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Verbal coding and visual memory in aphasics
Ncuropsyehologia, 1977, Vol. 15, pp. 51 to 60. Pergamon Press. Printed in England.
VERBAL CODING AND VISUAL MEMORY IN APHASICS STEPHANIE KELTER, RUDOLF COHEN, DOROTHEA ENGEL, GUDULA LIST, and HANS STROHNER
University of Konstanz, West Germany (Received30 October 1975)
Abstract--Fluent and non-fluent aphasics, non-aphasic brain-damaged patients, schizophrenics, and normal controls were tested in a non-verbal visual retention task (objectdrawings, snowflakes). All groups of neurological and psychiatric patients scored lower than normal controls under a rehearsal condition. Differences levelled off when a distractor task was interpolated. While fluent aphasics were impaired with both the object-drawings and the snowflakes, non-fluent aphasics were impaired only with the latter. Results are discussed with respect to the verbal-encoding hypothesis and other theories of aphasia. SEVERAL investigators have reported impaired performance of aphasic patients not only for verbal tasks but also for those tasks involving neither verbal stimulus material nor requiring verbal responses [1-4]. Such findings have been taken as evidence for a conceptual defect underlying aphasia [5, 6], but more often they were discussed within the framework of a "verbal mediation" hypothesis (e.g. [7, 8]) assuming that "non-verbal" tasks often either require silent verbalization or are, at least, facilitated by the use of implicit verbal coding. With regard to research on visual memory disorders in aphasic patients the verbal mediation hypothesis stimulated a series of studies, in most of which the degree of "verbality" of the visual stimulus material was varied [8-12]. However, contrary to expectations, most of these studies show the retention performance of aphasics to be impaired not only with stimulus material prone to implicit verbal coding but also with respect to tasks involving nonsense figures or geometric patterns which were presumed to have a low degree of verbality [9-12]. As a result some authors have concluded [e.g. 9, 10] that the verbal mediation hypothesis is insufficient as an explanation and have suggested aphasics to be additionally impaired in other than verbal factors. BREWER [13], on the other hand, has remained with the verbalization hypothesis arguing that most of the results can be reinterpreted within the framework of a more specific "verbal-encoding" hypothesis, such as the "verballoop" hypothesis proposed by GLANZER and CLARK [14, 15] for normal subjects. The hypothesis concentrates attention on the efficiency of a verbal mode of storing visual information. Visual stimuli are thought of as differing with regard to the ease with which they can be coded verbally, and not, as to whether or not they can be coded verbally at all. Subsequently, it may be considered that unfamiliar stimuli require more complex verbal codes than familiar stimuli which usually have well overtrained verbal labels. Thus, unfamiliar visual stimuli represent the more difficult "verbal test" items, and one can expect *Requests for reprints should be addressed to Stephanie Kelter, Universifftt Konstanz, D-775 Konstanz, Postfach 733, West Germany. 51
52
S. KELTER, R. COHEN, D. ENGEL, G. LIST and H. STROHNER
t h a t the aphasics' i m p a i r m e n t will p e r h a p s be even m o r e p r o n o u n c e d in such tests. T h e results o f AMMON [16] have fulfilled this expectation. I n a d d i t i o n to the type o f stimulus m a t e r i a l there are several other variables which m a y determine the relative efficiency o f the verbal m o d e o f storage. One o f the m a i n a d v a n t a g e s o f the verbal code seems to be t h a t it can be easily rehearsed [17, 18]. Items t h a t w o u l d otherwise have been quickly lost f r o m the s h o r t - t e r m store can be retained t h r o u g h silent rehearsal for quite a l o n g time. However, if such a silent rehearsal is prevented b y a filler t a s k presented between stimulus exposure a n d retention test the utility o f any v e r b a l code is greatly reduced. Some o f the r e p o r t e d negative findings [9 (Exp. 2), 19, 20] m a y be attrib u t a b l e to the insertion o f such a filler task. It can be hypothesized, t h a t the length o f the retention interval will have a differential effect d e p e n d i n g on whether it is filled or unfilled. I f there is no filler t a s k a longer retention interval will increase the difference between aphasic a n d control patients [cf. 12] as the controls have the a d v a n t a g e o f retaining the m a t e r i a l b y means o f silent v e r b a l rehearsal, while the aphasics being unable to rehearse will show a steady decrease o f performance. Such an increased difference should n o t be f o u n d if the retention interval is filled b y a d i s t r a c t o r task. A s to the type o f aphasic language i m p a i r m e n t it m a y be hypothesized t h a t those patients whose s y m p t o m a t o l o g y consists p r i m a r i l y o f slow, l a b o r i o u s speech [21] will show the m o r e p r o n o u n c e d i m p a i r m e n t s as longer a n d m o r e complex verbal codes for the stimuli are required. F l u e n t aphasics on the other h a n d should fail in tasks with simple visual stimuli as m u c h as in tasks with c o m p l e x stimuli for their verbal codes will be either misleading as in p a r a p h a s i a or will be completely lacking as in their word-finding difficulties. F o r c o n t r o l groups we used the following: n o r m a l n o n - b r a i n - d a m a g e d subjects, b r a i n - d a m a g e d subjects w i t h o u t aphasia, a n d schizophrenics, who are also k n o w n to p e r f o r m at a lower level in a variety o f m e m o r y tasks. METHOD Subjects Subjects were matched subgroups of 25 fluent and 25 non-fluent aphasics, 25 brain-damaged patients without aphasia, 25 schizophrenics, and 25 normal controls tested in 14 different hospitals in Western Germany [cf. 22]. All subjects were male native German speakers. The five groups were matched for age (43.0 < 2 < 44.3; F = 0.07; df= 4, 120; P > 0.10) and for a combined index of level of education and occupation (2.2 < 2 < 2.6; F = 1.62; dr= 4, 120; P > 0.10). A s a control for severity of impairment caused by brain-damage the two aphasic groups and the brain-damaged patients without aphasia were matched also with regard to their reaction time scores (logarithmically transformed seconds) on Form A of the Trail Making Test [23] (1.90 < 2 < 1.96; F = 0,45; dr= 2, 72; P > 0.10). This test has high discriminative power in separating heterogeneous groups of brain-damaged patients from normal controls [24, 251. Brain-damaged patients who were or had been left-handed or ambidextrous according to the items of OLDFIELD'Sscale [26] were excluded as were patients having defective vision or hearing, not corrected by glasses or hearing aids. Patients with epileptic seizures, agnosia, apraxia, or dysarthria mentioned in their clinical records were excluded. To be included in the brain-damaged control group it was crucial that there was no indication of aphasic symptoms at any time in the clinical files. All aphasic patients had been diagnosed as aphasics by the neurological staff of the respective hospitals. All of them scored either above 9 errors on the Token Test [271 or above an impairment score of 9 % in the Sklar Aphasia Scale [28]. The two aphasic groups did not differ with regard to their scores in these tests (z < 1.00; P > 0.10). Fluency of speech [cf. 21, 29, 30] was determined by the average rate of speech in the immediate reproduction of four short stories. A score of 50 words/rain (wpm) was used as a cut-off point to separate fluent (2 = 96.4; sd = 31.8; range 56-183 wpm) and non-fluent aphasics (2 = 32.8; sd = 10.0; range 14-46 wpm). The fourfold point correlation between the neurological diagnosis as to aphasic subgroup and the fluent/non-fluent dichotomy was q0 = 0.76 (P < 0.01). No member of the normal control group, two brain-damaged patients without aphasia, and one schizophrenic had a rate of speech lower than 50 wpm.
VERBAL CODING AND VISUAL MEMORY IN APHASICS
53
For the brain-damaged controls brain-damage had again been diagnosed independently by two neurologists. Subject selection occurred regardless of etiology or duration of illness, only patients with well circumscribed and minor lesions were excluded. Table 1 shows the distribution of etiology (gt = 11.37; dr= 6; 0.10 > P > 0.05) and duration of illness (g2 = 0.60; d f : 2; P > 0.10) in the three brain-damaged groups. Table 1.
