Acquisition and extinction of a classically conditioned response in hippocampectomized rabbits (Oryctolagus cuniculus).

Compared the responses of 10 male albino rabbits with bilateral hippocampal lesions to those of 15 unoperated and 10 neocortically-lesioned controls. Experimental Ss acquired a classically-conditioned nictitating membrane response faster than the 2 control groups. After initial acquisition, Ss were given extinction training, alternated with reacquisition sessions, and a test of spontaneous recovery. Experimental Ss extinguished normally during initial sessions, but failed to show the significant savings exhibited by controls during subsequent extinction sessions. The test of spontaneous recovery failed to differentiate among the 3 groups. Experimental Ss given preoperative training showed essentially the same extinction deficit as Ss who had not been trained. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Estrogen and estrogen-progesterone treatments counteract the effect of scopolamine on reinforced T-maze alternation in female rats.

Determined if steroid hormone treatments would attenuate the effect of the muscarinic receptor blocker scopolamine on a memory task. Ovariectomized rats were trained first to alternate for food reward between the arms of a T maze. Following training, Ss treated with scopolamine hydrobromide (0.2 mg/kg, ip) did not alternate correctly between the arms of the T maze and responded at chance levels. However, when estradiol benzoate (25 μg) was administered 72, 48, and 24 hrs before testing alone or in combination with progesterone (500 μg) administered 48 hrs before testing, Ss alternated successfully between the arms of the T maze following scopolamine administration. Results indicate that gonadal steroids can completely counteract the impairment of T maze performance induced by scopolamine in female rats. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Posterodorsal septal lesions impair performance on both shift and stay working memory tasks.

Two groups of male Long-Evans rats (N?=?42) were trained preoperatively on either a shift or a stay problem in a T-maze. Training trials consisted of 2 runs, an "information run" in which S was forced to go down 1 of the 2 arms of the T-maze, followed immediately by a "choice run" in which S could choose either arm. In the shift condition, Ss were rewarded with wet mash only for choosing the arm opposite the one they entered on the information run. In the stay condition, Ss were rewarded for entering the arm that was entered on the information run. The shift group reached 100% performance accuracy after fewer trials than the stay group. Choice accuracy in both groups declined as the delay increased and returned to 100% at the 0-sec delay. Half of the Ss in each condition then received either lesions of the posterodorsal septum—aimed at disconnecting the septum and hippocampus—or control surgery. Results indicate that deficits in maze performance by Ss with septo-hippocampal damage were not restricted to tasks that require alternation of spatial locations. This finding falsifies the notion that maze deficits reflect a spontaneous alternation deficit or changed "spatial strategy," but it supports the hypothesis of a working memory deficit in these Ss. (4 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Recovery of delayed alternation in rats after lesions in medial frontal cortex and septum.

Two experiments using contingently reinforced T-maze alternation with 48 male Long-Evans and hooded rats found that (a) normal Ss, after achieving high accuracy in alternation with brief (0 sec) intertrial intervals (ITIs), dropped to chance levels with longer ITIs (90 sec) but reacquired effective alternation with additional practice; (b) small lesions in mediodorsal pregenual cortex had no effect on postoperative retention of alternation at either short or long ITIs; (c) however, small lesions in posterodorsal septum temporarily disrupted alternation at brief ITIs, whereas at long ITIs Ss chose randomly and never recovered; and (d) large lesions in medial frontal cortex disrupted retention of alternation at brief ITIs of 10 sec but significant recovery did occur with additional experience. Implications regarding task difficulty and locus of lesion for recovery of function are discussed. (22 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Memory and septo-hippocampal connections in rats.

After receiving small lesions in the medial septal region or sham operations, 33 male hooded rats were tested for postoperative retention and transfer learning in a plus-shaped elevated maze. Only when the Ss worked on an alternation problem with start box reversals between sessions did performance depend on working memory. It was the working-memory conditions that sustained lesion-induced impairment on the tests of retention and transfer learning, and the lesion-induced behavioral impairment did not ameliorate during 4 additional training sessions. Performance on problems that could be solved by reference-memory mechanisms was not impaired by the lesions. Lesions were presumed to have severed a substantial number of connections comprising the major anterior input from the septum to the hippocampus but to have left intact much of the anterior hippocampal efferents. It is concluded that spatial cognitive mapping is dependent on a basic capability for working memory, which in turn depends on circuitry involving connections from septal region to hippocampus. (25 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)     

Effects of neonatal dopamine depletion on spatial ability during ontogeny.

