The neurochemical basis of motivation and coordinated behavior in an insect brain

Organisms select adaptive behaviors due to their internal states and their sensory environment. The interplay of neural and hormonal mechanisms activated by proprio- and exteroreceptors biases the selection of action patterns by decision making neuronal circuits. The acoustic communication of insects is a suitable preparation to study the selection of appropriate behaviors with combined methodological approaches including quantitative behavioral analysis, cytochemical studies, pharmacological interference with signalling pathways and molecular studies on identified brain neurons in primary cell culture.

Grasshoppers communicate with species-specific songs in order to attract and court reproductive partners, to signal reproductive readiness or to fend off competitors. Selection and coordination of type, intensity and timing of sound signals is mediated by the central complex, a highly structured brain neuropil known to integrate multimodal pre-processed sensory information by a large number of chemical messengers.

Activation of particular signalling pathways in the central complex were associated with sensory signals representing favourable or unfavourable situations for the performance of sound production In order to relate patterns of neural activity to situation-dependent motivational states we mapped the distribution of chemical signals and intracellular metabolites to particular types of central complex neurons. We identified a number of fast (ionotropic) and slow (metabotropic) acting signaling pathways that promote or suppress sound production and set the threshold for responding to species-specific communication signals. In summary, performance of sound production depends on a balance of inhibitory and excitatory inputs to the central body, with second messenger pathways playing a prominent role in regulating general motivation and behavioral pattern selection.

Seminar Hosted by: Dr. Geoffrey Ganter