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 trans femoral amputees.

Automated summary

The integration of vibrotactile sensory feedback (VF) with balancing exercises has been shown to improve postural stability in lower limb amputees. This study investigated the cortical processes involved in balance control and how they are influenced by VF. Data from six transfemoral amputees were collected, and the results showed that VF elicited strong theta and gamma oscillations, leading to improved limit of stability (LOS). The secondary somatosensory cortex-S2 processed the sensory information from VF by reducing theta power, while the fronto-central (FC) region executed the motor response to improve LOS by increasing gamma power. The functional connectivity between S2 and FC was stronger with VF, and the two regions were strongly connected during perception of VF. These findings provide insights into the cortical mechanisms of balance improvement in amputees.