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)     

Limbic lesions and the energizing, aversive, and inhibitory effects of non-reward in rats.

Tested 30 male albino Wistar rats with bilateral lesions in the amygdala, septum, hippocampus, stria terminalis, and fornix on a multiple reinforcement schedule in which barpressing in one component was associated with VI reinforcement (S+) and the other with extinction (S–). Responses on a 2nd lever turned off S– for 5-sec periods during the extinction component. All groups, with the exception of Ss with amygdaloid lesions exhibited behavioral contrast. Ss with hippocampal or fornical lesions showed greater resistance to extinction. Response rates on the lever that turned off S– were higher after stria terminalis and septal lesions, whereas lower rates were obtained from Ss with amygdaloid lesions. It is concluded that amygdaloid lesions attenuate the energizing and aversive effects of nonreward, septal and stria terminalis lesions increase the aversive effects, and hippocampal and fornical lesions interfere with the inhibitory effects of nonreward. (French summary) (28 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sparing of function after infant lesions of selected limbic structures in the rat.

The effects, in adult Ss, of limbic lesions produced in infancy were studied in 273 male Wistar rats using weight gain and conditioned emotional response (CER) and condtitioned avodiance response (CAR) acquisition as the critical measures. Ss received bilateral lesions of the amygdala, septum, postventral hippocampus (PH) anterodorsal hippocampus (AH), or frontal cortex either as infants (at 10 days of age) or as adults (at 60 days). Normal and anesthetized control groups were also used. Frontal cortical lesions, AH lesions, and anesthetization had no effect on weights or on CER and CAR acquisition. Both infant and adult amygdala and septal lesions significantly disrupted normal weight gain. Adult-accrued amygdala and PH lesions significantly retarded CER acquisition, and adult septal and PH lesions significantly facilitated CAR acquisition. Infant-accrued amygdala lesions significantly facilitated CAR acquisition, and infant PH lesions had no effect on either task. Results are interpreted to mean that the observed task-specific recovery in early-operated Ss may have been due to some form of functional reorganization. (30 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)     

Enhanced frustrative nonreward effect following 6-hydroxydopamine lesions of the lateral septum in the rat.

Tested the effect of local injections of 6-hydroxydopamine (6-OHDA [3 μg/1 μl]) into the lateral septum in a paradigm that leads to an energizing behavior, through a possible frustrative effect, induced by partial or total omission of reward in hungry adult male Sprague-Dawley rats. Biochemical assays in the septum showed that 6-OHDA reduced endogenous dopamine and, to a lesser extent, noradrenaline concentrations and left intact noncatecholaminergic neurons such as serotoninergic terminals. In a double straight alley, Ss were exposed to an acquisition phase, a partially reinforced phase, and an extinction phase. Ss with lesions ran faster for food than controls in the partial reinforcement or extinction situation. The 2 groups also behaved similarly after the 1st 6 trials of the extinction phase. When Ss were tested in a leverpress conditioning task, lesioned and control Ss learned this task equally well, both with respect to the number of leverpresses and the time to obtain a fixed number of food pellets. In the 1st 5 min following the omission of reward, the number of leverpresses increased more for the lesioned Ss than for controls, a difference that disappeared in the later stages of the test. Results indicate that the loss of septal dopaminergic innervation produces behavioral effects similar to those obtained after total destruction of the same areas by electrocoagulation. (30 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)     

Septal lesions and incentive expectancies in rats.

Tested male albino Wistar rats with bilateral septal lesions on a multiple DRL schedule with large and small rewards. The lesion produced less efficient DRL performance under both conditions. Small rewards produced more efficient DRL responding in controls and brain-damaged Ss. A 2nd study investigated runway conditioning under immediate, delayed, and no reward. Septal lesions increased running speeds with immediate reward, maintained faster speeds during the early delayed-reward trials, but produced no differences during extinction. A 3rd experiment investigated the effects of immediate and delayed rewards on auditory discrimination learning in septal and control Ss. Brain-damaged Ss showed inferior discrimination performance with delayed rewards but not with immediate rewards. Data suggest that septal lesions alter cognitive strategies (i.e., expectancies) based on incentive characteristics. (French abstract) (40 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of reinforcement omission on rats with lesions in the amygdala.

