Roles of octopaminergic and dopaminergic neurons in appetitive and aversive memory recall in an insect.

Full Abstract

BACKGROUND: In insect classical conditioning, octopamine (the invertebrate counterpart of noradrenaline) or dopamine has been suggested to mediate reinforcing properties of appetitive or aversive unconditioned stimulus, respectively. However, the roles of octopaminergic and dopaminergic neurons in memory recall have remained unclear. RESULTS: We studied the roles of octopaminergic and dopaminergic neurons in appetitive and aversive memory recall in olfactory and visual conditioning in crickets. We found that pharmacological blockade of octopamine and dopamine receptors impaired aversive memory recall and appetitive memory recall, respectively, thereby suggesting that activation of octopaminergic and dopaminergic neurons and the resulting release of octopamine and dopamine are needed for appetitive and aversive memory recall, respectively. On the basis of this finding, we propose a new model in which it is assumed that two types of synaptic connections are formed by conditioning and are activated during memory recall, one type being connections from neurons representing conditioned stimulus to neurons inducing conditioned response and the other being connections from neurons representing conditioned stimulus to octopaminergic or dopaminergic neurons representing appetitive or aversive unconditioned stimulus, respectively. The former is called 'stimulus-response connection' and the latter is called 'stimulus-stimulus connection' by theorists studying classical conditioning in higher vertebrates. Our model predicts that pharmacological blockade of octopamine or dopamine receptors during the first stage of second-order conditioning does not impair second-order conditioning, because it impairs the formation of the stimulus-response connection but not the stimulus-stimulus connection. The results of our study with a cross-modal second-order conditioning were in full accordance with this prediction. CONCLUSION: We suggest that insect classical conditioning involves the formation of two kinds of memory traces, which match to stimulus-stimulus connection and stimulus-response connection. This is the first study to suggest that classical conditioning in insects involves, as does classical conditioning in higher vertebrates, the formation of stimulus-stimulus connection and its activation for memory recall, which are often called cognitive processes.

Author information

Author/s: Mizunami, Makoto (M); Unoki, Sae (S); Mori, Yasuhiro (Y); Hirashima, Daisuke (D); Hatano, Ai (A); Matsumoto, Yukihisa (Y);

Affiliation: Graduate School of Life Sciences, Tohoku University, Aoba-ku, Sendai, Japan. mizunami(-atsign-)sci.hokudai.ac.jp

Journal and publication information

Publication Type: Journal Article; Research Support, Non-U.S. Gov't

Journal: BMC biology (BMC Biol), published in England. (Language: eng)

Reference: 2009-; vol 7 (issue ) : pp 46

Dates: Created 2009/08/20; Completed 2009/09/10; Revised 2009/09/15;

PMID: 19653886, status: MEDLINE (last retrieval date: 9/15/2009, IMS Date: )

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.

Adrenergic alpha-Antagonists - pharmacology
Animals
Appetitive Behavior - drug effects
Conditioning, Classical
Dopamine Antagonists - metabolism; pharmacology
Gryllidae - physiology
Mental Recall
Models, Biological

Models, Biological
Neurons - physiology
Odors
Photic Stimulation
Receptors, Biogenic Amine - antagonists & inhibitors; metabolism; physiology
Receptors, Dopamine - physiology
Smell - physiology
Statistics, Nonparametric

Associated Chemicals: Adrenergic alpha-Antagonists (0) ; Dopamine Antagonists (0) ; Receptors, Biogenic Amine (0) ; Receptors, Dopamine (0) ; norsynephrine receptor (0)

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