Medial septal lesions: Disruptions of microregulatory patterns and circadian rhythmicity in rats.

Examined the microregulatory patterns of food and water intake in 10 male and 10 female Long-Evans rats bearing medial septal lesions and in sham-operated controls. Medial septal ablation, although not affecting the total amount of food or water ingested, resulted in a profound disruption of the pattern of intake. Circadian rhythmicity was disrupted for a period, returning to normal by 25 days postlesion. Permanent disruptions occurred in feeding patterns in that Ss with septal lesions ingested more frequent but smaller meals. There was also a marked increase in food-intake-associated drinking and a decrease in non-food-intake-associated drinking. Results reflect 2 separate independent effects, a general circadian disruption and an alteration in regulatory behavior produced by a chronic depletion of body fluid. (33 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hormonal dissociation of limbic lesion effects on shuttle box avoidance in rats.

In a study with a total of 57 male albino Holtzman-derived rats, Ss with septal or hippocampal lesions showed facilitated acquisition of a shuttle box avoidance response compared to normal controls. Ss with septal lesions were also highly resistant to extinction compared with normal Ss. When the same lesion effects were examined in hypophysectomized Ss, the Ss with septal lesions continued to show facilitated performance, and Ss with hippocampal lesions performed no differently than nonoperated controls. These findings are consistent with the hypothesis that the facilitated avoidance performance found in rats with hippocampal lesions is attributable to lesion-induced changes in hypophyseal activity, but similar changes induced by septal lesions are not. (16 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Preoperative sodium experience and hypothalamic lesions in rats.

When a sodium deficit is induced in rats without lesions, they increase their saline intake regardless of prior experience. By contrast, the present experiment with 60 Sprague-Dawley rats found that Ss with lateral hypothalamic lesions increased their saline intake only when they had had preoperative experience ingesting saline in response to a sodium deficit. Ss were given natriuretic and mineralocorticoid treatments to induce sodium appetite. The role of preoperative experience in neural function is discussed. (32 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Suppressive and enhancing effects of footshock on food-reinforced operant responding following septal lesions in rats.

Measured effect of septal lesions on suppression of an intermittently food-reinforced lever press by contingent and noncontingent footshock, using a total of 48 experimentally naive male hooded Lister rats in 2 experiments. Ss with septal damage maintained higher response rates than did intact Ss under both contingent and noncontingent shock. Furthermore, the difference in suppression produced by the contingent and noncontingent conditions was approximately the same for the experimental Ss and controls. In Exp II performance was measured during counter-conditioning in which the correlation between contingent shock and positive reinforcement was varied. Ss with septal lesions responded at higher rates than did controls. When only reinforced responses were punished, this lesion-induced elevation represented an increase above baseline performance without punishment. This finding suggests that the effect of septal damage on appetitive instrumental performance cannot be due solely to a deficit in response inhibition. (27 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Escape from deficits in sodium intake after thalamic lesions as a function of preoperative experience.

Saline and water intakes in response to treatments with a natriuretic agent and a mineralocorticoid were studied in intact Sprague-Dawley male rats and in rats with lesions centered in the taste relay of the thalamus. Intact Ss responded to the treatments by increasing both saline and water intake. Ss with thalamic lesions that had never drunk saline prior to induction of the lesions generally did not increase their saline intake in response to the treatments but showed normal increases in water intake. In contrast, Ss with thalamic lesions that had drunk saline prior to induction of the lesions showed normal increases in both saline and water intake. Preoperative experience of sodium need did not protect Ss against the lesion-induced deficit. (22 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)     

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)     

Decrease in food intake following cortical spreading depression in static obese rats with ventromedial hypothalamic lesions.

Subjected 19 male and 23 female rats with ventromedial hypothalamic (VMH) lesions or with sham lesions to cortical spreading depression (CSD) 150 days after lesioning. Lesioned Ss showed a significantly lower food intake (as percentage of intake before CSD) than sham-lesioned Ss in the 14 days after CSD, but water intake did not differ between lesioned and sham-lesioned Ss. Both groups showed a slight decline in body weight, but lesioned Ss lost significantly more weight than sham-lesioned Ss. After 14 days, body weight, food intake, and water intake had returned to pre-CSD levels in both groups. Findings indicate that Ss with VMH damage are more sensitive to the effects of CSD than are normals and suggest that CSD acts to increase the activity of the VMH and to inhibit food intake, and this increase in activity is prolonged in VMH-lesioned Ss. (22 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Mouse killing induced by para-chlorophenylalanine injections or septal lesions but not olfactory bulb lesions is similar to that of food-deprived spontaneous killers.

