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The effect of postconditioning CS experience on recovery from radiation-induced taste aversion
Physiology & Behavior, Vol. 30, pp. 647-649. PergamonPress Ltd., 1983. Printedin the U.S.A.
BRIEF COMMUNICATION
The Effect of Postconditioning CS Experience on Recovery from RadiationInduced Taste Aversion A L A N C. S P E C T O R , z J A M E S C. S M I T H A N D G L E E R. H O L L A N D E R
D e p a r t m e n t o f Psychology, The Florida State University, Tallahassee, F L 32306 R e c e i v e d 6 M a y 1982 SPECTOR, A. C., J. C. SMITH AND G. R. HOLLANDER. The effect ofpostconditioning CS experience on recovery from radiation-induced taste aversion. PHYSIOL BEHAV 30(4) 647-649, 1983.1Seventy-two hours after saccharin (CS) was paired with either a 100R or sham radiation exposure, rats received a 0-, 3-, 6-, 12-, 24-, or 46-hour saccharin-alone presentation followed by a 23-hour two-bottle preference test. Generally, faster recovery from the aversion was observed in animals receiving longer CS-alone presentations. The present procedure differs from previous work done with other toxins in that animals were not fluid-deprived during the postconditioning period. This enabled animals to constantly control the volume, duration, and inter-bout interval of the saccharin drinking episodes independent of any experimentally imposed drinking schedule. In addition, the two-bottle test provided a sensitive measure of the status of the saccharin aversion following the saccharin-alone presentation. Taste aversion
Extinction
Radiation
Saccharin
T H E R E is evidence which suggests that postconditioning experience with the CS tastant is an important factor affecting recovery from a learned taste aversion [1, 3, 5, 7]. The goal of this study was to systematically examine the effects of 0--46 hours of postconditioning saccharin-alone experience on the rate of recovery from a radiation-induced saccharin aversion in rats. The present study differs from much of the previously reported work in primarily two ways. First, the animals in the present study were not deprived of fluid during the postconditioning period enabling the animals to constantly control the volume, duration, and inter-bout interval of the saccharin drinking episodes. Second, after the postconditioning CS-alone presentations a two-bottle preference test was administered. Although the postconditioning .saccharin-alone presentations served as single-bottle tests, a more sensitive measure of aversion is obtained by two-bottle preference tests [2, 4, 9]. METHOD
Subjects One hundred and fifty-seven Sprague-Dawley male, naive albino rats weighing 220--410 g and bred at the Southern Animal Farm in Pratville, Alabama served as subjects. Upon
arrival to the laboratory, the animals were individually housed in Hoeltge cages where both Wayne rat chow and tap water were available ad lib. The animals were adpated to the laboratory environment for a minimum of two weeks, where temperature, humidity and lighting were automatically controlled. A 12/12 hour LD cycle with lights on at 0700 was employed throughout the experiment.
Procedure A preconditioning regimen of restricted water presentation was initiated to ensure that the rats would drink the CS solution on the conditioning day. On Day 1, at 0800, all water bottles were removed from the individual cages. On Day 2, after 24 hours of fluid deprivation, the animals were given access to water for 60 minutes. At approximately the same time on Day 3, the animals were given 30 minutes water access and on Day 4, the rats received a 10 minute water presentation. The conditioning trial occurred on Day 5. All animals received a 10-minute saccharin (0.1% Sodium Saccharin, w/v) presentation (CS). After the saccharin drinking period 78 rats were given a gamma ray exposure (SRAD) and 79 rats were given a sham radiation exposure (SSHAM). Radiation treatment was administered to the rats by placing them into
~This investigation was supported by grant number CA22768 awarded by the National Cancer Institute, DHEW. 2Requests for reprints should be addressed to Alan C. Spector at the above address. aThe first author is sponsored by a State of Florida Psychobiology Predoctoral Fellowship.
