Deficits in fine-grained auditory pitch perception have been implicated in language learning disorders, certain forms of dyslexia, and more severe neurological conditions. Fine-grained frequency discrimination is believed to be a function of the primary auditory cortex (A1), but the mechanism responsible is still unclear. In the time-course of individual A1 neural responses to iso-frequency tones, relatively non-frequency- selective phasic excitation gives way to more narrowly selective tonic excitation that is sustained throughout the duration of the tone. Tonic responses in A1 may code for fine-grained spectral perception. This study will investigate the role and functionality of tonic responses with respect to pitch perception of pure tones in awake rats using a combination of neural recording, microstimulation, and behavioral techniques. Neural recordings from multichannel electrode arrays will be used to fully characterize tonic neural responses in A1 to iso-frequency tones. A simultaneous neural recording and microstimulation paradigm will be used to examine the contribution of intracortical modulation to processing of iso-frequency stimuli. Finally, microstimulation will be paired with a behavioral paradigm to investigate the perceived pitch of sensation elicited by artificial activation of A1 in a pattern mimicking natural iso-frequency responses. The combination of these techniques will provide a uniquely detailed view of the mechanisms and functionality of tonic responses in A1 with respect to fine-grained pitch perception. This study will help in understanding how the brain breaks down sound information into sound frequency. The knowledge gained from this study could be useful in developing better treatments for childhood language learning disorders or for language disorders stemming from strokes and other brain damage. [unreadable] [unreadable] [unreadable]