SFB TRR 31 The Active Auditory System, TP: Interaction of bottom-up and top-down processes in cortical processing of frequency-modulated signals

It is well established that variance of stimulus-related neuronal activity in auditory cortex (as well as in other sensory cortices) can in part be explained by the physical characteristics of the auditory stimuli (bottom-up processes), and not-stimulus-related factors, like attention, expectation, learning, or task in which the perceiving subject is engaged. This project aims at identifying physiological correlates of bottom-up and top-down processes and their interaction in the auditory cortex of Mongolian gerbils during the processing of frequency-modulated sounds, a stimulus class that is of importance for environmental sounds, communication sounds in gerbils and humans (speech), and for which relevance of cortical processing has previously been demonstrated. The project combines several approaches, including behavioral analysis, electrophysiological techniques and pharmacological manipulation, as well as experimental paradigms that have been developed in the first two funding periods. Three major aims are (1) the accomplishment of the newly developed residual CSD analysis, that allows dissociation of the recruitments of thalamocortical and intracortical circuits, while the animal develops its target-discrimination performance in a learning experiment, (2) the validation of the inferred dissociations of thalamocortical and intracortical circuit contributions to neuronal activity patterns across cortical laminae, and (3) the investigation of the modulatory effects of the neurotransmitter dopamine, the relevance of which for the investigated learned has previously been demonstrated, on the neuronal cortical circuits recruited during learning.