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Raymond P Kesner

Publications and source records attributed to Raymond P Kesner.

At least 37 records · Page 2Linked to original sources
PubMed2004

Differential contributions of dorsal hippocampal subregions to memory acquisition and retrieval in contextual fear-conditioning.

The hippocampus is an essential neural structure in developing contextual memory in a situation in which rapid development of associative learning should occur. We tested a subregion-specific contribution in the hippocampus to memory acquisition and retrieval, using the contextual fear-conditioning paradigm. The current results suggest that all three subregions (i.e., CA3, CA1, and dentate gyrus) of the hippocampus contribute to rapid acquisition of contextual memory in the initial phase of acquisition. The involvement of CA3 seems to be important at the earliest stage of acquisition, presumably for developing instant representation of a context. The role of CA3, however, was minimal in retrieving contextual memory after a long time period (i.e., 24 h), whereas the other subregions (i.e., CA1 and dentate gyrus) were critically involved. The results indicate time-dependent differential contributions of the hippocampal subregions to memory acquisition and retrieval in contextual fear-conditioning.

Animals↗
PubMed2004

Sequences assessed by declarative and procedural tests of memory in amnesic patients with hippocampal damage.

Previous research indicates that amnesic subjects tested on sequential learning or serial reaction time tasks can learn a repeated procedural sequence but are unable to explicitly recall the correct sequence when asked to generate the sequence. Rats with hippocampal lesions are also able to learn and remember procedural or implicit sequences but were impaired for declarative sequences. We used analogous procedures used in rats to assess the role of the hippocampus in the acquisition of declarative and procedural sequences in amnesic and control participants. Amnesic participants with damage restricted to the hippocampus and control participants were administered analogous tasks of declarative and procedural sequential learning using a computer version of the radial arm maze. The amnesic participants had slower response times during the acquisition of procedural sequences, but were not impaired compared to controls when switched to a random sequence, suggesting that both groups learned the sequence. Alternatively, the amnesic but not control participants were significantly impaired in the declarative sequence task. Our findings provide support for evolutionary continuity in cognitive function of the hippocampus in rats and humans and the dissociation between the declarative and procedural sequential learning. The performance differences on the two sequence learning tasks are likely due to the use of different strategies associated with learning sequences based on procedural versus declarative knowledge.

Adult↗
PubMed2004

An analysis of independence and interactions of brain substrates that subserve multiple attributes, memory systems, and underlying processes.

It is proposed that memory is organized into event-based, knowledge-based, and rule-based memory systems. Furthermore, each system is composed of the same set of multiple attributes and characterized by a set of process oriented operating characteristics that are mapped onto multiple neural regions and interconnected neural circuits. Based on this theoretical model of memory, it is possible to investigate the independence and interaction among brain regions between any two systems for any of the proposed attributes or processes. This applies also to the investigation of independence and interactions between any two attributes within a system and between processes associated with a system for any of the proposed attributes. In this article, research evidence is presented to suggest that there are both dissociations and interactions between the hippocampus and caudate nucleus in mediating spatial and response attributes within the event-based memory system, between the hippocampus and the parietal cortex in subserving the spatial attribute within the event-based and knowledge-based memory systems, and between the hippocampus and the prefrontal cortex in subserving the spatial attribute within the event-based and rule-based memory systems.

Animals↗
PubMed2004

Memory for objects and their locations: the role of the hippocampus in retention of object-place associations.

Computational models of hippocampal function have suggested that the hippocampus is involved in the formation and storage of arbitrary associations. Previous studies have shown that rats with hippocampal lesions are impaired in object-place associative learning. However, few studies have examined the role of the hippocampus in the retention of previously learned arbitrary associations. In the present study, male Long-Evans rats with either cortical control or hippocampal lesions were tested on a task measuring the retention of previously learned arbitrary associations using an object-place paired-associate task. To assess retention, each animal was trained on the paired-associate task for 360 trials, then received a lesion, and was retested to examine retention of the previously learned associations. The results indicate that all rats learned the task prior to surgery. Following surgery, rats with cortical control lesions were not impaired in the retention of object-place associations. In contrast, hippocampal lesions resulted in an initial deficit in retention of the paired-associate task followed by recovery. Therefore, the hippocampus may play a role in the retrieval of previously learned arbitrary association.

Animals↗
PubMed2004

Effects of hippocampus and medial caudate nucleus lesions on memory for direction information in rats.

