Scopolamine’s effect on passive avoidance

appcars that the 2-WH group is comparable to the 2-WN group early in training, whereas the performance of thc former group has improved considerably by the end of training, to a point more simiJar to the I-WH group. In order to assess this effect, analysis of variance and Scheffe's test were applied to both early (Trial Blocks 1-3) and late (Trial Blocks 6-8) portions of training. Results of the analysis of percent avoidance responses early in t r a i ning showed a significan t effect (F(2, I 5) = 177.42, p<.O I], with group means of 6.67 (2-WN), 6.00 (2-WH), and 75.00 (I-WH). Analysis of data from the late portion of training also showed a significant effect [F(2,1 5) = 94.63, p<.OI], with group means of 17.17 (2-WN), 81.00 (2-WH), and 99.00 (I-WH). Scheffe's test revealed significant differences between the 2-WN and 2-WH groups (p< .01), and also between the two-way and one-way handled groups, although in this case only at the .05 level. These effects are reflected in Fig. 1 by shift of the 2-WH function from the 2-WN level in early training to a level much c10ser to that of the I-WH group at the end of training. additional cue during training. That handling did not merely serve to disrupt frcczing behavior is suggested by the numbcr of trials required for thc two-way handled Ss to show an improvement in performance. In other words, the effects of such disruption should be evident earlier in training than these da ta show. The results of two other studies also seem to be related to the effects of additional cues in shuttle avoidance. OIton & Isaacson (I968) found a decrement in performance whcn a light in the safe compartment, which originally served as a discriminative stimulus (but not as a CS), was left on continuously. On the other hand, Freedman & Callahan (1968), using either light or tone as a CS on different trials, reported no differences between a group that always received a particular es on a particular side and a group that received these same CSs On a random schedule. Those authors conc1uded (p. 342) that rats do not attend to the es as a differential cue. Collectively, the data from the present study and these latter two suggest that shuttle-avoidance responding might be facilitated by use of an additional cue prior to es onset, which can serve a function analogous to a "ready signal" in signal-detection studies. Similarly, the spatial reorientation of the apparatus in the Baum & Bobrow (1966) and the OIton & Isaacson (1968) studies, since it occurred shortly before es onset, could also have served as a warning stimulus. REFERfNCES BAUM, M. An automated apparatus for the avoidance training of rats. Psychological Reports, 1965, 16, 1205-121l. BAUM, M., & BOBROW, S. A. An automated analogue of the one-way Miller-type avoidance box. Psychonomic Science, 1966, S, 361-362. FLAX, S. W., & HAHN, W. W. A solid-state shock "scram bier. " American Journal of Psychology, 1967,80,446-447. FREEDMAN, P. E., & CALLAHAN, B. S. Discriminative compartmental CSs in shu ttle-box avoidance acquisition. Psychonomic Science, 1968, 12,341-342. KENYON, J., & KRIECKHAUS, E. E. Decrement in one-way avoidance learning fo\1owing septal lesions in rats. Psychonomic Science, 1965, 3, 113-114. OLTON, D. S., & ISAACSON, R. L.lmportance of spatial location in active avoidance tasks. Journal of Comparative & Physiological Psychology, 1968,65,535-539. PETRINOVICH, L. F., & HARDYCK, C. D. Error rates for multiple comparison methods: Some evidence concerning frequency of erroneous conc\usions. Psychological Bu\1etin, 1969,71,43-54. RAY, A. J., JR. Non-incremental shuttle-avoidance acquisition to pressurized air USo Psychonomic Science, 1966, 5, 433-434. THEIOS, J., & DUNAWAY, J. E. One-way versus shuttle-avoidance conditioning. Psychonomic Science, 1964, 1,251-252. WAHLSTEN. D., COLE, M., SHARP, D., & FANTINO, E. Facilitation of bar-pressing avoidance by handling during the intertrial interval. Journal of Comparative & Physiological Psychology, 1968, 65, 170-175. WEDEKING, P. W. Rat avoidance behavior in a dual, one-way shuttle apparatus. Psychonomic Science, 1967,8,33-34. DIseUSSION The performance ofthe 2-WN and I-WN groups is in accord with results of other investigators making the same comparison (Theois & Dunaway, 1964; OIton & Jsaacson, 1968). By the end of training, the performance of the 2-WH group is what would be anticipated on the basis of the results presented by Wahlsten et aJ (1968)-in fact, both the I-WH and the 2-WH groups of the present study appear to be superior to the handled and handled-escape groups of the Wahlsten study at comparable points in training. The relatively poor performance of the 2-WN group requires a note of explanation, aIthough it is typical of standard shuttle WlLLIAM H. CALHOUN, ALLAN A. SMITH, and ROBERT BAUER groups run in this particuIar apparatus. The University ofTennessee, Knoxville, Tenn. 37916 low percentage of avoidance responses appears to be the result of the 2-WN Comparison in performance on active and passive retention tests was made for mice animals withdrawing or cringing from the that had received scopolamine prior to a single passive-avoidance training trial. Control noise of the door dropping. The Ss in this animals performed weIl with either retention test procedure, while the scopolamine group group then tend to remain crouched until performed weH for the active test but poorly for the passive test. shock onset causes them to run to the other compartment. In an earlier paper (Calhoun & Murphy, method if the initial training had been It is particularly important to consider 1969), we showed that mice could be effective. From results in separate the performance of the 2-WH group over trained under conditions of experiments, it appears that scopolamine the entire course of training. This group, passive-avoidance buttested for retention di srupts passive-avoidance performance which starts at a level identical with that of with either active- or passive-avoidance (Bohdanecky & Jarvik, 1967; Calhoun & the 2-WN group, improves rapidly during procedures. This technique is superior to Smith, 1968) but facilitates the middle phase of training, so that by the one where only a single measure of active-avoidance performance (Oliverio, end of training the 2-WH group is more retention is obtained; an animal should 1967). To test the drug effect more similar to the I-WH than to the 2-WN per form appropriately with either test thoroughly, we conducted the experiment group. This change is indicative of a reported here in which passive-avoidance conditioning effect and suggests that training was used, but retention was tested *Supported in part by NIMH Grant handling acquired some significance as an No. MH 16922. with active- and passive-avoidance Scopolamine's effect on passive avoidance* Psychon. Sei., 1970, Vo. 21 (3) 165 Table I Median Latency (.01 Sec) for the Response During Training and Retest Training Trial Treatment N Latency to (...truncated)