A TIME-BASED APPROACH TOWARDS CORTICAL FUNCTIONS - NEURAL MECHANISMS UNDERLYING DYNAMIC ASPECTS OF INFORMATION-PROCESSING BEFORE AND AFTER POSTONTOGENETIC PLASTIC PROCESSES

Under the assumptions that the entire temporal structure of neuron responses carries significant information and that single cell receptive fields (RFs) and representational maps (RMs) typify representative stages of cortical processing, dynamical properties of RFs and RMs were investigated in three modalities. The resulting time-dependent receptive fields and representational maps are interpreted as specific adaptations to processing of inherently time-variant signals. Based on experimental data about latency differences observed within different hierarchically organized areas of sensory pathways, a time-based concept of temporal distributed processing (TDP) across subcortical and cortical substrates is presented that accounts for dynamic aspects of cortical processing. The high percentage of simultaneously activated neurons makes it rather unlikely that proceeding stages wait until the end of the processing of a previous one. This lack of wait-states is the key feature of the TDP-scheme which poses special emphasis on late response components. To provide sufficient flexibility to slow changing conditions in the environment and individual performance requirements, postontogenetic plastic adaptive processes are assumed to act within this scenario by directly effecting the response dynamics thus altering the entire interareal interactions.