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Biomedical subjects

R P Kesner

Publications and source records attributed to R P Kesner.

At least 37 records · Page 2Linked to original sources
PubMed1998

Differential involvement of the dorsal anterior cingulate and prelimbic-infralimbic areas of the rodent prefrontal cortex in spatial working memory.

The present study examined the effects of quinolinic acid lesions of the dorsal anterior cingulate and prelimbic-infralimbic cortices on spatial working memory and spatial discrimination using go/no-go procedures. All testing occurred in a 12-arm radial maze. In a working memory task, rats were allowed to enter 12 arms for a cereal reward. Three or 4 arms were presented for a 2nd time in a session, which did not result in a reward. In a spatial discrimination task, rats had successive access to 2 different arms. One arm always contained a reward, and the other never contained a reward. Prelimbic-infralimbic lesions impaired spatial working memory but only produced a transient spatial discrimination deficit. Dorsal anterior cingulate lesions did not induce a deficit in either task. These findings suggest that the prelimbic-infralimbic cortices, but not the anterior cingulate cortex, are important in spatial working memory.

Analysis of Variance↗
PubMed1998

Effects of hippocampal and parietal cortex lesions on memory for egocentric distance and spatial location information in rats.

To assess the working memory system for egocentric distance and place information, delayed matching-to-sample (DMTS) go/no-go tasks were run for each rat. To assess the reference memory system, and to serve as a control for nonmemory deficits, successive discrimination go/no-go tasks were then conducted using the same rats. Rats with hippocampal, but not parietal cortex, lesions were impaired relative to controls in the working memory (DMTS) task for both egocentric distance and place information, although the deficit observed in the working memory task for egocentric distance information by rats with hippocampal lesions was mild. Neither hippocampal nor parietal cortex lesioned rats were impaired relative to controls in the reference memory (successive discrimination) task for either cue. The hippocampus appears to be involved in working memory for egocentric distance and in spatial location information, whereas the parietal cortex is not.

Analysis of Variance↗
PubMed1997

Intrahippocampal injections of phencyclidine but not naloxone disrupt acquisition of a spatial continuous recognition memory task.

Rats with 36 nM or 54 nM of phencyclidine (PCP), 36 nM of naloxone or saline injected into the dentate gyrus of the hippocampus were tested for acquisition of a spatial continuous recognition memory task. Results indicate that relative to controls and rats with 36 nM of PCP or 36 nM of naloxone injections, rats with 54 nM of PCP injections were impaired in acquisition of the task across all lags as measured by increased in latency for repeated items. Since it is assumed that successful learning of this continuous recognition memory task depends upon processes associated with consolidation of new learning into long term memory, it appears that high doses of PCP, but not naloxone are sufficient to impair this process.

Animals↗
PubMed1997

Short-term memory for food reward magnitude: the role of the prefrontal cortex.

Memory for magnitude of reinforcement was assessed in rats using a go/no-go short-term memory paradigm. During the task's study phase rats were given a piece of cereal comprised of either 25 or 50% sugar. For all trials, one of the cereal types was designated positive, the other negative. On the ensuing test phase the rat was presented with an object which covered a food well. If a positive food reward was given during the study phase, a second food reward was placed beneath the object. No food reward was placed under the object if the study phase consisted of a negative food reward. Latency to object displacement was used as the measure of performance. Following the establishment of a significant difference between latency to approach the object with reward compared to latency to approach the object without reward, rats were given either agranular insular cortex, anterior cingulate cortex, pre- and infralimbic cortex or control lesions. Agranular insular cortex lesioned animals demonstrated a mild post-surgery impairment. Trials consisting of 10 and 20 s delays between the study and test phases were then introduced. Delays exacerbated the previous deficit of the agranular insular cortex lesion group, but had little effect on the other lesion groups. All animals transferred to a new set of cereals containing 25 and 50% sugar and exhibited taste preferences to sugar solutions of different concentrations. These results indicate that the agranular insular cortex may play an important role in the processing of affect-laden information within a prefrontal cortex short-term or working memory system.

Animals↗
PubMed1997

Impaired place learning and unimpaired cue learning in hippocampal-lesioned pigeons.