Investigated the effects of neonatal dopamine (DA) depletion on spatial discrimination tasks. Ss were lesioned at 3 and 6 days of age with intraventricular 6-hydroxydopamine preceded by Desipramine. In Exp 1, Ss were tested before weaning for the ability to spontaneously alternate in a T maze both in the presence of their home cage shavings and with a screen covering the shavings. Lesioned Ss were significantly impaired in their ability to spontaneously alternate. Control and lesioned Ss both showed a decrease in performance when the screen prevented full access to the shavings and the magnitude of the impairment was significantly greater for the lesioned animals. In Exp 2, Ss were tested after weaning in an appetitively motivated task in T maze. The task required both a functional working and reference memory. Lesioned Ss were impaired on both the working and the reference components of the task; however, the magnitude of the impairment was greater in the working memory task. Results suggest that early lesions of general DA systems produce deficits in tasks requiring spatial alternation behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Spatial mapping, working memory, and the fimbria–fornix system.

13 Long-Evans male hooded rats with lesions severing either the subcallosal fornix (Fo) or the medial half of the fimbria (Fi) were compared with 9 control (Co) and sham-operated Ss in a working memory task (serial alternation) and a reference memory task (cue-guided alternation). Neither task required spatial mapping strategy. Findings indicate that damaging the Fi, but not the Fo, caused a severe deficit in the serial alternation task. Analysis of individual performance revealed that Fi Ss either adopted a "side strategy," resulting in chance performance, or actively repeated previous successful choices, resulting in worse than chance performance. This active perseveration required an intact working-memory mechanism. In the cue-guided alternation task, Fo Ss proved superior to Co and Fi Ss. Findings are inconsistent with notions that the exclusive role of the hippocampus is spatial mapping or storing of recent memories, and indicate differential involvement of the fimbria and fornix fibers in behavior. (39 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Memory deficits associated with senescence: A neurophysiological and behavioral study in the rat.

Neurophysiological and behavioral measures were obtained from 32 senescent (28–34 mo) and 32 mature adult (10–26 mo) Long-Evans hooded rats. Extracellularly recorded synaptic responses were obtained from electrodes chronically implanted in the fascia dentata and perforant path. Ss were first tested on a circular platform, which favored the use of spatial cues for its solution; the senescent Ss exhibited poorer memory for the rewarded place. When granule cell synaptic responses were recorded after a single session of very brief high-frequency stimulation, the amount of elevation and time course of decline were equivalent between age groups. After 3 repetitions, however, young Ss maintained the increased synaptic strength for at least 14 days, whereas old Ss declined after the 1st session. The amount of synaptic enhancement was statistically correlated with the ability to perform the circular platform task both within and between groups. Furthermore, the aftereffects of the high-frequency stimulation selectively impaired the old Ss' spontaneous alternation behavior on a –T maze. Results are discussed in terms of the synaptic theory of memory formation and the aging process. (78 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Locomotor, avoidance, and maze behavior in rats with selective disruption of hippocampal output.

Investigated behavioral correlates of selective disruption of hippocampal output in a series of 5 experiments. A total of 136 male albino Moll-Wistar rats were used as Ss. In 2 experiments an attempt was made through behavioral investigation to determine whether the CA1 neurons project to the fimbria or to the subiculum. Results support recent views that the subiculum is the recipient of CA1 axons. Disruption of the CA1 output in the dorsal hippocampus of Ss produced increased open-field activity, whereas passive avoidance and spontaneous alternation behaviors remained unchanged. No differentiation was obtained between CA1 damage and neocortical lesions in maze learning. Blocking of the fimbrial CA3 output from the dorsal hippocampus improved passive avoidance performance and impaired active avoidance performance, whereas open-field and spontaneous alternation behaviors were unaffected. Interruptions of the CA3 output from the ventral hippocampus improved active avoidance performance and reduced spontaneous alternation behavior. Open-field behavior and passive avoidance performance remained unchanged. Total fimbrial sections increased open-field activity, improved passive and active avoidance, and reduced spontaneous alternation. Results are discussed in terms of functional differentiation between the CA1 and CA3 of the dorsal hippocampus aknd in terms of functional in the fimbrial CA3 output from the dorsal and ventral hippocampus. (56 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of intracisternal 6-hydroxydopamine treatment on acquisition and performance of rats in a double T-maze.