Etiology and duration of illness in the three brain-damaged groups Fluent aphasics
Etiology
Duration of illness
vascular traumatic neoplastic other, several median in years range less than 3 months
8 11 3 3
Non-fluent~D !Brain-damaged aphasics without aphasia 14 8 1 2
5 18 1 1
1.29
1.21
1.04
0.08-30.0 5
0.25-32.5 3
0.08-30.0 4
The schizophrenics were all diagnosed as chronic process schizophrenics with insidious onset. All of them had been hospitalized continuously for at least 1 yr prior to our examination with neuroleptic medication kept unchanged for the last 3 months. Patients considered to be too uncooperative by the staff or showing mainly paranoid symptomatology were excluded. Normal control subjects were hospitalized because of diseases other than those involving the nervous system above the dorsal spinal level. According to the clinical staff none had any indication of neurological or psychiatric illness in their histories.
Stimulus material Stimulus material comprised 72 pairs of picture cards (8.5 × 13 cm). One member of each pair was used as a learning stimulus while the other was used as a test stimulus in the recognition task. Learning and test stimuli were identical in 50 ~ of the pairs. Presented on half of the stimulus cards were photos of single snowflakes, considered extremely difficult to code verbally, although easy to discriminate visually. When learning and test stimuli were not identical snowflakes of the same basic structure were shown. The other half of the stimulus pairs consisted of clear and simple object-drawings. Each stimulus consisted of three such drawings arranged one above the other. No object occurred in more than one stimulus pair. When learning and test stimulus were not identical, the two cards differed with regard to just one of the three objects (e.g. "knife, house, swan" instead of "fork, house, swan"). In each case the substituted object belonged to the same class of objects as that on the learning card.
Design and procedure There were two types of stimulus material: difficult and easy to code verbally; two types of activity during the first part of the retention interval: rehearsal and non-rehearsal; and three durations for the retention interval: 5 see, 10 sec, and 15 sec. Each subject was tested with respect to the 12 experimental conditions. Testing was distributed over three sessions on 3 consecutive days. There were 24 trials/session. Every trial consisted of the presentation of the learning and the test stimulus separated by a retention interval. The subject had to indicate verbally or by gesture whether the two stimuli were "same" or "different". In every session the same number of positive ("same") and negative ("different") recognition tests was given. The time limit for the response was 45 sec. Stimuli were presented manually in about 50 cm distance from the subject's eyes. A schema of the different parts of a trial is given in Fig. I. The 3 see presentation of the learning card was followed by the retention interval, the total time of which was either 5 see, 10 sec, or 15 see. The first part of the retention interval (in all conditions 5 see) was designed to test the effect of variations of the filler task: in half of the trials the subjects had to sort playing cards according to suit (non-rehearsal), while in the other trials the 5 see were unfilled, i.e. no special instructions were given (rehearsal). Card sorting was used instead of the more usual backward counting [31] because the latter might have put undue stress on most of the non-fluent aphasics. The second part of the retention interval was to study the forgetting process under non-rehearsal conditions: it was filled by card sorting in any case, but varied in length, i.e. was either 0 see, 5 see, or 10 see. There were two practice trials/session and a short training period for the card sorting. For each of the three sessions the 12 experimental conditions were presented an equal number of times. Random sequences of the 12 conditions were constructed and for each subject three were selected--again, on a random basis--a
54
S. KELTER,R. COHEN, D. ENGEL,G. LIST and H. STROHNER
different sequence for each session. Stimulus pairs were randomly assigned to the conditions for each subject. Presentation of learning curd
Retention interval
A
A
/ 3 sec
Recognition t e s t
I 5 sec Rehearsal or non-rehearsel
/ O, 5 or I0 sec Non-rehearsal
b Time limit 45sec
FIO. 1. Schema of trial sections.
Data analysis For each subject and each of the 12 experimental conditions the relative frequency of correct responses constituted the raw data. The raw data were normalized by an arc-sin transformation with x" = 2 sin-1 x/~ [cf. 32, p. 221]. Concerning the controversy about acquiescence set in aphasia [33, 34] there were no differences between the fly6 subject groups with regard to the preference of positive responses (F = 0.91 ; dr= 4, 120; P > 0.20). Mean number of "same" responses was $ = 37.0 for the schizophrenics, $ = 37.8 for the fluent aphasics, = 38.8 for the non-fluent aphasies and the normal controls, and ~ = 41.0 for the brain-damaged patients without aphasia. RESULTS In the following section we shall first discuss the analysis of the performances with 5 sec retention interval which is expected to reveal the group differences as well as the stimulus material differences and the influence of the distractor task most clearly. Afterwards we shall deal with the effects o f varying the length of the retention interval. F o r the first analysis the transformed data f r o m the trials with 5 sec retention interval were subjected to an analysis of variance with subject groups as a between factor and the stimulus material and the rehearsal/non-rehearsal condition as within factors. The results of the analysis are summarized in Table 2. There is a significant main effect due to the subject groups (F = 3.90; d f = 4, 120; P < 0.01). N e w m a n - K e u l s tests have shown the normal controls (~' = 2.41) to perform significantly (P < 0.05) better than the non-aphasic brain-damaged patients (~' = 2.11), the fluent aphasics (~' -- 2.10), and the schizophrenics (~' = 2.03). The non-fluent aphasics (.~' = 2.23) showed no differences in comparison with the other groups. The difference between the two types o f stimulus material is significant ( F = 7.72; df---- 1, 120; P < 0.01), as is the interaction " g r o u p s x stimulus material" ( F - 4.05; d f = 4, 120; P < 0.01). So, the simple effects were studied (see Fig. 2). According to N e w m a n - K e u l s tests the difference between the two kinds o f stimulus material is significant only for the schizophrenics and the non-fluent aphasics. F o r the stimuli easy to code verbally (objectdrawings) no differences between groups are found. However, for the stimuli difficult to code verbally (snowflakes) the normal controls are f o u n d to be significantly superior to the four pathological groups, the difference between which are insignificant. While the overall effect of "rehearsal/non-rehearsal" is not significant (F---- 2.15; df~- 1,120; P > 0.10), the interaction " g r o u p s × rehearsal/non-rehearsal" is significant at the 5 % level of significance (F---- 2.87; d f = 4, 120; P < 0.05). Only for the normal controls did the unfilled 5 sec interval allow for a better performance than when the interval was filled with a distractor task. There is a similar trend in all other groups except for the fluent aphasics (see Fig. 2). Fluent aphasics perform significantly better under the "non-rehearsal" than under the "rehearsal" condition. Pairwise group comparisons were performed separately for the "rehearsal" and the "non-rehearsal" condition. U n d e r "rehearsal" normal controls are
VERBAL CODING AND V I S U A L M E M O R Y IN APHASICS
Table 2.
Outcome of the analyses of variance Trials with 5 see retention interval
Source of variation
mean squares
df
Between subjects G (subject groups) subj. within groups
2.1794 0.5594
4 120
Within subjects S (stimulus material) S x G S × subj. w. gr.
2.0149 1.0579 0.2610
R (rehear./non-rehear.) R x G R x subj. w. gr.
0.4831 0.6453 0.2252
All trials mean squares
df
F
3.90t
6.4265 1.3826
4 120
4.65t
1 4 120
7.72t 4.05t
10.9472 0.8312 0.3751
1 4 120
29.18t 2.22
1 4 120
2.15 2.87*
0.0081 0.3203 0.2671
1 4 120
0.03 1.20
0.3070 0.3184 0.2140
2 8 240
1.43 1.49
0.5412 0.3089 0.2317
1 4 120
2.34 1.33
0.4109 0.4000 0.2181
2 8 240
1.88 1.83
0.3363 0.3203 0.2326
2 8 240
1.45 1.38
0.3257 0.0626 0.2589
2 8 240
1.26 0.24
F
I (retention interval) I x G I × subj. w. gr. S x R S x R x G S x R x subj. w. gr. S S S
x x x
R R R
x x
S S S
I I I
0.0695 0.2059 0.2852
1 4
0.24 0.72
G subj. w. gr
x x
x
x
I I 1
x
G subj. w. gr.
x x x
R R R
x x x
I I I
x x
55
G subj. w. gr.
*P < 0.05. t P < 0.01. ANormal controls Non-aphasic brain-damaged • Non-fluent aphosics • Fluent aphasics x Schizophrenics
90 -
9C-
~, 2.40
~
220
x
80y.
