  Maintaining upright posture is a complex task governed by the integration of
afferent sensorimotor and visual information with compensatory neuromuscular
reactions. The objective of this work was to characterize the visual dependency
and functional dynamics of cortical activation during postural control.
Proprioceptic vibratory stimulation of calf muscles at 85 Hz was performed to
evoke postural perturbation in open-eye (OE) and closed-eye (CE) experimental
trials, with pseudorandom binary stimulation phases divided into four segments
of 16 stimuli. 64-channel EEG was recorded; with perturbation epochs defined
using bipolar electrodes placed proximal to each vibrator. Finally, functional
connectivity assessment was explored via network segregation and integration
analyses. Spectra variation showed waveform and vision-dependent activation
within cortical regions specific to both postural adaptation and habituation.
Generalized spectral variation yielded significant shifts from low to high
frequencies in CE adaptation trials, with overall activity suppressed in
habituation; OE trials showed the opposite phenomenon, with both adaptation and
habituation yielding increases in spectral power. Finally, our analysis of
functional dynamics reveals novel cortical networks implicated in postural
control using EEG source-space brain networks. In particular, our reported
significant increase in local theta connectivity may signify the planning of
corrective steps and/or the analysis of falling consequences, while alpha band
network integration results reflect an inhibition of error detection within the
cingulate cortex, likely due to habituation. Our findings suggest that specific
cortical waveforms are dependent upon the availability of visual feedback, and
we present the first evidence that local and global brain networks undergo
characteristic modification during postural control.