Compared mouse killing induced by septal lesions, olfactory bulb lesions, or parachlorophenylalanine (PCPA) injections in 21 rats with the behavior of 14 sated or 10 food-deprived spontaneous mouse-killing rats to evaluate whether the experimentally induced killing corresponded to killing that occurred spontaneously. On the 1st mouse kill, the intensity of the initial reaction to the mouse, the site of the initial attack, and the time required to kill by all groups were similar except that bulbectomized Ss required longer to kill. Following the kill, only Ss with septal lesions and bulbectomized Ss bit the mouse significantly more than spontaneous killers. With the 2nd mouse kill, there was an increase in the intensity of the response to the mouse and a decrease in attack latency by all groups except the bulbectomized Ss and the nondeprived spontaneous killers. When presented with a freshly killed mouse, Ss with septal lesions attacked with the greatest intensity, but PCPA-injected Ss and food-deprived spontaneous killers also attacked more intensely than nondeprived killers. (31 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Developmental analysis of behavioral dysfunction in rats with septal lesions.

At 7 days of age, 48 male Long-Evans hooded rats received lesions of the septal nuclei or control operations. Ss then received 30 hrs of training on a DRL 20-sec schedule for 1 hr/day beginning at either 27 or 96 days of age. At 126 days of age, all Ss received 10 additional training sessions. After operant testing, all Ss received 10 additional training sessions. After operant testing, all Ss were tested on spontaneous alternation, spatial reversal, and passive avoidance. Results indicate that on a DRL 20-sec schedule Ss that received lesions of the septum neonatally and were tested at different ages performed in a similar manner. Approximately 50% of the Ss with lesions of the septal nuclei reached efficiency levels comparable with those of normal controls. When tested for retention, these efficient Ss still performed similarly to normal Ss. Ss with septal lesions were facilitated in the acquisition of a spatial habit, were deficient in spatial habit reversal, were less likely to demonstrate spontaneous alternation, and were deficient in passive avoidance. It is concluded that neonatal lesions of the septal nuclei produce permanent behavioral impairments on a diversity of measures and that, although juvenile animals with limbic system damage often manifest behaviors different from adult Ss, the difference is not evident during operant testing (26 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

DRL performance, extinction, and secondary reinforcement: Role of appetitive value of food in mice with septal lesions.

Conducted 5 experiments with a total of 116 B6D2F-sub-1/J mice. Normal Ss and Ss with septal lesions were trained on a DRL 8-sec schedule for food reinforcement varying in incentive value. Dilution of diet increased the number of reinforcements received by Ss with septal lesions. In Exps II and III the effects of septal lesions on resistance to extinction after continuous reinforcement training and the strength of secondary reinforcement were investigated. Changes in reinforcement value modified the septal lesion effects in both cases. All 3 experiments demonstrated the alteration of the septal lesion effect through a change in the appetitive value of the reinforcement. Results suggest that one of the mechanisms by which septal lesions impair DRL performance is an enhancement of reinforcing properties of food. (25 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect of septal and frontal ablations on species-typical behavior in the rat.

Assigned 15 male and 15 female Long-Evans rats to 3 groups: septal lesions, frontal lesions, and control. Behavioral measures were taken both pre- and postoperatively while Ss were freely interacting in a series of 5 large interconnecting chambers. Main categories of behavior observed included exploration, sleep, grooming, aggression, eating, mating, and drinking. The numerous differences found were related more often to sex and phase (pre- vs. postoperative), irrespective of lesion effects. Following behavioral observations, 2-way active-avoidance measures were obtained, and Ss with septal lesions showed the expected facilitation of avoidance behavior. The problem of comparing results derived from studies of brain damage using observational methods with those from laboratory task studies is discussed. (22 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of simultaneous and successive septal and amygdaloid lesions on social behavior of the rat.