136 male Sprague-Dawley rats in 4 experiments were subjected to various treatments with 6-hydroxydopamine (6-OHDA) to produce decrements in brain catecholamine content either before or after learning to respond in an appetitively motivated double –T maze task. Intracisternal injections of 6-OHDA not only impaired acquisition of the required behavioral response but also decreased performance of Ss which had previously acquired the task. Although reduced food consumption found in 6-OHDA-treated Ss may contribute to the observed deficits in –T maze responding, the behavioral deficit produced by 6-OHDA injection did not seem to be due only to a simple decrease in food intake. The decrements in acquisition and performance were clearly related to amount of central catecholamine depletion produced by 6-OHDA treatment. Further analysis suggested that the behavioral deficits were more related to the reductions in dopamine than they were to the depletion of brain norepinephrine. (33 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Delayed alternation in rats after pre- or postcommissural fornicotomy.

Investigated the contribution of the pre- and postcommissural fornices to short-term spatial memory in 15 male Long-Evans rats by evaluating the effect of small electrolytic lesions, located stereotaxically, with texts of reinforced alternation in a T-maze. Lesions in the postcommissural fornix were without behavioral effect. Ss with lesions that damaged the precommissural fornix were temporarily impaired in alternation with massed trials. They largely recovered their efficiency by the end of 5 postoperative sessions. Both the interpolation of irrelevant vestibular input (rotation) and lengthened intertrial intervals (1–4 min) reinstated an alternation deficit that had recovered in the massed-trial condition of testing. It is suggested that the recovery did not represent relearning to alternate but represented experience-dependent switching to parallel neural circuits that also mediate short-term spatial memory. (18 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Delayed alternation learning under electrical (blocking) stimulation of the caudate nucleus in the cat.

Of 9 young adult cats with electrodes implanted in the dorsolateral caudate nucleus, 4 had previously reached criterion on a delayed alternation task. Tested under alternating conditions of stimulation and nonstimulation, these 4 Ss showed a significant performance decline with stimulation. When a marker was placed on 1 response panel, performance under stimulation did not decline. Stimulation did not affect the learning of a visual discrimination. The remaining 5 Ss were trained on delayed alternation with alternating stimulation and nonstimulation conditions. Under stimulation, performance remained near chance levels. These Ss were tested on position learning and reversal, and under unilateral stimulation. Results support the view that the caudate nucleus and prefrontal cortex mediate separate aspects of delayed response behavior. (35 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Pilocarpine and physostigmine attenuate spatial memory impairments produced by lesions of the nucleus basalis magnocellularis.

Three experiments, with 63 male Long-Evans rats, investigated the effects of bilateral ibotenic acid-induced lesions of the nucleus basalis magnocellularis (NBM) on the acquisition and retention of several spatial memory tasks. Maintenance of spatial memory in a food-search task was impaired following NBM lesions. Acquisition of spontaneous alternation and reinforced alternation in a T-maze, but not the acquisition of a position habit, was also significantly impaired in Ss with these lesions. In several of the tasks, there was evidence of some learning in the lesioned Ss after substantial training, although they were significantly deficient when compared with controls. Intraperitoneal administration of the cholinergic agonists physostigmine sulfate (0.5 mg/kg) or pilocarpine nitrate (3 mg/kg) prior to behavioral testing resulted in a rapid and significant improvement in the performance of the lesioned Ss. Lesions significantly reduced the activity of choline acetyltransferase in the anterior and the posterior neocortex but not the hippocampus. Results indicate that the cholinergic projections originating in the NBM are involved in the learning and memory of spatial tasks. (48 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)     

Prelimbic cortex specific lesions disrupt delayed-variable response tasks in the rat.

The role of the prelimbic cortex (PL) in rats was investigated with excitotoxic lesions. PL lesions altered the alternation scores in spontaneous and reinforced spatial delayed-alternation tasks. PL lesions induced a delay in conditioning under a temporal go/no-go alternation schedule but not under a continuous food-reinforcement schedule in a runway. PL lesions had no effect on the acquisition of a standard radial-arm-maze task nor on a fixed-goal location task but disrupted the acquisition of a variable-goal location task in a radial-arm maze. The present results indicate that PL lesions replicated most of the behavioral deficits obtained with larger prefrontal lesions. PL lesions disrupted the acquisition of delayed-variable response tasks while leaving unaffected fixed-response tasks. These results are discussed in relation with a working-memory, a response-selection, and an attentional hypothesis. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hormonal influences during the ontogeny of maternal behavior in female rats.