_ 70
L
'~
~, 2.40 8C -
I~
%
2.2C T=
"~ 2.00 04
7C -
'~ 2.00 t"4
1.80
6C -
18C
÷ ×
II +
•
×
/
60 ~ k_
Objects
Snowflakes
Rehearsal
Non - rehearsal
FIG. 2. Mean percentage correct for the two types of stimulus material (left) and for the rehearsal/non-rehearsal variation (right) in trials with 5 see retention interval.
56
S. KELTER, R. COHEN,D. ENGEL, G. LIST and H. STROHNER
superior to schizophrenics, fluent aphasics, and brain-damaged controls. Non-fluent aphasics are again not significantly different from any of the other four groups. Under "nonrehearsal" no group differences are significant. A second analysis of variance was carried out to evaluate the effect of different lengths of the retention interval. While the first analysis was only with regard to the perfomance with a 5 sec retention interval, the following was with regard to all trials. As the first analysis had shown the other factors to account for significant portions of variance, the data were now submitted to an analysis with four factors, three of which having repeated measurement. The results of the analysis are summarized in the right part of Table 2. Analogous to the first analysis a significant main effect is found for "groups" (F = 4.65; df= 4, 120; P < 0.01) and "stimulus material" ( F = 29.18; df= 1, 120; P < 0.001). The interaction "groups x stimulus material" which had been significant in the first analysis now falls short of the 5 ~ level (F = 2.22; df= 4, 120; 0.10 > P > 0.05). Similar to the first analysis, a significant difference between the two types of stimulus material is found for the non-fluent aphasics and the schizophrenics, but not for the other three groups. And again, for the snowflakes the normal controls prove to be significantly superior to the four pathological groups. However, in contrast to the first analysis the performance of the normal controls for the object drawings is also significantly better than that of the fluent aphasics, the schizophrenics, and the brain-damaged patients without aphasia. The difference between the normal controls and the non-fluent aphasics is not significant. The interaction "group x rehearsal/non-rehearsal" which had been significant in the first analysis is now far from being significant (F = 1-20; df= 4, 120; P > 0.30). Concerning the length of the retention interval only the triple interaction "groups x stimulus material x length of retention interval" is of borderline significance (F = 1.83; df= 8, 240; 0.10 > P > 0.05). Newman-Keuls tests revealed unexpected results: in neither group is a significant decrease of performance found with increasing length of the retention interval. Apparently the triple interaction is mainly due to an increase of performance in some groups and a relatively constant performance in others. An improvement of performance is found for the normal controls on the object-drawing task going from the 5 sec through the 15 see retention interval and for the schizophrenics on the snowflake task after a delay of 15 sec. Correlations were calculated between the aphasics' retention performance and their performance in three verbal tests: (a) the Token Test [27], (b) the Sklar Aphasia Scale [28], and (c) the number of false responses in a naming task with drawings of 50 familiar objects. The correlations were determined separately for the retention performance for objectdrawings and for snowflakes. All coefficients are low (--0.02 > p > --0.39) and throughout insignificant (P > 0.05). However, there is a noteworthy trend: for fluent aphasics the verbal ability scores tend to correlate somewhat higher with the retention scores of the object-drawings (--0.15 > p ~ --0.39) than with the retention scores of the snowflakes (--0.02 > p > --0.04). The reverse is true for the non-fluent aphasics where the correlations for object-drawings are lower (---0.07 > p >/ ---0.16) than those for the snowflakes (--0.19 >~ 19 ~ ---0.30). Following this the correlation between retention scores and paraphasic errors in the naming task were computed. This correlation could only be assessed for the fluent aphasics as there were two few paraphasias in the group of the non-fluent aphasics. The correlation is somewhat higher for the object-drawings (p --0-36) than for the snowflakes (p = --0.09). The correlation between the retention performance for the object-drawings and for the
VERBAL CODING AND VISUAL MEMORY IN APHASICS
57
snowflakes is p = 0.64 (P <: 0.01) for the fluent aphasics and p = 0.44 (P < 0.05) for the non-fluent aphasics. DISCUSSION The aim of the present study was to gather information about the role of aphasic language disorders in visual, non-verbal retention tasks. Contrary to expectations, no significant differences between the retention performance of the aphasic patients and the non-aphasic brain-damaged controls were observed. This result, which is at variance with the results of several other studies [9-12] may be due to the randomization of experimental conditions within the same session. It is possible that this may have required a degree of flexibility that placed the pathological groups at an undue disadvantage [35, 36] thereby increasing the differences between these groups and the normal controls and reducing the differences between the pathological groups. Nevertheless, it is still possible to extract information from the comparisons of groups with respect to the specific effects resulting from the other experimental variables. Variations in the filler task revealed a significant decrease in performance from the rehearsal to the non-rehearsal condition for the normal controls. This finding provides some evidence that the normal controls may have used a verbal encoding strategy. The same tendency (albeit not significant) was noted for the non-fluent aphasics, the non-aphasic brain-damaged controls, and the schizophrenics, while for the fluent aphasics we found a significant effect in the opposite direction. It appears then that for the fluent aphasics the distractor task may have suppressed interferring processes which were effective under free rehearsal. From this we assume that the retention performance for the fluent aphasics was impaired because of the use of false and misleading verbal labels. In agreement with this is the tendency for the number of paraphasic errors in the naming task to correlate with the retention scores on the object-drawing task. We can say then that for the fluent aphasics the rehearsal/non-rehearsal seems to have been most crucial, while for the non-fluent aphasics the variation of the stimulus material appears to have been the more critical. This can be seen in the amount of variance common to the snowflake and the object-drawing task which was considerably lower for the nonfluent aphasics (19~) than for the fluent aphasics (41 ~). The main finding is, however, that the retention performance of the non-fluent aphasics was significantly different for the two types of stimulus material. A significant difference was also found for the schizophrenics, but their retention scores were still lower than that of the normal control for both types of stimulus material (considering all trials), while the non-fluent aphasics showed no appreciable impairment on the object-drawing task, but only on the snowflake task. Apparently the disorders of the non-fluent aphasics are detrimental only for the retention of complex stimuli, and in line with this are the verbal test scores for this group which show some tendency to correlate with the snowflake task, but not with the objectdrawing task. Our findings agree with BREWER'S "verbal-encoding" hypothesis, especially if we take the symptomatology of the aphasics into account. Non-fluent aphasics who have special difficulties in the more elaborate verbalizations appear impaired in tasks that call for complex verbal labels, while fluent aphasics are impaired with respect to the familiar tasks as well as the unfamiliar tasks because of their word-finding problems and paraphasie errors. However, one criticism which may be raised is, that we have focused our attention solely on verbal aspects and ignored non-verbal factors. Indeed, if we take the study of GOODGLASS, DEYES and CALDERON [37] into consideration, which has shown that neither
58
S. KELTER, R. COHEN, D. ENGEL,G. LIST and H. STROHNER
fluent n o r n o n - f l u e n t aphasics are capable of covert verbal mediation, the good performance of our non-fluent aphasics o n the object-drawing task suggests that the verbal c o m p o n e n t was relatively u n i m p o r t a n t in our task, or at least could be compensated for by some n o n verbal strategy. We can then consider that the failure of the aphasic patients o n the snowflake task may reflect a non-verbal, associative or analytical defect, similar to that which DE RENZl a n d his co-workers f o u n d to be c o n c o m i t a n t in aphasia [4, 10]. U n f o r t u n a t e l y we are n o t able to distinguish between these possibilities, b u t we can say that, in every case, our findings suggest that the factors which are responsible for the retention performance impairm e n t may be different dependent on the s y m p t o m a t o l o g y of the aphasic sub-group being considered. Acknowledgemet, ts--The research was conducted at the following clinics and rehabilitation centers; Abteilung Neurologie der Medizinischen Fakult~.t an der Rhein-Westf.-Technischen Hochschule Aachen: Neurologische Klinik und Institut f. Rehabilitation, Bad Homburg; Rheinische Landesklinik ftir Sprachgest6rte, Bonn; Neurologische Klinik der Universit~it Freiburg; Neurologische Kliniken, Dr. Schmieder, Gailingen; Neurologische Universit/itsklinik, Heidelberg; Psychiatrisches Landeskrankenhaus Reichenau, Konstanz; St/idtische Krankenanstalten, Konstanz; Stidwestdeutsches Rehabilitationskrankenhaus, Abt. Neurologie, Karlsbad-Langensteinbach; Neurologische Klinik und Hirnverletztenheim, Mtinchen; MaxPlanck-Institut f/Jr Psychiatrie, Mfinchen; Nervenkreiskrankenhaus Haar, bei Mfinchen; Neurologische Klinik des Bfirgerhospitals, Stuttgart; Neurologische Klinik und Hirnverletztenversorgungskrankenhaus, Tiibingen.
