A Frequency Domain Technique for Using Evoked Magnetic Fields to Test Multi-Stage Models of Sensory Processing

Abstract

One aim of neuromagnetic studies of human sensory pathways is to obtain data that can test quantitative models of these sensory pathways. The human auditory and visual pathways are composed of neurons, many of which can be modelled as a rectifier (Figure 1). Here we describe a method for characterizing one or more rectifiers arranged in a sequential or parallel/sequential order. The procedure is to calculate the response of such a neural model to an input that consists of the sum of two sinusoids. The calculation is repeated for each candidate model. Then the magnetic response of the brain to a sum of sinewaves input is measured, and the empirical result compared with the catalogue of theoretical predictions. We have published a preliminary catalogue (Regan & Regan, 1988) and are currently engaged in assembling a more extensive catalogue. The method allows a small population of specialized neurons to be isolated, and magnetic recording offers a precise localization of the selected neurons.