Date of Degree


Document Type


Degree Name





Charles E. Schroeder

Subject Categories

Cognitive Psychology | Neuroscience and Neurobiology


attention, auditory, oscillations


Although it has been over 100 years since William James stated that "everyone knows what attention is", its underlying neural mechanisms are still being debated today. The goal of this research was to describe the physiological mechanisms of auditory attention using direct electrophysiological recordings in macaque primary auditory cortex (A1). A major focus of my research was on the role ongoing neuronal oscillations play in attentional modulation of auditory responses in A1.

For all studies, laminar profiles of synaptic activity, (indexed by current source density analysis) and concomitant firing patterns in local neurons (multiunit activity) were acquired simultaneously via linear array multielectrodes positioned in A1. The initial study of this dissertation examined the contribution of ongoing oscillatory activity to excitatory and inhibitory responses in A1 in passive (no task) conditions. Next, the function of ongoing oscillations in modulating the frequency tuning of A1 during an intermodal selective attention oddball task was investigated. The last study was aimed at establishing whether there is a hemispheric asymmetry in the way neuronal oscillations are utilized by attention, corresponding to that noted in humans.

The results of the first study indicate that in passive conditions, ongoing oscillations reset by stimulus related inputs modulate both excitatory and inhibitory components of local neuronal ensemble responses in A1. The second set of experiments demonstrates that this mechanism is utilized by attention to modulate and sharpen frequency tuning. Finally, we show that as in humans, there appears to be a specialization of left A1 for temporal processing, as signified by greater temporal precision of neuronal oscillatory alignment. Taken together these results underline the importance of neuronal oscillations in perceptual processes, and the validity of the macaque monkey as a model of human auditory processing.