Separation of stimulus-selective and nonselective components in intrinsic optical signals

Abstract

Optical imaging based on intrinsic optical signals has been widely used in studies on the functional organization of visual cortical areas. The presentation of a visual stimulus usually generates non-stimulus-selective global darkening and stimulus-selective localized spots superposed on it. It is critical to extract the stimulus-selective component for the investigation of the cortical functional organization. In this study, we propose a novel method based on a principal component analysis (PCA) of the spatial optical response patterns, and apply it to the separation of the global darkening in the cat visual cortex. The images submitted to PCA were those responding to the gratings with eight orientations from 0° to 180° in steps of 22.5°. The first principal component represents most of the common signals such as the global darkening and large blood vessels, and occupies more than 80% of the signal energy. By removing the first principal component, the stimulus-selective dark patches in the reconstructed images have higher contrasts and high orientation selectivity consistent with electrophysiological single-cell recording. The results suggest that the proposed method can be used to exclude the stimulus-nonselective component, which provides an alternative method for signal extraction. © 2014 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.