TEMPORAL CODES AND CORTICOCORTICAL COMMUNICATION

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The broad aim of the proposed studies is to define the role of temporal codes in corticocortical information processing. Current models of coincidence detection and temporal integration of average firing rates are directly examined with an experimental approach. Pattern recognition and directing attention are chosen as related cortical functions which are likely to select for different processing strategies. Pattern recognition which requires fast, parallel and exhaustive, binding of multiple features within and across many scales is likely to depend on the fast timing schemes identified in coincidence detection models. Directing attention, on the other hand, reflects the deploying of a narrow information channel. This process is likely to depend on slower, serial search schemes that are well supported by rate coding strategies that mark more highly active neural sub-populations. Specific experimental methods are proposed to test the utilization of these strategies by neurons in the awake animal engaged in simple but well-defined behavioral tasks. The significance of these studies is to build our understanding of the nature of temporal processing in cortical dynamics. Knowledge of the mechanisms of temporal integration is the next crucial step in approaching the varied problems of brain injury. Increasing evidence points to the disruption of temporal processing as a fundamental mechanism underlying developmental and acquired cognitive disabilities. Morever, the first hints of therapeutic approaches based on models of temporal processing suggest that further detailed knowledge of the timing of information flow in the cortex will assist the efforts to improve the lives of patients with dyslexia, head trauma and stroke. Ultimately, the brain is organized with parallel and vertical subcortical connections (limbic, striatal, thalamocortical) as well as the corticocortical connections emphasized here. The studies proposed will seek to frame the understanding of corticocortical interactions in a context that will support further studies of thalamocortical integration. Building out from this framework will enlarge the possible scope of significance for the treatment of brain disorders.