STATE-DEPENDENT INFORMATION PROCESSING IN THE RAT VIBRISSA PATHWAY
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To navigate the world, we must efficiently extract relevant information from complex sensory inputs to form perceptions and make decisions on a moment-to-moment basis. The efficient encoding of sensory information necessarily relies on the ability of the pathway to dynamically interpret the sensory input according to the context under which external stimuli are processed. Internally, this context is represented by the state of the brain, which can be modulated by bottom-up processes such as sensory adaptation, intrinsic mechanisms such as neuromodulators, and top-down processes such as arousal. This thesis examines the modulation of brain state induced via bottom-up sensory adaptation and the intrinsic brain states, the relationship between brain state and sensory-evoked activity, and the potential implications of brain state modulation for the perception of the stimulus. Using voltage-sensitive dye imaging in anesthetized rats and the paradigm of detection / spatial discrimination task by the ideal observer, I quantified, in the adapted state, how the cortical response to a stimulus in the vibrissa pathway was shaped and how the information for detecting and spatially discriminating the stimulus was differentially optimized. Cortical activation and detection / discrimination tradeoff were quantified in relation to the degree of adaptation, which was modulated continuously by the frequency and velocity of the adapting stimulus. Finally, I investigated the intrinsic brain states reflected in the spontaneous cortical activity and how it modulated sensory evoked response. This thesis investigates the regulation of brain state via bottom-up sensory adaptation and intrinsic mechanisms, providing a glimpse into a high-dimensional continuum of cortical dynamics.