Trained 12 male Wistar rats with bilateral lesions in the amygdala to barpress on an FI schedule of reinforcement. During test trials, when reinforcement was occasionally omitted, response rates of 12 controls increased in the subsequent interval, whereas lesioned Ss showed no significant change. In Exp II Ss received fixed-ratio reinforcement on 1 lever, which was followed by a time-out period and fixed-ratio reinforcement on a 2nd lever. Results indicate that after reinforcement was withheld Ss with damage in the amygdala did not increase responding in the subsequent time-out period, whereas controls showed significantly higher rates. Differential latencies to initiation of response after nonreinforcement were also found. The deficits following brain damage are attributed to a reduction in nonreinforcement-induced frustration. (20 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Maternal behavior of mice with cingulate cortical, amygdala, or septal lesions.

Evaluated nest building, pup retrieving, and pup survival and growth in 11 primiparous female CF-1 strain mice and in 36 others with cingulate cortical, neocortical, amygdala, or septal lesions. Ss with neocortical or amygdala lesions showed little or no deficits in maternal behavior. Ss with septal lesions were severely impaired in all aspects of maternal care. These did not build nests, showed a variety of aberrant behaviors during pup retrieving, and their pups died or gained significantly less weight than those of controls. Ss with cingulate cortical lesions retrieved pups more slowly than controls, and retrieving deficits were correlated with the extent of retrograde degeneration found in the anterior thalamic nuclei. (26 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The effect of differential hippocampal lesions and pre- and postoperative training on extinction.

Examined resistance to extinction of a food-motivated response in a total of 78 male albino Wistar rats with sham operations or bilateral dorsal hippocampal, ventral hippocampal, or combined dorsal and ventral hippocampal lesions in 2 experiments. Surgery occurred either before or after acquisition of the to-be-extinguished response. Ss with combined hippocampal lesions showed greater resistance to extinction than controls if acquisition occurred preoperatively, but less resistance if acquisition occurred postoperatively. Ss with ventral hippocampal lesions were affected in a similar manner but to a lesser degree by differential prior experience. In contrast, dorsal hippocampal-lesioned Ss exhibited no change in approach latency during extinction, irrespective of the timing of surgery. It is suggested that both ventral and combined hippocampal lesions interfere with the changing of an established approach "set." (French summary) (16 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)     

Slower acquisition of positively reinforced behavior following medial, but not dorsolateral, septal lesions in rats.

Examined the effects of medial septal lesions (MSLs) and dorsolateral septal lesions (DSLs) on acquisition of leverpressing for water established with a modified autoshaping task. 22 male Sprague-Dawley rats were randomly assigned to receive either MSLs, DSLs, or control operations. Results show that, following MSLs, leverpressing responses had long latencies and were fewer than following either DSLs or control operations. However, during later sessions, MSL Ss started to press. It is suggested that the long response latencies and low response rates shown initially by MSL Ss may have been due to delayed classical conditioning. Following MSLs, the acetylcholinesterase activities of the different subdivisions of the hippocampus correlated positively with the number of leverpress responses emitted during Session 1. DSL Ss acquired the task just as fast as the control group and showed higher response rates than the other 2 groups during the final sessions. These findings are ascribed to generally increased locomotor activity. (24 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Syndrome produced by lesions of the amygdala in monkeys (Macaca mulatta).

12 male rhesus monkeys received bilateral stereotaxic lesions centered in the basolateral, lateral, and dorsal amygdala, or the temporal white matter lying adjacent to the lateral amygdala. Ss were compared with 4 others with control operations. Controls then received total amygdaloid lesions (AMX). AMX Ss exhibited the typical amygdaloid syndrome of hypoemotionality, meat eating, coprophagia, and excessive exploration. In contrast, Ss with subtotal amygdaloid lesions would not eat meat or feces, though they were more willing than controls to investigate inanimate objects. Extreme emotional changes after total amygdalectomy were found only in the S with the largest subtotal lesion. Only Ss that were hypoemotional showed a deficit in learning successive reversals of an object discrimination. This suggests that both the hypoemotionality and the successive reversal deficit arise from the same underlying dysfunction. (31 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Immediate effect of septal area damage on DRL performance in the rat.

Investigated the immediate and long-term effects of septal area lesions on performance on a differential reinforcement of low rates (DRL) 10-sec schedule. Ss were 43 male albino rats. Septal area lesions produced immediate disruption of DRL responding in unanesthetized Ss, but cingulate area lesions or sham treatments did not. The induction of septal seizures without lesions produced only minimal disruption. For the first few testing sessions, Ss tested 7 days after receiving septal area lesions were indistinguishable in DRL performance from those tested immediately; the former, however, showed poorer recovery. It is concluded that neural or other changes requiring time to develop postoperatively are not essential to the disruption of DRL performance, but they may impede behavioral recovery. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

"Effects of Reinforcement Omission on Rats with Lesions in the Amygdala": Erratum.