This research was supported by a Research Grant from the Deutsche Forschungsgemeinschaft. The authors wish to acknowledge the assistance of BARBARABONFIGand MARGARETO'BRIEN. REFERENCES 1. LEBRUN,Y. and HooPs, R. (Editors). Intelligence and Aphasia. Neurolinguistics 2, Swets & Zeitlinger B. V., Amsterdam, 1974. 2. ORGASS,B., HARTJE,W., KERSCHENSTEINER,M. and POECK,K. Aphasic und nichtsprachliche Intelligenz. Nervenarzt 43, 623-627, 1972. 3. TEUBER,H.-L. and WEINSTEIN,S. Ability to discover hidden figures after cerebral lesions. Archs Neurol. Psychiat. 76, 369-379, 1956. 4. VIGNOLO, L. A. Beitr~ige zum Problem der nichtsprachlichen Defekte bei der Aphasic. In Die Rehabilitation der Aphasie in den romanischen L~indern nebst Beitrflgen zur Aphasieforschung, A. LEISCHNER (Editor). 2. Symposium fiber Sprache und Sprachst6rungen, veranstaltet vonder Abt. Gesundheitspflege des Landschaftsverbandes Rheinland, am 26, 27. April 1968 in Bonn. Thieme, Stuttgart, 1970. 5. BAY,E. Aphasia and non-verbal disorders of language. Brain 85, 411-426, 1962. 6. GOLDSTEIN,K. Language and Language Disturbances. Grune & Stratton, New York, 1948. 7. BENTON, A. L. Clinical symptomatology in right and left hemisphere lesions. In Interhemispheric Relations and Cerebral Dominance, V. B. MOUNTCASTLE(Editor). Johns Hopkins Press, Baltimore, 1962. 8. IOMURA,D. Right temporal lobe damage. Archs Neurol. 8, 264-271, 1963. 9. DE RENZI, E. Nonverbal memory and hemispheric side of lesion. Neuropsychologia 6, 181-189, 1968. 10. BOLLER,F. and DE RENZI, E. Relationship between visual memory defects and hemispheric locus of lesion. Neurology 17, 1052-1058, 1967. 11. BOLLER, F. and SHNNLER, H. Visual memory for colors in patients with unilateral brain damage. Cortex 3, 395-405, 1967. 12. BISlACH,E. and FAGLIONI,P. Recognition of random shapes by patients with unilateral lesions as a function of complexity, association value and delay. Cortex 10, 101-I10, 1974. 13. BREWER,W. F. Visual memory, verbal encoding and hemispheric localization. Cortex 5, 145-151, 1969. 14. GLANZER,M. and CLARK,W. H. Accuracy of perceptual recall: an analysis of organization. J. Verbal Learn. & Verbal Behav. 1, 289-299, 1962. 15. GLANZER,M. and CLARK, W. H. The verbal-loop hypothesis: conventional figures. Am. J. Psychol. 77, 621-626, 1964. 16. AMMON,K. H. Verbal-loop-Hypothese und Kurzzeitged/ichtnis. Neuropsychologia 11,301-309, 1973. 17. ATKINSON,R. C. and SHIFFRIN,R. M. Human memory: a proposed system and its control processes. In The Psychology of Learning and Motivation: Advances in Research and Theory (Vol. 2), K. W. SPENCE and J. T. SPENCE(Editors). Academic Press, New York, 1968.
VERBAL CODING AND VISUAL MEMORY IN APHASICS
59
18. SHAFFER,W. D. and SHIRRFRIN, R. M. Rehearsal and storage of visual information. J. Exp. Psychol. 92, 292-296, 1972. 19. DE RENZl, E. and SPINNLER, H. The influence of verbal and non-verbal defects on visual memory tasks. Cortex 2, 322-336, 1966. 20. SAMUELS,I., BUTTERS,N. and FEDIO, P. Short-term memory disorders following temporal lobe removal in humans. Cortex 8, 283-298, 1972. 21. HOWLS, D. Application of the word-frequency concept to aphasia. In Ciba Foundation Symposium on Disorders of Language. A. V. S. DE REUCK and M. O'CoNNER (Editors), pp. 47-75. Churchill, London, 1964. 22. COHEN, R., ENGEL, D., HARTMANN,P., KELTER, S., LIST, G. and STROHNER,H. Experimentalpsychologische Untersuchungen zur linguistischen Erfassung aphatischer Stdrungen. Unver6ffentlichter Bericht an die DFG, Konstanz, 1975. 23. REITAN,R. M. A manual for the administration and scoring of the trail making test. Indiana University, 1959. 24. GORDON, N. G. The Trail Making Test in neuropsychologieal diagnosis. J. Clin. Neuropsych. 28, 167-169, 1972. 25. HEGENSCHEIDT,M. and COHEN, R. Zur Erfassung der Umstellungsf/ihigkeit bei hirnorganisch geschiidigten Personen. Z. Klin. Psychol. 1, 1-20, 1972. 26. OLDFIELD,R. C. The assessment and analysis of handedness: The Edinburgh Inventory. Neuropsychologia 9, 97-113, 1971. 27. DE RENZI, E. and VIGNOLO,L. A. The Token Test: a sensitive test to detect receptive disturbances in aphasics. Brain 85, 665-678, 1962. 28. SKLAR,M. Sklar Aphasia Scale. Manual. Beverly Hills, Ca., 1966. 29. BENSON,D. F. Fluency in aphasia: Correlation with radioactive scan localization. Cortex 3, 373-394, 1967. 30. KERSCHENSTEINER,i . , POECK, K. and BRUNNER, E. The fluency non-fluency dimension in the classification of aphasic speech. Cortex 8, 233-247, 1972. 31. PETERSON,L. R. and PETERSON,M. J. Short-term retention of individual verbal items. J. Exp. Psychol. 58, 193-198, 1959. 32. WINER, B. J. Statistical Principles in Experimental Design. McGraw-Hill, New York, 1962. 33. HowLs, D. Comments on the so-called acquiescence set in aphasia..L Abnorm. Psychol. 71, 151-154, 1966. 34. JENKINS,J. and SCHUELL,H. Acquiescence response set in aphasics. J. Abnorm. Psychol. 70, 111-113, 1965. 35. LURIA,A. R. Higher Cortical Functions in Man. Tavistock, London, 1966. 36. BROEN, W. E. Schizophrenia: Research and Theory. Academic Press, New York, 1968. 37. GOODGLASS,H., DENE$, G'. and CALDERON, M. The absence of covert verbal mediation in aphasia. Cortex 10, 264-269, 1974. R6sum6
: On a s o u m i s
bale
(dessins
non
fluents,
le,
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de sujets, n e u r o l o g i q u e s
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des
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d~ficitaide neige, cette hypotheses
60
S. KELTER,R. COHEN,D. ENGEL, G. LIST and H. STROHNER Zusammenfassung Aphatiker mit f]~ssigem und mit nicht-fl~ssigem Sprechverlauf, Hirngesch~digte
ohne Aphasie, chronisch Schizophrene und
normale Kontrollpersonen wurden in einer non-verbslen, visuellea Merkf~higkeitsaufgsbe
mit Zeichnungen yon Objekten und Photo-
graphien yon Schneekristallen vergllchen. Die Unterschiede zwischen den Gruppen waren unerheblich, wenn im Behaltensintervall eine Zwischent~tigkeit durchgef~hrt werden muBte; war dies zicht der Fall, zeigten alle vier pathologischen Gruppen Beeintrgchtigungen gegenHber der Kontrollgruppe. Aphatiker mit flGssigem Bprechverlauf evbrachten eowohl bei den 0bjekten als auch bei den Schneekristallen deutliehe ~inderleistungen, Aphatiker mit nicht-flHssigem $prechverbauf hingegen nut bei Schneekristallen. Die Ergebnisse werden im Zusammenhang mit der 'verbal-encoding'-Hypothese dlskutiert,
und anderen Aphasie-Theorien
VERBAL CODING AND VISUAL MEMORY IN APHASICS STEPHANIE KELTER, RUDOLF COHEN, DOROTHEA ENGEL, GUDULA LIST, and HANS STROHNER
University of Konstanz, West Germany (Received30 October 1975)
