Comparative learning and memory deficits following hippocampal and caudate lesions in mice.

Examined the effects of hippocampal, caudate, combined hippocampal-caudate, and sham lesions on the passive avoidance and active escape performances of groups of female CF1 mice. Bilateral hippocampal or caudate lesions produced similar impairments of passive-avoidance retention 1 day after training in Ss operated upon 1 day prior to training. Hippocampal and caudate lesions similarly facilitated active-escape retention. When surgery was performed immediately after training, hippocampal or caudate lesions each impaired both passive-avoidance and active-escape retention 1 day later; no retention deficits were observed when surgery was performed 1 hr. after training. When surgery was performed immediately after training and passive-avoidance retest was conducted 1 hr. later, only hippocampal lesions impaired retention. These and other data suggest the mediation of different neuroanatomical substrates for short- and long-term memory and different processes for storage and forgetting. (19 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)     

Enhanced cue function of olfactory stimulation in mice with septal lesions.

Trained a total of 121 male hybrid normal mice and mice with septal lesions on a go-no-go discrimination task (multiple fixed interval of 15 sec, 15-sec extinction schedule) in 4 experiments. When the discrimination stimulus (the one which indicated to the S whether responding at the end of the interval would be reinforced) was a pellet of food (delivered at the start of the interval) or odor of food or non-nutritive substance (present throughout the 15-sec interval), acquisition of septum-damaged mice was enhanced. These lesions did not, however, alter performance when the discrimination was cued by a buzzer or flashing light. Results suggest that septal lesions produce an increased reactivity to olfactory stimuli and to stimuli associated with the delivery of food reinforcement. (24 ref) (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)     

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)     

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)     

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)     

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)     

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)     

Differential effects of posterior septal lesions on dispositional and representational memory.

[Correction Notice: An erratum for this article was reported in Vol 101(1) of Behavioral Neuroscience (see record 2008-10683-001). A phrase was erroneously deleted from the text. In the seventh paragraph on p. 713, the second sentence should read as follows: Early in training individual differences were great, but by the end of adaptation training, individual differences were quite small and all rats responded at close to asymptotic speeds.] A distinction between 2 classes of memory has been made in terms of the sensory availability of cues at the time of making discriminations that are influenced by past experience. Three tasks objectively defining this distinction were learned in a T-maze by 36 male Long-Evans rats in 3 groups: (a) a delayed non-matching-to-sample (DNMTS) that depended on representational memory; (b) a simple sensory discrimination (SD) that depended on dispositional memory; and (c) a more difficult discrimination that also depended on dispositional memory, called the simultaneous conditional discrimination (SCD). The DNMTS and SD tasks were acquired quickly; the SCD task took many more trials. Posterior septal lesions impaired DNMTS performance but had no effect on retention of tasks that depended on dispositional memory. Results indicate that dispositional and representational memory systems have at least partially distinct anatomical substrates in the brain and that it is the representational and not the conditional aspects of the DNMTS task that are impaired by the septal lesions. (21 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)     

Opposite effects of lateral septal LTP and lateral septal lesions on contextual fear conditioning in mice.

The effect of fimbrial high-frequency stimulation (HFS)-induced long-term potentiation (LTP) in the lateral septum (LS) on contextual fear conditioning was studied in mice. Mice were conditioned for fear toward a novel context through the use of footshocks. The 1st experiment showed that pretraining HFS reduced significantly conditional freezing to contextual stimuli. The 2nd experiment was designed to determine whether the reduction of freezing produced by fimbrial HFS resulted from LTP in the LS rather than from LTP in other brain structures. Accordingly, mice with lesions of the LS were used and submitted to the same protocol as in the 1st experiment. Results showed that LS lesions completely abolished the impairing effect of fimbrial HFS and, as a whole, potentiated the freezing response. These data suggest that contextual fear conditioning is strongly modulated by the level of hippocampal–LS synaptic neurotransmission. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Differential effects of unilateral and bilateral caudate lesions on side preferences and timing behavior in rats.

