Electrophysiological and behavioral reactivity to photic stimuli following septal lesions and pharmacological treatments in rats.

Conducted 4 experiments, with a total of 86 male Holtzman albino rats, which investigated behavioral reactivity and cortical visual evoked response (VER) to photic stimulation. Analysis revealed 2 patterns of lesion-induced changes. One pattern of VERs reflected a hypoarousal electrophysiological condition. This pattern, present initially under all conditions, could be simulated with administration of scopolamine. A 2nd pattern of VERs developed gradually and appeared to reflect a hyperaroused electrophysiological condition. This pattern could be simulated with dextroamphetamine. While both lesion-induced electrophysiological patterns were associated with augmented behavioral reactivity to flashes, the hyperarousal pattern related to more intense conditions of stimulation and more sustained behavioral reactivity. Scopolamine, as opposed to dextroamphetamine, reproduced the heightened behavioral reactivity to the flashes. Results are interpreted in terms of a hypoarousal hypothesis of sensory hyperreactivity. (42 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Comparison of behavioral deficits caused by lesions in septal and ventromedial hypothalamic areas of female rats.

41 female Holtzman rats with lesions in ventromedial hypothalamic (VMH) area and 37 Ss with lesions in septal area were compared with 30 normal Ss for passive-avoidance performance (Exp I), reversal learning (Exp II), and spontaneous alternation (Exp III). Lesions in both septal and VMH areas produced a deficit in passive-avoidance performance, a greater number of errors in reversal learning, and reduced spontaneous alternation in a -maze. The qualitatively similar behavioral deficits produced by septal and VMH lesions suggests that at least part of the functions of both of these areas may overlap in a single system. An attempt was made to identify such a functional system, and an explanation for the behavioral deficits produced by VMH damage was offered. (20 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stimulus perseveration and choice behavior in rats with septal lesions.

Conducted 3 experiments to test a total of 56 Sprague-Dawley rats with lesions in the septal area and 45 controls for spontaneous-alternation behavior under various stimulus conditions. Ss with septal lesions exhibited perseveration to olfactory and visual cues presented either alone or in conjunction. This behavior was largely independent of response or spatial contingencies. Placement of the olfactory and visual cues in opposition eliminated the perseverative responding of these Ss. Normal controls exhibited the expected spontaneous-alternation behavior which was largely independent of the olfactory and visual contingencies. Results are discussed in terms of the role of the septum in the utilization of stimulus cues. (28 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sidman avoidance performance and response suppression in rats with septal lesions.

Ran 10 male Long-Evans hooded rats with septal lesions on 3 Sidman avoidance schedules which differed only in length of response-shock (RS) interval. Of the 5 septal Ss run on postoperative acquisition, all emitted responses at lower rates than the 5 controls, maintained shock rates equivalent to those of controls, and distributed their responses more efficiently than controls. Successive reductions in length of the RS interval produced suppression of avoidance responding in all Ss. However, for septal Ss, more sessions and a shorter RS interval were required to suppress avoidance responding. Performance of 5 Ss given preoperative experience was not changed by septal ablation. Both the lower response rate and the difficulty in suppressing avoidance responding are interpreted in terms of a deficit related to acquisition of stimulus control by conditioned aversive stimuli. (15 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Bar pressing for illumination change in albino rats with septal lesions.

Gave 43 sham-operated and septally-lesioned male Sprague-Dawley albino rats the opportunity to control illumination with a bar press. Ss with septal lesions changed illumination conditions more often, but spent less total time in the light, than controls. Therefore, compared with controls, Ss with septal lesions displayed both a greater preference for stimulus change and enhanced aversion for the illumination level used. A finding that such alterations in reactivity to light were maintained for 14 days is interpreted as being analogous to the effects of septal lesions on consumption of palatable and unpalatable fluids. (20 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Persistence of runway performance after septal lesions in rats.

Assigned 32 male Wistar albino rats to groups receiving bilateral septal lesions or control operations. Septal lesions prevented the partial reinforcement extinction effect after 48 acquisition trials. Septal Ss showed increased resistance to extinction following continuous reinforcement but decreased resistance to extinction following partial reinforcement. Analysis of the acquisition data indicated that the lesions retarded the development of approach-avoidance conflicts associated with reward and nonreward. In a 2nd study, 16 septal and 16 control Ss received 96 acquisition trials. Extended training allowed the development of conflict responses under partial reinforcement, and the Ss with lesions were indistinguishable from controls during extinction. Following continuous reinforcement, septal lesions produced slower extinction of response. It is concluded that the lesions interfered with the development of feedback from frustration, approach-avoidance conflicts, and frustration tolerance. (21 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Factors underlying deficient passive-avoidance behavior by rats with septal lesions.

Analyzed passive-avoidance behavior in male Holtzman rats (N = 83) with septal lesions in 5 experiments. Results reveal 2 independent sources of the deficit in retention of passive-avoidance responding. One factor, increased responsiveness to positive reinforcement, caused a persistent deficit in passive-avoidance retention which could not be alleviated by previous training on a different passive-avoidance task. A 2nd factor, described as a temporary defect in response inhibition, produced a transient deficit in passive-avoidance retention which could be alleviated by prior training on another passive-avoidance task or continued testing on the same task. (25 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Collateral behaviors and the DRL deficit of rats with septal lesions.

