Concurrent Performance in Septally Operated Rats: One and Two Response Extinction'

Transcription

1 Physiology and Behavior, Vol. 6, pp hu~non Pros, Printed in Great Britain Concurrent Performance in Septally Operated Rats: One and Two Response Extinction' JOHN F. SCHNELLE s, STEPHEN F. WALKER AND H. M. B. HURWTZ Psychology Department, University of Tennessee, Knoxville, Tennessee 37916, U.S.A. (Received 20 June 1970) SCHNELLE, J. F., S. F. WALKER AND H. M. B. HURWTZ. Concurrent performance in septally operated rats: one and two response extinction. PHYSOL. B~HAV. 6 (6) , n Experiment, five male hooded rats underwent surgery for septal lesions and were tested in procedures in which two responses were concurrently reinforced. t was found that septally operated animals responded at higher rates for sucrose reinforcement than did controls. When reinforcement was withdrawn for both concurrent responses, the scptal animals continued to respond at a higher level than controls. When reinforcement was withdrawn for one of the concurrent responses, but maintained on the other, septal animals suppressed levels of nonreinforced responding as quickly as controls. These results were replicated in a second experiment on nine septally operated animals and with water reinforcement instead of sucrose. Operant response levels taken in this experiment showed that septals responded at significantly higher operant levels than controls. The importance of the high septal operant and reinforced response rates for the extinction data is discussed. Concurrent reinforcement Variable interval Extinction MANY investigators have attempted to analyze the behavior of septally operated animals by employing some variation of the operation of positive reinforcement withdrawal. This research includes DRL studies [3, 7], reversal studies [5, 10, 13], and extinction studies [3, ll]. A consistent result has been reported in these experiments and labelled variously as response perseveration, response disinhihition, and increased resistance to extinction. The terms all describe the fact that septal animals respond at higher levels than controls after an established reinforcement contingency is changed to a condition in which positive reinforcement is withdrawn or postponed. Although these studies have been quite explicit in describing the behavior of septal animals after the reinforcement contingency has been changed, the description of behavior before the contingency was altered has received only scant attention. A description of behavior during all stages of an experiment seems to be important if the effect of changes in reinforcement contingencies are to be evaluated. This consideration becomes particularly relevant in the light of evidence that septauy operated animals respond differently for reinforcement than controls. Thus, Beatty and Schwartzbaum [1, 2] showed that septally operated animals responded at a highrate for sucrose and saccharine reinforcement. Harvey and Hunt [6] reported that septally operated animals made more bar presses than controls under continuous (CRF) and fixed interval (F) schedules for water reinforcement, and Clody and Carlton [4] reported that septal animals have high running speeds for food reinforcement. The latter body of evidence suggests a direct relationship between the increased septal response levels for positive reinforcement and the fact that these animals respond at higher levels than controls when positive reinforcement is withdrawn. A similar suggestion was made by Harvey and Hunt [6] but they did not extend their analysis of the relationship between the animal's behavior in responding for positive reinforcement and its responding when reinforcement was withdrawn. Part of the present experiment attempts to describe and analyze this relationship. The present study used a concurrent variable interval (V) reinforcement procedure. During training two manipulative responses were reinforced. Subsequently, reinforcement was withdrawn from one manipulandum--a door--while it was maintained on the alternative door: reinforcement was then withdrawn from both manipulanda so that no response resulted in reinforcement. This experimental procedure, therefore, allowed the investigators to study the effects of withdrawing reinforcement in two distinct paradigms. The first procedure has boon called one door extinction, the second, two door extinction. The one door extinction condition provided information on the ability of a septally operated animal to withhold responding on a nonreinforced door when an alternative behavior was concurrently reinforced. The effect of this reinforced outlet on responding at the non-reinforeed door can be measured by comparing it with the results of the two door extinction condition, which is similar to the usual extinction procedure. f the results of the two types of extinction procedures differ, one would need to describe the set of operations that uniquely accounts for such differences. The present experiment was an attempt to describe the relationship between two XThis research was supported by a USPHS GRANT # to Dr. Harry M. B. Hurwitz. rl'his was in partial fulfillment of the Ph.D. requirements of John F. Schnelle. Reprints may be obtained from Dr. John F. Schnelle, Department of Psychology, Middle Tennessee State University, Murfrcesboro, Tenn. or Dr. H. M. B. Hurwitz, Department of Psychology, University of Guelph, Guelph, Canada. 649

