The level of cholinergic nucleus basalis activation controls the specificity of auditory associative memory.

Full Abstract

Learning involves not only the establishment of memory per se, but also the specific details of its contents. In classical conditioning, the former concerns whether an association was learned while the latter discloses what was learned. The neural bases of associativity have been studied extensively while neural mechanisms of memory specificity have been neglected. Stimulation of the cholinergic nucleus basalis (NBs) paired with a preceding tone induces CS-specific associative memory. As different levels of acetylcholine may be released naturally during different learning situations, we asked whether the level of activation of the cholinergic neuromodulatory system can control the degree of detail that is encoded and retrieved. Adult male rats were tested pre- and post-training for behavioral responses (interruption of ongoing respiration) to tones of various frequencies (1-15 kHz, 70 dB, 2 s). Training consisted of 200 trials/day of tone (8.0 kHz, 70 dB, 2 s) either paired or unpaired with NBs (CS-NBs = 1.8 s) at moderate (65.7+/-9.0 microA, one day) or weak (46.7+/-12.1 microA, three training days) levels of stimulation, under conditions of controlled behavioral state (pre-trial stable respiration rate). Post-training (24 h) responses to tones revealed that moderate activation induced both associative and CS-specific behavioral memory, whereas weak activation produced associative memory lacking frequency specificity. The degree of memory specificity 24 h after training was positively correlated with the magnitude of CS-elicited increase in gamma activity within the EEG during training, but only in the moderate NBs group. Thus, a low level of acetylcholine released by the nucleus basalis during learning is sufficient to induce associativity whereas a higher level of release enables the storage of greater experiential detail. gamma waves, which are thought to reflect the coordinated activity of cortical cells, appear to index the encoding of CS detail. The findings demonstrate that the amount of detail in memory can be directly controlled by neural intervention.

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Author information

Author/s: Weinberger, Norman M (NM); Miasnikov, Alexandre A (AA); Chen, Jemmy C (JC);

Affiliation: Center for the Neurobiology of Learning and Memory, Department of Neurobiology and Behavior, University of California, Irvine, CA 92697-3800, USA. nmweinbe(-atsign-)uci.edu

Grants: DC-02938 (Agency:NIDCD NIH HHS) ; DC-05592 (Agency:NIDCD NIH HHS)

Journal and publication information

Publication Type: Comparative Study; Journal Article; Research Support, N.I.H., Extramural

Journal: Neurobiology of learning and memory (Neurobiol Learn Mem), published in United States. (Language: eng)

Reference: 2006-Nov; vol 86 (issue 3) : pp 270-85

Dates: Created 2006/10/02; Completed 2006/12/07; Revised 2007/11/14;

PMID: 16750916, status: MEDLINE (last retrieval date: 12/26/2008)

Sourced from the National Library of Medicine. Abstract text and other information may be subject to copyright.

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MeSH headings (categories)

This article was linked to the MESH Headings shown below.

Animals
Association Learning - physiology
Auditory Perception - physiology
Basal Nucleus of Meynert - cytology; physiology
Behavior, Animal - physiology
Cholinergic Fibers - physiology
Electric Stimulation

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