral connections. Although it would be convenient as well as simple to ascribe the results of the current experiments to a difference in commissural connections between single- and ambi-handers, the available anatomical data does not allow this simple interpretation of the results. Bilateral connections within somatosensory systems are complex, The evidence presented in this paper would imply that the integrity of function for localized cortical areas associated with specific cutaneous mechanoreceptors is preserved across the body. Furthermore, it is reasonable to hypothesize that there is a difference in bilateral connections between individuals who have a strong right- or left-handed orientation and those who may be characterized as ambi-handed. It is not possible, however, at this time to specify the locus of that difference.
REFERENCES I. BAUER, J. W. and GLAMBOS, R. Evoked 2. 3. 4.
5. 6. 7. X. 9. 10.
I I. 12. 13. 14. 15. 16. 17.
potentials in cat auditory nerves: Suppression by prior tonal stimulation. Percept. Psychophys. 17, 43-47. 1975. BAUER, J. W., ELMMIAN. R. and GALAMBOS, R. Loudness enhancement in man: I. Brainstem evoked response correlates. J. acoust. Sot. Am. 57, 165-171, 1975. BENNEIT, R. E., FERRINCTON, D. G. and ROWE, M. Tactile neuron classes within second somatosensory area (SII) of cat cerebral cortex. J. Neurophysiol. 43, 292-309, 1980. BROWN, A. G. Ascending and long spinal pathways: Dorsal columns, spinocenical tract and spinothalamic tract. In Handbook of Sensory Physiology. Vol. II: Somatosensory Svstem, A. IGGO (Editor), pp. 315-338. Springer-Verlag, New York, 1973. ELMASIAN, R., GALAMBOS, R. and BERNHEIM,A.. Jr. Loudness enhancement and decrement in four paradigms. J. ucoust. Sot. Am. 67, 601-607, 1980. FERRINGTON. D. G. and ROWE, M. Differential contributions to coding of cutaneous vibratory information by cortical somatosensory areas I and II. J. Neurophysiol. 43, 310-33 I, 1980. GALAMBOS, R., BAUER. J.. PICTON, T., SQUARES, K. and SQUIRES, N. Loudness enhancement following contralateral stimulation. J. ucoust. Sot. Am. 52, 1127-I 130, 1972. GAZZANIGA, M. and LE Dovx, J. E. The Integrated Mind. Plenum Press, New York, 197% GEXHEIDER, G. A., VERRILLO. R. T.. CAPRARO, A. J. and HILMER,R. D. Enhancement ofvibrotactile sensation magnitude and predictions from the duplex model of mechanoreception. Sensory Processes 1, 187-203. 1977. GESCHEIDER. G. A. and VERRILLO. R. T. Contralateral enhancement and suppression of vibrotactile sensation. Percept. Psychophys. (in press). HARRIS, L. J. Left-handedness: Early theories, facts and fancies. In Neurops.~cholo,g)- of Left-Handedness, J. HERRON (Editor), pp. 3-78. Academic Press, New York, 19SO. HERRON, J. Two hands, two brains, two sexes. In Neuropsycholog,v oflefi-Handedness. J. HERRON (Editor). pp. 233-260. Academic Press, New York. 1980. HYV~INEN, J. and PORANES, A. Receptive field integration and submodality convergence in the hand area of the post-central gyrus of the adult monkey. J. Physiol. 283, 539-556. 1978. IRWIN, R. J. and ZWISLOCKI, J. J. Loudness effects in pairs of tone bursts. Percept. Psychophps. 10, 189-192, 1971. JOhT.3, E. G. and POWELL, T. P. S. The commissural connections of the somatic sensory cortex in the cat. J. Anat.. Land. 103, 433455. 1968. Jon. E. G. and POWELL, T. P. S. Connections of the somatic sensory cortex of the rhesus monkey. II. Contralateral cortical connections. Brain 92, 717-730. 1969. MARTIN, J. H. Somatic sensory system II: Anatomical substrates for somatic sensation. In Principles of Neuroscience, E. R. KANDEL and J. H. SCHWARTZ (Editors), pp. 170-183. Elsevier/North Holland. New York, 1951.