2 650 SCHNELLE, WALKER AND HURWTZ such sets of extinction operations and the behavior produced by them. EXPERM METHOD Animals Ten, naive, male Long-Evans rats, weighing about 230 g, served in this experiment. Seven animals underwent surgery for septal lesions. Data were collected for the five animals which survived the surgery and five non-operated controls. All animals were housed in individual cages. Surgery and Histology All surgery was performed under sodium pentobarbital anesthetic (60 mg Diabutal per kg body weight). Lesions were produced by aspirating through the barrel of a 20 G hypodermic needle embedded in a glass pipette. The pipette was introduced through holes drilled in the skull 1.5 mm anterior to the mid-bregma and 0.5 mm anterior to the sagittal sinus. The pipette was inserted perpendicular to the skull to 5.5 mm below the cortical surface and then tilted toward the midline at an angle of approximately 10 degrees from the perpendicular position. Aspiration pressure was maintained at 0 mm Hg during entrance and exit through the cortex but approached 25 mm Hg when inserted to its maximum depth. All operated animals were injected with 60,000 U procaine penicillin.m. Control animals were injected with the same dosages of Diabutal as the operated animals but controls were not subjected to the surgical procedure. Following experimental testing, operated animals were injected with a lethal dose of Diabutal and perfused intracardically with normal saline followed by 10% formalin in saline solution. Frozen tissue 50~ sections of the brains were subsequently taken for evaluation. Apparatus The apparatus consisted of two operant chambers 23 cm 20 cm 28 cm each housed in a separate sound-deadened chamber. Two Plexiglas doors 5 cm 1.4 cm served as the manipulanda in this experiment. They were positioned 1.4 cm from each other on a single wall of the chamber. The doors were hinged from the top so that a push of 13 g on either door would be recorded as a response and would allow the animal to gain access to a 16 % sucrose solution. This solution was made available by pumping a horizontal jet of the solution 0.6 cm below a 1.3 cm hole drilled in a platform behind the door. The actual reinforcement was three see access to the sucrose. The entire chamber was lighted by a 24 V light which was turned off during reinforcements. During reinforcements at the left door a constant 24 V magazine light was turned on above the platform in the left door and during reinforcement at the right door another 24 V magazine light flashed on-off above the platform in the right door. Both lights remained on for the duration of the reinforcement. For the concurrent V schedules, two Gerbrands tape programmers ran continuously, independently programming reinforcements for the two doors (one programmer per door). When a reinforcement was programmed for a given door, a response on that door turned on the magazine light and the sucrose pump for three sec. However, a change-over delay of two see was programmed so that only responses which occurred at least two see after a response on the alternative door could be reinforced. This arrangement was used to reduce the chance of superstitious reinforcement of response alternations. The number of reinforcements and responses were recorded on counters. Procedure Food and water were available ad lib for a two week postoperative period, Water consumption was measured at 24 hr intervals during this time. At the end of this period the animals were given access to only two 3 g Purina lab pellets per day, while water was continuously available in the home cage. This deprivation condition was maintained throughout the experiment. Response shaping consisted of three stages: (1) for the first three days both doors to the sucrose magazine were propped open and sucrose was pumped continuously at both magazines; (2) during the next three days the doors were closed but a response on either door was reinforced on a CRF schedule with three sec access to sucrose; and (3) for three more days all door responses were reinforced on a concurrent V 30 sec schedule. At the end of this period all subjects were reinforced on the concurrent V 80 sec schedule used throughout the remainder of the experiment. A septal and control animal were next randomly matched and this pair was tested at the same time each day for a 40 rain session per day, six days per week. Testing continued for any one pair of animals with both doors reinforced on thev180 sec schedule until a criterion of four stable baseline days was attained for both animals. Stability was defined as less than a 10 per cent change in response rate from the rate of the previous session. Pairs of animals did differ as to how long they were in this reinforcement condition before criterion was met, but a given pair of animals (septal and control) remained in this condition until both animals were performing at the criterion stability level. mmediately after the criterion was attained, both subjects were changed to the one door extinction condition in which reinforcements at one door were discontinued while reinforcements were continued at the other door. This condition was maintained for nine sessions. The reinforcement at the second door was discontinued on the tenth session and the pair tested for a total of five additional sessions (two door extinction). RESULTS AND DSCUSSON During the two week post-operative period average daily water consumption by the septal group was 44 g of water; control animals consumed an average of 37 g. The difference was statistically significant as tested by the Mann-Whitney U-Test (U = 15, p < 0.05). Group comparisons for the door response data were made separately for each door. The lower graph of Fig. 1 illustrates average rates for septal and control animals on the door response that was extinguished while the alternative door response was being reinforced in Panel D. The upper graph shows average rates for the remaining door that was extinguished (Panel E) nine sessions after the first door was extinguished. The data are graphed for reinforcement conditions for each door in the order in which they were employed in the experiment. The points on the graphs represent a session by session score except for the V 80 sec condition. n this condition the pairs of animals varied in the number of sessions needed to reach criterion (Range 13-42). The points of the graphs for the V 80 sec condition represent a session by session analysis for the first five sessions and last five sessions only. Statistical comparisons were done by a two-tailed Mann-Whitney U Test.

