Measuring the haemodynamic responses elicited in the visual cortex from various spatial and temporal frequencies using NIRS

Abstract

Previous research has found the optimum spatial and temporal frequency of a stimulus can elicit peak activation in the visual cortex. In this study eight participants looked at bullseye gratings with low and high spatial frequencies (0.5 & 3 c/deg) at varying temporal frequencies (1, 4, 8 & 30Hz). Their haemoglobin response in the visual cortex was recorded using Near Infra-red Spectroscopy (NIRS). Insignificant results were found in all measures, including oxygenated haemoglobin which reported F (1, 8, 5.63) = .75, p<.44. Trigonometric regression did illustrate increased visual activation when the bullseye grating was presented. It appears different frequencies can cause different haemodynamic response, but a larger sample and the elimination of disadvantages in NIRS is required to obtain significance.