• Copyright © 1983 Pergamon Press Ltd.--0031-9384/83/040647-03503.00
648
S P E C T O R SMITH AND H O L L A N D E R
individual Plexiglas chambers and transporting them to the room containing the Cobalt-60 source (Gamma beam 150, Atomic Energy of Canada, Ltd.) which was calibrated by a Victoreen thimble chamber. The SRAD groups received a whole body exposure of 100 R. Rats receiving sham exposure were treated identically except that the Cobalt-60 source was not raised from its shielded housing. Following the radiation or sham exposure, the animals were returned to their home cages where they remained without fluid until the next day. Starting on Day 6, 24 hours after the CS presentation, all groups received a 48 hour two-bottle water presentation to allow recovery from water deprivation. On Day 8, rats from both the SRAD and SSHAM groups were subdivided into 6 groups which received saccharin as their sole fluid source for either 0, 3, 6, 12, 24, or 46 hours. After the saccharin-alone period a 23-hour two-bottle preference test was initiated for all groups. The postconditioning saccharin-alone presentations were administered according to the following regimen. The rats in the SRAD-24 (n= 12) and SSHAM-24 (n= 12) groups were presented with two bottles of saccharin which remained on their cages for 24 hours. Rats in the SRAD-46 (n= 15) and SSHAM-46 (n= 15) groups were presented with two bottles of saccharin which remained on their cages for 23 hours after which they were refilled with fresh saccharin and returned to the cages for an additional 23 hours (Day 9). Rats in the SRAD-0 (n= 15) and SSHAM-0 (n= 16) received no saccharin-alone experience, so their two-bottle preference test was initiated immediately on Day 8 following the 48-hour water presentation. Water bottles were left on the cages of the remaining groups (SRAD-3, SRAD-6, SRAD-12, SSHAM-3, SSHAM-6, and SSHAM-12; n= 12/group) for an additional 11 hours, until the beginning of the dark phase of the LD cycle, at which time all of these animals were presented with two bottles of saccharin. Three hours after the initiation of their postconditioning saccharin-alone presentation, groups SRAD-3 and SSHAM-3 had their saccharin bottles replaced with water bottles. Six hours after the start of their postconditioning saccharin presentation groups SRAD-6 and SSHAM-6 had their saccharin bottles replaced with water bottles. Groups SRAD-12, SSHAM-12, SRAD-24, and SSHAM-24 never received a water presentation after their saccharin-alone episode on Day 8. By Day 9, all groups were on the 23-hour two-bottle preference test between water and saccharin, except for the -46 groups which had their two-bottle test initiated on Day 10. A Kruskal-Wallis H-test was used to determine the presence of group differences. Paired comparisons were conducted using Mann-Whitney U-tests. Correlations were calculated using Spearman's rank-order correlation procedure. The standard 0.05 level of significance was employed [8]. RESULTS AND DISCUSSION The median saccharin consumptions for all groups during their postconditioning saccharin-alone presentations are illustrated in Fig. 1. All of the irradiated groups differed from each other (all Us<33.5, all ps<0.05), with the exception of the SRAD-12 and SRAD-24 groups (U=71, p>0.05). The failure to find a significant difference in the posteonditioning saccharin consumptions between the SRAD-24 and SRAD12 groups is not surprising since the animals in the SRAD-12 group were presented their saccharin at the start of the dark phase of their L/D cycle during which rats normally drink.
L~:
[
~:SRAD
SSHAM
220
2
200
~ 180 160 140 ._c 120 100 8o -~
80
[
3
I
I
6
1
12
I
I
24
I
46
1
Hours of Saccharin Alone
FIG. Median saccharin consumption (+SIQR: Semi-Interquartile Range) during the saccharin-alone presentations on Day 8 (SRAD GROUPS: H=54. I, "p<0.001). .
[]SSHAM
[~SRAD
10 90
8o 7O
/
6O 5O
3O
Hours of Saccharin Alone
FIG. 2. Median saccharin preference scores (+SIQR) for all groups (SRAD GROUPS: H=45.7, p<0.001). (Note: Saccharin Preference Score=Saccharin Intake/Total Intake.)