393
ROSALD T VERRILLO
18. PAUL. R. L.. GOODMAN. H. and .MERZENICH. Xl. Alterations in mechanoreceptor Input to Brodmann‘s areas I and 3 of the postcentral hand area of .tfacaca mukrrn after nene section and regeneration. Brain Res. 39, 1-19, 1972. PAL.L. R. L.. MERZENICH. 1M. and GOODMAN. H. Representation of slowly and rapidly adapting mechanoreceptors of the hand in Brodmann’s areas 3 and 1 of .Ifacaca nurk~~a. Brain 36, X9-249. 1972. POMPEIANO, 0. Reticular formation. In Handbook of Semor_v Ph.vsiology. Vol. II: Somaiosensory .S.vsrem. A. IGCO (Editor). pp. 38 I-455. Springer-Verlag. New York. 1973 PORAC. C. and COREN. S. Lareral Preferences and Human Behmior. Springer-Verlag. New York. 198 I. RACZKOWSKI, D., KALAT. J. W. and NEBES. R. Reliability and validity ofsome handedness questionnaire times. Neurophysiologia 12, 43-47, 1974. SPRISGER, S. P. and DEUTSCH. G. Lef Brain, Righr Brain. Freeman. San Francisco. CA, 1991. VERRILLO. R. T. A duplex mechanism of mechanoreception. In The Skin Sertses, D. R. KEMHALO (Editor), pp. 139-159. C. C. Thomas, Springfield, IL, 1968. VERRILLO. R. T. Effects of aging on the suprathreshold responses to vibration. Percept. Ps~choph~s. (in press). VERRILLO. R. T. and GESCHEIDER, G. A. Enhancement and summation in the perception of two successive vibrotactile stimuli. Percept. Psychophys. 18, 128-136. 1975. VERRILLO. R. T. and GFXHEIDER. G. A. Effect of double ipsilateral stimulation on vibrotactile sensation magnitude. Sensor) Processes 1, 127-137, 1976. VERRILLO. R. T. and GESCHEIDER, G. A. Psychophysical measurements of enhancement, suppression, and surface gradient effects in vibrotaction. In Sensory Frtncrions of Ihe Skin o,fHumnns. D. R. KENSHALO (Editor), pp. 153-182. Plenum Press. New York, 1979. 29. VERRILLO, R. T. and GEXHEIDER, G. A. Backward enhancement and suppression of vibrotactile sensation. Sens0r.v Processes 3, 249-160. 1979. in somatosensory area I in primates. J. 30. WERMR, G. and WHITSEL, B. L. Topology of the body representation Neurophysiol. 31, 856-869, 1968. 31. WOOLSEY.C. M. and WANG, G. H. Somatic sensory areas I and 11 of the somatic cortex of the rabbit. Fed. Proc. Fed. .4m. Sow. e.rp. Biol. 4, 79, 1945. and summation in pairs of short sound bursts. J. 32. ZWISLOCKI, J. J. and KETKAR. I. Loudness enhancement arousr. Sot. ilm. 51, 140(A), 1972. and summation tn 33. ZWISLOCKI, J. J., KETKAR, I.. CANNON. M. W. and NODAR, R. H. Loudness enhancement pairs of short sound bursts. Percept. Psychophys. 16, 91-95. 1974. ofa tone burst by a preceding tone burst. Perceppl. 31. ZWISLOCKI, J. J. and SOKOLICH, G. On loudnessenhancement Psr’chophys. 16, 87-90. 1974.
APPENDIX
A
Date
Name
This is a survey to discover which hand you use in the following manual tasks. Circle L if you perform the task with your left hand; circle R ifyou perform the task with your right hand; circle B if you perform the task equally well with both hands. Assume that your hands are empty (except as indicated) before attempting each task. If you have no experience with a given task, do not mark a preference. With which hand do vou: 1. draw’? 2. write’? 3 remove the top card of a deck of cards (i.e. dealing)? 4: throw a baseball to hit a target’? 5. use a hammer’! 6. use a toothbrush’! 7. use a screwdriver? 8. use an eraser on paper’.’ 9. use a tennis racket? 10. use scissors’! Il. stir a liquid or semi-solid? 12. on which shoulder do you rest a bat before swinging?
L L L L L L L L L L L L
R R R R R R R R R R R R
B B B B B B B B B B B B
VIBROTACTILE
SLwECTlVE
btACNITuDE
AS A FUNCTION
OF HASD
PREFERENCE
L'amolitude subiective 4e stimuli-tests vibrotactil's a et6 GtcrminPe nar une technique d'aooariwent osych+ohysiwp en fonction rln J'+qt~rvalle 40 terms entre fun stimulus conditionnant et le stimulus-tnst. Chew 4-s wiets L'aoolication 4~s 4wx stimuli sur droitiers. oauchers et anbidrxtres. l'uv ou l'autre win a orovoqu$ une auvwntation IS= l'amolitt~dn Flthiecsuiets. L'anolication 411 stimnlils conditinnnant d tive chw tous les une main et du test d l'autr~ main a nrovorr116 uw sunnrpssioq sllivip d'auqmentation chez les droitiers et les qauchers mais oas chw 1~s 'es r6sultatf suqn$rPnt 17~9 les covwxions wrvn~~scs bilatialbidextres. rales sont diffirentes chez let amhidextres et chew 1~s droitiprs ou chez les qauchers.
Zusammenfassung:
Mit
einer
St;irke Funktion und
psychophysischen
der
Wahrnehmung
des
Zeitintervalls
Teststimuli
bei
ambitextrischen lationen der
jeder
einer war. bei
den.
rief
war
Van
die
bei
RechtsDie
bilateralen denen
eine
von
van
linksh
bei
einer
und
Linkshandern,
Nervenverbindungen Rechts-
und
Versuchsfijhrte
Verstarkung
legen
und Stimu-
Empfindung allen
Stimulierung
Ergebnisse
die
eine
konditfionierenden
gleichstarke
Kontralaterale
Ambidextern.
wurde als
Gleichseitipe
Vibrationsschwelle
UnterdrUckung,
dal3 die sich
Hand
hervor.
und
zwischen
rechtshandigen.
Personen"rersucht.
subjektiven
personen
Zuordnunostechnik fiir Vibrationsreize
die van
Linkshandern
zu
gefolgt aber
Annahme
nicht nahe.
Ambidextern unterschei-
395