We review recent progress in the study of roles of octopaminergic (OA-ergic) and dopaminergic (DA-ergic) signaling in insect classical conditioning, focusing on our studies on crickets. Studies on olfactory learning in honey bees and fruit-flies have suggested that OA-ergic and DA-ergic neurons convey reinforcing signals of appetitive unconditioned stimulus (US) and aversive US, respectively. Our work suggested that this is applicable to olfactory, visual pattern, and color learning in crickets, indicating that this feature is ubiquitous in learning of various sensory stimuli. We also showed that aversive memory decayed much faster than did appetitive memory, and we proposed that this feature is common in insects and humans. Our study also suggested that activation of OA- or DA-ergic neurons is needed for appetitive or aversive memory recall, respectively. To account for this finding, we proposed a model in which it is assumed that two types of synaptic connections are strengthened by conditioning and are activated during memory recall, one type being connections from neurons representing conditioned stimulus (CS) to neurons inducing conditioned response and the other being connections from neurons representing CS to OA- or DA-ergic neurons representing appetitive or aversive US, respectively. The former is called stimulus–response (S–R) connection and the latter is called stimulus–stimulus (S–S) connection by theorists studying classical conditioning in vertebrates. Results of our studies using a second-order conditioning procedure supported our model. We propose that insect classical conditioning involves the formation of S–S connection and its activation for memory recall, which are often called cognitive processes.
Keywords: octopamine, dopamine, classical conditioning, memory recall, olfactory learning, visual learning, crickets
Citation: Mizunami M and Matsumoto Y (2010) Roles of aminergic neurons in formation and recall of associative memory in crickets. Front. Behav. Neurosci. 4:172. doi: 10.3389/fnbeh.2010.00172
Received: 29 June 2010;
Paper pending published: 01 September 2010;
Accepted: 19 October 2010; Published online: 17 November 2010.
Edited by:Jean-Christophe Sandoz, National Center for Scientific Research, France
Reviewed by:Jean-Christophe Sandoz, National Center for Scientific Research, France;
Copyright: © 2010 Mizunami and Matsumoto. This is an open-access article subject to an exclusive license agreement between the authors and the Frontiers Research Foundation, which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are credited.
*Correspondence: Makoto Mizunami, Graduate School of Life Sciences, Hokkaido University, Sapporo 060-0810, Japan. e-mail: email@example.com