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A noninvasive stimulus onset device for use in gustatory research
Physiology&Behavior,Vol. 40, pp. 255-258. Copyright©PergamonJournals Ltd., 1987. Printed in the U.S.A.
0031-9384/87 $3.00 + .00
BRIEF COMMUNICATION
A Noninvasive Stimulus Onset Device For Use in Gustatory Research THOMAS
C. P R I T C H A R D , .1 A L A N L I P T O N t
AND CARL PFAFFMANN:~
*The Pennsylvania State University College of Medicine, Department of Behavioral Science tThe Rockefeller University Laboratory of Electronics and Microprocessors and ~:Laboratoo' of Physiological Psychology R e c e i v e d l l N o v e m b e r 1985 PRITCHARD, T. C., A. LIPTON AND C. PFAFFMANN. A noninvasive stimulus onset devicefor use in gustatory research. PHYSIOL BEHAV 40(2) 255-258, 1987.--A simple device for precise, noninvasive measurement of stimulus onset time in gustatory research is described. This device utilizes an ultrafast, self-heated, micro-thermistor to sense the cooling effect of the fluid stream that bathes the tongue. Detection of fluid onset
Gustation
by using the fluid stimulus to interrupt a light beam [2, 15, 16, 21], induce a capacitance change [7,8], or complete the circuit of a conductivity cell [9, 11, 12] or lickometer [10, 19, 20]. Photocells, phototransistors, and the capacitance change technique provide accurate measurement of stimulus delivery time (1-50 msec resolution) when the sensors are placed in close proximity to the tongue [2, 15, 16, 21]. Lickometer circuits and conductivity cells are more accurate, but must be used with care to avoid inadvertent stimulation o f the gustatory system, which is very sensitive to the flow of electric current across the tongue [14]. This report describes a device suitable for gustatory research that is capable of precise, but noninvasive, detection of stimulus onset time. This device utilizes an ultrafast, self-heated, micro-thermistor to sense the cooling effect of the fluid stream that bathes the tongue.
IN gustatory research sapid stimuli are applied to the dorsal surface of the tongue in a variety of way s depending upon the goals of the experiment. Eye droppers, fine brushes [18], wetted filter paper [1], and pipettes [3] are used when discrete stimulus application is required. Flow chambers that enclose part of the anterior tongue [4,15], squeeze bottles and intraoral spray nozzles [5,6] are used when a large portion o f the receptor surface must be stimulated. Although many factors must be weighed when choosing among these techniques, one consideration should be the ease with which stimulus onset time can be determined. Currently, few investigators in gustation accurately measure stimulus arrival time or report response latency. This contrasts sharply with research in vision, audition, and somesthesis where stimulus onset time is routinely recorded and reported. There are several possible reasons for this obvious lapse in experimental protocol. First, fluids are less tractable than light, sound, or mechanical stimulation making measurement of stimulus onset technically challenging. Second, the errors introduced by inaccurate specification of stimulus onset may be considered inconsequential since long periods (3-5 sec) of evoked activity are usually analyzed in taste research. In some studies the entire problem is circumvented by beginning data analysis at the time o f response onset [17]. This solution, though satisfactory in principle for a number of applications, is difficult to apply to slowly firing neurons and neurons that gradually increase their rate of firing following stimulus application. Both of these characteristics have been observed among gustatory neurons. Previous investigators have marked stimulus onset time
METHOD Most thermistors are solid, semi-conductors that exhibit a large negative resistance-temperature coefficient. Since response time usually varies directly with the size of a thermistor, a miniature (TC=7 msec; dia.=.007") fastip thermoprobe was used for the present application. This thermistor, when used in conjuction with the circuit described below, had a response time of less than 2 msec. Table 1 lists the electronic components used in the stimulus onset detector. The dissipation constant (5 x 10-5 W#C; still air) and maximum power rating (6x 10-a W) of the thermistor theoretically allow the bead to be heated 120°C above the ambient temperature. F o r
1Requests for reprints should be addressed to T. C. Pritchard, Department of Behavioral Science, Milton S. Hershey Medical Center, P.O. Box 850, Hershey, PA 17033.