Trained a total of 31 male Long-Evans hooded normal and septally-lesioned rats to lever press for food on a DRL 20-sec schedule in either a conventional operant chamber or 1 containing wood blocks and cardboard strips. The DRL behavior of normals trained in modified chambers was most efficient, and that of Ss with septal lesions trained in conventional chambers was least efficient. After 35 hr. of training, normals tested in conventional chambers and Ss with septal lesions tested in modified chambers did not differ significantly. Ss chewed the blocks and cardboard, and prevention of these collateral behaviors reduced DRL efficiency. Results show that colalteral behaviors facilitate the development of efficient DRL behavior and indicate that the DRL deficit of rats with septal lesions can be modified. (17 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Running-wheel avoidance behavior following septal area lesions in rats.

Studied acquisition of a running-wheel avoidance response in 52 male Wistar rats with (a) septal lesions, (b) septal and postcommissural fornix lesions, or (c) septal, postcommissural fornix, and anterior thalamic damage. Ss with lesions confined to the septum were deficient in acquiring the avoidance response compared with both normal Ss and Ss with the more posterior lesions. Ss sustaining combined septal-fornical and septal-fornical-thalamic lesions did not differ from normal Ss or from each other in their acquisition scores. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Medial septal lesions disrupt spatial mapping ability in rats.

Rats with lesions of the medial septum were more likely to begin swimming in the wrong direction, swim farther, and, therefore, require more time to find a platform hidden in a Morris water tank than were control rats. Although the performance of the rats with medial septal lesions did improve over trials, their asymptotic performance also failed to equal that of the controls. Movement of the platform to a new position in the tank disrupted the performance of both groups, and, again, the rats with medial septal lesions were slower to locate the moved platform. However, this deficit was completely eliminated when a visual cue indicating the location of the moved platform was introduced. We suggest that these data indicate that damage to the septo-hippocampal cholinergic projection system produces a deficit in the formation or utilization of a spatial map (reference memory) that represents the location of a place with respect to the surrounding distal cues. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Defensive behaviors in rats following septal and septal-amygdala lesions.

Results of 2 experiments, utilizing 88 male albino Wistar rats, indicated that septal damage produced hyperdefensiveness rather than attack behavior or general hyperreactivity. Further division of this group indicated that damage to sites anterior and ventral to the septal area, sites previously implicated in the "septal syndrome," produced maximal effect on these behaviors. When amygdala lesions were combined with septal damage, enhanced defensive responding was almost eliminated. Results also indicate that amygdaloid mechanisms are involved in the regulation of conspecific defensive behaviors. (19 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Thirst and sodium appetite after colloid treatment in rats with septal lesions.

Previous experiments in which angiotensin II (AII) and mineralocorticoids were administered to rats have suggested that these hormones play a natural role in mediating thirst and sodium appetite. This hypothesis was examined by making use of 20 male Sprague-Dawley rats with septal lesions, which have an apparent sensitivity to the central effects of AII, and by studying their behavioral response to sc treatment with 5 ml of a 30% polyethylene glycol solution, which produces hypovolemia and thereby stimulates the secretions of renin and aldosterone. The induced thirst and sodium appetite both were markedly enhanced in the brain-damaged Ss. However, water intake was not increased when the hypovolemia was moderate, and sodium appetite was augmented only when Ss had been sodium deprived, a procedure known to potentiate aldosterone secretion. Findings support suggestions that while AII normally contributes little to thirst, it may help to mediate sodium appetite in rats when aldosterone is abundant. The 2 drives were not elicited uniformly; those Ss that drank the most water after colloid treatment consumed the least saline. While septal lesions may sensitize the rat's brain to the sodium-appetite-eliciting effects of AII as well as to its dipsogenic effects, sodium appetite may emerge only if the induced thirst is not too pronounced. (16 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Developmental aspects of recovery of function following septal lesions in the infant rat.

In an experiment with 4 litters of Long-Evans hooded rats (14 pups/litter), 1/2 of each litter received septal lesions at the age of 7 days, and the remaining 1/2 received control operations (incision). Septal lesions in infant Ss resulted in hyperemotionality and altered open-field behaviors at the ages of 21, 42, 63, and 90 days. When Ss reached 90 days of age, their behavior was compared with that of normal adult rats and rats that had received septal lesions in adulthood. Measures of active avoidance, fixed-ratio responding, and social facilitation were collected for all groups. Results show that septal lesions in infancy or adulthood enhanced avoidance responding, fixed-ratio responding, and social behavior when compared with infant or adult controls. Failure to observe recovery of function was interpreted in terms of phylogeny and hierarchical cerebral organization. (26 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Role of pituitary-adrenocortical system in mediating avoidance behavior of rats with septal lesions.