Hippocampal processing is often crucial for normal spatial learning and memory in both birds and mammals, suggesting a general similarity in avian and mammalian hippocampal function. However, few studies using birds have examined the effect of hippocampal lesions on spatial tasks analogous to those typically used with mammals. Therefore, we examined how hippocampal lesions would affect the performance of pigeons in a dry version of the water maze. Experiment 1 showed that hippocampal-lesioned birds were impaired in acquiring the location of hidden food in the maze. Experiment 2 showed that hippocampal-lesioned birds were not impaired when a single cue indicated the location of hidden food. These results support the notion that avian and mammalian hippocampal functions are quite similar, in terms of the tasks for which their processing is crucial and the tasks for which it is not.

Animals↗
PubMed1997

Comparison of temporal order memory in early and middle stage Alzheimer's disease.

Four tests, each including a new learning and a prior learning component were developed to investigate temporal order memory in subjects with early and middle stage Alzheimer's disease (AD). For newly learned information, both AD groups performed worse than controls but did not differ from each other. For previously learned information, the subjects with AD performed worse than controls. The early AD group performed better than the middle AD group. It appears then, that progression of the disease is associated with decreased access to knowledge systems.

Aged↗
PubMed1996

Involvement of entorhinal cortex or parietal cortex in long-term spatial discrimination memory in rats: retrograde amnesia.

Twenty-four rats assigned to 1 of 3 matched groups (control, entorhinal cortex [EC], and parietal cortex [PC]) were trained on 6 successive discrimination problems (2 in an 8-arm for pretraining and 4 in a 12-arm radial maze for training per se). The training on the 12-arm maze started 6, 4, 2, and 0.5 weeks before surgery. On the day after the rats learned the last problem, they were given surgery according to groups. Postoperative retention was measured by presenting 16 trials per session for each of the problems during 4 sessions. Results indicate that the EC lesions produced a retention deficit for problems learned immediately and up to 4 weeks before surgery, but not for the problem acquired 6 weeks before the lesions. The PC lesions produced a significant retrograde amnesia that was not temporally graded. Results demonstrate that the EC and PC make important, albeit distinct, contributions to spatial memory storage and retrieval in rats.

Amnesia, Retrograde↗
PubMed1996

The effects of dorsal versus ventral hippocampal, total hippocampal, and parietal cortex lesions on memory for allocentric distance in rats.

To test for the contribution of the parietal cortex and hippocampus to memory for allocentric spatial cues, the authors trained rats on a go/no-go task that required the rat to remember the distance between two visual cues. Total hippocampal lesions impaired working-memory representation for allocentric distance, whereas parietal cortex lesions resulted in only a transient impairment. In a second experiment, neither hippocampal nor parietal cortex lesions impaired allocentric distance discrimination. A third experiment showed that both the dorsal and ventral areas of the hippocampal formation must be destroyed to impair working memory for allocentric distance information. There appears to be a dissociation between the hippocampus and parietal cortex in mediating memory for allocentric distance information.

Animals↗
PubMed1995

Item and order recognition memory in subjects with hypoxic brain injury.

Subjects with hypoxic brain injury resulting in significant cell loss in the hippocampus but not the parahippocampal gyrus or temporal lobes and normal control subjects were tested for memory impairments. The Denman Memory Scale was given to all subjects as a baseline memory assessment. All subjects were then tested for item and order recognition memory for lists of six words, pictures, abstract pictures, spatial locations, and motor responses. Results indicated that hypoxic subjects are impaired compared to control subjects on the Denman memory scale for verbal, non-verbal, and full-scale memory quotients. In addition, results indicated that compared to control subjects, hypoxic subjects displayed item and order recognition deficits for words, pictures, abstract pictures, and spatial locations. A recency effect for item recognition of abstract pictures, spatial locations, and hand positions was found. For motor response order recognition, both primacy and recency effects were found, with deficits in performance for the middle items of the list. It appears that subjects with hypoxic brain injury in the face of severe memory deficits for words, pictures, abstract pictures, and spatial locations display residual capacity for remembering the last items for spatial locations, abstract designs, and hand positions. Hypoxic subjects also display residual capacity for remembering motor responses using episodic or data-based memory.

Adult↗
PubMed1995

Memory for magnitude of reinforcement: dissociation between the amygdala and hippocampus.

