Notes

Telencephalon: Basal Ganglia

The basal ganglia are the principal subcortical components of a family of neuronal circuits which link the thalamus and cerebral cortex. The basal ganglia are crucial for the initiation and modulation of voluntary movement by sending their output to the motor cortex via the thalamus. In addition, the basal ganglia also contribute to a variety of behavioral and cognitive function other than voluntary movement.

Basal Ganglia: Striatum In humans (and most primates), the striatum consists of three major subdivisions: the caudate nucleus, the putamen, and the nucleus accumbens. In rats and mice, the striatum is typically divided into two subdivisions: the caudate putamen, which is often referred to as the "dorsal striatum" (and which would correspond to the human caudate nucleus + putamen); and the nucleus accumbens, which is referred to as the "ventral striatum". The striatum is the major recipient of inputs from the substantia nigra, cerebral cortex, thalamus and brain stem. Striatal neurons, which are primarily GABAergic spiny neurons (90/95%), send afferent projections to the globus pallidus and reciprocal projections to the substantia nigra.

Basal Ganglia: Globus Pallidus The globus pallidus lies medial to the putamen and is divided into external and internal segments. The globus pallidus give rise to the major output projections from the basal ganglia:

• The Internal Segment (GPi) sends projections to the thalamus and pedunculopontine nucleus (a group of cells located in the brain stem).
• The External Segment (GPe) sends projections to the internal segment of the globus pallidus and to the subthalamic nucleus.

Basal Ganglia: Substantia Nigra The substantia nigra is a midbrain (mesencephalon) structure, which contains a dense population of dopamine cells. The substantia nigra can be subdivided into substantia nigra pars compacta and pars reticulata. Dopamine cells in the substantia nigra pars compacta project to dorsal parts of the striatum (in humans: to caudate nucleus and dorsal part of putamen; in rats and mice: to caudate putamen), forming the nigrostriatal dopamine pathway.

Disorders of the Basal Ganglia: Parkinson's Disease Parkinson's disease is a chronic and progressive degenerative disease of the brain that impairs motor skills, speech, and other functions. In patients with Parkinson's disease, the dopaminergic cells in the substantia nigra pars compacta are lost.

Telencephalon: Limbic System

Limbic System: Hippocampal Formation In Alzheimer's disease, the hippocampus is one of the first regions of the brain to suffer damage; memory problems (especially spatial memories) and disorientation appear among the first symptoms. People with extensive, bilateral hippocampal damage (such as in patients with progressed AD) may experience anterograde amnesia - the inability to form or retain new memories.

Limbic System: Amygdalar Complex Functional involvement of amygdala in emotions. Human brain activity (measured by functional MRI) in response to emotional stimuli.