fNIRS-based analysis of brain activation with knee extension induced by functional electrical stimulation

Patients suffering from paralysis due to aging, accidents, or brain injuries are increasing worldwide. Conse-quently, there is a compelling need for effective methods for the recovery of motor functions. The involvement of brain plasticity has been suggested effective and previous studies have reported that lost motor function and efficiency due to brain damage can be regained by repeatedly increasing and decreasing brain activation. Functional electrical stimulation (FES) has shown its effectiveness in the recovery of motor function. Brain activity usually decreases with the improve-ment of muscle control by FES. This study investigated the generality of brain responses during rehabilitation with FES in order to elucidate the recovery mechanism. We monitored the brain activity of one healthy subject with fNIRS over a ten-day period (one experiment per day) during which the knee joint movement was induced by FES with different parameters. The subject was seated in the chair of a leg extension device (Fig.1). The measurement regions covered the primary motor cortex and the somatosensory cortex with transmitters and receivers shown in the right of Fig. 1. Receiver No. 5 in Fig. 1 was posi-tioned on the Cz of the international 10-20 system. We stimu-lated his left quadriceps muscle with the FES device for 4 sec-onds. The results suggest that the observed increases and decreases of brain activity induced by FES are common (Fig.2). It is suggested that increasing and decreasing brain activation was evoked by long-term FES stimulation. Further research is needed to examine greater numbers of healthy subjects and patients suffering from paralysis to determine the optimum stimulation parameters for brain activation to involve brain plasticity.