Rats were trained on a successive delayed conditional discrimination task measuring memory for magnitude of reinforcement. In the study phase of the task, the rats were given one of two cereals. One cereal contained 25% sugar; the other 50% sugar. One of the two cereals was always designated the positive stimulus and the other the negative stimulus. This study phase was followed by the test phase in which the rat was shown an object which covered a food well. If the rat was given the negative stimulus in the study phase of the trial, no food reward was placed beneath the object. Whenever the positive stimulus was presented a food reward was available beneath the object. Performance was measured as the latency to uncover the food well. After reaching criterion level, the rats were given amygdala, hippocampal, or control lesions. Amygdala-lesioned rats showed significant deficits in performance, whereas no long-term deficits were observed for the hippocampal-lesioned groups even at longer retention delays. In additional experiments, it was shown that amygdala-lesioned, like normal, rats had similar taste preferences. Finally, normal and hippocampal-, but not amygdala-, lesioned rats transferred readily to different cereals containing 25% or 50% sugar. Thus, it appears that the amygdala, but not the hippocampus, plays a significant role in explicit data-based or working memory for affect information based on magnitude of reinforcement.

Affect↗
PubMed1995

Phencyclidine injections into the dorsal hippocampus disrupt long- but not short-term memory within a spatial learning task.

Since the hippocampus is likely to be a major site of phencyclidine (PCP) action, the effects of various doses of PCP (1.8, 18 or 36 nM) as well as 3.6 nM MK-801 or saline injected directly into the dentate gyrus of the hippocampus was tested for acquisition of a spatial navigation task (dry land version of a water maze) using a paradigm that assesses short term memory based on learning within a day and long term memory based on learning between days. Results indicated that relative to saline or 1.8 nM PCP injected rats, rats with 18 or 36 nM PCP or 3.6 nM MK-801 injections were impaired in acquisition of the task as measured by increased distances traveled to find the food location between days but not within days. In additional experiments 36 nM PCP or 3.6 nM MK-801 did not produce any deficits in the acquisition of an object discrimination task. It is suggested that PCP through its blocking action of the NMDA receptor in the dentate gyrus or CA1 region of the dorsal hippocampus mediates the consolidation of new spatial location information.

Animals↗
PubMed1995

Spatial recognition memory deficits without notable CNS pathology in rats following herpes simplex encephalitis.

Survivors of herpes simplex encephalitis (HSE) experience intellectual impairment and an inability to store and recall information. Because the temporal lobes and associated limbic structures are central to storage and retrieval of memories, and are predominantly affected in adult HSE, injury to these areas is postulated to cause behavioral and learning disabilities. A previous study (Beers et al., 1993) demonstrated that intranasal inoculation of Lewis rats with herpes simplex virus type-1 (HSV-1) induced acute partial complex seizures, and hemorrhagic and inflammatory lesions of the hippocampus and entorhinal cortex. Consequently, it was of interest to determine whether rats that had recovered from HSE had limbic system-associated memory impairments. Therefore, rats were evaluated when signs and symptoms of encephalitis were no longer apparent using an eight arm radial maze to assess the acquisition and retention of learned information. An allocentric-spatial location paradigm revealed HSV-1 infected rats performed at chance levels on both acquisition and retention which were statistically different from sham-inoculated controls. However, using an egocentric-spatial left/right discrimination task, infected rats performed statistically similar to sham-inoculated controls. Furthermore, HSV-1 nucleic acids were detected in the nuclei of neurons within the hippocampus and entorhinal cortex using in situ hybridization techniques. Of interest was the observation that rats with learning and memory deficits had no apparent histopathological or immunocytochemical evidence of antecedent CNS infection. This is the first experimental demonstration that HSV-1 can cause behavioral impairments in the absence of obvious inflammatory injury to the temporal lobe memory system.

Animals↗
PubMed1995

Effects of ibogaine on sensory-motor function, activity, and spatial learning in rats.

Ibogaine, a naturally occurring alkaloid, has been show to reduce naloxone-precipitated withdrawal symptoms from morphine. Given the clinical possibilities, it is important to determine ibogaine's effects on sensory-motor function, activity, learning, and memory. Long-Evans rats injected with doses of 20-60 mg/kg of ibogaine displayed slower response times on sensory and sensory-motor tests and were impaired in performing specific motor reflexes at doses of 40-60 mg/kg. Furthermore, these rats showed a marked reduction in locomotor and nonlocomotor activity, as well as emotionality at doses ranging from 10-40 mg/kg. At the higher doses the rats appeared to be virtually inactive. There were also deficits in learning a spatial location task (a dry-land version of the Morris water-maze). The deficits, however, were probably due to a reduction in locomotor activity and reduction in detection of sensory information. In a final experiment, a single injection of 40 mg/kg of ibogaine had marked deleterious effects on the acquisition of the spatial location task 1 but not 7 days after the injection, even though in this case there were no effects on sensory motor function 1 or 7 days after the injection. Thus, there are severe sensory-motor activity and learning problems while the animal is under the influence of ibogaine (acute effect) as well as long-term consequences on learning without concomitant changes in sensory-motor function.