A delayed matching-to-sample task was designed to assess memory for direction information in rats. During the study phase, rats traversed a maze arm oriented in 1 of 3 directions. After a delay period, a test phase was presented that required a choice between the study phase direction and a foil direction. Once rats reached a learning criterion, probe trials suggested that normal rats favor the use of direction, rather than turning response, information and use vestibular feedback. Rats were then given hippocampus, medial caudate nucleus (MCN), or cortical control lesions. Unlike control rats, those with hippocampus and MCN lesions exhibited marked impairments when retested. However, all rats were able to learn a direction discrimination task. These results suggest that the hippocampus and MCN support processes associated with short-term memory for direction information.

Animals↗
PubMed2004

A behavioral assessment of hippocampal function based on a subregional analysis.

The purpose of this review is to determine whether specific subregions (dentate gyrus [DG], CA3, and CA1) of the hippocampus provide unique contributions to specific processes associated with intrinsic information processing exemplified by novelty detection, encoding, pattern separation, pattern association, pattern completion, retrieval, short-term memory and intermediate-term memory. Based on anatomical neural network organization, electrophysiology of cellular activity, lesions, early gene activation, and computational modeling, it can be shown that there exists extensive cooperation among the three subregions of the hippocampus, but there also exists reliable specificity of function for each of the subregions of the hippocampus. The primary process supported by the DG subregion of the hippocampus can be characterized by orthogonalization of sensory inputs to create a metric spatial representation. Furthermore the DG participates in conjunction with CA3 in supporting spatial pattern separation. The CA3 subregion of the hippocampus supports processes associated with spatial pattern association, spatial pattern completion, novelty detection, and short-term memory. The CA1 subregion of the hippocampus supports processes associated with temporal pattern association, temporal pattern completion, and intermediate-term memory. Furthermore, the CA3 in conjunction with CA1 supports temporal pattern separation. All the above-mentioned processes are assumed to reflect intrinsic processing of information within the hippocampus. The diversity of functions associated with the different subregions of the hippocampus suggests that one should not treat the hippocampus as a single entity, but rather that one should concentrate on elucidating further the functions of both dorsal and ventral subregions of the hippocampus and pathways that directly connect each of the subregions as well as their connections with the entorhinal cortex.

Animals↗
PubMed2003

The role of the prefrontal cortex in object-place learning: a test of the attribute specificity model.

In order to test an attribute specificity model of prefrontal cortex function, rats with lesions in the prelimbic-infralimbic (PL-IL) or anterior cingulate and precentral (AC-PC) subregions of the medial prefrontal cortex and controls were trained on an object-place paired associate task. Rats with AC-PC lesions acquired the task as readily as controls. In contrast, the PL-IL lesioned rats did not learn the task. Whenever higher order processing is required to solve a task, the data support an attribute-specificity model of prefrontal cortex function in that the PL-IL cortices support both object and place attribute information in a variety of tasks including object-place paired associate learning.

Animals↗
PubMed2003

Time-dependent relationship between the dorsal hippocampus and the prefrontal cortex in spatial memory.

The prefrontal cortex and the dorsal hippocampus have been studied extensively for their significant roles in spatial working memory. A possible time-dependent functional relationship between the prefrontal cortex and the dorsal hippocampus in spatial working memory was tested. A combined lesion and pharmacological inactivation technique targeting both the dorsal hippocampus and the medial prefrontal cortex was used (i.e., axon-sparing lesions of the dorsal hippocampus combined with reversible inactivation of the medial prefrontal cortex, or vice versa, within a subject). A delayed nonmatching-to-place task on a radial eight-arm maze with short-term (i.e., 10 sec) versus intermediate-term (i.e., 5 min) delays was used as a behavioral paradigm. Here we report that the dorsal hippocampus and the medial prefrontal cortex process short-term spatial memory in parallel, serving as a compensatory mechanism for each other. The role of the dorsal hippocampus, however, becomes highlighted as the time-window for memory (i.e., delay) shifts from short-term to a delay period (i.e., intermediate-term) exceeding the short-term range. The results indicate that the time window of memory is a key factor in dissociating multiple memory systems.

Animals↗
PubMed2003

Recognition memory for hand positions and spatial locations in patients with Huntington's disease: differential visuospatial memory impairment?

Allocentric and egocentric memory was investigated in patients with Huntington's disease (HD) and matched controls. Patients with HD and age- and education-matched healthy normal controls (NC) were administered two visuospatial recognition memory tasks, one assessing memory for hand positions (egocentric) and the other assessing memory for spatial locations (allocentric). HD patients showed normal primacy and recency effects, but their overall performance was impaired relative to controls on both tasks. Correlation analyses indicated that HD patients' performance on the Hand Position Memory task, but not the Spatial Location Memory task, was associated with global cognitive status (Mattis Dementia Rating Scale) and disease severity (Shoulson and Fahn Rating Scale), and HD patients' performances on the two tasks were not associated. Results provide preliminary support for the role of the caudate nucleus in both allocentric and egocentric spatial memory.