255
256
PRITCHARD, L l t r r O N AND P F A F F M A N N TABLE 1 LIST OF COMPONENTS USED IN T H E S T I M U L U S O N S E T DETECTOR
8.2VZ, 5% IN4454 5082-4684, LED 0.1 /~F, disk 10/xF, tant. 0.005/zF
R1 R2 R3 R4, R5 R6 R7 R8
12 Kit, 5% 1.3 Kf~, 5% 1 Kit, 5% 1.5 Kit, 1% 2.2 Kit, 5% 220 Kit, 5% 10 Kit, 5%
D1 D2, D3, D4, D6 D5 C1, C3, C6 C2, C4 C5
R9
100 Kit, 5%
Rp~, Rp:~
10 Kit, O 10 Kit, 10 Turn, WW
Re4 100 It, O
R p2
RT~
FP07DA332N-C
Thermometrics, Inc. 808 U.S. Highway No. 1 Edison, NJ 08817
0 Denotes Trimmer. WW Denotes Wire-wound.
+L5V l
+I5V
4-15V TEMPERATURE SENSE BRIDGE
RI
I
VOLTAGE
)
BUFFER-
["--..]
RpI ~ ' ~ - - - - 4 + ~ f 0 I 7
R~Tt/~.
/
LIMITER n
,
,
~,f
I
r'~ ""L,R4 )
~
T//~'~T C2
I
~.. ~ _ ~ "",~ D 2 ~ - 3 1 4
r'~ /
/c,LTJ ..~-.
VOLTAGE ) COMPARATOR
R6
'---T-S3__...... L ; I HCPL IL-
Isolated
ll~a~. I
BNC
I,-4 " )
I
: •
1
~" ~
I
%
_L _
I
"
~
J_ =
±tF~W
""~
I
J_
,
- ,sv
CD4OllA
--'--
II ! /
,SOL T O
OUTPUT
~
[
,
u
k,.._.JJ
[
"
THRESHOLD INDICATOR
k,.,__JJ i
!"
FIG. 1. Circuit diagram for the stimulus onset detector. Table 1 contains the list of components.
the present application the thermistor was self-heated to 40°C (1 × 10-3 W) above the ambient temperature. Due to the small thermal mass of the thermistor bead, there was only negligible local heating within the flow chamber. The air temperature 4 mm from the thermistor bead (the normal thermistor-tongue distance) was only 0.5°C higher than a reference area 10 mm further away. Neither rapid heating nor cooling of the thermistor evoked a neural response in the chorda tympani, which contains a significant population of thermally sensitive axons [22]. The electronic circuit for the stimulus onset device is shown in Fig. 1. The regulated DC power supply (--_15 V), voltage buffer-limiter, and potentiometer Rp~ provide voltage control of the temperature sense bridge which varies the
self-heated temperature of thermistor RT1. Thermistor RT1 is protected from power transients by zener diode DI which clamps the bridge excitation voltage to a safe level. The high sensitivity of thermistor RT1 is used effectively by adjusting the voltage comparator reference level (+ level) to be very nearly equal to its signal input level ( - level)just prior to the time of fluid arrival. The 10 KIq, 10 turn precision wire wound potentiometer (Rw9 used to make the precise voltage comparator adjustment (_+0.1%), also allows for direct measurement of the thermistor (RT0 environment (-+ 1.0%). Both high and low frequency noise to the 3140 voltage comparator are attenuated by C1, C2, C3, C4 which heavily AC-bypass the DC-power pins (-+ 15 V). The voltage comparator is differential-input-voltage limited by fast diodes D2
GUSTATORY ONSET DETECTOR
257
6.5 6.0
;2'
5.5
T h.,,,,., .e~r, ~ .-~ mistor..,.,~..;:
i u,ou,
. . . . . . .
~'/~
• ~ .;",~
~,~:.:.: - ~" "-'~:'~
.