3 CONCURRENT RENFORCEMENT ,~ 2000 o 1800 z o 1600,,oo! ~ ~ z 800 bj 0E 600 4O oj o Q t~ 1600 ~ 1400 o 1200 t.i u. OO0 ta 800 o 600 r, O i v, L st. FVE SESS ONS Jr 3-4" q )p.e-.4 1 C V 80" LAST FVE isessons SEPTAL CONTROL B 1 c SEPTAL... CONTROL V 80" V 80" lit. RVE LAST FVE SESSONS SESSONS P t.m..8- ~ DOOR RENFORCED SESSONS SESSONS,L',m..~ J' 2 DOOR EXTNCTON 18 2 DOOR EXTNCTON \ E taz DOOR EXTNCTON FG. 1. Response frequency on Door 1 (upper graph) and Door 2 (lower graph) for septals and controls in Experiment. Panel D presents data during extinction of one of the two doors; Panel E presents data when both door-responses were under extinction. required a larger number of trials to reach criterion (Range ) so that, in general, control animals were run for longer periods than septal animals. The septals also responded at a higher rate on the reinforced door when reinforcement was withdrawn at the alternative door (Panel D), although this difference was not significant (U~ 23, p < 0.10). The only other comparisons that reached significantly different response levels was when reinforcement was withdrawn from both doors; the septal animals responded at either door with a higher rate than controls (Panel E, U , p < 0.05). The response rates on each door at the time reinforcement was discontinued for that door (Panel D, lower graph and Panel E, upper graph) were transformed to a per cent of baseline measure for each daily extinction session. The data is shown in Fig. 2. The baseline was taken as the average reinforced response rate for each animal on the last three days of the reinforcement condition immediately previous to the extinction condition. Septals were still only significantly different from controls in the two door extinction condition (Fig. 2, Panel B, U , p < 0.05). This suggested that septal animals not only made more responses in the two door extinction but that they did not suppress responding from baseline as quickly as controls. Z 3C,,, 50 x 0 6O g 7e Z 9C 0c A DOOR EXTNCTON 2 DOOR EXTNCTON S 55 L \ )NS B SEPTAL : ; CONTROL*--, FG. 2. Per cent decline from baseline for each session in the one and two door extinction conditions in Experiment. The septals responded at a significantly higher rate than controls over the entire V 30 see reinforcement condition for both doors and for the first five sessions of the V 80 see reinforcement condition (Panel A, upper graph, U----7, p < 0.002; Panel A, lower graph, U : 6, p < 0.002; Panel B, both doors, U : 15, p < 0.05). The rates of the two groups came together in the terminal five sessions of the V 80 sec condition. The differences of the data over these last five sessions was not significant (Panel C, both doors, U , p < 0.10). t seemed clear that the groups came together in the final five sessions because of the criterion of pairing employed. A pair consisting of a septal and a control animal was maintained in the V 80 see reinforcement condition until both reached criterion before they were shifted to the next condition. All control animals managed to reach the criterion within the first 13 sessions. All septal animals, but one, n summary, these data were consistent with the reports that septal animals responded at a higher rate for reinforcement than controls, and that they also responded more when all reinforcements were withdrawn. n addition, comparisons made on the basis of the per cent of base line transformation revealed that in the two door extinction condition--which was analogous to the standard extinction procedure--septals did not show as rapid or as large a decline from their generally higher response baselines as controls showed from their generally lower baselines. n contrast to these results, data like that obtained from the one door extinction condition has not been previously reported. The fact that septal animals suppressed response levels as quickly as controls in this condition provides an interesting point of comparison with the outcome of the two

4 652 SCHNELLE, WALKER AND HURWTZ door extinction condition. t suggests that the simplest explanation of these results may be that septal animals respond at higher rates for reinforcement so that when this reinforced responding is extinguished these higher rates are reflected in an increased number of responses on the non-reinforced door. On the other hand, when there is a reinforced response concurrent with the extinguished response, the higher septal response rates are reflected in response rates on the reinforced door and not in responses on the extinguished door. n essence, the prolonged extinction behavior of septally operated rats may reflect nothing more than a generalized higher rate of responding. When the results for the one door extinction condition are examined, it seems obvious that there were no septal deficits, and, therefore, no need for a theory to account for such deficits. The experimental operations performed in the one door extinction condition of this experiment have much in common with the reversal