Inhibitory transcranial direct current stimulation enhances weak beta event-related synchronization after foot motor imagery in patients with lower limb amputation.

Purpose: Sensorimotor rhythm patterns in patients with lower limb amputations might be altered because of reorganization of the sensorimotor cortices. The authors evaluated the sensorimotor rhythm of motor imagery (MI) in healthy subjects and patients with lower limb amputations. In addition, the authors investigated whether transcranial direct current stimulation (tDCS) could modulate sensorimotor rhythm control.

Methods: Six healthy subjects and six patients with lower limb amputations were assigned to receive anodal, cathodal, or sham tDCS over the foot motor area in a randomized order. The authors evaluated event-related desynchronization and event-related synchronization (ERS) of unilateral hand and bilateral foot MI before and after tDCS.

Results: Beta ERS of foot MI in patients with lower limb amputations was significantly lesser than that in healthy subjects. Compared with sham stimulation, cathodal tDCS enhanced beta ERS of foot MI in patients with lower limb amputations. In contrast, anodal tDCS decreased beta ERS of foot MI in healthy subjects.

Conclusions: This is the first study to demonstrate that cathodal tDCS can enhance a weak beta ERS of foot MI in patients with lower limb amputations. These findings might contribute in improving the effectiveness of sensorimotor rhythm-based brain computer interface for gait restoration after lower limb amputation.