Abstract--Fluent and non-fluent aphasics, non-aphasic brain-damaged patients, schizophrenics, and normal controls were tested in a non-verbal visual retention task (objectdrawings, snowflakes). All groups of neurological and psychiatric patients scored lower than normal controls under a rehearsal condition. Differences levelled off when a distractor task was interpolated. While fluent aphasics were impaired with both the object-drawings and the snowflakes, non-fluent aphasics were impaired only with the latter. Results are discussed with respect to the verbal-encoding hypothesis and other theories of aphasia. SEVERAL investigators have reported impaired performance of aphasic patients not only for verbal tasks but also for those tasks involving neither verbal stimulus material nor requiring verbal responses [1-4]. Such findings have been taken as evidence for a conceptual defect underlying aphasia [5, 6], but more often they were discussed within the framework of a "verbal mediation" hypothesis (e.g. [7, 8]) assuming that "non-verbal" tasks often either require silent verbalization or are, at least, facilitated by the use of implicit verbal coding. With regard to research on visual memory disorders in aphasic patients the verbal mediation hypothesis stimulated a series of studies, in most of which the degree of "verbality" of the visual stimulus material was varied [8-12]. However, contrary to expectations, most of these studies show the retention performance of aphasics to be impaired not only with stimulus material prone to implicit verbal coding but also with respect to tasks involving nonsense figures or geometric patterns which were presumed to have a low degree of verbality [9-12]. As a result some authors have concluded [e.g. 9, 10] that the verbal mediation hypothesis is insufficient as an explanation and have suggested aphasics to be additionally impaired in other than verbal factors. BREWER [13], on the other hand, has remained with the verbalization hypothesis arguing that most of the results can be reinterpreted within the framework of a more specific "verbal-encoding" hypothesis, such as the "verballoop" hypothesis proposed by GLANZER and CLARK [14, 15] for normal subjects. The hypothesis concentrates attention on the efficiency of a verbal mode of storing visual information. Visual stimuli are thought of as differing with regard to the ease with which they can be coded verbally, and not, as to whether or not they can be coded verbally at all. Subsequently, it may be considered that unfamiliar stimuli require more complex verbal codes than familiar stimuli which usually have well overtrained verbal labels. Thus, unfamiliar visual stimuli represent the more difficult "verbal test" items, and one can expect *Requests for reprints should be addressed to Stephanie Kelter, Universifftt Konstanz, D-775 Konstanz, Postfach 733, West Germany. 51
52
S. KELTER, R. COHEN, D. ENGEL, G. LIST and H. STROHNER
t h a t the aphasics' i m p a i r m e n t will p e r h a p s be even m o r e p r o n o u n c e d in such tests. T h e results o f AMMON [16] have fulfilled this expectation. I n a d d i t i o n to the type o f stimulus m a t e r i a l there are several other variables which m a y determine the relative efficiency o f the verbal m o d e o f storage. One o f the m a i n a d v a n t a g e s o f the verbal code seems to be t h a t it can be easily rehearsed [17, 18]. Items t h a t w o u l d otherwise have been quickly lost f r o m the s h o r t - t e r m store can be retained t h r o u g h silent rehearsal for quite a l o n g time. However, if such a silent rehearsal is prevented b y a filler t a s k presented between stimulus exposure a n d retention test the utility o f any v e r b a l code is greatly reduced. Some o f the r e p o r t e d negative findings [9 (Exp. 2), 19, 20] m a y be attrib u t a b l e to the insertion o f such a filler task. It can be hypothesized, t h a t the length o f the retention interval will have a differential effect d e p e n d i n g on whether it is filled or unfilled. I f there is no filler t a s k a longer retention interval will increase the difference between aphasic a n d control patients [cf. 12] as the controls have the a d v a n t a g e o f retaining the m a t e r i a l b y means o f silent v e r b a l rehearsal, while the aphasics being unable to rehearse will show a steady decrease o f performance. Such an increased difference should n o t be f o u n d if the retention interval is filled b y a d i s t r a c t o r task. A s to the type o f aphasic language i m p a i r m e n t it m a y be hypothesized t h a t those patients whose s y m p t o m a t o l o g y consists p r i m a r i l y o f slow, l a b o r i o u s speech [21] will show the m o r e p r o n o u n c e d i m p a i r m e n t s as longer a n d m o r e complex verbal codes for the stimuli are required. F l u e n t aphasics on the other h a n d should fail in tasks with simple visual stimuli as m u c h as in tasks with c o m p l e x stimuli for their verbal codes will be either misleading as in p a r a p h a s i a or will be completely lacking as in their word-finding difficulties. F o r c o n t r o l groups we used the following: n o r m a l n o n - b r a i n - d a m a g e d subjects, b r a i n - d a m a g e d subjects w i t h o u t aphasia, a n d schizophrenics, who are also k n o w n to p e r f o r m at a lower level in a variety o f m e m o r y tasks. METHOD Subjects Subjects were matched subgroups of 25 fluent and 25 non-fluent aphasics, 25 brain-damaged patients without aphasia, 25 schizophrenics, and 25 normal controls tested in 14 different hospitals in Western Germany [cf. 22]. All subjects were male native German speakers. The five groups were matched for age (43.0 < 2 < 44.3; F = 0.07; df= 4, 120; P > 0.10) and for a combined index of level of education and occupation (2.2 < 2 < 2.6; F = 1.62; dr= 4, 120; P > 0.10). A s a control for severity of impairment caused by brain-damage the two aphasic groups and the brain-damaged patients without aphasia were matched also with regard to their reaction time scores (logarithmically transformed seconds) on Form A of the Trail Making Test [23] (1.90 < 2 < 1.96; F = 0,45; dr= 2, 72; P > 0.10). This test has high discriminative power in separating heterogeneous groups of brain-damaged patients from normal controls [24, 251. Brain-damaged patients who were or had been left-handed or ambidextrous according to the items of OLDFIELD'Sscale [26] were excluded as were patients having defective vision or hearing, not corrected by glasses or hearing aids. Patients with epileptic seizures, agnosia, apraxia, or dysarthria mentioned in their clinical records were excluded. To be included in the brain-damaged control group it was crucial that there was no indication of aphasic symptoms at any time in the clinical files. All aphasic patients had been diagnosed as aphasics by the neurological staff of the respective hospitals. All of them scored either above 9 errors on the Token Test [271 or above an impairment score of 9 % in the Sklar Aphasia Scale [28]. The two aphasic groups did not differ with regard to their scores in these tests (z < 1.00; P > 0.10). Fluency of speech [cf. 21, 29, 30] was determined by the average rate of speech in the immediate reproduction of four short stories. A score of 50 words/rain (wpm) was used as a cut-off point to separate fluent (2 = 96.4; sd = 31.8; range 56-183 wpm) and non-fluent aphasics (2 = 32.8; sd = 10.0; range 14-46 wpm). The fourfold point correlation between the neurological diagnosis as to aphasic subgroup and the fluent/non-fluent dichotomy was q0 = 0.76 (P < 0.01). No member of the normal control group, two brain-damaged patients without aphasia, and one schizophrenic had a rate of speech lower than 50 wpm.
VERBAL CODING AND VISUAL MEMORY IN APHASICS
53
For the brain-damaged controls brain-damage had again been diagnosed independently by two neurologists. Subject selection occurred regardless of etiology or duration of illness, only patients with well circumscribed and minor lesions were excluded. Table 1 shows the distribution of etiology (gt = 11.37; dr= 6; 0.10 > P > 0.05) and duration of illness (g2 = 0.60; d f : 2; P > 0.10) in the three brain-damaged groups. Table 1.