During the postconditioning saccharin-alone presentation, all of the irradiated groups drank significantly less than their respective sham controls (all ps<0.01) with the exception of the SRAD-46. However, the SRAD-46 group drank significantly less saccharin than the SSHAM-46 group (U=33, p <0.001) during the first 23 hours of the 46 hour saccharinalone presentation, which makes them comparable to the other groups in this experiment. The taste aversion appeared to have competed with the growing motivation to drink during the CS-alone presentation. This finding is consistent with the notion put forth by Revusky and Garcia [6] that the onebottle test creates a conflict situation for fluid-deprived animals. Figure 2 contains the median saccharin preference scores from the postconditioning two-bottle test for all of the groups. Inspection of Fig. 2 indicates a distinct trend in which the irradiated groups that had longer saccharin-alone presentations also had higher saccharin preference scores. A
POSTCONDITIONING CS E X P E R I E N C E IN TASTE AVERSION statistical analysis indicated three primary clusters among the irradiated groups. The SRAD-46 group had significantly higher preference scores than all of the other groups (all Us<27, all ps<0.001). While the medians of the saccharin preference scores from the SRAD-6, SRAD-12, and SRAD24 groups are consistent with the suggested trend, the substantial variance within these groups did not support the presence of statistically significant differences among these groups (all Us>44, all ps>0.05), but all had significantly higher preference scores than the SRAD-3 and SRAD-0 groups (all ps<0.05). The preference scores in the SRAD-3 and SRAD-0 groups did not differ (U=68, p>0.05). The correlation between the postconditioning saccharin-alone consumption (Day 8) and the following day's saccharin preference scores (Day 9), for all animals in the 3, 6, 12, and 24 hour SRAD groups, was r = .64 (p <0.001). This indicates that while there is a substantial relationship between postconditioning CS experience and the extent of recovery from a taste aversion, there can be other factors influencing the variability such as differences in baseline saccharin preference or differences in initial levels of acquisition. The two-bottle test preference scores from each experimental group were compared to those from their respective sham control groups. The SRAD-46 and the SRAD-24 groups were the only groups which did not statistically differ from their respective control groups (all other p s <0.01). This seems to imply either that recovery is complete following a postconditioning 24 hour CS-alone presentation even though the total consumption does not appear so, or that a certain amount of extinction is occurring during the two-bottle test.
649
It should be emphasized that recovery was quite homogeneous in the SRAD-46 group with only 3 out of 15 rats having preference scores less than .90 and none less than .67. On the contrary, 7 out of 12 animals in the SRAD-24 group had preference scores less than .90 and 4 of these were less than .40. This indicates that while the SRAD-24 group on the average had recovered (when compared to their controls), some animals in this group were still demonstrating signs of aversion. These results demonstrate that: (I) A single CS-alone presentation is sufficient in eliminating a radiation-induced taste aversion (at 100 R) provided its duration allows for adequate levels of CS experience. (2) Generally, the more postconditioning nonreinforced CS-alone experience on animal encounters the more rapidly it will recover from a radiation-induced taste aversion (at I00 R). This is in agreement with the findings of other investigators using different procedures and different toxins [ 1,5]. (3) Postconditioning, essentially ad lib, single-bottle tests, of 6 hours or more duration, promote more rapid extinction of a radiation-induced taste aversion (at 100 R) than do two-bottle choice testing procedures. This result is consistent with the conclusions from other experiments comparing one- and two-bottle tests [3,7]. ACKNOWLEDGEMENTS The authors would like to express thanks to Dr. Lewis M. Barker for his helpful suggestions. We also appreciate the help provided by Beth Creary for her collection of some of the data and to Debra Brock for her clerical assistance.
REFERENCES
1. Colby, J. J. and N. F. Smith. The effect of three procedures for eliminating a conditioned taste aversion in the rat. Learn Motiv 8: 41)4-413, 1977. 2. Dragoin, W., G. E. McCleary and P. McCleary. A comparison of two methods of measuring conditioned taste aversions. Behav Res Meth lnstru 3: 309-310, 1971. 3. Elkins, R. L. Individual differences in bait shyness: Effects of drug dose and measurement technique. Psychol Rec 23: 349-358, 1973. 4. Grote, F. W., Jr. and R. T. Brown. Conditioned taste aversions: Two stimulus tests are more sensitive than one-stimulus tests. Behav Res Meth lnstru 3: 311-312, 1971. 5. Grote, F. W., Jr. and R. T. Brown. Deprivation level effects extinction of a conditioned taste aversion. Learn Motiv 4: 314319, 1973.
6. Revusky, S. and J. Garcia. Learned association over long delays. In: Psychology o f Learning and Motivation: Advances in Research and Theory, Vol. 4, edited by G. W. Bower and J. T. Spence. New York: Academic Press, 1970, pp. 1-84. 7. Sengstake, C. B., K. C. Chambers and J. H. Thorwer. Interactive effects of fluid deprivation and testosterone on the expression of a sexually dimorphic conditioned taste aversion. J Comp Physiol Psychol 92:1150-1155, 1978. 8. Siegel. S. Nonparametric Statistics for the Behavioral Sciences. New York: McGraw-Hill, 1956. 9. Spector, A. C., J. C. Smith and G. R. Hollander. A comparison of dependent measures used to quantify radiation-induced taste aversion. Physiol Behav 27: 887-901, 1981.