Tested the social cohesiveness in an open field of 96 male hooded Long-Evans rats which had been subjected to either simultaneous or successive septal and amygdaloid lesions. Both the increased cohesiveness of Ss with septal lesions and the decreased cohesiveness of Ss with amygdaloid lesions were attenuated by the addition of the 2nd lesion. Ss with simultaneous lesions did not differ from controls. The 2 structures also were demonstrated to be reciprocally involved in mediating activity levels. (16 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A multivariate approach to the analysis of genetic and septal lesion effects on maze performance in mice.

Reports univariate and multivariate analyses concerning spatial discrimination behavior of Binghamton heterogeneous (HET), C57BL/6J, and RF/J mice that had received either septal lesions or control surgery (N?=?80). In acquisition of an appetitively motivated T-maze task, lesions impaired HET but improved RF performance relative to their respective controls. When Ss with lesions were reversed on a spatial discrimination acquired in a 17°C water maze, their performance was worse than control Ss; the magnitude of the deficit was strain-specific. Measures of reactivity to handling suggested that HET and RF Ss with lesions were more reactive than their controls; there was no such difference in C57 Ss. Multivariate approaches broadly corroborated the importance of complex Gene?×?Environment interactions that mold experience and thus behavior. They appeared to give some potentially important insights into the differential "behavioral profiles" of Ss with lesions and control Ss of the 3 genotypes; for instance, reactivity to handling and repeated error measurements were important variables in discriminating among the groups in both learning tasks. Thus, multivariate techniques should be considered as useful, additional tools for the development and evaluation of explanatory theories regarding functions of CNS regions. (34 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of septal and amygdaloid lesions on social behavior of the cat.

Tested 3 male and 43 female cats for social behavior and activity in an open field. Ss were then subjected to either septal or amygdaloid lesions and retested. Ss with septal lesions exhibited dramatic increases in social awareness as measured by the percentage of time they watched the Ss with which they were paired. Ss with amygdaloid lesions were twice as active postoperatively as they had been preoperatively. Both the enhanced social behavior of Ss with septal lesions and the enhanced activity with amygdalectomized Ss were independent of the locus of the lesion in the Ss with which they were paired. Results are discussed in terms of an alteration in disposition as opposed to an alteration of the response system after lesions of the septal region in the forebrain. (24 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)     

Effects of lateral hypothalamic lesions on food intake of rats during exposure to cold.

Two experiments investigated the feeding behavior of 41 male Sprague-Dawley rats with lateral hypothalamic (LH) lesions and 13 Ss with chemical lesions of central dopaminergic neurons. LH damage impaired both physiological and behavioral responses of Ss during exposure to a 5°C environment. The LH-lesioned Ss usually did not conserve heat in the cold as well as did controls (n?=?13), nor did they always increase their caloric intake to meet their energy needs. However, when given sucrose solution to drink instead of water, LH-lesioned Ss increased their ingestion of chow in response to cold exposure. It is likely that the elevated consumption of palatable fluid served to relieve dehydration and thereby removed its constraints on eating, thus permitting hyperphagia to occur. In contrast to these results, Ss with large dopamine-depleting brain lesions, produced by intraventricular 6-hydroxydopamine treatments, always increased food intake when exposed to cold stress and demonstrated no apparent problems in peripheral vasoconstriction. Thus, it is unlikely that striatal dopamine depletions account for either the impaired feeding response or the inadequate heat conservation of rats with lateral hypothalamic lesions during cold stress. (33 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect of size of food on food consumption: Some neurophysiological considerations.

Reports results of 3 experiments with 42 B6D2F1/J mice and 3 groups of 2 CAF1/J, C3D2F1/J, and LAF1/J mice. Ss that normally ate about 3.4 g of food in a 24-hr period increased food consumption 20% when offered their food in the form of 2 7.5-g pellets. This effect disappeared when Ss were offered 2 5.0-g pellets instead, or random-sized pellets. This finding indicates that the presence of large food pellets potentiates food intake in normal mice. Blinding disrupted this food-size-food-intake phenomenon. Lateral hypothalamic lesions disrupted the overeating under large pellet conditions, while both ventromedial hypothalamic and septal lesions affected eating of small pellets. Septal lesions increased consumption of small pellets, while ventromedial hypothalamic lesions reduced the intake of small pellets. (22 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)     

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)