Robust Spectro-Temporal Reverse Correlation for the Auditory System: Optimizing Stimulus Design
Technical research rept.
MARYLAND UNIV COLLEGE PARK INST FOR SYSTEMS RESEARCH
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The spectro-temporal receptive field STRF is a functional descriptor of the linear processing of time-varying acoustic spectra by the auditory system. By cross-correlating sustained neuronal activity with the dynamic spectrum of a spectro-temporally rich stimulus ensemble, one obtains an estimate of the STRF. In this paper, the relationship between the spectro-temporal structure of any given stimulus and the quality of the STRF estimate is explored, and exploited. Invoking the Fourier theorem, arbitrary dynamic spectra are described as sums of basic sinusoidal components, i.e., moving ripples. Accurate estimation is found to be especially reliant on the prominence of components whose spectral and temporal characteristics are of relevance to the auditory locus under study, and is sensitive to the phase relationships between components with identical temporal signatures. These and other observations have guided the development and use of stimuli with deterministic dynamic spectra composed of the superposition of many temporally orthogonal moving ripples having a restricted, relevant range of spectral scales and temporal rates. The method, termed sum-of-ripples, is similar in spirit to the whitenoise approach, but enjoys the same practical advantages - which equate to faster and more accurate estimation - attributable to the time-domain sum-of-sinusoids method previously employed in vision research. Application of the method is exemplified with both modeled data and experimental data from ferret primary auditory cortex AI.
- Anatomy and Physiology