EEG frequency analysis of cortical brain activities induced by effect of light touch

Abstract

In human postural control, touching a fingertip to a stable object with a slight force (<1 N) reduces postural sway independent of mechanical support, which is referred to as the effect of light touch (LT effect). The LT effect is achieved by the spatial orientation according to haptic feedback acquired from an external spatial reference. However, the neural mechanism of the LT effect is incompletely understood. Therefore, the purpose of this study was to employ EEG frequency analysis to investigate the cortical brain activity associated with the LT effect when attentional focus was strictly controlled with the eyes closed during standing (i.e., control, fixed-point touch, sway-referenced touch, and only fingertip attention). We used EEG to measure low-alpha (about 8-10 Hz) and high-alpha rhythm (about 10-12 Hz) task-related power decrease/increase (TRPD/TRPI). The LT effect was apparent only when the subject acquired the stable external spatial reference (i.e., fixed-point touch). Furthermore, the LT-specific effect increased the high-alpha TRPD of two electrodes (C3, P3), which were mainly projected from cortical brain activities of the left primary sensorimotor cortex area and left posterior parietal cortex area. Furthermore, there was a negative correlation between the LT effect and increased TRPD of C3. In contrast, the LT effect correlated positively with increased TRPD of P3. These results suggest that central and parietal high-alpha TRPD of the contralateral hemisphere reflects the sensorimotor information processing and sensory integration for the LT effect. These novel findings reveal a partial contribution of a cortical neural mechanism for the LT effect.

Consolidation of the postural set during voluntary intermittent light finger contact as a function of hand dominance

“…This could mean that the left IPG plays a role in the detection of multisensory conflict or the directing of tactile attention. This is in correspondence with reports by Ishigaki and colleagues [13], who suspected involvement of the left primary somatosensory and posterior parietal cortices in the processing and integration of steadystate right hand light touch. On the other hand, we disrupted the left and right PPC by cTBS and did not find any alterations in sway progression following removal of active light touch [10].…”

Disruption of right posterior parietal cortex by continuous Theta Burst Stimulation alters the control of body balance in quiet stance

“…Ishigaki et al . (), however, did not report bilateral activity changes during quiet stance with light touch but exclusively in the dominant hemisphere contralateral to the contacting hand. As both hemispheres were undisturbed physiologically in their experiment, it may be that any ipsilateral activity changes in the right hemisphere were suppressed.…”

“…Ishigaki et al . () demonstrated that processing of a haptic signal when it contains information about body sway relative to an earth‐fixed reference reduces cortical activity in the contralateral left‐hemisphere parietal lobe as determined by EEG. Unfortunately, they did not assess the effect of contact with the non‐dominant (left) hand.…”

Dysesthesia symptoms produced by sensorimotor incongruence in healthy volunteers: an electroencephalogram study

“…EEG data were band-pass filtered in the range of 0.1–50.0 Hz and applied to a common average reference montage. We removed artifacts using previously described methods 24,25. Briefly, artifacts generated by blinking, eye movements, facial muscle activity, or body movements were removed using a specially designed spatial filter in EMSE Suite 5.4 and visual inspection of the frontal EEG trace (Fp1, Fp2).…”