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)     

One-way avoidance behavior and septal lesions in the rat.

Compared 73 male Holtzman rats with septal lesions with 36 sham-operated and 41 unoperated controls on the acquisition of a 1-way avoidance response under several different stimulus and procedural conditions. Ss with septal damage were deficient in acquiring the avoidance response under several 1-way avoidance conditions involving an auditory CS, could not be distinguished from the controls in 2 experiments not involving auditory cues, and were superior to them in both a 2-way avoidance task and a conflictful 1-way avoidance task. (25 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dissociating the anti-fear effects of septal and amygdaloid lesions using two pharmacologically validated models of rat anxiety.

Compared the effects of septal and amygdaloid lesions in 2 models of rat anxiety. Septal lesions decreased burying behavior in the shock-probe burying test and increased open-arm exploration in the elevated plus-maze test, whereas amygdaloid lesions produced neither of these anxiolytic effects. However, amygdaloid lesions increased rats' contacts of the electrified probe, an anxiolytic effect not produced by septal lesions. Each of these distinct, anxiolytic effects of septal or amygdaloid lesions were displayed together in animals with lesions of both structures. Furthermore, the magnitude of these anxiolytic effects after combined lesions were comparable to their magnitude after individual lesions. Taken together, these results suggest that the amygdala and the septum independently control the expression of different fear-related behaviors. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dissociations among the anxiolytic effects of septal, hippocampal, and amygdaloid lesions.

Fear reactions of rats given bilateral lesions to the septum, hippocampus, or amygdala were compared with those of rats given sham lesions, in 2 animal models of anxiety: the shock-probe burying test and the elevated plus-maze test. Septal lesions produced anxiolytic effects in both tests (i.e., an increase in open-arm activity and a decrease in burying), whereas hippocampal and amygdaloid lesions produced neither of these effects. On the other hand, hippocampal and amygdaloid lesions impaired rats' passive avoidance of the electrified shock-probe, whereas septal lesions did not. These dissociations suggest that limbic structures such as the septum, amygdala, and hippocampus exert parallel but distinct control over different fear reactions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect of dexamethasone on affective behavior and adrenal reactivity following septal lesions in the rat.

Dexamethasone blockade of ACTH secretion from the pituitary gland did not alter the characteristic appearance or duration of the septal syndrome in male Wistar rats observed at 2, 9, and 16 days postoperatively. Despite the lack of a behavioral effect dexamethasone blocked the normal plasma corticosterone response to the stimulus of behavior rating in all groups studied. In the absence of dexamethasone, Ss with a septal lesion had a 65% greater corticosterone level 15 min. following the behavior rating than nonlesion Ss 2 days after surgery and an average increase of 35% over the 3 postoperative observation times of 2, 9, and 16 days. Results provide evidence that, in addition to the adrenal, the pituitary-adrenal axis is not essential for disturbance of affective behavior following septal ablation. (34 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of amygdaloid lesions on exploration by rats

Diagnostic separation of infants with signs of cardiac failure (hypoglycemia, sepsis, myocarditis, hypoxemia) but no congenital cardiocirculatory malformation from those with a large left to right shunt is crucial in newborn management. Echocardiographic studies of 218 infants and children allowed group separation and distinction from normal by the assessment of mean velocity of circumferential fiber shortening (Vcf) and the ratio of left atrial to aortic root diameter at end-systole (LA/Ao). In normal premature and full-term infants, Vcf (1.51 +/- 0.04 [mean +/- standard error]) was significantly lower than in infants with a large shunt (2.12 +/- 0.08, P less than 0.01) and higher than in infants with nonstructural heart disease (1.18 +/- 0.06, P less than 0.001). LA/Ao ratios were comparable in the groups with a large shunt and nonstructural heart disease (1.14 +/- 0.1 and 1.26 +/- 0.2, respectively) and were significantly higher in both groups than in normal subjects (0.77 +/- 0.01, P less than 0.001). Similar echocardiographic distinctions could be made when 10 older children (aged 2 to 10 years) with cardiomyopathy were compared with 45 normal older children. Serial determination of these variables was of major assistance in patient management.     

