Abstract
Cognitive processes are almost exclusively investigated under highly controlled settings during which voluntary body movements are suppressed. However, recent animal work suggests differences in sensory processing between movement states by showing drastically changed neural responses in early visual areas between locomotion and stillness. Does locomotion also modulate visual cortical activity in humans, and what are the perceptual consequences? Our study shows that walking increased the contrast-dependent influence of peripheral visual input on central visual input. This increase is prevalent in stimulus-locked electroencephalogram (EEG) responses (steady-state visual evoked potential [SSVEP]) alongside perceptual performance. Ongoing alpha oscillations (approximately 10 Hz) further positively correlated with the walking-induced changes of SSVEP amplitude, indicating the involvement of an altered inhibitory process during walking. The results predicted that walking leads to an increased processing of peripheral visual input. A second study indeed showed an increased contrast sensitivity for peripheral compared to central stimuli when subjects were walking. Our work shows complementary neurophysiological and behavioural evidence corroborating animal findings that walking leads to a change in early visual neuronal activity in humans. That neuronal modulation due to walking is indeed linked to specific perceptual changes extends the existing animal work.
Highlights
Perception is a function of the stimulus and very much influenced by internal factors such as arousal and attention
Assessing steady-state visual evoked potential (SSVEP), which is known to be a stimuluslocked signal originating from the early visual cortex [40], we could demonstrate in a first study that walking modulated how visual input from the periphery influences central foveal input in a contrast-dependent fashion
Analysing the 2-second time window prior to target onset, an SSVEP response introduced by the central 15 Hz flickering grating was readily detected during standing as well as walking and showed an occipital focus (Fig 1C)
Summary
Perception is a function of the stimulus and very much influenced by internal factors such as arousal and attention. We combined the latest mobile EEG/EOG (electrooculogram) technology (for the assessment of brain activity and eye movements), mobile visual stimulation, and behavioural measurements to study human visual processing during free walking. Assessing steady-state visual evoked potential (SSVEP), which is known to be a stimuluslocked signal originating from the early visual cortex [40], we could demonstrate in a first study that walking modulated how visual input from the periphery influences (suppresses) central foveal input in a contrast-dependent fashion. This modulation was paralleled by a behavioural effect in the concurrently probed target-detection performance. These findings led to the hypothesis that peripheral visual processing is enhanced during walking, which was confirmed in a second (behavioural) study
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