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Biomedical subjects

H Eichenbaum

Publications and source records attributed to H Eichenbaum.

84 records · Page 5Linked to original sources
PubMed1980

Thalamocortical mechanisms in odor-guided behavior. I. Effects of lesions of the mediodorsal thalamic nucleus and frontal cortex on olfactory discrimination in the rat.

The "core" subnucleus of the mediodorsal thalamic nucleus (MD) receives direct input from olfactory cortex in the rat. This part of MD projects to the frontal neocortex of the rhinal sulcus (RS), while other parts of the MD project to the anterior medial wall of the neocortex (MW). In this study, rats were tested on odor threshold, detection of specific odors, and three odor discriminations both before and after lesions of MD, MW, RS, or sham lesions. Olfactory threshold and detection ability remained unaffected by any of these lesions; however, subjects with MD and RS lesions were markedly impaired on odor discriminations. Furthermore, subjects were more profoundly impaired when the stimuli to be discriminated were novel or difficult to associate. Thus, MD and its "olfactory" projection target, RS, seem to mediate cognitive, rather than sensory aspects of odor-guided behavior in the rat.

Animals↗
PubMed1980

Thalamocortical mechanisms in odor-guided behavior. II. Effects of lesions of the mediodorsal thalamic nucleus and frontal cortex on odor preferences and sexual behavior in the hamster.

The role of the thalamocortical "olfactory" pathway in odor preferences and sexual behavior was examined in the hamster, a species which depends crucially upon olfaction for mating. Before and after ablation of primary or secondary olfactory structures, male hamsters were tested for threshold, interest, and preference for the odor of an estrus female hamster and other odors. Sexual competency was also observed in daily mating sessions. Disruption of the primary olfactory pathway resulted in an absence of interest in odors and mating. Lesions of the mediodorsal thalamic nucleus or frontal neocortex of the rhinal sulcus did not result in anosmia, but did eliminate or alter odor preferences and resulted in inappropriate, inefficient, precopulatory and copulatory behavior. It appears that substructures in the thalamofrontal pathway playa role in discriminative or cognitive aspects of processing adaptively significant stimuli.

Animals↗
PubMedDate not supplied

Memory for items and memory for relations in the procedural/declarative memory framework.

A major area of research in memory and amnesia concerns the item specificity of implicit memory. In this paper we address several issues about the nature of implicit memory phenomena and about what constitutes an "item", using the procedural/declarative memory theory to guide us. We consider the nature of memory for items and of memory for relations among items, within the context of the procedural/declarative framework, providing us with the foundation necessary to analyse the basis for item-specific implicit memory phenomena. We review recent work from our laboratories demonstrating the fundamentally relational and flexible nature of declarative memory representation, in both humans and animals, and the essential role of the hippocampal system in relational memory processing. We show, further, that the memory representations supporting implicit memory phenomena are inflexible and nonrelational, and are tied to specific processing modules. Finally, we introduce empirical approaches that blur the distinction between skill learning and repetition priming, and show computational modelling results that demonstrate how these two implicit memory phenomena can be mediated by a single incremental learning mechanism, in accord with the claims of the procedural-declarative theory. Taken together, these various analyses of memory for items and memory for relations help to illuminate the nature of the functional deficit in amnesia and the memory systems of the brain.

Amnesia↗
PubMedDate not supplied

Cognitive decline associated with normal aging in rats: a neuropsychological approach.

The effects of aging on cognitive capacities were examined by comparing the performance of young and old rats on tasks characterized as dependent on different brain systems. This neuropsychological approach was employed to determine the extent to which multiple neural systems are compromised in aging and whether deterioration of one system correlates with that of another. The two tasks used in the present study were an odor-guided recognition memory task, for which different aspects of performance have been shown to be dependent on the integrity of the orbital prefrontal and perirhinal-entorhinal cortex, and the Morris water maze, for which performance depends on the medial prefrontal cortex and hippocampus. Rats were trained on the recognition memory task under minimal memory load and then challenged with longer memory delays and higher levels of inter-item interference. Considerable variation was observed in the performance of aged rats on acquisition of the recognition memory task, and unlike young rats, some aged rats could not acquire the task. Nevertheless, those aged rats who did acquire the cDNM task performed as well as young animals when the memory delay was extended and interference was elevated. In addition, consistent with previous findings, the performance of the same aged rats was highly variable in the Morris water maze task. Furthermore, although correlations between scores on the two tasks for individual aged rats were not reliable, only those aged rats that performed outside the performance range of young rats in the water maze were impaired on acquisition of the recognition memory task. This pattern of findings is consistent with age-related dysfunction in multiple subdivisions of the prefrontal cortex as well as the hippocampus and suggests that these brain regions may deteriorate in the same subgroup of aged rats.

Aging↗
PubMedDate not supplied

Learning from LTP: a comment on recent attempts to identify cellular and molecular mechanisms of memory.

In recent years disappointing evidence has emerged regarding all main lines of evidence supporting connections between long-term potentiation (LTP) and memory. The history of this research, including studies focusing on synaptic alterations following learning experience, on saturation of LTP, and on pharmacological and genetic manipulations of LTP, are discussed briefly and interpreted in light of their observed and inherent limitations. Other approaches, aimed at showing a continuity of plasticity from molecular to synaptic to circuit and systems levels of analysis, are highlighted as potentially more compelling future directions for this research.

Animals↗
PubMedDate not supplied

Differential effects of damage within the hippocampal region on memory for a natural, nonspatial Odor-Odor Association.

Debate continues on whether the role of rodent hippocampus in memory is limited to the spatial domain. Recently, this controversy has been addressed with studies on the social transmission of food preference, an odor-odor association task with no spatial requirements. Multiple reports have concluded that damage to the hippocampal region impairs memory in this task, but there remain questions about the extent of damage essential to produce an impairment. Furthermore, a recent study () found no effect of hippocampal lesions on memory in this task. We tested animals with complete lesions of the hippocampus (H) lesions of the hippocampus plus subiculum (HS), and lesions of the adjacent, anatomically related cortices of the parahippocampal region (PHR). H lesions produced an impairment on spatial delayed alternation, but not on memory for the social transmission of food preference, whereas HS and PHR lesions produced severe and equivalent impairments on memory for the socially acquired food preference. We discuss possible explanations for the discrepancy with the results of and conclude that the hippocampus and subiculum together play a critical role in the formation of this form of nonspatial, relational memory.

Animals↗