BRIEF COMMUNICATION
The Effect of Postconditioning CS Experience on Recovery from RadiationInduced Taste Aversion A L A N C. S P E C T O R , z J A M E S C. S M I T H A N D G L E E R. H O L L A N D E R
D e p a r t m e n t o f Psychology, The Florida State University, Tallahassee, F L 32306 R e c e i v e d 6 M a y 1982 SPECTOR, A. C., J. C. SMITH AND G. R. HOLLANDER. The effect ofpostconditioning CS experience on recovery from radiation-induced taste aversion. PHYSIOL BEHAV 30(4) 647-649, 1983.1Seventy-two hours after saccharin (CS) was paired with either a 100R or sham radiation exposure, rats received a 0-, 3-, 6-, 12-, 24-, or 46-hour saccharin-alone presentation followed by a 23-hour two-bottle preference test. Generally, faster recovery from the aversion was observed in animals receiving longer CS-alone presentations. The present procedure differs from previous work done with other toxins in that animals were not fluid-deprived during the postconditioning period. This enabled animals to constantly control the volume, duration, and inter-bout interval of the saccharin drinking episodes independent of any experimentally imposed drinking schedule. In addition, the two-bottle test provided a sensitive measure of the status of the saccharin aversion following the saccharin-alone presentation. Taste aversion
Extinction
Radiation
Saccharin
T H E R E is evidence which suggests that postconditioning experience with the CS tastant is an important factor affecting recovery from a learned taste aversion [1, 3, 5, 7]. The goal of this study was to systematically examine the effects of 0--46 hours of postconditioning saccharin-alone experience on the rate of recovery from a radiation-induced saccharin aversion in rats. The present study differs from much of the previously reported work in primarily two ways. First, the animals in the present study were not deprived of fluid during the postconditioning period enabling the animals to constantly control the volume, duration, and inter-bout interval of the saccharin drinking episodes. Second, after the postconditioning CS-alone presentations a two-bottle preference test was administered. Although the postconditioning .saccharin-alone presentations served as single-bottle tests, a more sensitive measure of aversion is obtained by two-bottle preference tests [2, 4, 9]. METHOD
Subjects One hundred and fifty-seven Sprague-Dawley male, naive albino rats weighing 220--410 g and bred at the Southern Animal Farm in Pratville, Alabama served as subjects. Upon
arrival to the laboratory, the animals were individually housed in Hoeltge cages where both Wayne rat chow and tap water were available ad lib. The animals were adpated to the laboratory environment for a minimum of two weeks, where temperature, humidity and lighting were automatically controlled. A 12/12 hour LD cycle with lights on at 0700 was employed throughout the experiment.
Procedure A preconditioning regimen of restricted water presentation was initiated to ensure that the rats would drink the CS solution on the conditioning day. On Day 1, at 0800, all water bottles were removed from the individual cages. On Day 2, after 24 hours of fluid deprivation, the animals were given access to water for 60 minutes. At approximately the same time on Day 3, the animals were given 30 minutes water access and on Day 4, the rats received a 10 minute water presentation. The conditioning trial occurred on Day 5. All animals received a 10-minute saccharin (0.1% Sodium Saccharin, w/v) presentation (CS). After the saccharin drinking period 78 rats were given a gamma ray exposure (SRAD) and 79 rats were given a sham radiation exposure (SSHAM). Radiation treatment was administered to the rats by placing them into
~This investigation was supported by grant number CA22768 awarded by the National Cancer Institute, DHEW. 2Requests for reprints should be addressed to Alan C. Spector at the above address. aThe first author is sponsored by a State of Florida Psychobiology Predoctoral Fellowship.
