Significance
In the real word, visual tasks may be concurrent with other activity that imposes mental load. While the brain’s capacity to process information is limited, attention can improve visual performance by selectively allocating processing resources. Therefore, measuring visual performance under such circumstances can reflect patients' vision more accurately.
Purpose
The aim of this study was to evaluate the effect of non-visual task induced mental load on visual performance at both attended and unattended locations in stimulus-driven captured attention.
Methods
Visual function was measured with an orientation-discrimination task for Gabor patches with contrasts of 10, 15, 30, 50, and 80%. Three attentional conditions (valid-cue condition, invalid-cue, and neutral-cue) were randomly interleaved within runs. To modulate mental load, the visual task was performed either with or without a simultaneous auditory n-back task (2-back for maximum mental load, and 0-back to control for the effect of having to perform a simultaneous task).
Results
Our result showed the effect of mental load on correct responses was significant (P = .02). Correct responses decreased significantly during the 2-back task when compared to the baseline condition (P = .03) but there was no significant difference between baseline and 0-back conditions (P = .06). The effect of attention and spatial frequencies on the percentage of correct responses was significant (P < .001). There was no significant interaction between mental load and spatial frequency, contrast level or attention (P > .05).
Conclusions
Mental load had a similar decreasing effect on attended and unattended visual stimuli. This may be due to a generalized effect on processing resources upstream to where spatial attention is allocated.
