Characterizing the Visual Cortex Function in Cognitive Task-Induced Mental Load: An Functional Magnetic Resonance Imaging Study

Abstract

Introduction:

The mental load caused by simultaneous multitasking can affect visual information processing and reduce its ability. This study investigated the effect of mental load caused by cognitive tasks simultaneously with visual task on the number of active voxels in the visual cortex.

Methods:

This study recruited 22 individuals with a mean age of 24.72 ± 5.47 years. 3-Tesla functional magnetic resonance imaging (fMRI) was used to examine the functions of the visual cortex and amygdala region during three different task conditions: visual task alone, visual task with an auditory n-back task, and visual task with an arithmetic task. The visual stimuli consisted of Gabor patches with a contrast of 55% at spatial frequencies of 0.25, 4, and 9 cycles per degree (cpd). These were presented in three trials of eight blocks with a stimulation time of 12 sec and a rest time of 14 sec.

Results:

Activated brain voxels in the primary, secondary, and associated visual cortex areas were reduced in response to the mental load imposed by the n-back and arithmetic tasks. This reduction was greater for a spatial frequency of 0.25 cpd in the n-back task condition and spatial frequency of 9 cpd in the arithmetic task condition. In addition, the amygdala was stimulated in 2-back task and arithmetic task conditions.

Conclusions:

This study revealed a decline in the number of activated voxels of the visual cortex due to the mental load caused by simultaneous cognitive tasks, confirming the findings of previous psychophysical studies.

Impact statement

Concurrent cognitive task-induced mental load can affect visual information processing and reduce its ability. The number of activated voxels of the visual cortex was investigated in three conditions of visual task alone and visual tasks simultaneously with 2-back task and arithmetic task. Visual stimuli consisted of Gabor patches with 55% contrast at spatial frequencies of 0.25, 4, and 9 cycles per degree (cpd). The results showed that the mental load imposed by n-back and arithmetic task decreased the number of activated voxels in the primary, secondary, and associated visual cortex areas.