Etiology and duration of illness in the three brain-damaged groups Fluent aphasics
Etiology
Duration of illness
vascular traumatic neoplastic other, several median in years range less than 3 months
8 11 3 3
Non-fluent~D !Brain-damaged aphasics without aphasia 14 8 1 2
5 18 1 1
1.29
1.21
1.04
0.08-30.0 5
0.25-32.5 3
0.08-30.0 4
The schizophrenics were all diagnosed as chronic process schizophrenics with insidious onset. All of them had been hospitalized continuously for at least 1 yr prior to our examination with neuroleptic medication kept unchanged for the last 3 months. Patients considered to be too uncooperative by the staff or showing mainly paranoid symptomatology were excluded. Normal control subjects were hospitalized because of diseases other than those involving the nervous system above the dorsal spinal level. According to the clinical staff none had any indication of neurological or psychiatric illness in their histories.
Stimulus material Stimulus material comprised 72 pairs of picture cards (8.5 × 13 cm). One member of each pair was used as a learning stimulus while the other was used as a test stimulus in the recognition task. Learning and test stimuli were identical in 50 ~ of the pairs. Presented on half of the stimulus cards were photos of single snowflakes, considered extremely difficult to code verbally, although easy to discriminate visually. When learning and test stimuli were not identical snowflakes of the same basic structure were shown. The other half of the stimulus pairs consisted of clear and simple object-drawings. Each stimulus consisted of three such drawings arranged one above the other. No object occurred in more than one stimulus pair. When learning and test stimulus were not identical, the two cards differed with regard to just one of the three objects (e.g. "knife, house, swan" instead of "fork, house, swan"). In each case the substituted object belonged to the same class of objects as that on the learning card.
Design and procedure There were two types of stimulus material: difficult and easy to code verbally; two types of activity during the first part of the retention interval: rehearsal and non-rehearsal; and three durations for the retention interval: 5 see, 10 sec, and 15 sec. Each subject was tested with respect to the 12 experimental conditions. Testing was distributed over three sessions on 3 consecutive days. There were 24 trials/session. Every trial consisted of the presentation of the learning and the test stimulus separated by a retention interval. The subject had to indicate verbally or by gesture whether the two stimuli were "same" or "different". In every session the same number of positive ("same") and negative ("different") recognition tests was given. The time limit for the response was 45 sec. Stimuli were presented manually in about 50 cm distance from the subject's eyes. A schema of the different parts of a trial is given in Fig. I. The 3 see presentation of the learning card was followed by the retention interval, the total time of which was either 5 see, 10 sec, or 15 see. The first part of the retention interval (in all conditions 5 see) was designed to test the effect of variations of the filler task: in half of the trials the subjects had to sort playing cards according to suit (non-rehearsal), while in the other trials the 5 see were unfilled, i.e. no special instructions were given (rehearsal). Card sorting was used instead of the more usual backward counting [31] because the latter might have put undue stress on most of the non-fluent aphasics. The second part of the retention interval was to study the forgetting process under non-rehearsal conditions: it was filled by card sorting in any case, but varied in length, i.e. was either 0 see, 5 see, or 10 see. There were two practice trials/session and a short training period for the card sorting. For each of the three sessions the 12 experimental conditions were presented an equal number of times. Random sequences of the 12 conditions were constructed and for each subject three were selected--again, on a random basis--a
54
S. KELTER,R. COHEN, D. ENGEL,G. LIST and H. STROHNER
different sequence for each session. Stimulus pairs were randomly assigned to the conditions for each subject. Presentation of learning curd
Retention interval
A
A
/ 3 sec
Recognition t e s t
I 5 sec Rehearsal or non-rehearsel
/ O, 5 or I0 sec Non-rehearsal
b Time limit 45sec
FIO. 1. Schema of trial sections.
Data analysis For each subject and each of the 12 experimental conditions the relative frequency of correct responses constituted the raw data. The raw data were normalized by an arc-sin transformation with x" = 2 sin-1 x/~ [cf. 32, p. 221]. Concerning the controversy about acquiescence set in aphasia [33, 34] there were no differences between the fly6 subject groups with regard to the preference of positive responses (F = 0.91 ; dr= 4, 120; P > 0.20). Mean number of "same" responses was $ = 37.0 for the schizophrenics, $ = 37.8 for the fluent aphasics, = 38.8 for the non-fluent aphasies and the normal controls, and ~ = 41.0 for the brain-damaged patients without aphasia. RESULTS In the following section we shall first discuss the analysis of the performances with 5 sec retention interval which is expected to reveal the group differences as well as the stimulus material differences and the influence of the distractor task most clearly. Afterwards we shall deal with the effects o f varying the length of the retention interval. F o r the first analysis the transformed data f r o m the trials with 5 sec retention interval were subjected to an analysis of variance with subject groups as a between factor and the stimulus material and the rehearsal/non-rehearsal condition as within factors. The results of the analysis are summarized in Table 2. There is a significant main effect due to the subject groups (F = 3.90; d f = 4, 120; P < 0.01). N e w m a n - K e u l s tests have shown the normal controls (~' = 2.41) to perform significantly (P < 0.05) better than the non-aphasic brain-damaged patients (~' = 2.11), the fluent aphasics (~' -- 2.10), and the schizophrenics (~' = 2.03). The non-fluent aphasics (.~' = 2.23) showed no differences in comparison with the other groups. The difference between the two types o f stimulus material is significant ( F = 7.72; df---- 1, 120; P < 0.01), as is the interaction " g r o u p s x stimulus material" ( F - 4.05; d f = 4, 120; P < 0.01). So, the simple effects were studied (see Fig. 2). According to N e w m a n - K e u l s tests the difference between the two kinds o f stimulus material is significant only for the schizophrenics and the non-fluent aphasics. F o r the stimuli easy to code verbally (objectdrawings) no differences between groups are found. However, for the stimuli difficult to code verbally (snowflakes) the normal controls are f o u n d to be significantly superior to the four pathological groups, the difference between which are insignificant. While the overall effect of "rehearsal/non-rehearsal" is not significant (F---- 2.15; df~- 1,120; P > 0.10), the interaction " g r o u p s × rehearsal/non-rehearsal" is significant at the 5 % level of significance (F---- 2.87; d f = 4, 120; P < 0.05). Only for the normal controls did the unfilled 5 sec interval allow for a better performance than when the interval was filled with a distractor task. There is a similar trend in all other groups except for the fluent aphasics (see Fig. 2). Fluent aphasics perform significantly better under the "non-rehearsal" than under the "rehearsal" condition. Pairwise group comparisons were performed separately for the "rehearsal" and the "non-rehearsal" condition. U n d e r "rehearsal" normal controls are
VERBAL CODING AND V I S U A L M E M O R Y IN APHASICS
Table 2.
Outcome of the analyses of variance Trials with 5 see retention interval
Source of variation
mean squares
df
Between subjects G (subject groups) subj. within groups
2.1794 0.5594
4 120
Within subjects S (stimulus material) S x G S × subj. w. gr.
2.0149 1.0579 0.2610
R (rehear./non-rehear.) R x G R x subj. w. gr.
0.4831 0.6453 0.2252
All trials mean squares
df
F
3.90t
6.4265 1.3826
4 120
4.65t
1 4 120
7.72t 4.05t
10.9472 0.8312 0.3751
1 4 120
29.18t 2.22
1 4 120
2.15 2.87*
0.0081 0.3203 0.2671
1 4 120
0.03 1.20
0.3070 0.3184 0.2140
2 8 240
1.43 1.49
0.5412 0.3089 0.2317
1 4 120
2.34 1.33
0.4109 0.4000 0.2181
2 8 240
1.88 1.83
0.3363 0.3203 0.2326
2 8 240
1.45 1.38
0.3257 0.0626 0.2589
2 8 240
1.26 0.24
F
I (retention interval) I x G I × subj. w. gr. S x R S x R x G S x R x subj. w. gr. S S S
x x x
R R R
x x
S S S
I I I
0.0695 0.2059 0.2852
1 4
0.24 0.72
G subj. w. gr
x x
x
x
I I 1
x
G subj. w. gr.
x x x
R R R
x x x
I I I
x x
55
G subj. w. gr.
*P < 0.05. t P < 0.01. ANormal controls Non-aphasic brain-damaged • Non-fluent aphosics • Fluent aphasics x Schizophrenics
90 -
9C-
~, 2.40
~
220
x
80y.
