Exercise does not enhance short-term deprivation-induced ocular dominance plasticity: evidence from dichoptic surround suppression

Abstract

The input from the two eyes is combined in the brain. In this combination, the relative strength of the input from each eye is determined by the ocular dominance. Recent work has shown that this dominance can be temporarily shifted. Covering one eye with an eye patch for a few hours makes its contribution stronger. It has been proposed that this shift can be enhanced by exercise. Here, we test this hypothesis using a dichoptic surround suppression task, and with exercise performed according to American College of Sport Medicine guidelines. We measured detection thresholds for patches of sinusoidal grating shown to one eye. When an annular mask grating was shown simultaneously to the other eye, thresholds were elevated. The difference in the elevation found in each eye is our measure of relative eye dominance. We made these measurements before and after 120 minutes of monocular deprivation (with an eye patch). In the control condition, subjects rested during this time. For the exercise condition, 30 minutes of exercise were performed at the beginning of the patching period. This was followed by 90 minutes of rest. We find that patching results in a shift in ocular dominance that can be measured using dichoptic surround suppression. However, we find no effect of exercise on the magnitude of this shift. We further performed a meta-analysis on the four studies that have examined the effects of exercise on the dominance shift. Looking across these studies, we find no evidence for such an effect.

Aerobic Exercise and Human Visual Cortex Neuroplasticity: A Narrative Review

“…In a subsequent study, the group was also unable to replicate Lunghi and Sale's [ 17 ] results despite using an identical visual task [ 21 , 67 ]. An absence of exercise effects has also been reported in studies using EEG [ 65 ], psychophysical surround suppression [ 64 , 65 ], and perceptual learning [ 68 ] to assess visual cortex neuroplasticity.…”

“…Whether this effect of exercise intensity holds for the visual cortex is unknown. For instance, no enhancement of visual cortex neuroplasticity following high intensity exercise has been shown across multiple studies [ 16 , 64 , 66 , 67 ], while others found evidence of neuroplasticity enhancement [ 17 , 18 , 21 , 63 ]. On the other hand, moderate exercise seems to have no effect on visual cortex neuroplasticity [ 16 , 65 , 68 ].…”

“…However, as noted above, another treatment was also administered at the same time as the exercise. However, the majority of studies have reported no enhancement in visual cortex plasticity following one session of exercise [ 16 , 64 , 65 , 67 ] or multiple sessions of exercise [ 66 , 68 ]. While the use of consecutive sessions of exercise in humans was adapted from animal model studies that showed longer lasting effects and larger enhancement as compared to a single bout of exercise [ 46 , 81 ], it remains to be seen whether these results apply to adult humans and are consistent across populations.…”

“…A wide variety of vision tasks and outcome measures have been used by studies of exercise and visual cortex neuroplasticity which may have contributed to the variability in results. Psychophysical tasks that have been employed include binocular rivalry [ 17 , 21 , 67 ], orientation discrimination [ 63 ], vernier acuity [ 66 ], surround suppression [ 64 , 65 ], and motion direction discrimination [ 68 ]. The variety of psychophysical tasks complicate the comparison of results across studies, particularly since different tasks may recruit differing networks of visual cortical areas ( Table 1 ).…”

“…The ability of exercise to enhance visual cortex neuroplasticity is evident in animal models; however, these effects have yet to be unequivocally demonstrated in human adults, while there is some evidence to support the notion that exercise can augment visual cortex neuroplasticity in healthy young adults [17,18,21,62,63], other studies report no effect of exercise [16,[64][65][66][67] and possibly a counterproductive effect depending on the timing of exercise [68] (see Table 1). Nonetheless, structural and neurochemical changes within the human brain have been associated with exercise [69,70].…”