Reports an error in "Effects of Reinforcement Omission on Rats with Lesions in the Amygdala" by Peter G. Henke (Journal of Comparative & Physiological Psychology, 1973[Jul], Vol 84[1], 187-193). On page 188, the sentence beginning on Line 20, Column 1 should read: "Prior to any behavioral training, six animals received bilateral RF lesions in the amygdaloid complex." (The following abstract of this article originally appeared in record 1974-06538-001.) Trained 12 male Wistar rats with bilateral lesions in the amygdala to barpress on an FI schedule of reinforcement. During test trials, when reinforcement was occasionally omitted, response rates of 12 controls increased in the subsequent interval, whereas lesioned Ss showed no significant change. In Exp II Ss received fixed-ratio reinforcement on 1 lever, which was followed by a time-out period and fixed-ratio reinforcement on a 2nd lever. Results indicate that after reinforcement was withheld Ss with damage in the amygdala did not increase responding in the subsequent time-out period, whereas controls showed significantly higher rates. Differential latencies to initiation of response after nonreinforcement were also found. The deficits following brain damage are attributed to a reduction in nonreinforcement-induced frustration. (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)     

Effects of amygdala, hippocampus, and periaqueductal gray lesions on short- and long-term contextual fear.

Examines the effects of amygdala, hippocampus, and periaqueductal gray (PAG) lesions on contextual fear conditioning in 48 female rats. Freezing behavior served as the measure of conditioning. Unlesioned control Ss showed reliable conditional freezing in the testing chamber when observed both immediately and 24 hrs after footshocks. In contrast, Ss with amygdala or ventral PAG lesions exhibited a significant attenuation in freezing both immediately and 24 hrs after the shocks. Dorsal PAG lesions had no effect on freezing at either time. Ss with hippocampal lesions displayed robust freezing behavior immediately following the shock, even though they showed a marked deficit in freezing 24 hrs after the shock. These results indicate that there are anatomically dissociable short- and long-term conditional fear states. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Lesions of the amygdala, but not of the cerebellum or red nucleus, block conditioned fear as measured with the potentiated startle paradigm.

In Exp I, 97 male Sprague-Dawley albino rats were given 10 light–shock pairings on 2 successive days. At 24–48 hrs following training, groups of Ss received bilateral transection of the cerebellar peduncles, bilateral lesions of the red nucleus (which receives most of the cerebellar efferents), or bilateral lesions of the central nucleus of the amygdala. Controls were sham operated. At 3–4 days after surgery, Ss were tested for potentiated startle (PS [increased acoustic startle in the presence of the light previously paired with shock]). PS was blocked by lesions of the central nucleus of the amygdala but not by transection of the cerebellar peduncles or lesions of the red nucleus. Exp II, in which a visual prepulse test was used with 14 Ss, indicated that the blockade of PS observed in Ss with amygdala lesions could not be attributed to optic tract damage. Exp III, with 20 Ss, demonstrated that the absence of potentiation in Ss with amygdala lesions was not simply due to a lowered startle level ceiling, because these Ss could show increased startle with increased stimulus intensity and with administration of intraperitoneal strychnine, (0.75 mg/kg), a drug that increases startle. Results are consistent with the hypothesis that the amygdala is involved in fear conditioning. (64 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)     

Effects of acute trimethyltin exposure on appetitive acquisition and extinction performance in the adult rat.

16 adult male Sprague-Dawley rats were given an intragastric infusion of 7 mg/kg of trimethyltin chloride (TMT), and 16 additional Ss (controls) received saline, to investigate TMT's effect on Ss' appetitive acquisition and extinction performance. Ss from each condition were divided into 2 equal groups and trained with either partial or continuous reinforcement (PRF or CRF) in a straight-alley maze 21 days after dosing. The acquisition training phase contained 40 trials (4 trials/day) and was followed by 20 trials of extinction training (4 trials/day). Analyses performed on total speed revealed that TMT Ss performed at lower levels during acquisition than controls, regardless of schedule condition. Also, the rate of resistance to extinction was significantly reduced for TMT Ss compared with that of controls, regardless of the training schedules used during acquisition. A PRF extinction effect was observed for both control and TMT Ss, independent of dose regimen. PRF training occasioned greater persistence during extinction than did CRF training. Findings are discussed in terms of issues relating to TMT-induced hippocampal lesions. (19 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)