The function of different classes of inhibitory neurons in the auditory cortex - direct shaping of receptive fields or short-term modulation of the functional circuitry?

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The auditory cortex constitutes an end point of several stages of our brain that process sound. It allows us to classify and recognize complex sounds, such as the voice of a familiar person. On the other hand, it plays a decisive role in gating the attention to specific auditory objects, for example when we try to pick out a particular signal against a noisy environment.However, the mechanisms behind these functions remain largely unknown. Inhibitory neurons in the cortex are likely to play a major role, and they are also of great interest because their dysfunction is associated with several pathologies. Progress in the understanding of inhibitory elements of the cortical circuitry has been largely obscured by the fact that they fall into several distinct classes, which are difficult to identify in vivo. I propose to examine different classes of inhibitory neurons in the auditory cortex of mice using new optogenetic techniques. With the help of these techniques, light sensitive channels can be introduced genetically into well defined classes of inhibitory neurons. As a result these can be targeted and manipulated selectively by shining light on the brain. My goal is to test different hypotheses on the function of inhibitory cells: first, there is evidence for these cells to be important for temporal precision and tuning accuracy in the cortex, thereby enhancing the classification and recognition of complex sounds. Second, a recent hypothesis claims that inhibition controls short-term plasticity of the functional connectivity between excitatory cells in the cortex. Such a mechanism could support selective attention by quickly allocating more computational resources to important aspects of the auditory environment. The identification of the cell types that are responsible for these functions would contribute significantly to our understanding of the cortical circuitry.