Speaker: Atsushi Nambu Division of System Neurophysiology, National Institute for Physiological Sciences, Okazaki, Japan Department of Physiological Sciences, SOKENDAI, Okazaki, Japan
Time: 2017-11-01 13:00 - 14:30
Venue: Room 1113, Wang Kezhen Building
Abstract: The basal ganglia (BG) govern cortical activity through the thalamus and control voluntary movements. The striatum and subthalamic nucleus (STN) are the input structures of the BG, while the internal segment of the globus pallidus (GPi) and substantia nigra pars reticulata (SNr) are the output nuclei. There are three major pathways that connect the input and output stations of the BG to modulate GPi/SNr activity: the cortico-STN-GPi/SNr hyperdirect, cortico-striato-GPi/SNr direct, and cortico-striato-external pallido (GPe)-STN-GPi/SNr indirect pathways. A signal through the direct pathway inhibits a specific population of GPi/SNr neurons, resulting in disinhibition of the thalamus and cortex and a release of only a selected motor program at a selected timing. On the other hand, signals through the hyperdirect and indirect pathways excite the surrounding wide areas of the GPi/SNr, resulting in inhibition of the thalamus and cortex and suppression of other competing motor programs.
Malfunctions of the BG cause severe disturbances in the execution of voluntary movements. In Parkinson’s disease, the hyperdirect and indirect pathways dominate over the direct pathway in both spatial and temporal domains, and thus, intended motor programs cannot be released, causing akinesia. On the other hand, in dystonia, the direct pathway dominates over the other pathways spatiotemporally, and thus, unintended movements are randomly released, causing involuntary movements.
Such symptoms of movement disorders can be ameliorated by stereotactic surgery by making a small lesion or applying high-frequency electrical stimulation (deep brain stimulation, DBS) in the BG. Our study showed that GPi-DBS inhibits cortically induced responses and spontaneous discharges in the GPi by strong GABAergic inhibition, suggesting that GPi-DBS blocks information flow through the GPi. Thus, both DBS and lesions seem to block abnormal information flow from the BG to the thalamus and cortex and suppress the expression of motor symptoms of movement disorders.
Host: Dr. Yuji Naya
