Basal ganglia: functional anatomy and physiology. Part 2

Area of Science:

• Neuroscience
• Neurobiology
• Systems Neuroscience

Background:

• Basal ganglia function and circuitry knowledge is advancing.
• The precise role of basal ganglia in health and disease remains debated.
• Extensive literature exists on basal ganglia, yet controversy persists.

Purpose of the Study:

• Review advances in basal ganglia function and circuitry.
• Summarize experimental data on basal ganglia stimulation and ablation.
• Discuss established and emerging roles of basal ganglia.

Main Methods:

• Review of experimental data on basal ganglia stimulation and ablation.
• Analysis of information flow concepts within basal ganglia circuitry.
• Description of anatomical substrates for parallel functional loops.

Main Results:

• The "funnel" system of information flow is outdated; parallel, segregated loops (motor, oculomotor, cognitive, limbic) are now favored.
• Specific roles of striatum, pallidum, substantia nigra, and thalamus in movement-related information flow are detailed.
• Basal ganglia's role in reinforcing/suppressing behavior via direct/indirect striatal loops is discussed.

Conclusions:

• Basal ganglia function is better understood through parallel loops rather than a single funnel system.
• These parallel loops are implicated in the pathophysiology of Parkinson's disease and Huntington's chorea.
• Neurotransmitter and neuromodulator alterations in basal ganglia are linked to several neurological disorders.