Adolescent↗
PubMed2003

The role of the amygdala in conditioned flavor preference.

Long-Evans rats with control or amygdala lesions were tested in a conditioned flavor preference task. Half of the rats in each lesion group received an unsweetened grape-flavored solution on odd-numbered days and a sweetened cherry-flavored solution on even-numbered days. The remaining rats received a sweetened grape-flavored solution on odd-numbered days and an unsweetened cherry-flavored solution on even-numbered days. The appropriate solution was presented once a day for 15 min to each rat in the homecage. After six days of testing, each rat received unsweetened cherry and grape flavored solutions simultaneously for 15 min daily across four days. When the two unsweetened flavored solutions were presented simultaneously control rats showed a significant preference for the flavor that was sweetened during training compared to the unsweetened solution. However, amygdala-lesioned rats did not show a preference. The data suggest that the amygdala may be critically involved in mediating reward-based conditioned flavor preference.

Amygdala↗
PubMed2003

Cholinergic modulation of the hippocampus during encoding and retrieval.

The present experiments were aimed at determining whether acetylcholine (ACh) plays a role in encoding and retrieval of spatial information using a modified Hebb-Williams maze. In addition, the present experiments tested two computational models of hippocampal function during encoding and retrieval using a maze sensitive to hippocampal disruption. Thirty male, Long-Evans rats served as subjects. Chronic cannulae were implanted bilaterally into the CA3 (n=26) and CA1 (n=5) subregions of the hippocampus. Rats were tested using a modified Hebb-Williams maze. In the first experiment, rats were injected with either saline or scopolamine hydrobromide 10 min before testing for each day. The number of errors made per day per group was used as the measure of learning. Encoding was assessed by the average number of errors made on the first five trials of Day 1 compared to the last five trials of Day 1, whereas the average number of errors made on the first five trials of Day 2 compared to the last five trials of Day I was used to assess retrieval. No deficit was found for the saline group. The scopolamine group showed a deficit in encoding, but not retrieval. In the second experiment, rats were injected with either saline or physostigmine 10 min before testing each day. In contrast to the scopolamine groups, the physostigmine group showed a deficit in retrieval, but not encoding. To test whether the retrieval deficit was due to a disruption in storage or gaining access to the information two groups of rats received either saline on Day 1 and physostigmine on Day 2 or physostigmine on Day 1 and saline on Day 2. In addition, one group received physostigmine immediately after testing on Day 1. Data indicate that physostigmine causes a disruption of retrieval by means of a disruption in consolidation process. In conclusion, the cholinergic antagonist, scopolamine, disrupts encoding in both CA3 and CA1 subregions of the hippocampus. Furthermore, the cholinesterase inhibitor, physostigmine, boosts ACh action during a time when cholinergic levels need to decline for proper consolidation.

Animals↗
PubMed2003

Differential roles of dorsal hippocampal subregions in spatial working memory with short versus intermediate delay.

In order to determine the role of subregions of the hippocampus in spatial working memory, this study combined selective neurotoxic lesions of the hippocampal subregions with a simple delayed nonmatching-to-place task on a radial maze in rats. Lesions of the dentate gyrus or the CA3, but not the CA1, subregion of the hippocampus induced a deficit in the acquisition of the task with short-term delays (i.e., 10 sec) and impaired performance of the task in a novel environment. All subregional lesions produced sustained impairment in performing the task with intermediate-term delays (i.e., 5 min) when rats were tested in a familiar environment. The results suggest a dynamic interaction among the dorsal hippocampal subregions in processing spatial working memory, with the time window (i.e., delay) of a task recognized as an essential controlling factor.

Animals↗
PubMed2003

Localization of function within the dorsal hippocampus: the role of the CA3 subregion in paired-associate learning.

Computational models and electrophysiological data suggest that the CA3 subregion of the hippocampus supports the formation of arbitrary associations; however, no behavioral studies have been conducted to test this hypothesis. Rats with neurotoxin-induced lesions of dorsal dentate gyrus (DG), CA3, or CA1 were tested on object-place and odor-place paired-associate tasks to test whether the mechanism that supports paired-associate learning is localized to the CA3 subregion of the dorsal hippocampus or whether all hippocampal subregions contribute to paired-associate learning. The data indicate that rats with DG or CA1 lesions learned the tasks as well as controls; however, CA3-lesioned rats were impaired in learning the tasks. Thus, the CA3 subregion of the dorsal hippocampus contains a mechanism to support paired-associate learning.