_ 70
L
'~
~, 2.40 8C -
I~
%
2.2C T=
"~ 2.00 04
7C -
'~ 2.00 t"4
1.80
6C -
18C
÷ ×
II +
•
×
/
60 ~ k_
Objects
Snowflakes
Rehearsal
Non - rehearsal
FIG. 2. Mean percentage correct for the two types of stimulus material (left) and for the rehearsal/non-rehearsal variation (right) in trials with 5 see retention interval.
56
S. KELTER, R. COHEN,D. ENGEL, G. LIST and H. STROHNER
superior to schizophrenics, fluent aphasics, and brain-damaged controls. Non-fluent aphasics are again not significantly different from any of the other four groups. Under "nonrehearsal" no group differences are significant. A second analysis of variance was carried out to evaluate the effect of different lengths of the retention interval. While the first analysis was only with regard to the perfomance with a 5 sec retention interval, the following was with regard to all trials. As the first analysis had shown the other factors to account for significant portions of variance, the data were now submitted to an analysis with four factors, three of which having repeated measurement. The results of the analysis are summarized in the right part of Table 2. Analogous to the first analysis a significant main effect is found for "groups" (F = 4.65; df= 4, 120; P < 0.01) and "stimulus material" ( F = 29.18; df= 1, 120; P < 0.001). The interaction "groups x stimulus material" which had been significant in the first analysis now falls short of the 5 ~ level (F = 2.22; df= 4, 120; 0.10 > P > 0.05). Similar to the first analysis, a significant difference between the two types of stimulus material is found for the non-fluent aphasics and the schizophrenics, but not for the other three groups. And again, for the snowflakes the normal controls prove to be significantly superior to the four pathological groups. However, in contrast to the first analysis the performance of the normal controls for the object drawings is also significantly better than that of the fluent aphasics, the schizophrenics, and the brain-damaged patients without aphasia. The difference between the normal controls and the non-fluent aphasics is not significant. The interaction "group x rehearsal/non-rehearsal" which had been significant in the first analysis is now far from being significant (F = 1-20; df= 4, 120; P > 0.30). Concerning the length of the retention interval only the triple interaction "groups x stimulus material x length of retention interval" is of borderline significance (F = 1.83; df= 8, 240; 0.10 > P > 0.05). Newman-Keuls tests revealed unexpected results: in neither group is a significant decrease of performance found with increasing length of the retention interval. Apparently the triple interaction is mainly due to an increase of performance in some groups and a relatively constant performance in others. An improvement of performance is found for the normal controls on the object-drawing task going from the 5 sec through the 15 see retention interval and for the schizophrenics on the snowflake task after a delay of 15 sec. Correlations were calculated between the aphasics' retention performance and their performance in three verbal tests: (a) the Token Test [27], (b) the Sklar Aphasia Scale [28], and (c) the number of false responses in a naming task with drawings of 50 familiar objects. The correlations were determined separately for the retention performance for objectdrawings and for snowflakes. All coefficients are low (--0.02 > p > --0.39) and throughout insignificant (P > 0.05). However, there is a noteworthy trend: for fluent aphasics the verbal ability scores tend to correlate somewhat higher with the retention scores of the object-drawings (--0.15 > p ~ --0.39) than with the retention scores of the snowflakes (--0.02 > p > --0.04). The reverse is true for the non-fluent aphasics where the correlations for object-drawings are lower (---0.07 > p >/ ---0.16) than those for the snowflakes (--0.19 >~ 19 ~ ---0.30). Following this the correlation between retention scores and paraphasic errors in the naming task were computed. This correlation could only be assessed for the fluent aphasics as there were two few paraphasias in the group of the non-fluent aphasics. The correlation is somewhat higher for the object-drawings (p --0-36) than for the snowflakes (p = --0.09). The correlation between the retention performance for the object-drawings and for the
VERBAL CODING AND VISUAL MEMORY IN APHASICS
57
snowflakes is p = 0.64 (P <: 0.01) for the fluent aphasics and p = 0.44 (P < 0.05) for the non-fluent aphasics. DISCUSSION The aim of the present study was to gather information about the role of aphasic language disorders in visual, non-verbal retention tasks. Contrary to expectations, no significant differences between the retention performance of the aphasic patients and the non-aphasic brain-damaged controls were observed. This result, which is at variance with the results of several other studies [9-12] may be due to the randomization of experimental conditions within the same session. It is possible that this may have required a degree of flexibility that placed the pathological groups at an undue disadvantage [35, 36] thereby increasing the differences between these groups and the normal controls and reducing the differences between the pathological groups. Nevertheless, it is still possible to extract information from the comparisons of groups with respect to the specific effects resulting from the other experimental variables. Variations in the filler task revealed a significant decrease in performance from the rehearsal to the non-rehearsal condition for the normal controls. This finding provides some evidence that the normal controls may have used a verbal encoding strategy. The same tendency (albeit not significant) was noted for the non-fluent aphasics, the non-aphasic brain-damaged controls, and the schizophrenics, while for the fluent aphasics we found a significant effect in the opposite direction. It appears then that for the fluent aphasics the distractor task may have suppressed interferring processes which were effective under free rehearsal. From this we assume that the retention performance for the fluent aphasics was impaired because of the use of false and misleading verbal labels. In agreement with this is the tendency for the number of paraphasic errors in the naming task to correlate with the retention scores on the object-drawing task. We can say then that for the fluent aphasics the rehearsal/non-rehearsal seems to have been most crucial, while for the non-fluent aphasics the variation of the stimulus material appears to have been the more critical. This can be seen in the amount of variance common to the snowflake and the object-drawing task which was considerably lower for the nonfluent aphasics (19~) than for the fluent aphasics (41 ~). The main finding is, however, that the retention performance of the non-fluent aphasics was significantly different for the two types of stimulus material. A significant difference was also found for the schizophrenics, but their retention scores were still lower than that of the normal control for both types of stimulus material (considering all trials), while the non-fluent aphasics showed no appreciable impairment on the object-drawing task, but only on the snowflake task. Apparently the disorders of the non-fluent aphasics are detrimental only for the retention of complex stimuli, and in line with this are the verbal test scores for this group which show some tendency to correlate with the snowflake task, but not with the objectdrawing task. Our findings agree with BREWER'S "verbal-encoding" hypothesis, especially if we take the symptomatology of the aphasics into account. Non-fluent aphasics who have special difficulties in the more elaborate verbalizations appear impaired in tasks that call for complex verbal labels, while fluent aphasics are impaired with respect to the familiar tasks as well as the unfamiliar tasks because of their word-finding problems and paraphasie errors. However, one criticism which may be raised is, that we have focused our attention solely on verbal aspects and ignored non-verbal factors. Indeed, if we take the study of GOODGLASS, DEYES and CALDERON [37] into consideration, which has shown that neither
58
S. KELTER, R. COHEN, D. ENGEL,G. LIST and H. STROHNER
fluent n o r n o n - f l u e n t aphasics are capable of covert verbal mediation, the good performance of our non-fluent aphasics o n the object-drawing task suggests that the verbal c o m p o n e n t was relatively u n i m p o r t a n t in our task, or at least could be compensated for by some n o n verbal strategy. We can then consider that the failure of the aphasic patients o n the snowflake task may reflect a non-verbal, associative or analytical defect, similar to that which DE RENZl a n d his co-workers f o u n d to be c o n c o m i t a n t in aphasia [4, 10]. U n f o r t u n a t e l y we are n o t able to distinguish between these possibilities, b u t we can say that, in every case, our findings suggest that the factors which are responsible for the retention performance impairm e n t may be different dependent on the s y m p t o m a t o l o g y of the aphasic sub-group being considered. Acknowledgemet, ts--The research was conducted at the following clinics and rehabilitation centers; Abteilung Neurologie der Medizinischen Fakult~.t an der Rhein-Westf.-Technischen Hochschule Aachen: Neurologische Klinik und Institut f. Rehabilitation, Bad Homburg; Rheinische Landesklinik ftir Sprachgest6rte, Bonn; Neurologische Klinik der Universit~it Freiburg; Neurologische Kliniken, Dr. Schmieder, Gailingen; Neurologische Universit/itsklinik, Heidelberg; Psychiatrisches Landeskrankenhaus Reichenau, Konstanz; St/idtische Krankenanstalten, Konstanz; Stidwestdeutsches Rehabilitationskrankenhaus, Abt. Neurologie, Karlsbad-Langensteinbach; Neurologische Klinik und Hirnverletztenheim, Mtinchen; MaxPlanck-Institut f/Jr Psychiatrie, Mfinchen; Nervenkreiskrankenhaus Haar, bei Mfinchen; Neurologische Klinik des Bfirgerhospitals, Stuttgart; Neurologische Klinik und Hirnverletztenversorgungskrankenhaus, Tiibingen.