studies described by Donovik [5], Schwartzbaum and Donovik [10] and by Zucker [13]. n reversal experiments, the animals are required to suppress a response. for which they were originally rewarded in favour of some other response. The primary operation employed in the reversal sessions could be summarized as follows: response A is reinforced and response B is non-reinforced followed by reinforcement of response B and non-reinforcement of response A. The operations performed in the one door extinction condition of this experiment differs from this reversal operation in that both response A and B were reinforced followed by continued reinforcement of response A and nonreinforcement of response B. The present experiment permitted the animal to suppress one response while an alternative response which already had an extensive history of being positively reinforced continued to be reinforced. The reversal studies on the other hand, required the animals to suppress one response while the response which was being reinforced had a history of nonreinforcement. t is possible that this operational dissimilarity between the reversal studies and the present experiment is responsible for the difference in the results of the present study and those reported by Donovik [5] and Schwartzbaum and Donovik [10] which showed that septally operated animals perseverated the non-reinforced response in reversal procedures significantly more than controls. Zucker [13] reported no differences in the behavior of septals and controls in a simultaneous discrimination reversal procedure. His subjects had post-operative experience on a passive avoidance, successive discrimination and an extinction task before they were tested in the simultaneous reversal procedure. McCleary [8] suggested that such post-operative experience may have an ameliorative effect on the deficiency that septally operated animals usually demonstrated when they are later tested in procedures which require them to withhold responding. Anatomical Considerations Histological evaluations were accomplished by comparing sections of brains with corresponding plates extending from Ag000 to A7000 in Pelligrino and Cushman [9]. The lesions were rated by two experimenters on a 3 point scale of injury in respect to the lateral and medial septal nuclei. A score of one was given for damage estimated in excess of 60 per cent, two for per cent damage, and three for less than 30 per cent damage. Examples of lesions with approximate ratings are shown in Fig. 3. The results of the evaluation on lesion damage is given separately for the lateral and medial septal nuclei in Table. TABLE 1 EVALUATON OF SEPTAL ABLATONS Septal Lesions Experiment Septal Lesions Experiment Subjects Lateral l Medial See text for rating'method. n addition to considerable damage to the medial and lateral nuclear groups, several animals in Experiment also sustained damage to the nucleus accumbens, hippocampus pars anterior, and tract of the diagonal band of Broca. Damage to the overlying cortex was comparable to that produced when lesion electrodes are used. EXPERMENT A replication of the previous experiment was undertaken with several design changes. First, water instead of sucrose was used to reinforce responses because there is some evidence that septal animals may behave in an atypical manner for sucrose reinforcement [2]. Secondly, levels of responding in the apparatus were measured before the animals were reinforced in the experimental situation. This was done to obtain a baseline against which the extinction data could be compared. Thirdly, the fact that the rates of response for the two groups of animals converged in the last five sessions of the V 80 sec reinforcement condition may have been influenced by the selection procedure which resulted in controls receiving more training than septals. n the present experiment septals and controls were exposed to a V 30 sec for an equal number of sessions before they were shifted to the one door extinction condition. Finally, the animals in the present experiment were trained under a V 30 sec schedule rather than a V 80 sec schedule in an attempt to reduce the time needed to attain stable response rates. Animals The animals were 18 naive, male, Long-Evans hooded rats weighing g. The subjects were maintained in individual cages. The apparatus and scheduling technique were identical to that used in the previous experiment. Surgery and Histology Surgery in the second experiment took place in a semisterile environment and was similar to the technique described by Clody and Carlton [4]. Holes were drilled bilaterally to the sagittal sinus 1.6 mm anterior to the mid-bregma. The skull was clipped over the middle between the holes. The sagittal sinus was then gently displaced and a stereotaxic guided pipette was lowered directly below the midline to a depth of 5.5 ram. Aspiration pressure as well as all other surgical and histological details were identical to those employed in the previous experiment.

