Central Processing of Intraspecific Chemical Signals in Mice

Excerpt

The previous chapters explored the peripheral anatomy and physiology of sensory organs responsible for detection of chemical signals shared among members of the same species. This chapter deals with the central processing of intraspecific chemo-signals in the mouse; in particular, it will present data on the stimulus processing in the olfactory bulb, the amygdala, and the olfactory cortex, mainly in relation to neuroendocrine and behavioral modulation.

Communication is a primary function of living systems, from unicellular to complex organisms. It is necessary to mediate the responses of organisms to environmental changes and also to organize the actions of multiple members of the same species, to increase the fitness of both message sender and receiver, or either. Communication via chemical signals allows an honest and sensitive transmission of information, which requires the attribution of a specific link between a molecule (or blend of molecules) and a given response. Hence, central processing of intraspecific chemical signals allows stimulus detection and feature encoding, and involves different associative areas of the brain in mediating the responses to chemosignals.

Signaling molecules (not referred to here as “pheromones” due to the lack of consensus on the use of this term) are released in the environment together with biologic fluids, including tears, saliva, and genital secretions. Most of the data available for the mouse was obtained using as stimuli the molecules emitted with urine, which is excreted in larger amounts. Several sensory organs detect the relevant molecules and send information to various centers in the brain, using different, yet interconnected, pathways.

This chapter reviews what is known about signal processing in key chemosensory areas of the brain to show how chemical cues from conspecifics may influence both the behavior (including exploration, social, and sexual behavior) and the physiology of the organism that sends or receives the chemosignals.