Animals↗
PubMed2002

The effects of prelimbic and infralimbic lesions on working memory for visual objects in rats.

The present experiment investigated the effects of quinolinic acid (90 mM) lesions of the prelimbic-infralimbic cortices on working memory for visual objects and on acquisition of a visual object discrimination. In both tests a GO/NO-GO procedure was used. In the working memory task, rats were tested before and after surgery. A continuous recognition procedure was used to assess working memory, which involved successive exposure to different three-dimensional objects that could be displaced to receive a cereal reinforcement. Of the 12 object presentations/session, 4 objects were presented for a second time in which displacing the object did not result in a reinforcement. The number of trials between the first and second presentations of an object ranged from 0 to 3 (lags). Memory was assessed by the latency to displace an object during the second presentation. In the visual object discrimination, rats had successive exposure to two different objects. Displacement of one object resulted in a cereal reinforcement, while displacement of the other did not. The findings indicated that prelimbic-infralimbic lesions significantly impaired memory for visual objects across all lags. Prelimbic-infralimbic lesions did not impair acquisition of the visual object discrimination. The results suggest that the prelimbic-infralimbic areas are part of neural system important in the short-term memory for visual objects.

Animals↗
PubMed2002

The amygdala but not the hippocampus is involved in pattern separation based on reward value.

A total of 32 male Long-Evans rats were tested on a modified version of Flaherty, Turovsky, and Krauss's (1994) anticipatory contrast paradigm to assess pattern separation for reward value. Prior to testing, each rat received either a control, a hippocampal, or an amygdala lesion. In the home cage, each rat was allowed to drink a water solution containing 2% sucrose for 3 min followed by a water solution containing 32% sucrose for 3 min. Across 10 days of testing, the rats in each lesion group showed significantly increased anticipatory discriminability as a function of days. To assess the operation of a pattern separation mechanism, each rat was then tested using the same procedure except the 2% solution was followed by a 16% solution for 10 days and then by an 8% solution for 10 days. Control and hippocampal-lesioned rats continued to show high discriminability when the 2% solution was followed by a 16% solution; however, the amygdala-lesioned rats showed low anticipatory discriminability. On trials where the 2% sucrose solution was followed by an 8% sucrose solution, all groups showed low discriminability scores, suggesting that when two reward values are very similar even control animals are not able to separate the reward values in memory. However, the results of a preference task revealed that all groups can perceptually discriminate between a 2% and an 8% sucrose solution. The data suggest that the amygdala but not the hippocampus is involved in the separation of patterns based on reward value.

Amygdala↗
PubMed2002

Role of the dorsomedial striatum in behavioral flexibility for response and visual cue discrimination learning.

These experiments examined the effects of dorsomedial striatal inactivation on the acquisition of a response and visual cue discrimination task, as well as a shift from a response to a visual cue discrimination, and vice versa. In Experiment 1, rats were tested on the response discrimination task followed by the visual cue discrimination task. In Experiment 2, the testing order was reversed. Infusions of 2% tetracaine did not impair acquisition of the response or visual cue discrimination but impaired performance when shifting from a response to a visual cue discrimination, and vice versa. Analysis of the errors revealed that the deficit was not due to perseveration of the previously learned strategy, but to an inability to maintain the new strategy. These results contrast with findings indicating that prelimbic inactivation impairs behavioral flexibility due to perseveration of a previously learned strategy. Thus, specific circuits in the prefrontal cortex and striatum may interact to enable behavioral flexibility, but each region may contribute to distinct processes that facilitate strategy switching.

Animals↗
PubMed2002

Role of the rodent hippocampus in paired-associate learning involving associations between a stimulus and a spatial location.

The ability of rats with control or hippocampal lesions to learn an object-place, odor-place, or object-odor paired-associate task was assessed in a cheeseboard maze apparatus. The data indicate that rats with hippocampal lesions were significantly impaired, compared with controls, in learning both the object-place and the odor-place paired-associate tasks. However, rats with hippocampal lesions learned the object-odor paired-associate task as readily as did controls. The data suggest that the rodent hippocampus is involved in paired-associate learning when a stimulus must be associated with a spatial location. However, the hippocampus is not involved in paired-associate learning when the association does not involve a spatial component.

Animals↗