It’s a well established fact—and intuitive truth—that vision guides movement, and that information flows readily from the visual cortex to motor centers. However, the inverse relation is far less well understood. Does engaging in movement affect how our vision is processed? Three researchers from City College of New York, USA, devised a clever experiment to test this hypothesis. Their results are published in the European Journal of Neuroscience.
One of the main difficulties in designing an experiment to test what influence the motor system exerts on visual processing is that motor activity elicits confounding evoked potentials (stable electrical patterns in the brain in response to some stimulus or activity).
To disentangle these signals, the authors developed a “sham” motor task, in which a portion of the 24 participants (14 female) were made to believe they were controlling a racing video game with their brain activity (“sham play”). A second group passively watched the video game, while a third controlled it with traditional hand controls (“active play”).
A second difficulty comes from the fact that movement (real or imagined) also produces increased attention, which may itself account for changes in visual processing. For this reason, the authors developed a second study in which participants were asked to count the appearance of specific images on the screen while passively viewing the game.
The authors were able to confirm activation of the motor cortex during sham play, thus validating their experimental design, by measuring disturbances in alpha-band (8 to 12 Hz) electrical oscillations (“alpha waves”) over the motor cortex, which are known to appear when performing motor actions.
The results of the study demonstrated significant differences in visual evoked potentials (specifical, stable electrical signals following a particular stimulus) during active and sham game play versus passive viewing.
Counting did not elicit these differences, suggesting that attention was not responsible for the observed differences, although this discrepancy failed to reach statistical significance. This likely stemmed from the fact that only 30% of subjects were fully deceived by the sham task, or the fact that participants may have noticed discrepancies between the car’s movement and their intended command.
Despite this, the study provides some evidence for the view that visual signals are enhanced during movement, and also provides a novel method for “decoding active versus passive vision from non-invasive measurements of neural activity.” This will allow for future studies with larger population sizes and thus greater statistical significance, such that the results of the present study may be more definitively verified.
The study, “Visually evoked responses are enhanced when engaging in a video game“, was authored by Jason J. Ki, Lucas C. Parra, and Jacek P. Dmochowski.