Animals↗
PubMed1995

Phencyclidine impairs temporal order memory for spatial locations in rats.

The effects of phencyclidine (PCP), an NMDA antagonist, was assessed on a complex task that has been shown to be dependent on hippocampal function. This task required memory for the temporal order of spatial locations. Rats were given IP injections of saline or PCP (3-4 mg/kg) on a double alternation schedule. With PCP injections rats were severely impaired relative to saline injections. Furthermore, PCP was shown to have no effects on the ability of rats to discriminate three-dimensional objects (a task that is not dependent on hippocampal function). The present data, in conjunction with previous results, suggest that the involvement of NMDA receptors in the hippocampus might be a function of the complexity of the task.

Animals↗
PubMed1995

Relational object association learning in rats with hippocampal lesions.

The contribution of the hippocampus to relational association learning was examined using a paired associate task in the rat. Using a go/no-go paradigm, rats were trained to respond quickly on positive pair presentations, and to withhold responding on negative pair presentations. Using four constant three-dimensional objects (A, B, C and D), pairing of either AB or CD was assigned as positive pairs, whereas the other possible object combinations (AC, DB, AD, and CB) were never associated with reinforcement. A further type of negative pair trial was also studied which involved object-pairs composed of one of the four constant objects and another object, which varied from trial, and which was selected from a set of 120 junk objects. Electrolytic lesions of the hippocampus were performed on the rats which had previously acquired the paired associate task. Results indicated that hippocampal lesions did not significantly impair the ability of the animals to solve the paired associate task. To study further the exact nature of the learned associations, a transfer test which involved a reversal of the spatial position within each of the six positive as well as negative pair-types was conducted. Results of the transfer test demonstrated that hippocampal-lesioned as well as control rats performed normally by distinguishing the positive from negative pairs regardless of the relative location of stimuli within the object pairs. These data suggest that the hippocampus might not be critical for relational object associations.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Memory for novel and familiar spatial and linguistic temporal distance information in hypoxic subjects.

Hypoxia is known to cause damage to the hippocampus as well as memory impairments in humans. Subjects who have experienced a hypoxic episode and age-, gender-, and education-matched control subjects were tested for memory for spatial and linguistic temporal distance information using sentences and spatial locations. Each test contained a familiar component based on information that is meaningful and is thought to be stored as part of the knowledge system (prior knowledge) as well as a novel component based on new information. Subjects were presented a list of eight-word sentences or eight spatial locations (Xs) on a grid on a Macintosh computer and tested for memory for temporal distances. Temporal distance is defined as the number of items that occur between the two test items, in the study phase. Compared to control subjects, hypoxic subjects were impaired across all temporal distances on the novel spatial and linguistic tasks. As the temporal distance increased, hypoxic subjects showed some improvement in memory performance. In addition, memory of familiar temporal distance information was also assessed. Hypoxic subjects were impaired, compared to control subjects, for familiar temporal distance information. For hypoxic subjects there was a proportionally greater impairment for novel compared to familiar spatial and linguistic temporal distance information. There was a significant difference in their performance on the familiar temporal distance tasks compared to their performance on the novel tasks. Prior knowledge appears to attenuate the deficits seen in the familiar temporal distance tasks. It appears that hypoxia may cause more selective damage to the hippocampus and this damage is sufficient to produce profound memory impairments for primarily novel and less severe memory impairments for familiar spatial and linguistic temporal distance information.

Adult↗
PubMed1995

The temporal-distance effect in subjects with dementia of the Alzheimer type.

The efficacy of temporal-distance processing for spatial locations was evaluated in college students, elderly controls, and subjects with mild and moderate dementia of the Alzheimer type (DAT). The elderly controls showed a slightly lower level of performance than college students, but both elderly controls and college students displayed a temporal-distance effect. The mild DAT subjects performed the task accurately only at the greatest temporal distances. The moderate DAT subjects performed at chance levels for all distances. Because similar changes in the temporal-distance function have been described for humans and animals with small hippocampal or prefrontal cortex damage, there might be important hippocampal or prefrontal cortex involvement or both in early stages of Alzheimer disease.

Adult↗