Effects of sequential preoptic and mammillary lesions on male rat sexual behavior.

Observed the sexual behavior of 52 male Sprague-Dawley rats prior to and following bilateral medial preoptic, unilateral medial preoptic, bilateral posterior preoptic, bilateral mammillary, and sham lesions. Bilateral medial preoptic lesions and mammillary lesions were made either simultaneously or sequentially within the same Ss in separate groups. Mammillary lesions had no effect on sexual behavior. Complete destruction of the medial preoptic area made prior to, simultaneous with, and following mammillary lesions completely abolished mating behavior. Partial destruction of the medial preoptic area increased mount and intromission latencies and slightly increased ejaculation latency. Results suggest that since there was no change in the postejaculatory-refractory interval, the medial preoptic area mediates sexual arousal but apparently is not involved in a copulatory-ejaculatory mechanism. (32 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of posterior hypothalamic lesions on voluntary behavior and hippocampal electroencephalograms in the rat.

Postoperatively rated 126 male hooded rats with posterior hypothalamic lesions for somnolence. Ss were later subjected to formal testing. Ss showed deficits in initiating voluntary movements (walking, swimming) but more automatic movements seemed less impaired (grooming, scratching, tail rattling). Somnolent Ss swam in but could not escape cold water, but they could not swim in warm water. Initial somnolence was related to deficits in shock avoidance and the initiation of walking and swimming. Ss could learn a T maze to escape shock and an E maze to escape cold but not warm water. Hippocampal rhythmical slow activity frequency was reduced postoperatively; amplitude was normal. Results support the idea that the posterior hypothalamus is part of a trigger mechanism for the initiation and maintenance of voluntary movement. (44 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of septal lesions on factors of mouse emotionality.

60 mice from 2 emotionally divergent inbred strains, BALB/Alb and C57BL/10Alb, were assigned to 1 of 3 experimental groups: septal surgery, control surgery, and intact. All Ss were then administered a battery of 5 tasks that yielded 19 measures of emotionality. Factor scores wre computed on 6 invariant factors obtained previously from these measures. Each factor was assessed by an ANOVA design with main effects for Strain, Sex, Lesion, and Days of Testing. Strain and Lesion main effects were found on the Motor Discharge and Autonomic Balance factors, Strain by Lesion interaction effects on Motor Discharge and Tunneling 1, and a Lesion by Sex interaction effect on Territorial Marking. Results suggest that the septum affects distinct processes modulating Autonomic Balance and Motor Discharge factors. (49 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)     

Exploratory behavior and reaction to novelty in rats: Effects of medial and lateral septal lesions.

This study was carried out to investigate whether medial septal (MS) or lateral septal (LS) lesions may differentially affect rats' ability to react to novelty or environmental change. Three types of task were used based on various sets of stimuli: visual and tactile, olfactory only, and visual only. The results showed that MS and LS lesions reduced preference for novelty, with different effects. The MS group displayed decreased exploration of both neutral and novel objects, whereas the LS group exhibited increased exploration of the objects compared with the control group. A reduced level of locomotor and rearing activity was initially seen among the MS animals. These results were compared with previous findings of behavioral changes after regional hippocampal perforant path lesions in the same test as used in this study. The comparisons imply that disruption of septal input to the hippocampal formation produces cognitive deficits different from those seen after disruption of entorhinal input. (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)     

Effects of anesthetics and septal lesions and stimulation on 3H-acetylcholine formation in rat hippocampus

The rate of 3H-acetylcholine (ACh) formation from i.v. injected 3H-choline was studied in the rat hippocampus after various treatments which alter the activity of cholinergic septal hippocampal neurons. Administration of pentobarbital and placement of acute septal lesion reduced the formation of 3H-ACh but did not change 3H-choline content. Chloral hydrate administration reduced the formation of 3H-ACh and also increased 3H-choline content. The chloral hydrate induced increase in 3H-choline occurred also in animals with chronic septal lesions. Electrical stimulation of the septum caused an increase in both 3H-ACh and 3/-choline. Chronic septal lesion caused a reduction in both radioactive and endogenous ACh, but did not affect radioactive or endogenous choline. These findings suggest that there are multiple pools of choline in the brain and that the precursor pool for ACh synthesis is difficult to measure. Overall, the parameter that best correlated with cholinergic activity was the level of 3H-ACh. Possible mechanisms, for this finding are discussed.     

