Cortical Competitive Processing Produces Interference in Color-Word Tests

Abstract

A hypothesis that cortical processing of the millisecond time range is performed with a competitive mechanism is tested with a neural network model of the Stroop interference. The model cortex is assumed to consist of columns which include populations of pyramidal cells and inhibitory interneurons. They are given by a Hodgkin-Huxley type of model neurons. Model analysis shows first the cortical circuitry performs temporal competition that lateral inhibition between the columns restricts firing to the first activated columns by suppressing the others before firing. Second, assuming the fasciculus arcuatus is stronger than the projections from the color-processing pathways of temporal cortex, incongruent word and color stimuli for the color-naming task compete to activate the columns of the Broca cortex. This delays vocal response to the color stimuli for several milliseconds. Third, in the reading task, incongruent color stimuli hardly activate the columns because the projections from the color-processing pathways are not strong. No interference is produced in reading. These are in good accordance with psychophysical data and therefore support the present hypothesis.