5 2 FG. 3. Evaluation of septal lesion damage on three sections which illustrate differing types of damage observed in both experiments. (facing page 652)

6 CONCURRENT RENFORCEMENT 653 Procedure For seven post-operative days the animals were maintained on ad lib food and water with water consumption measurements being taken every 24-hr period. Two days prior to the behavioral testing and for the duration of the experiment, the animals were allowed 30 min access to water per day in the home cage. The water was supplied for 15 min after each daily session whereas food was continuously available in the home cage at all stages in the experiment. Operant response levels were measured from the 1 l th post-operative day to the 19th post-operative day. The training procedure was similar to the procedure described in the previous experiment. All animals were trained under a concurrent V 30 sec schedule with three sec duration of water reinforcement. This condition was maintained for three sessions and then one sec duration of water was used as the reinforcement for eight more sessions. Finally, the duration of reinforcement was reduced to one-half sec and this duration was maintained throughout the experiment. The reductions in reinforcement durations were needed to minimize satiation effects which appeared with both the three sec and one sec durations of reinforcement. Both doors were reinforced concurrently with one-half sec of water reinforcement for fourteen sessions and then the reinforcements at one door were discontinued while the alternative door was maintained on the V 30 sec schedule with one-half sec of water reinforcement. The door at which reinforcement was discontinued was randomly determined before the experiment. After fourteen sessions in this condition the reinforcements at both doors were discontinued for six remaining sessions. Anatomical Considerations RESULTS AND DSCUSSON Histological evaluation was accomplished by the same means described in the first experiment. The results of these evaluations are presented in Table 1. All damage described for the animals of the previous experiment was found for the operated animals of the present experiment. n addition all operated animals in Experiment were found to have damage to the corpus callosum and superior fornix, Behavioral Results The septal group of animals consumed an average of 36 g of water over the first seven post-operative days while control animals consumed an average of 34 g. These figures were not significantly different (U ~ 21, p > 0.05). This finding suggests that the differences in response rates between septal and control animals can not be entirely attributed to altered motivation for water. Group comparisons for the door response data were made separately for each door. The upper graph of Fig. 4 illustrates average rates for septal and control animals on the door that was first extinguished while the alternative door was being concurrently reinforced. The lower graph of Fig. 4 shows average rates for the remaining door that was extinguished 15 sessions after the first door was extinguished. The points on the graph are average responses for each group taken over each daily session. All statistical tests were done by the Mann-Whitney U Test and were two tailed comparisons. The septal group responded at a significantly higher rate than controls on both doors for all reinforcement conditions. These data are presented in Fig. 4. Panel A, U -~ 0, p < ; A c OPERAN1 ;RF f& 180 o.evel TS ~1400 ~!200 ooo ua 800 Z 8oo 4oo 2oo o ~.'~.- ~ A B C OPERNqT CRF ~ 1800 LEVEL " ' 4oo,oo 0 0 E V3.~130 ],.S ~S r V Z.: SESSONS D V30 rsr SESSONS E V30.5"St F 1DOOR EXTNCTON F G SEPTALS.-... CONTROLS-.-. 1&2DOOR EXTNCTON G 2 O00R 1&2 DOOR RENFORCED EXTNGUSHE.D /.< FG. 4. Response frequency on Door 1 (upper graph) and Door 2 (lower graph) for septals and controls in Experiment. Panel D presents data during extinction of Door 1 ; Panel E presents data when both door responses were under extinction. Panel B, U = 6, p < 0.002; Panel C, U = 16, p < 0.05; Panel D, U = 16, p < 0.05; Panel E, U = 6, p < 0.002; Panel F, upper graph, U = 16, p < 0.05; Panel F, lower graph, U 17, p < 0.05; Panel G, upper graph, U = 15, p < 0.05; Panel G, lower graph, U : 17, p < Panels A-D are two tailed Mann-Whitney U comparisons of the total response rates on both doors by septals vs. controls. Two tailed Mann- Whitney U comparisons for Panels G and F were made separately for each door. These results essentially extend and replicate those of the previous experiment with three exceptions. First, the operant level measurement provided data that were not collected in the previous experiment. The higher septal operant level was probably an important determinant of the higher septal response levels reported in the extinction conditions of this and other experiments. Secondly, the differences between the response rates of septals and controls on the reinforced door in the one door extinction condition (upper graph, Panel E) were significantly different (p = 0.05) whereas in the previous experiment the difference was not significant (p > 0.10). Thirdly, septal animals made significantly more responses than controls on the extinguished