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)     

Effects of septal lesions on inter- and intraspecies aggression in rats.

Conducted 3 experiments with septally lesioned and sham-operated male Sprague-Dawley albino rats (n = 97). Septal lesions affected shock-induced fighting, mouse killing, and fighting in a dominance situation differentially, depending on situational and temporal variables. Immediately following the lesion, preoperatively dominant Ss became submissive in a food competition test, displayed increased fighting in response to electric shock, and killed mice. 15 days after surgery, these effects on fighting behavior were no longer present. If tested for the 1st time 10-15 days after the lesion, septal Ss maintained their dominance in the food competition test, did not show an increase in shock-elicited fighting, and did not turn into "killer" rats. The effects on the muricide response were not reversible once they had been induced. (32 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of amygdaloid and amygdaloid-hippocampal lesions on object recognition and spatial working memory in rats.

Neurotoxic lesions of the amygdala did not affect the postoperative acquisition of a nonspatial test of object recognition (delayed nonmatching to sample) even when retention delays were increased from 0 sec to 20 or 60 sec, or when test stimuli were deliberately repeated within a session. Although these amygdaloid lesions did not alter forced-choice spatial alternation, they slightly increased neophobic responses to novel foods and environments. In contrast, combined amygdalohippocampal (A?+?H) lesions impaired performance on the object recognition task when the retention intervals were increased beyond 0 sec and when test stimuli were repeated within a session. The A?+?H rats were also severely impaired on the spatial alternation task, and they showed reduced neophobia. Comparisons with a previous study show that damage to the amygdala or hippocampus does not affect object recognition, whereas A?+?H damage produces clear deficits. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Interactive effects of training condition and septal lesions on perseverative responding in the rat.

In a study with 30 male Wistar rats, Ss that had received septal lesions either prior to acquisition of a position habit (Group SAR) or immediately after position habit acquisition (Group SR) were tested on 2 reversals of the task. Compared with control-operated Ss, both groups of Ss with septal lesions exhibited position-habit reversal deficits. The 2 groups with septal lesions could not be distinguished in terms of the total number of errors made during reversal learning, but could be distinguished on the basis of the type of error committed. Compared with Group SR, Group SAR made significantly more perseverative errors on the 1st reversal and significantly fewer perseverative errors on the 2nd reversal. Group SR made significantly more nonperseverative errors than Group SAR on both reversals. (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)     

Effects of inferotemporal lesions on the behavior of monkeys.

Monkeys with inferotemporal (IT) lesions learn visual discriminations abnormally slowly. The evidence for various explanations of this defect is reviewed. It is concluded that the defect does not result from the disorders of perception, attention, or memory for either visual stimuli or visual associations that have so far been postulated. Two other explanations remain viable: that IT animals have a reduced capacity either to (a) categorize visual stimuli or (b) form associations with them. Since the existing evidence on these 2 hypotheses is inadequate, ways of testing them are suggested. (123 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of cerebellar lesions on activity, social interactions, and other motivated behaviors in the rat.

In a total of 36 male rats, lesions of the cerebellar fastigial nucleus, but not lateral nuclear lesions or cerebellar cortical lesions, resulted in significant reductions in activity, open-field exploratory behavior, and social interactions. These deficits showed no recovery over a 4-wk testing period and were not related to the motor effects of the lesions. Other motivated behaviors (e.g., eating, grooming, gnawing, and pain responsiveness) were minimally affected. Results suggest the existence of 2 separate fastigial output pathways to neurobehavioral substrates: (a) the direct fastigio-bulbar pathway, which mediates the eating, grooming, and gnawing behaviors elicited by fastigial stimulation, and (b) the ascending fastigial projection to limbic structures, which may mediate fastigial influences on activity and social interaction. (43 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)