• Copyright © 1983 Pergamon Press Ltd.--0031-9384/83/040647-03503.00
648
S P E C T O R SMITH AND H O L L A N D E R
individual Plexiglas chambers and transporting them to the room containing the Cobalt-60 source (Gamma beam 150, Atomic Energy of Canada, Ltd.) which was calibrated by a Victoreen thimble chamber. The SRAD groups received a whole body exposure of 100 R. Rats receiving sham exposure were treated identically except that the Cobalt-60 source was not raised from its shielded housing. Following the radiation or sham exposure, the animals were returned to their home cages where they remained without fluid until the next day. Starting on Day 6, 24 hours after the CS presentation, all groups received a 48 hour two-bottle water presentation to allow recovery from water deprivation. On Day 8, rats from both the SRAD and SSHAM groups were subdivided into 6 groups which received saccharin as their sole fluid source for either 0, 3, 6, 12, 24, or 46 hours. After the saccharin-alone period a 23-hour two-bottle preference test was initiated for all groups. The postconditioning saccharin-alone presentations were administered according to the following regimen. The rats in the SRAD-24 (n= 12) and SSHAM-24 (n= 12) groups were presented with two bottles of saccharin which remained on their cages for 24 hours. Rats in the SRAD-46 (n= 15) and SSHAM-46 (n= 15) groups were presented with two bottles of saccharin which remained on their cages for 23 hours after which they were refilled with fresh saccharin and returned to the cages for an additional 23 hours (Day 9). Rats in the SRAD-0 (n= 15) and SSHAM-0 (n= 16) received no saccharin-alone experience, so their two-bottle preference test was initiated immediately on Day 8 following the 48-hour water presentation. Water bottles were left on the cages of the remaining groups (SRAD-3, SRAD-6, SRAD-12, SSHAM-3, SSHAM-6, and SSHAM-12; n= 12/group) for an additional 11 hours, until the beginning of the dark phase of the LD cycle, at which time all of these animals were presented with two bottles of saccharin. Three hours after the initiation of their postconditioning saccharin-alone presentation, groups SRAD-3 and SSHAM-3 had their saccharin bottles replaced with water bottles. Six hours after the start of their postconditioning saccharin presentation groups SRAD-6 and SSHAM-6 had their saccharin bottles replaced with water bottles. Groups SRAD-12, SSHAM-12, SRAD-24, and SSHAM-24 never received a water presentation after their saccharin-alone episode on Day 8. By Day 9, all groups were on the 23-hour two-bottle preference test between water and saccharin, except for the -46 groups which had their two-bottle test initiated on Day 10. A Kruskal-Wallis H-test was used to determine the presence of group differences. Paired comparisons were conducted using Mann-Whitney U-tests. Correlations were calculated using Spearman's rank-order correlation procedure. The standard 0.05 level of significance was employed [8]. RESULTS AND DISCUSSION The median saccharin consumptions for all groups during their postconditioning saccharin-alone presentations are illustrated in Fig. 1. All of the irradiated groups differed from each other (all Us<33.5, all ps<0.05), with the exception of the SRAD-12 and SRAD-24 groups (U=71, p>0.05). The failure to find a significant difference in the posteonditioning saccharin consumptions between the SRAD-24 and SRAD12 groups is not surprising since the animals in the SRAD-12 group were presented their saccharin at the start of the dark phase of their L/D cycle during which rats normally drink.
L~:
[
~:SRAD
SSHAM
220
2
200
~ 180 160 140 ._c 120 100 8o -~
80
[
3
I
I
6
1
12
I
I
24
I
46
1
Hours of Saccharin Alone
FIG. Median saccharin consumption (+SIQR: Semi-Interquartile Range) during the saccharin-alone presentations on Day 8 (SRAD GROUPS: H=54. I, "p<0.001). .
[]SSHAM
[~SRAD
10 90
8o 7O
/
6O 5O
3O
Hours of Saccharin Alone
FIG. 2. Median saccharin preference scores (+SIQR) for all groups (SRAD GROUPS: H=45.7, p<0.001). (Note: Saccharin Preference Score=Saccharin Intake/Total Intake.)