7 654 SL]Nlq_[ :. WAt.K-:t~ AN) tl!rv~. / door in the one door extinction condition (upper graph, Panel F) in this experiment. This comparison was not significant in Experiment. The discrepancy in the results of Experiment and can be partially explained by the fact that septal animals responded at higher rates than controls immediately prior to the one door extinction condition in Experiment but not in Experiment. A comparison between septals and controls using the per cent of baseline transformation described in Experiment yielded results consistent with those described for the one door extinction in Experiment ; in both experiments septals suppressed responding from baselines as quickly and extensively as controls (Fig. 5, Panel A). Also consistent with the previous experiment was the finding that septally operated animals were significantly different from controls in the two door extinction condition in terms of rates of response and in per cent drop from baseline estimates (Fig. 5, Panel B). The difference between the two groups in the one door as compared to the two door extinction condition again suggests that septals can suppress responding as adequately as controls if there is a strongly conditioned alternative response available. This indicates that septal animals can switch responses from a non-reinforced to a reinforced manipulandum as efficiently as controls and they can do this despite the fact that they have higher operant response levels and higher rates of responding for reinforcement. The most important conclusion to be drawn from the data of both experiments is that septally operated animals behave differently from controls under a wide variety of experimental conditions so that explanatory attempts directed al any one specific septal behavioral phenomenon, e.g. suppressiol~ deficits or atypical-incentive reward functioning, would seem at best to be premature and at worst misleading. An experimental program whose aim is to simply categorize and describe the internal and external environmental variables that control the response rates of septal animals would seem to be the more valuable approach. ~ 1 DOOR EXTNCTON A 2 DOOR E~'TNCTON 3 SEPTAL -- ; SESSONS FG. 5. Per cent decline from baseline for each sesssion in the one and two door extinction conditions in Experiment. REFERENCES 1. Beatty, W. W. and J. S. Schwartzbaum. Enhanced reactivity to 8. McCleary, R. A. Response-modulating functions of the limbic quinine and saccharine solutions following septal lesions in the system: nitiation and suppression. n: Progress in Physiologirat. Psychonom. ScL 8: , cal Psychology, edited by E. Stellar and J. S. Sprague. New 2. Beatty, W. W. and J. S. Schwartzbaum. Consummatory be- York: Academic Press, 1966, pp havior for sucrose following septal lesions in the rat. J. comp. 9. Pellegrino, L. J. and A. J. Cushman. A Stereotaxic Atlas ~ff" physiol. Psychol. 65: , the Rat Brain. New York: Appleton-Century-Crofts, Carey, R. J. A retention loss following septal ablations in the 10. Schwartzbaum, J. S. and P. J. Donovik. Discrimination rat. Psychonom. Sci. 7: , reversal and spatial alternation associated with septal and 4. Clody, E. D. and P. L. Carlton. Behavioral effects of lesions of caudate dysfunction in rats. J. comp. physiol. Psychol. 65: the medial septum of rats. J. comp. physiol. Psychol. 67: 83-92, , Schwartzbaum, J. S., M. H. Kellicut, T. M. Speith and J. S. 5. Donovick, P. J. Effects of localized septal lesions on hippo- Thompson. Effect of septal lesions in rats on response inhibicampal EEG activity and behavior in rats. J. comp. physiol. tion associated with food reinforced behavior. J. comp. physiol Psychol. 66: , Psychol. 58: , Harvey, J. A. and H. F. Hunt. Effect of septal lesions on thirst 12. Winocur, G. and J. A. Mills. Hippocampus and septum in in the rat as indicated by water consumption and operant response inhibition. J. comp.physio.psychol. 67: , responding for water reward. J. comp. physiol. PsychoL 59: 13. Zucker,. Effects of lesions of the septal-limbic area on the 49-56, behavior of cats. J. comp. physiol. Psychol. 60: , Macdougall, J. M., G. W. Van Hoesen and J. C. Mitchell. Anatomical organization of septal projections in the maintenance of DRL behavior in rats. J. comp. physiol. PsychoL 63: , 1969.