Two experiments involving a total of 223 female and 46 male CD rats examined the influence of ovarian hormones on sensitization latencies at different periods in ontogeny and on the olfactory inhibition of maternal behavior, maternal nest building, and pup retrievals from a T-maze extension of the home cage. Ss ovariectomized before puberty failed to show a decline in sensitization latencies when tested 3.5 wks postoperatively; Ss ovariectomized during and after puberty had significantly longer latencies than sham operates when tested 8 or more weeks later. Interrupting olfaction by intranasal ZnSO? reduced latencies. Ovariectomized Ss built less compact maternal nests, and fewer retrieved pups from a –T maze than did sham operates. Estradiol benzoate prior to pup exposure significantly reduced sensitization latencies of ovariectomized Ss, increased the proportion retrieving pups from the maze, and tended to increase maternal nest ratings. Findings indicate that ovarian hormones, primarily estrogen, exert a tonic facilitatory influence on maternal responsiveness, beginning at puberty. (31 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Chemical senses involved in garter snake prey training.

Trained 8 garter snakes to follow earthworm-extract trails in a multiple-choice maze and then subjected them to either sham surgery or complete bilateral vomeronasal nerve transection. Ss with sham surgery trailed and ate at preoperative levels; Ss lacking a functional vomeronasal system developed a feeding deficit and trailed at chance levels. In Exp II 16 Ss were preoperatively tested for ability to follow a battery of trails including a range of trail concentrations and 2 trail manipulations. After baseline testing, 2 Ss were subjected to sham surgery, 7 to olfactory nerve transection, and 7 to vomeronasal nerve transection. Ss with vomeronasal nerve lesions demonstrated trailing and feeding deficits commensurate with the extent of nerve damage. Ss with olfactory nerve cut and sham surgery followed all trails at preoperative levels and maintained high tongue-flick rates when following stronger extract trails. Four Ss (2 with sham lesions, 1 with olfactory nerve lesion, and 1 with a partial vomeronasal nerve lesion) were tested with the vomeronasal ducts sutured closed. These Ss were unable to follow any trails at better than chance levels, but most continued to attack and ingest earthworm bits. Results suggest that garter snakes are heavily dependent on the vomeronasal system for following chemical prey trails. (43 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Correction to Thomas.

Reports an error in the article "Delayed Alternation in Rats After Pre- or Postcommissural Fornicotomy" by Garth J. Thomas (Journal of Comparative and Physiological Psychology, 1978, Vol. 92, No. 6, pp. 1128-1136), on p. 1128, line 3 in the abstract, "text" should read "test." On p. 1130, the right-hand column should begin as follows: "on a deprivation regimen of about 7 g of wet mash once a day." (This abstract originally appeared in the following article see record 1980-09224-001) Investigated the contribution of the pre- and postcommissural fornices to short-term spatial memory in 15 male Long-Evans rats by evaluating the effect of small electrolytic lesions, located stereotaxically, with texts of reinforced alternation in a T-maze. Lesions in the postcommissural fornix were without behavioral effect. Ss with lesions that damaged the precommissural fornix were temporarily impaired in alternation with massed trials. They largely recovered their efficiency by the end of 5 postoperative sessions. Both the interpolation of irrelevant vestibular input (rotation) and lengthened intertrial intervals (1-4 min) reinstated an alternation deficit that had recovered in the massed-trial condition of testing. It is suggested that the recovery did not represent relearning to alternate but represented experience-dependent switching to parallel neural circuits that also mediate short-term spatial memory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Acquisition of conditional associations and operant delayed spatial response alternation: Effects of lesions in the medial prefrontal cortex.

8 male rats received bilateral lesions of the medial prefrontal cortex, another 8 rats were control operated. Three weeks after surgery, they were exposed to an autoshaping procedure in which the insertion of a lever into the experimental chamber (conditioned stimulus) always preceded the delivery of a response-independent food pellet (unconditioned stimulus). Ss with lesions acquired this conditional association faster than control. Ss as evidenced by the fact that they were more likely than control Ss to contact the conditioned stimulus at higher rates. Locomotor activity, observed in a standard open-field preceding autoshaping sessions, decreased for both groups of Ss with repeated exposure to the open-field, whereas differences between groups were not observed. Ss were also exposed to an operant delayed spatial response alternation procedure in which they were required to alternate responding between two levers that were inserted into the experimental chamber after delay intervals of either 5, 10, or 20 s had elapsed. Alternation response accuracy of Ss with lesions and control Ss decreased as a function of the duration of the delay interval, but control-operated Ss responded more accurately at each interval duration. Response accuracy increased with prolonged training for both groups of Ss, but faster for control than for Ss with lesions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)