*
/
~
.,-,:
o 4.5
,
Fluid Drain
50
>.-
4o
oz 3.5 ILl
FIG. 2. Illustration oitthe thermistor, flow chamber, and gravity feed stimulus delivery system in situ.
and D3 and has a minimum gain of 2x 104 (typ. 1 x l 0 b . A reduction of 0.5°C in thermistor temperature is easily detected, causing a pulse output. Figure 2 shows a hamster with its tongue drawn gently through a latex diaphragm into a glass flow chamber. The micro-thermistor is positioned approximately 4 mm above the tongue surface. The onset latency of the thermistor and electronic circuit was measured by reproducing this spatial arrangement with the tongue replaced by a molded rubber plug containing two uninsulated wires. Electrical continuity between the two wires was made by flowing a saline solution through the flow system. The difference in time between fluid detection by the thermistor and electrical conduction between the wires embedded in the rubber plug was considered the latency of detection. Following a distilled water rinse all residual fluids within the flow system were evacuated with a short burst of compressed air. Although fluid application and evacuation of the flow system cooled the thermistor below its operational temperature (40°C above ambient), the recovery time for the thermistor was less than 20 sec, shorter than the time most researchers use for an interstimulus interval. RESULTS AND DISCUSSION
The latency between thermistor detection and fluid contact with the tongue was tested with a gravity feed system with flow rates between 4.6 and 11.3 ml/sec. As Fig. 3 shows, the latency of detection asymptotes at approximately 2 msec for flow rates between 8 and 11 ml/sec. The latency increased with flow rates slower than 7 ml/sec. Flow rates slower than 4.6 ml/sec would be expected to produce even longer detection latencies with more variability of response unless special measures were taken to ensure optimal laminar flow of the solutions. This device provides satisfactory resolution of the time of stimulus onset for most applications in gustatory research.
3.c
-J 2.5
]
zo
1
t
FLOW RATE (ml/sec.) FIG. 3. Latency between thermistor detection and fluid contact with the tongue as a function of flow rate. For more demanding applications, a design based upon the concept of a closed-loop constant power regulator [13] could be used. This method uses a negative-feedback loop to maintain constant power dissipation in the thermistor, thereby significantly reducing its temperature swing and improving its speed of response. Ultimate limitations are caused by the column of air that precedes the fluid and cools the thermistor. In the present system detectability was sacrificed somewhat by setting potentiometer R~z just prior to fluid onset to allow for the rush of air. A closed-loop constant power regulator would increase the resolution of R~z, theoretically allowing a closer approach to an optimum pre-onset condition. The 2 msec resolution described in this report is due not only to the set level of potentometer R~, but also to the distance of the thermistor from the tongue (4 mm). This relatively constant interval, made "transparent" by a simple hardware or software delay triggered by the signal from the thermistor, would allow specification of the onset time to approximately 0.5 msec. These figures would be expected to vary with the dimensions of the flow chamber being used as well as the laminar flow characteristics of the fluid delivery system. ACKNOWLEDGEMENTS This research was supported, in part, by a postdoctoral traineeship from training grant MH15125 awarded to T.C.P. and NSF Grant BNS78-16533 to C.P.
REFERENCES 1. Collings, V. B. Human taste responses as a function of locus of stimulation on the tongue and soft palate. Percept Psychophys 16: 169-174, 1974. 2. Faull, J, R. and B. P. Halpern. Taste stimuli: Time course of peripheral nerve response and theoretical models. Science 178: 73-75, 1972.
3. Frank, M. E. Single fiber responses in the glossopharyngeal nerve of the rat to chemical, thermal, and mechanical stimulation of the posterior tongue. Doctoral disseration. Brown University, Providence, RI, University Microfilms No. 69-9957, 1968.
258 4. Frank, M. E. An analysis of hamster afferent taste nerve response functions. J Gen Physiol 61: 588--618, 1973. 5. Grill, H. J. and R. Norgren. The taste reactivity test. 1. Mimetic responses to gustatory stimuli in neurologically normal rats. Brain Res 143: 263-279, 1978. 6. Grill, H. J. and R. Norgren. The taste reactivity test. II. Mimetic responses to gustatory stimuli in chronic thalamic and chronic decerebrate rats. Brain Res 143: 281-297, 1978. 7. Halpern, B. P. The use of vertebrate laboratory animals in research on taste. In: Methods o f Animal Experimentation Vol 4. edited by W. I. Gay. New York: Academic Press, 1973. 8. Halpern, B. P. and L. A. Marowitz. Taste responses to lickduration stimuli. Brain Res 57: 473-478, 1973. 9. Harper, H. W. and M. Rossetto. An "artificial tongue" for calibrating solution flow characteristics of taste stimulus delivery systems. Chern Senses Flavor 3: 267-280, 1978. 10. Hill, J. H. and E. Stellar. An electric drinkometer. Science 114: 43-44, 1951. 11. Kelling, S. T. and B. P. Halpern. Taste flashes: Reaction times, intensity, and quality. Science 219: 412-414, 1983. 12. Lester, B. and B. P. Halpern. Effect of stimulus presentation duration on gustatory reaction time. Phy~iol Behav 22:31%324, 1979. 13. Miyara, J. Measuring air flow with a self-balancing bridge. Analog Dialog 5: 13-14, 1971.