This research was supported by a Research Grant from the Deutsche Forschungsgemeinschaft. The authors wish to acknowledge the assistance of BARBARABONFIGand MARGARETO'BRIEN. REFERENCES 1. LEBRUN,Y. and HooPs, R. (Editors). Intelligence and Aphasia. Neurolinguistics 2, Swets & Zeitlinger B. V., Amsterdam, 1974. 2. ORGASS,B., HARTJE,W., KERSCHENSTEINER,M. and POECK,K. Aphasic und nichtsprachliche Intelligenz. Nervenarzt 43, 623-627, 1972. 3. TEUBER,H.-L. and WEINSTEIN,S. Ability to discover hidden figures after cerebral lesions. Archs Neurol. Psychiat. 76, 369-379, 1956. 4. VIGNOLO, L. A. Beitr~ige zum Problem der nichtsprachlichen Defekte bei der Aphasic. In Die Rehabilitation der Aphasie in den romanischen L~indern nebst Beitrflgen zur Aphasieforschung, A. LEISCHNER (Editor). 2. Symposium fiber Sprache und Sprachst6rungen, veranstaltet vonder Abt. Gesundheitspflege des Landschaftsverbandes Rheinland, am 26, 27. April 1968 in Bonn. Thieme, Stuttgart, 1970. 5. BAY,E. Aphasia and non-verbal disorders of language. Brain 85, 411-426, 1962. 6. GOLDSTEIN,K. Language and Language Disturbances. Grune & Stratton, New York, 1948. 7. BENTON, A. L. Clinical symptomatology in right and left hemisphere lesions. In Interhemispheric Relations and Cerebral Dominance, V. B. MOUNTCASTLE(Editor). Johns Hopkins Press, Baltimore, 1962. 8. IOMURA,D. Right temporal lobe damage. Archs Neurol. 8, 264-271, 1963. 9. DE RENZI, E. Nonverbal memory and hemispheric side of lesion. Neuropsychologia 6, 181-189, 1968. 10. BOLLER,F. and DE RENZI, E. Relationship between visual memory defects and hemispheric locus of lesion. Neurology 17, 1052-1058, 1967. 11. BOLLER, F. and SHNNLER, H. Visual memory for colors in patients with unilateral brain damage. Cortex 3, 395-405, 1967. 12. BISlACH,E. and FAGLIONI,P. Recognition of random shapes by patients with unilateral lesions as a function of complexity, association value and delay. Cortex 10, 101-I10, 1974. 13. BREWER,W. F. Visual memory, verbal encoding and hemispheric localization. Cortex 5, 145-151, 1969. 14. GLANZER,M. and CLARK,W. H. Accuracy of perceptual recall: an analysis of organization. J. Verbal Learn. & Verbal Behav. 1, 289-299, 1962. 15. GLANZER,M. and CLARK, W. H. The verbal-loop hypothesis: conventional figures. Am. J. Psychol. 77, 621-626, 1964. 16. AMMON,K. H. Verbal-loop-Hypothese und Kurzzeitged/ichtnis. Neuropsychologia 11,301-309, 1973. 17. ATKINSON,R. C. and SHIFFRIN,R. M. Human memory: a proposed system and its control processes. In The Psychology of Learning and Motivation: Advances in Research and Theory (Vol. 2), K. W. SPENCE and J. T. SPENCE(Editors). Academic Press, New York, 1968.
VERBAL CODING AND VISUAL MEMORY IN APHASICS
59
18. SHAFFER,W. D. and SHIRRFRIN, R. M. Rehearsal and storage of visual information. J. Exp. Psychol. 92, 292-296, 1972. 19. DE RENZl, E. and SPINNLER, H. The influence of verbal and non-verbal defects on visual memory tasks. Cortex 2, 322-336, 1966. 20. SAMUELS,I., BUTTERS,N. and FEDIO, P. Short-term memory disorders following temporal lobe removal in humans. Cortex 8, 283-298, 1972. 21. HOWLS, D. Application of the word-frequency concept to aphasia. In Ciba Foundation Symposium on Disorders of Language. A. V. S. DE REUCK and M. O'CoNNER (Editors), pp. 47-75. Churchill, London, 1964. 22. COHEN, R., ENGEL, D., HARTMANN,P., KELTER, S., LIST, G. and STROHNER,H. Experimentalpsychologische Untersuchungen zur linguistischen Erfassung aphatischer Stdrungen. Unver6ffentlichter Bericht an die DFG, Konstanz, 1975. 23. REITAN,R. M. A manual for the administration and scoring of the trail making test. Indiana University, 1959. 24. GORDON, N. G. The Trail Making Test in neuropsychologieal diagnosis. J. Clin. Neuropsych. 28, 167-169, 1972. 25. HEGENSCHEIDT,M. and COHEN, R. Zur Erfassung der Umstellungsf/ihigkeit bei hirnorganisch geschiidigten Personen. Z. Klin. Psychol. 1, 1-20, 1972. 26. OLDFIELD,R. C. The assessment and analysis of handedness: The Edinburgh Inventory. Neuropsychologia 9, 97-113, 1971. 27. DE RENZI, E. and VIGNOLO,L. A. The Token Test: a sensitive test to detect receptive disturbances in aphasics. Brain 85, 665-678, 1962. 28. SKLAR,M. Sklar Aphasia Scale. Manual. Beverly Hills, Ca., 1966. 29. BENSON,D. F. Fluency in aphasia: Correlation with radioactive scan localization. Cortex 3, 373-394, 1967. 30. KERSCHENSTEINER,i . , POECK, K. and BRUNNER, E. The fluency non-fluency dimension in the classification of aphasic speech. Cortex 8, 233-247, 1972. 31. PETERSON,L. R. and PETERSON,M. J. Short-term retention of individual verbal items. J. Exp. Psychol. 58, 193-198, 1959. 32. WINER, B. J. Statistical Principles in Experimental Design. McGraw-Hill, New York, 1962. 33. HowLs, D. Comments on the so-called acquiescence set in aphasia..L Abnorm. Psychol. 71, 151-154, 1966. 34. JENKINS,J. and SCHUELL,H. Acquiescence response set in aphasics. J. Abnorm. Psychol. 70, 111-113, 1965. 35. LURIA,A. R. Higher Cortical Functions in Man. Tavistock, London, 1966. 36. BROEN, W. E. Schizophrenia: Research and Theory. Academic Press, New York, 1968. 37. GOODGLASS,H., DENE$, G'. and CALDERON, M. The absence of covert verbal mediation in aphasia. Cortex 10, 264-269, 1974. R6sum6
: On a s o u m i s
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d~ficitaide neige, cette hypotheses
60
S. KELTER,R. COHEN,D. ENGEL, G. LIST and H. STROHNER Zusammenfassung Aphatiker mit f]~ssigem und mit nicht-fl~ssigem Sprechverlauf, Hirngesch~digte
ohne Aphasie, chronisch Schizophrene und
normale Kontrollpersonen wurden in einer non-verbslen, visuellea Merkf~higkeitsaufgsbe
mit Zeichnungen yon Objekten und Photo-
graphien yon Schneekristallen vergllchen. Die Unterschiede zwischen den Gruppen waren unerheblich, wenn im Behaltensintervall eine Zwischent~tigkeit durchgef~hrt werden muBte; war dies zicht der Fall, zeigten alle vier pathologischen Gruppen Beeintrgchtigungen gegenHber der Kontrollgruppe. Aphatiker mit flGssigem Bprechverlauf evbrachten eowohl bei den 0bjekten als auch bei den Schneekristallen deutliehe ~inderleistungen, Aphatiker mit nicht-flHssigem $prechverbauf hingegen nut bei Schneekristallen. Die Ergebnisse werden im Zusammenhang mit der 'verbal-encoding'-Hypothese dlskutiert,
und anderen Aphasie-Theorien