Chapter 3 - Cell Types in the Different Nuclei of the Basal Ganglia

Abstract

Publisher Summary This chapter reviews that the basal ganglia (BG) can be subdivided into dorsal and ventral aspects. The dorsal aspect of the basal ganglia in rodents and higher vertebrates consists of four major nuclei. These nuclei are the striatum, the globus pallidus, the subthalamic nucleus (STN) and the substantia nigra (SN). The striatum in rodents is a single nucleus, also called the caudateputamen. In higher vertebrates the striatum is comprised of the caudate nucleus and the putamen, which are partitioned by the internal capsule. The globus pallidus consists of external (GPe) and internal (GPi) segments. In rodents, the external segment is also known as the globus pallidus and the internal segment is equivalent to the entopeduncular nucleus. The chapter discusses that GPe is used when referring to the rodent globus pallidus and GPi is used when referring to the rodent entopeduncular nucleus. Each pallidal segment has different afferents and efferents and is functionally unique. The SN is also divided into two parts that are functionally distinct. The pars reticulata (SNr) and the pars compacta (SNc) share mostly similar afferents but have different outputs. The main output of the SNr is to the thalamus, while the SNc primarily consists of dopaminergic neurons that principally innervate the striatum. The SNr and GPi are the major output nuclei of the basal ganglia. Cconsiderable knowledge on the different types of neurons and interneurons in the basal ganglia has been gained in the past 10–15 years. There has also been an advance in knowledge of the absolute number of neurons, interneurons and astrocytes within the dorsal aspect of the basal ganglia, as well as the absolute number of neurons in associated structures.