PRITCHARD, LIPTON AND PFAFFMANN 14. Pritchard, T. C. and C. Pfaffmann. Electro-chemical stimulation of taste. Neurosci Abstr 7: 730, 1981. 15. Pritchard, T. C. and T. R. Scott. Amino acids as taste stimuli. II: Taste quality. Brain Res 253: 93-104, 1982. 16. Scott, T. R. and R. P. Erickson. Synaptic processing of taste quality information in thalamus of the rat. J Neurophysiol 34: 868-884, 1971. 17. Smith, D. V,, J. B. Travers and R. L. Van Buskirk. Brainstem correlates of gustatory similarity in the hamster. Brain Res Bull 4: 359-372, 1979. 18. Travers, S. P., C. Pfaffmann and R. Norgren. Convergence of lingual and palatal gustatory neural activity in the nucleus of the solitary tract. Brain Re.s 365: 305-320, 1986. 19. Yamamoto, T. and Y. Kawamura. Gustatory reaction time in human adults. Physiol Behav 26: 715-719, 1981. 20. Yamamoto, T. and Y. Kawamura. Gustatory reaction time to various salt solutions in human adults. Physiol Behav 32: 4%53, 1984. 21. Yamamoto, T., H. Takee and Y. Kawamura. A simple device detecting onset time of taste stimulation. Physiol Behav 26: 721-723, 1981. 22. Yamashita, S., H. Ogawa, T. Kiyohara and M. Sato. Modification by temperature change of gustatory impulse discharges in chorda tympani fibres of rats. Jpn J Phy.~iol 20: 348-363, 1970.
0031-9384/87 $3.00 + .00
BRIEF COMMUNICATION
A Noninvasive Stimulus Onset Device For Use in Gustatory Research THOMAS
C. P R I T C H A R D , .1 A L A N L I P T O N t
AND CARL PFAFFMANN:~
*The Pennsylvania State University College of Medicine, Department of Behavioral Science tThe Rockefeller University Laboratory of Electronics and Microprocessors and ~:Laboratoo' of Physiological Psychology R e c e i v e d l l N o v e m b e r 1985 PRITCHARD, T. C., A. LIPTON AND C. PFAFFMANN. A noninvasive stimulus onset devicefor use in gustatory research. PHYSIOL BEHAV 40(2) 255-258, 1987.--A simple device for precise, noninvasive measurement of stimulus onset time in gustatory research is described. This device utilizes an ultrafast, self-heated, micro-thermistor to sense the cooling effect of the fluid stream that bathes the tongue. Detection of fluid onset
Gustation
by using the fluid stimulus to interrupt a light beam [2, 15, 16, 21], induce a capacitance change [7,8], or complete the circuit of a conductivity cell [9, 11, 12] or lickometer [10, 19, 20]. Photocells, phototransistors, and the capacitance change technique provide accurate measurement of stimulus delivery time (1-50 msec resolution) when the sensors are placed in close proximity to the tongue [2, 15, 16, 21]. Lickometer circuits and conductivity cells are more accurate, but must be used with care to avoid inadvertent stimulation o f the gustatory system, which is very sensitive to the flow of electric current across the tongue [14]. This report describes a device suitable for gustatory research that is capable of precise, but noninvasive, detection of stimulus onset time. This device utilizes an ultrafast, self-heated, micro-thermistor to sense the cooling effect of the fluid stream that bathes the tongue.
