EEG-explained cortical correlates of transfemoral amputees during balancing with vibrotactile feedback: A pilot study

Improving postural stability of lower limb amputees by integrating vibrotactile sensory feedback (VF) with balancing exercises has been proved advantageous. However, the cortical processes engaged in human balance control which process the VF and help to improve postural stability remain elusive. To this end, Electroencephalography in synchronization with the center of pressure (CoP) signals was collected from six transfemoral amputees during a balance control task in two sessions: with and without VF. The improved limit of stability (LOS) during the balance task with VF was in response to elicited strong theta and gamma oscillations. The secondary somatosensory cortex-S2 (contralateral to amputated side) processes the sensory information from VF by significantly reducing the theta spectral power. Additionally, the fronto-central (FC) region executed the motor response to improve the LOS by significantly increasing the gamma power. The intra-regional functional-connectivity at the S2 and FC region was significantly stronger with VF, in comparison to no feedback condition, and the two regions (S2 and FC) were strongly connected while perceiving the VF during forward voluntary sway in comparison to no feedback sessions. These findings provide fundamental insights into the cortical activity associated with the VF and helps in understanding the cortical mechanism of balance improvement in transfemoral amputees.