Sparse Spectro-Temporal Receptive Fields Based on Multi-Unit and High-Gamma Responses in XXXX Auditory Cortex.

@entity1 @entity3628
UNASSIGNED: Spectro-Temporal Receptive Fields (STRFs) were estimated from both multi-unit sorted clusters and high-gamma power responses in @entity1 auditory cortex. Intracranial electrophysiological recordings were used to measure responses to a random chord sequence of Gammatone stimuli. Traditional methods for estimating STRFs from single-unit recordings, such as spike-triggered-averages, tend to be noisy and are less robust to other response signals such as local field potentials. We present an extension to recently advanced methods for estimating STRFs from @entity3628 ( @entity3628 ). A new variant of regression using regularization that penalizes non-zero coefficients is described, which results in a sparse solution. The frequency-time structure of the STRF tends toward grouping in different areas of frequency-time and we demonstrate that group sparsity-inducing penalties applied to @entity3628 estimates of STRFs reduces the background noise while preserving the complex internal structure. The contribution of local spiking activity to the high-gamma power signal was factored out of the STRF using the @entity3628 method, and this contribution was significant in 85 percent of the cases. Although the @entity3628 methods have been used to estimate STRFs in animals, this study examines the detailed structure directly from auditory cortex in the awake @entity1 brain. We used this approach to identify an abrupt change in the best frequency of estimated STRFs along posteromedial-to-anterolateral recording locations along the long axis of Heschl's gyrus. This change correlates well with a proposed transition from core to non-core auditory fields previously identified using the temporal response properties of Heschl's gyrus recordings elicited by click-train stimuli.