IN gustatory research sapid stimuli are applied to the dorsal surface of the tongue in a variety of way s depending upon the goals of the experiment. Eye droppers, fine brushes [18], wetted filter paper [1], and pipettes [3] are used when discrete stimulus application is required. Flow chambers that enclose part of the anterior tongue [4,15], squeeze bottles and intraoral spray nozzles [5,6] are used when a large portion o f the receptor surface must be stimulated. Although many factors must be weighed when choosing among these techniques, one consideration should be the ease with which stimulus onset time can be determined. Currently, few investigators in gustation accurately measure stimulus arrival time or report response latency. This contrasts sharply with research in vision, audition, and somesthesis where stimulus onset time is routinely recorded and reported. There are several possible reasons for this obvious lapse in experimental protocol. First, fluids are less tractable than light, sound, or mechanical stimulation making measurement of stimulus onset technically challenging. Second, the errors introduced by inaccurate specification of stimulus onset may be considered inconsequential since long periods (3-5 sec) of evoked activity are usually analyzed in taste research. In some studies the entire problem is circumvented by beginning data analysis at the time o f response onset [17]. This solution, though satisfactory in principle for a number of applications, is difficult to apply to slowly firing neurons and neurons that gradually increase their rate of firing following stimulus application. Both of these characteristics have been observed among gustatory neurons. Previous investigators have marked stimulus onset time
METHOD Most thermistors are solid, semi-conductors that exhibit a large negative resistance-temperature coefficient. Since response time usually varies directly with the size of a thermistor, a miniature (TC=7 msec; dia.=.007") fastip thermoprobe was used for the present application. This thermistor, when used in conjuction with the circuit described below, had a response time of less than 2 msec. Table 1 lists the electronic components used in the stimulus onset detector. The dissipation constant (5 x 10-5 W#C; still air) and maximum power rating (6x 10-a W) of the thermistor theoretically allow the bead to be heated 120°C above the ambient temperature. F o r
1Requests for reprints should be addressed to T. C. Pritchard, Department of Behavioral Science, Milton S. Hershey Medical Center, P.O. Box 850, Hershey, PA 17033.
255
256
PRITCHARD, L l t r r O N AND P F A F F M A N N TABLE 1 LIST OF COMPONENTS USED IN T H E S T I M U L U S O N S E T DETECTOR
8.2VZ, 5% IN4454 5082-4684, LED 0.1 /~F, disk 10/xF, tant. 0.005/zF
R1 R2 R3 R4, R5 R6 R7 R8
12 Kit, 5% 1.3 Kf~, 5% 1 Kit, 5% 1.5 Kit, 1% 2.2 Kit, 5% 220 Kit, 5% 10 Kit, 5%
D1 D2, D3, D4, D6 D5 C1, C3, C6 C2, C4 C5
R9
100 Kit, 5%
Rp~, Rp:~
10 Kit, O 10 Kit, 10 Turn, WW
Re4 100 It, O
R p2
RT~
FP07DA332N-C
Thermometrics, Inc. 808 U.S. Highway No. 1 Edison, NJ 08817
0 Denotes Trimmer. WW Denotes Wire-wound.
+L5V l
+I5V
4-15V TEMPERATURE SENSE BRIDGE
RI
I
VOLTAGE
)
BUFFER-
["--..]
RpI ~ ' ~ - - - - 4 + ~ f 0 I 7
R~Tt/~.
/
LIMITER n
,
,
~,f
I
r'~ ""L,R4 )
~
T//~'~T C2
I
~.. ~ _ ~ "",~ D 2 ~ - 3 1 4
r'~ /
/c,LTJ ..~-.
VOLTAGE ) COMPARATOR
R6
'---T-S3__...... L ; I HCPL IL-
Isolated
ll~a~. I
BNC
I,-4 " )
I
: •
1
~" ~
I
%
_L _
I
"
~
J_ =
±tF~W
""~
I
J_
,
- ,sv
CD4OllA
--'--
II ! /
,SOL T O
OUTPUT
~
[
,
u
k,.._.JJ
[
"
THRESHOLD INDICATOR
k,.,__JJ i
!"
