H&E-LFB stain. The<unk>  is a structure in the forebrain. Along with the caudate nucleus it forms the dorsal striatum. The caudate and<unk>  contain the same types of neurons and circuits – many neuroanatomists consider the dorsal striatum to be a single structure, divided into two parts by a large fiber tract, the internal capsule, passing through the middle. The<unk> , together with the globus pallidus, makes up the lentiform nucleus. The<unk>  is the outermost portion of the basal ganglia. These are a group of nuclei in the brain that are interconnected with the cerebral cortex, thalamus, and brainstem. Basal ganglia include the dorsal striatum, substantia nigra, nucleus accumbens, and the subthalamic nucleus. In mammals, the basal ganglia are associated with motor control, cognition, emotions, learning, and domain-general functions important for executive functioning as well as support for domain-specific languages. The basal ganglia are located bilaterally, and have rostral and caudal divisions. The<unk>  is located in the rostral division as part of the striatum. The basal ganglia receive input from the cerebral cortex, via the striatum. The<unk>  is interconnected with the following structures: alt=This is a transverse section of the striatum from a structural MR image. The striatum includes the caudate nucleus (top) and<unk>  (right) and the globus pallidus (left).|This is a transverse section of the striatum from a structural MR image. The striatum includes the caudate nucleus (top) and<unk>  (right) and the globus pallidus (left). This description is rudimentary and does not nearly exhaust even the basic established circuitry of the<unk> . The cortico-subcortico-cortical circuits with<unk> al involvement are dense and complicated, consisting of a wide range of axonal, dendritic, chemical, afferent, and efferent substrates. The<unk> 's outputs are highly arborized across output structures, and cortical efferents arise from layers III-VI of the cortex, dependent on gyri and location within the<unk> . Topographical organization of the<unk>  combines the following elements: anterior-to-posterior functional and somatotopic gradients, lateral-to-medial functional and somatotopic gradients, diffuse terminal output, patchy localized terminal output, segregated terminals from adjacent regions, finely interdigitated terminals from distal cortical regions in a seemingly overlapping fashion. Caudate nucleus The caudate works with the<unk>  to receive the input from cerebral cortex. Collectively, they can be considered the "entrance" to the basal ganglia. Projections from the<unk>  reach the caudate directly via the caudolenticular grey bridges. The<unk>  and caudate are jointly connected with the substantia nigra, however the caudate outputs more densely to the substantia nigra pars reticulata while the<unk>  sends more afferents to the internal globus pallidus. Substantia nigra The substantia nigra contains two parts: the substantia nigra pars compacta (SNpc) and the substantia nigra pars reticulata (SNpr). The SNpc obtains input from the<unk>  and caudate, and sends information back. The SNpr also obtains input from the<unk>  and caudate. However, it sends the input outside the basal ganglia to control head and eye movements. The SNpc produces dopamine, which is crucial for movements. The SNpc is the part that degenerates during Parkinson's disease. Globus pallidus The globus pallidus contains two parts: the globus pallidus pars externa (GPe) and the globus pallidus pars interna (GPi). Both regions acquire input from the<unk>  and caudate and communicate with the subthalamic nucleus. However, mostly the GPi sends GABAergic inhibitory output to the thalamus. The GPi also sends projections to parts of the midbrain, which have been assumed to affect posture control.
Putamen
Inferior colliculus
Arcuate nucleus 
Periventricular nucleus
Barrel cortex
Medulla
Medulla 
Piriform cortex