The Role of Auditory Cortex in Sound Perception and Discrimination: Insights from Optogenetics

The modern era of neuroscience is characterized by massive amounts of data from various methods of recording neuronal activity, but the role of this activity in behavior remains elusive in many cases. Traditional manipulations of activity such as surgical lesions or muscimol application often provide inconclusive information due to their limitations. In this dissertation, I focus on the role of mouse auditory cortex in simple and complex sound discrimination, using PV-ChR2 optogenetic suppression to establish a causal relationship between activity and behavioral performance. I first examined pure tone discrimination, comparing the effects of optogenetic suppression and electrolytic lesions. Performance was unaffected by lesions but impaired by optogenetic suppression time-locked to stimulus presentation, showing the necessity of auditory cortex activity for successful discrimination. When optogenetic suppression was extended to multiple trials and then the entire lesion recovery duration, the impairment remained, suggesting a fundamental difference between the brain’s adaptation to optogenetic suppression and permanent lesion damage. Optogenetic suppression also impaired phoneme discrimination ability in mice. This effect remained when either the “consonant” or “vowel” segments were temporally targeted for suppression. Finally, I observed potential laser-related learning that could complicate optogenetic suppression analysis, showing that mice can learn to associate random rewards with the laser light cue or adapt to suppression when laser trials are reinforced