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 res ponses carries significant information and that single cell receptive fields (RFs) and representational maps (RMs) typify representative sta ges of cortical processing, dynamical properties of RFs and RMs were i nvestigated in three modalities. The resulting time-dependent receptiv e fields and representational maps are interpreted as specific adaptat ions to processing of inherently time-variant signals. Based on experi mental data about latency differences observed within different hierar chically 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 ma kes it rather unlikely that proceeding stages wait until the end of th e processing of a previous one. This lack of wait-states is the key fe ature of the TDP-scheme which poses special emphasis on late response components. To provide sufficient flexibility to slow changing conditi ons in the environment and individual performance requirements, poston togenetic plastic adaptive processes are assumed to act within this sc enario by directly effecting the response dynamics thus altering the e ntire interareal interactions.