Computation and Neural Systems Program, Caltech.
Stimulus-evoked oscillatory synchronization of activity has been observed in many neural systems, including the cerebral cortex of mammals and the brain of insects. The possible functions of such rhythmic synchronization in neural coding, however, remain largely speculative. In the locust, odors evoke activity in dynamic (evolving) ensembles of transiently synchronized neurons. The active neurons composing these ensembles change in a stimulus-specific manner and with a high degree of reliability on a cycle-by-cycle basis during an odor response. Hence, information about an odor is contained not only in the neural assembly active at each oscillation cycle, but also in the precise temporal sequence in which these assemblies are updated during an odor response. Neural coding with oscillations thus allows combinatorial representations in time as well as in space. Finally, behavioral experiments using honey bees and pharmacological manipulations to desynchronize the odor-coding neural ensembles reveal the role of synchronization for odor learning and discrimination.