Fundamental Neuroscience, Third Edition

The basal ganglia are large subcortical structures comprising several interconnected nuclei in the forebrain, midbrain, and diencephalon (Fig. 31.1). Because of certain features, it is generally agreed that basal ganglia participate in the control of movement. The largest portion of basal ganglia inputs and outputs are connected with motor areas. Second, the discharge of many basal ganglia neurons correlates with movement. Third, basal ganglia lesions cause severe movement abnormalities. In addition to their role in motor control, basal ganglia are involved in cognitive and affective functions. This chapter concentrates on the motor functions of the basal ganglia, but participation of the basal ganglia in cognition is discussed after the basic framework of basal ganglia function is presented for motor control. The anatomy of the basal ganglia is discussed fi rst, as it is the anatomy that provides the infrastructure for the physiology. Next we consider the activity of the individual components of the basal ganglia during movement. Then we discuss the effect of placing a lesion in one component while leaving the rest of the nervous system intact. The combined strategy of measuring the activity of a structure during movement and then determining the effect a selective lesion on that movement has been fruitful in studying the function of the motor system. After presentation of current models of basal ganglia motor function, the chapter concludes with a discussion of basal ganglia participation in cognitive function.