Trained 24 female Sprague-Dawley rats to barpress on a DRL-16 sec schedule for water reinforcement. Ss were allowed to barpress on either of 2 levers (left and right). All Ss showed consistent side preferences. For the nonsignaled condition, normal rates were related to the strength of side preferences; lower rates and better timing performance were significantly correlated with greater preferences. Unilateral lesions in the caudate nucleus ipsilateral to side preferences facilitated performance during nonsignaled test sessions and increased side preferences during both. Unilateral lesions contralateral to side preferences impaired performance during nonsignaled test sessions and decreased side preferences during all sessions. Bilateral lesions transiently depressed response rates without significantly affecting timing performance or side preferences. It is suggested that side preferences are intimately involved in the control of behavior by internal stimuli and that an inherent asymmetry in nigrostriatal function underlies side preferences; the effect of a unilateral striatal lesion will depend on whether the lesion is placed in the more or less active striatum. (22 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Little and often: Ingestive behavior patterns following hippocampal lesions in rats.

Lesions of both dorsal and ventral hippocampus were produced by multiple infusions of the excitotoxin AMPA. Meal patterns recorded before and after lesioning showed no change in total food intake, but a striking behavioral syndrome in which the lesioned rats took smaller meals 2–3 times as frequently and showed a similar change in drinking. In addition, lesioned rats alternated more frequently between feeding and drinking during a single bout of ingestive behavior. There were no group differences in the satiety sequence that followed a meal. In an open field test, lesioned rats showed enhanced locomotion in the periphery and reduced rearing. An olfactory habituation–dishabituation task showed that the lesioned rats investigated olfactory stimuli less but dishabituation to a changed stimulus was normal. The data are discussed in terms of changes in behavioral switching or a possible interoceptive agnosia following hippocampal damage. (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)     

Environmental influences on locomotor recovery following cortical lesions in rats.

Six groups of 8 Charles River male rats with sham or sensorimotor cortex lesions were or were not exposed to an enriched environment that allowed social interaction and a variety of movement experiences for 2 hrs/day for 30 days during the immediate pre- and/or postoperative period. Ss were trained preoperatively to locomote across a narrow elevated runway. Testing on the locomotor task began 31 days after surgery and continued until preoperative performance levels were achieved. Preoperative enrichment had the most potent influence on initial deficit and recovery of locomotion. Ss that were enriched preoperatively failed to demonstrate any deficit postoperatively, and the topology of their hindlimb movement appeared to be normal. In preoperatively impoverished Ss, postoperative enrichment reduced the degree of initial deficit and speeded recovery of locomotion. However, preoperatively impoverished Ss demonstrated an aberrant topology of hindlimb movement even after they were behaviorally recovered. (32 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Behavioral activity and visual evoked potentials to photic stimuli following septal lesions in rats.

Conducted 4 experiments with a total of 63 male Holtzman albino rats to analyze electrophysiological correlates of hyperreactivity to stimuli following septal lesions, locomotor reactivity, and averaged visual evoked response (VER) to photic stimuli. While septal lesions exaggerated behavioral reactivity to flashes, they enhanced elaboration of late components of VERs at the visual cortex, a development normally associated with reduced behavioral reactivity. This lesion-induced dissociation between behavioral reactivity and VERs occurred under test conditions in which intensity of flashes, background illumination, and spacing of flash series were varied. Results suggest that septal lesions reduce electrocortical arousal to photic stimuli, but it remains unclear to what extent the changes are cortical and/or subcortical in origin. (32 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Comparative recovery following simultaneous- and successive-stage frontal brain damage in mice.

Conducted 5 experiments with female CF1 mice sustaining sham-operations, simultaneous, or successive bilateral frontal pole transections. Recovery of a passive-avoidance deficit occurred following both simultaneous and successive transsections. Recovery was a function of time either following the simultaneous procedure or between the 2 stages of the successive procedure. Recovered simultaneous Ss were hyposensitive to impairment of passive-avoidance learning by d-amphetamine, whereas recovered successive Ss were not. Alpha-methyltyrosine facilitated recovery following either simultaneous or successive brain damage. Results are consistent with a denervation supersensitivity model of recovery of function. (PsycINFO Database Record (c) 2010 APA, all rights reserved)