During the postconditioning saccharin-alone presentation, all of the irradiated groups drank significantly less than their respective sham controls (all ps<0.01) with the exception of the SRAD-46. However, the SRAD-46 group drank significantly less saccharin than the SSHAM-46 group (U=33, p <0.001) during the first 23 hours of the 46 hour saccharinalone presentation, which makes them comparable to the other groups in this experiment. The taste aversion appeared to have competed with the growing motivation to drink during the CS-alone presentation. This finding is consistent with the notion put forth by Revusky and Garcia [6] that the onebottle test creates a conflict situation for fluid-deprived animals. Figure 2 contains the median saccharin preference scores from the postconditioning two-bottle test for all of the groups. Inspection of Fig. 2 indicates a distinct trend in which the irradiated groups that had longer saccharin-alone presentations also had higher saccharin preference scores. A
POSTCONDITIONING CS E X P E R I E N C E IN TASTE AVERSION statistical analysis indicated three primary clusters among the irradiated groups. The SRAD-46 group had significantly higher preference scores than all of the other groups (all Us<27, all ps<0.001). While the medians of the saccharin preference scores from the SRAD-6, SRAD-12, and SRAD24 groups are consistent with the suggested trend, the substantial variance within these groups did not support the presence of statistically significant differences among these groups (all Us>44, all ps>0.05), but all had significantly higher preference scores than the SRAD-3 and SRAD-0 groups (all ps<0.05). The preference scores in the SRAD-3 and SRAD-0 groups did not differ (U=68, p>0.05). The correlation between the postconditioning saccharin-alone consumption (Day 8) and the following day's saccharin preference scores (Day 9), for all animals in the 3, 6, 12, and 24 hour SRAD groups, was r = .64 (p <0.001). This indicates that while there is a substantial relationship between postconditioning CS experience and the extent of recovery from a taste aversion, there can be other factors influencing the variability such as differences in baseline saccharin preference or differences in initial levels of acquisition. The two-bottle test preference scores from each experimental group were compared to those from their respective sham control groups. The SRAD-46 and the SRAD-24 groups were the only groups which did not statistically differ from their respective control groups (all other p s <0.01). This seems to imply either that recovery is complete following a postconditioning 24 hour CS-alone presentation even though the total consumption does not appear so, or that a certain amount of extinction is occurring during the two-bottle test.
649
It should be emphasized that recovery was quite homogeneous in the SRAD-46 group with only 3 out of 15 rats having preference scores less than .90 and none less than .67. On the contrary, 7 out of 12 animals in the SRAD-24 group had preference scores less than .90 and 4 of these were less than .40. This indicates that while the SRAD-24 group on the average had recovered (when compared to their controls), some animals in this group were still demonstrating signs of aversion. These results demonstrate that: (I) A single CS-alone presentation is sufficient in eliminating a radiation-induced taste aversion (at 100 R) provided its duration allows for adequate levels of CS experience. (2) Generally, the more postconditioning nonreinforced CS-alone experience on animal encounters the more rapidly it will recover from a radiation-induced taste aversion (at I00 R). This is in agreement with the findings of other investigators using different procedures and different toxins [ 1,5]. (3) Postconditioning, essentially ad lib, single-bottle tests, of 6 hours or more duration, promote more rapid extinction of a radiation-induced taste aversion (at 100 R) than do two-bottle choice testing procedures. This result is consistent with the conclusions from other experiments comparing one- and two-bottle tests [3,7]. ACKNOWLEDGEMENTS The authors would like to express thanks to Dr. Lewis M. Barker for his helpful suggestions. We also appreciate the help provided by Beth Creary for her collection of some of the data and to Debra Brock for her clerical assistance.
REFERENCES
1. Colby, J. J. and N. F. Smith. The effect of three procedures for eliminating a conditioned taste aversion in the rat. Learn Motiv 8: 41)4-413, 1977. 2. Dragoin, W., G. E. McCleary and P. McCleary. A comparison of two methods of measuring conditioned taste aversions. Behav Res Meth lnstru 3: 309-310, 1971. 3. Elkins, R. L. Individual differences in bait shyness: Effects of drug dose and measurement technique. Psychol Rec 23: 349-358, 1973. 4. Grote, F. W., Jr. and R. T. Brown. Conditioned taste aversions: Two stimulus tests are more sensitive than one-stimulus tests. Behav Res Meth lnstru 3: 311-312, 1971. 5. Grote, F. W., Jr. and R. T. Brown. Deprivation level effects extinction of a conditioned taste aversion. Learn Motiv 4: 314319, 1973.
6. Revusky, S. and J. Garcia. Learned association over long delays. In: Psychology o f Learning and Motivation: Advances in Research and Theory, Vol. 4, edited by G. W. Bower and J. T. Spence. New York: Academic Press, 1970, pp. 1-84. 7. Sengstake, C. B., K. C. Chambers and J. H. Thorwer. Interactive effects of fluid deprivation and testosterone on the expression of a sexually dimorphic conditioned taste aversion. J Comp Physiol Psychol 92:1150-1155, 1978. 8. Siegel. S. Nonparametric Statistics for the Behavioral Sciences. New York: McGraw-Hill, 1956. 9. Spector, A. C., J. C. Smith and G. R. Hollander. A comparison of dependent measures used to quantify radiation-induced taste aversion. Physiol Behav 27: 887-901, 1981.