2022 年 39 巻 4 号 p. 706-710
Neurorehabilitation encompasses the process of improving motor and cognitive functions by modifying the functions and network of the brain, based on neuroscience. The synaptic transmission efficiency varies in the brain and exhibits dynamic changes because of synaptic activity levels and interactions with other synaptic inputs. Synaptic plasticity refers to the physiological basis of motor learning by modifying synaptic connections in an activity–dependent manner. Transcranial direct current stimulation (tDCS) and repetitive transcranial magnetic stimulation (rTMS) are types of non–invasive brain stimulation. They synergistically increase synaptic plasticity upon combination with rehabilitation treatment. The duration of depolarization by electrical stimulation to the motor field began expansion from the 1960s. Subsequently, researchers developed stimulation methods using high–voltage current and magnetic fields that did not decay even in skulls with high electrical resistance in the 1980s. tDCS and circular coil rTMS have a wide range of stimulation ; nonetheless, the figure–eight rTMS coil developed in Japan enables local stimulation and is being clinically applied. The effect of rTMS on neural activity depends on the frequency of stimulation. High frequency ≥5Hz enhances neural activity, whereas low frequency ≤1Hz suppresses it. It is necessary to increase the neural activity of the site that compensates for the impaired function in patients with cerebrovascular accidents. Thus, researchers have proposed the following two approaches : (i) applying high frequency rTMS to the ipsilesional primary motor cortex (M1) and (ii) applying inhibitory low frequency rTMS to the contralateral M1. The application of inhibitory low frequency attenuates the interhemispheric inhibition from the stimulated cerebral hemisphere to the functional compensation site. In addition, it indirectly activates the functional compensation site by releasing it from the interhemispheric inhibition. The aforementioned patients are divided into groups effective for the high frequency on the diseased side and for the low frequency on the healthy side. Neurorehabilitation promotes functional improvement when used in combination with contemporary rehabilitation treatment.
