Abstract
In our daily lives, we use eye movements to actively sample visual information from our environment (“active vision”). However, little is known about how the underlying mechanisms are affected by goal-directed behavior. In a study of 31 participants, magnetoencephalography was combined with eye-tracking technology to investigate how interregional interactions in the brain change when engaged in two distinct forms of active vision: freely viewing natural images or performing a guided visual search. Regions of interest with significant fixation-related evoked activity (FRA) were identified with spatiotemporal cluster permutation testing. Using generalized partial directed coherence, we show that, in response to fixation onset, a bilateral cluster consisting of four regions (posterior insula, transverse temporal gyri, superior temporal gyrus, and supramarginal gyrus) formed a highly connected network during free viewing. A comparable network also emerged in the right hemisphere during the search task, with the right supramarginal gyrus acting as a central node for information exchange. The results suggest that all four regions are vital to visual processing and guiding attention. Furthermore, the right supramarginal gyrus was the only region where activity during fixations on the search target was significantly negatively correlated with search response times. Based on our findings, we hypothesize that, following a fixation, the right supramarginal gyrus supplies the right supplementary eye field (SEF) with new information to update the priority map guiding the eye movements during the search task.
Highlights
In neurocognitive experiments, researchers generally perform multiple repetitions of the same experimental condition in a tightly controlled environment with the goal of isolating specific aspects of the cognitive process in question
We found a temporoparietal cluster with significant fixation-related evoked activity consisting of the PI, TTG, STG, and SMG, as well as a dorsal cluster composed of the occipital area and areas associated with the ventral and dorsal visual streams
The right SMG exhibited the highest degree of causal interactions during the search task, indicating its central role in guided visual searching
Summary
Researchers generally perform multiple repetitions of the same experimental condition in a tightly controlled environment with the goal of isolating specific aspects of the cognitive process in question. Compared to common experimental paradigms where participants either have to fixate on a specific point continuously or where eye movements are elicited by the appearance of a stimulus, the exploration of natural still images is driven by selfpaced gaze shifts over a longer period of time (“active vision”) (Nikolaev et al, 2016). This use of unrestricted exploration of naturalistic stimuli may lead to new insights compared to experiments where eye movements are tightly controlled (Kamienkowski et al, 2012)
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