3 experiments with a total of 186 male Sprague-Dawley rats examined the hypothesis that the effects of septal lesions and systemic injections of scopolamine on avoidance acquisition could be attributed to the effects of either of these treatments on ACTH secretion. Septal lesions and scopolamine facilitated 2-way conditioned avoidance response acquisition, and the lesions retarded passive avoidance acquisition. However, neither the injections of dexamethasone, a synthetic glucocorticoid which inhibited ACTH secretion as did septal lesions, nor injections of ACTH which mimicked the facilitatory effects of scopolamine on basal ACTH secretion, affected avoidance in these paradigms. Thus, the main hypothesis was not supported. The finding that scopolamine did not affect passive avoidance indicates that a cholinergic system may not be involved in mediating the suppressive effects of punishment. (26 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Discrimination of emitted behavior following septal area lesions in rats.

Conducted 4 experiments with a total of 57 Long-Evans rats to investigate the behavioral consequences of septal lesions on acquisition, retention, and tracking performance on a 2-bar ratio schedule of reinforcement. This schedule requires S to monitor its amount of emitted behavior and match this information with reinforcement contingencies of the schedule for adaptive and efficient performance. On schedules requiring only a moderate amount of response output, septal lesions led to stereotyped and maladaptive performance. However, on very stringent schedules requiring a large amount of response output, septal lesions led to adaptive, and even enhanced, performance relative to operated controls (n = 26). Results suggest that septal lesions do not impair the sensory discrimination of emitted behavior but act differentially on numerous psychological dispositions vital for 2-bar ratio schedule performance. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Asymmetrical state dependency from temporary septal area dysfunction in rats.

40 male Long-Evans rats with cannulas implanted in the septal area were conditioned, tested, or both conditioned and tested shortly after intracerebral injection of local anesthetic via the cannulas. A 2–2 factorial design was used to determine whether the presumed state of temporary septal area dysfunction, previously shown to produce amnesia, has state-dependent properties. Results show a state-dependent learning effect: Ss that had been both conditioned and tested in the dysfunctional state remembered the aversive conditioning better than those conditioned in the dysfunctional state but tested in the normal state. Since Ss conditioned in the normal state but tested during septal dysfunction did appear to exhibit conditioned fear when tested, the state-dependent effect was asymmetrical. Performance effects of the procaine injection were observed and accounted for in determining the state-dependent nature of temporary septal area dysfunction. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of prefeeding on the DRL performance of rats with septal lesions.

Conducted 2 experiments with a total of 17 Long-Evans male hooded rats (8 with septal lesions and 9 unoperated controls) to study the effects of prefeeding prior to daily sessions on a DRL-20 schedule. Prefeeding reduced responses and increased reinforcement in the case of septal Ss, regardless of the level of body weight. In the case of normal Ss, prefeeding led to a decrease in responding and an increase in the number of reinforcements obtained only when the Ss were at 85% of ad lib body weight. At ad lib levels, prefeeding, although it decreased responding, also decreased the frequency of obtained reinforcements. Results suggest an impairment in normal Ss in the discrimination of response feedback by stimulation arising from stomach distention. (18 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The role of hyperdipsia in aggression following septal lesions in rats.

Lesions of the septum in animal Ss are known to produce an increase in aggressiveness and an increase in water intake. A series of 5 experiments with 120 female Sprague-Dawley rats examined the possibility that aggression is secondary to hyperdipsia. When Ss with septal lesions were restricted to preoperative levels of water intake, aggression scores declined significantly. When Ss without lesions were preloaded with either water or saline, aggression increased. Neither decreased shock threshold nor increased cell hydration provided a full explanation for the results. It is suggested that the aversive nature of the stomach turgescence caused by increased water intake may be an additional mediating factor in septal aggression. (31 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Lowered response to postingestive cues following septal lesions in rats.

Conducted 3 experiments with a total of 36 male albino Sprague-Dawley rats and 54 male albino Carworth CFE rats. Ss with septal lesions were tested in a variety of consummatory situations (e.g., solution intake, direct stomach loads preceding pellet intake, and stomach preloads preceding glucose intake). The lesions resulted in exaggerated responding to taste factors and a decrease in responsivity to postingestive cues relative to control Ss. Results support the view that the septum is an important link in the feeding circuit. (15 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The relation of feeding and activity following septal lesions in rats.

The patterns of intake of liquid diet (Exp I) and water (Exp II) were recorded in 12 female Long-Evans diet-deprived rats with septal lesions and 13 neurologically intact controls during the 1st hr of diet access. The occurrences of grooming, resting/sleeping, and exploring were also recorded. Findings show that both groups consumed similar amounts of diet in 1 meal during the 1-hr diet access period. Controls consumed the meal in 1 prolonged bout of eating, while lesioned Ss consumed the meal in numerous small bouts of eating. Lesioned Ss were active for longer periods, exhibiting continuous alternation of brief bouts of eating, drinking, exploring, and resting throughout the meal. In tests in which water was not available during the diet access period, both groups increased their intrameal bout size, but lesioned Ss still showed much smaller bouts of ingestion than did controls. Data suggest that the small-bout pattern of ingestion may reflect a general disruption in the control of behavioral sequences, rather than processes uniquely related to the regulation of eating or drinking. (16 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)