FIG. 1. Circuit diagram for the stimulus onset detector. Table 1 contains the list of components.
the present application the thermistor was self-heated to 40°C (1 × 10-3 W) above the ambient temperature. Due to the small thermal mass of the thermistor bead, there was only negligible local heating within the flow chamber. The air temperature 4 mm from the thermistor bead (the normal thermistor-tongue distance) was only 0.5°C higher than a reference area 10 mm further away. Neither rapid heating nor cooling of the thermistor evoked a neural response in the chorda tympani, which contains a significant population of thermally sensitive axons [22]. The electronic circuit for the stimulus onset device is shown in Fig. 1. The regulated DC power supply (--_15 V), voltage buffer-limiter, and potentiometer Rp~ provide voltage control of the temperature sense bridge which varies the
self-heated temperature of thermistor RT1. Thermistor RT1 is protected from power transients by zener diode DI which clamps the bridge excitation voltage to a safe level. The high sensitivity of thermistor RT1 is used effectively by adjusting the voltage comparator reference level (+ level) to be very nearly equal to its signal input level ( - level)just prior to the time of fluid arrival. The 10 KIq, 10 turn precision wire wound potentiometer (Rw9 used to make the precise voltage comparator adjustment (_+0.1%), also allows for direct measurement of the thermistor (RT0 environment (-+ 1.0%). Both high and low frequency noise to the 3140 voltage comparator are attenuated by C1, C2, C3, C4 which heavily AC-bypass the DC-power pins (-+ 15 V). The voltage comparator is differential-input-voltage limited by fast diodes D2
GUSTATORY ONSET DETECTOR
257
6.5 6.0
;2'
5.5
T h.,,,,., .e~r, ~ .-~ mistor..,.,~..;:
i u,ou,
. . . . . . .
~'/~
• ~ .;",~
~,~:.:.: - ~" "-'~:'~
.
*
/
~
.,-,:
o 4.5
,
Fluid Drain
50
>.-
4o
oz 3.5 ILl
FIG. 2. Illustration oitthe thermistor, flow chamber, and gravity feed stimulus delivery system in situ.
and D3 and has a minimum gain of 2x 104 (typ. 1 x l 0 b . A reduction of 0.5°C in thermistor temperature is easily detected, causing a pulse output. Figure 2 shows a hamster with its tongue drawn gently through a latex diaphragm into a glass flow chamber. The micro-thermistor is positioned approximately 4 mm above the tongue surface. The onset latency of the thermistor and electronic circuit was measured by reproducing this spatial arrangement with the tongue replaced by a molded rubber plug containing two uninsulated wires. Electrical continuity between the two wires was made by flowing a saline solution through the flow system. The difference in time between fluid detection by the thermistor and electrical conduction between the wires embedded in the rubber plug was considered the latency of detection. Following a distilled water rinse all residual fluids within the flow system were evacuated with a short burst of compressed air. Although fluid application and evacuation of the flow system cooled the thermistor below its operational temperature (40°C above ambient), the recovery time for the thermistor was less than 20 sec, shorter than the time most researchers use for an interstimulus interval. RESULTS AND DISCUSSION
The latency between thermistor detection and fluid contact with the tongue was tested with a gravity feed system with flow rates between 4.6 and 11.3 ml/sec. As Fig. 3 shows, the latency of detection asymptotes at approximately 2 msec for flow rates between 8 and 11 ml/sec. The latency increased with flow rates slower than 7 ml/sec. Flow rates slower than 4.6 ml/sec would be expected to produce even longer detection latencies with more variability of response unless special measures were taken to ensure optimal laminar flow of the solutions. This device provides satisfactory resolution of the time of stimulus onset for most applications in gustatory research.
3.c
-J 2.5
]
zo
1
t
FLOW RATE (ml/sec.) FIG. 3. Latency between thermistor detection and fluid contact with the tongue as a function of flow rate. For more demanding applications, a design based upon the concept of a closed-loop constant power regulator [13] could be used. This method uses a negative-feedback loop to maintain constant power dissipation in the thermistor, thereby significantly reducing its temperature swing and improving its speed of response. Ultimate limitations are caused by the column of air that precedes the fluid and cools the thermistor. In the present system detectability was sacrificed somewhat by setting potentiometer R~z just prior to fluid onset to allow for the rush of air. A closed-loop constant power regulator would increase the resolution of R~z, theoretically allowing a closer approach to an optimum pre-onset condition. The 2 msec resolution described in this report is due not only to the set level of potentometer R~, but also to the distance of the thermistor from the tongue (4 mm). This relatively constant interval, made "transparent" by a simple hardware or software delay triggered by the signal from the thermistor, would allow specification of the onset time to approximately 0.5 msec. These figures would be expected to vary with the dimensions of the flow chamber being used as well as the laminar flow characteristics of the fluid delivery system. ACKNOWLEDGEMENTS This research was supported, in part, by a postdoctoral traineeship from training grant MH15125 awarded to T.C.P. and NSF Grant BNS78-16533 to C.P.
REFERENCES 1. Collings, V. B. Human taste responses as a function of locus of stimulation on the tongue and soft palate. Percept Psychophys 16: 169-174, 1974. 2. Faull, J, R. and B. P. Halpern. Taste stimuli: Time course of peripheral nerve response and theoretical models. Science 178: 73-75, 1972.
3. Frank, M. E. Single fiber responses in the glossopharyngeal nerve of the rat to chemical, thermal, and mechanical stimulation of the posterior tongue. Doctoral disseration. Brown University, Providence, RI, University Microfilms No. 69-9957, 1968.
258 4. Frank, M. E. An analysis of hamster afferent taste nerve response functions. J Gen Physiol 61: 588--618, 1973. 5. Grill, H. J. and R. Norgren. The taste reactivity test. 1. Mimetic responses to gustatory stimuli in neurologically normal rats. Brain Res 143: 263-279, 1978. 6. Grill, H. J. and R. Norgren. The taste reactivity test. II. Mimetic responses to gustatory stimuli in chronic thalamic and chronic decerebrate rats. Brain Res 143: 281-297, 1978. 7. Halpern, B. P. The use of vertebrate laboratory animals in research on taste. In: Methods o f Animal Experimentation Vol 4. edited by W. I. Gay. New York: Academic Press, 1973. 8. Halpern, B. P. and L. A. Marowitz. Taste responses to lickduration stimuli. Brain Res 57: 473-478, 1973. 9. Harper, H. W. and M. Rossetto. An "artificial tongue" for calibrating solution flow characteristics of taste stimulus delivery systems. Chern Senses Flavor 3: 267-280, 1978. 10. Hill, J. H. and E. Stellar. An electric drinkometer. Science 114: 43-44, 1951. 11. Kelling, S. T. and B. P. Halpern. Taste flashes: Reaction times, intensity, and quality. Science 219: 412-414, 1983. 12. Lester, B. and B. P. Halpern. Effect of stimulus presentation duration on gustatory reaction time. Phy~iol Behav 22:31%324, 1979. 13. Miyara, J. Measuring air flow with a self-balancing bridge. Analog Dialog 5: 13-14, 1971.
PRITCHARD, LIPTON AND PFAFFMANN 14. Pritchard, T. C. and C. Pfaffmann. Electro-chemical stimulation of taste. Neurosci Abstr 7: 730, 1981. 15. Pritchard, T. C. and T. R. Scott. Amino acids as taste stimuli. II: Taste quality. Brain Res 253: 93-104, 1982. 16. Scott, T. R. and R. P. Erickson. Synaptic processing of taste quality information in thalamus of the rat. J Neurophysiol 34: 868-884, 1971. 17. Smith, D. V,, J. B. Travers and R. L. Van Buskirk. Brainstem correlates of gustatory similarity in the hamster. Brain Res Bull 4: 359-372, 1979. 18. Travers, S. P., C. Pfaffmann and R. Norgren. Convergence of lingual and palatal gustatory neural activity in the nucleus of the solitary tract. Brain Re.s 365: 305-320, 1986. 19. Yamamoto, T. and Y. Kawamura. Gustatory reaction time in human adults. Physiol Behav 26: 715-719, 1981. 20. Yamamoto, T. and Y. Kawamura. Gustatory reaction time to various salt solutions in human adults. Physiol Behav 32: 4%53, 1984. 21. Yamamoto, T., H. Takee and Y. Kawamura. A simple device detecting onset time of taste stimulation. Physiol Behav 26: 721-723, 1981. 22. Yamashita, S., H. Ogawa, T. Kiyohara and M. Sato. Modification by temperature change of gustatory impulse discharges in chorda tympani fibres of rats. Jpn J Phy.~iol 20: 348-363, 1970.