Quiz 3: Basal Ganglia

What structures make up the basal ganglia?

Corpus striatum + subthalamic nucleus + substantia nigra.

What is the main function of the basal ganglia?

Controls, initiates, and regulates voluntary movements; smooths movement; involved in motor learning and cognitive processes related to movement.

What are the anatomical divisions of the corpus striatum?

Caudate nucleus (head, body, tail)

Lentiform nucleus: putamen + globus pallidus (GPi + GPe)

What are the functional divisions of the corpus striatum?

Striatum = caudate + putamen (input hub)

Pallidum = globus pallidus (GPi + GPe, output & regulation)

Where is the subthalamic nucleus located?

In the diencephalon.

Where is the substantia nigra located and what are its divisions?

Midbrain; SNc (dopamine) & SNr (GABA, always inhibitory).

What are the anatomical divisions of the corpus striatum?

Caudate, putamen, globus pallidus.

What separates the lentiform nucleus from the thalamus?

The posterior limb of the internal capsule.

What is the main cortical input to the basal ganglia?

Corticostriate projections → cortex to caudate + putamen; excitatory and topographically organized

What thalamic input goes to the basal ganglia?

Intralaminar nuclei → project to striatum

Which cortical areas project directly to the subthalamic nucleus?

BA 4 (M1) and BA 6 (premotor cortex) → excitatory projections

What is the striatonigral pathway?

Striatum → SNr (inhibitory)

What is the nigrostriatal pathway?

SNc → Striatum (dopaminergic)

What is the subthalamic fasciculus?

Subthalamic nucleus ↔ pallidum (excites GPi, inhibited by GPe)

What is the striatopallidal projection?

Inhibitory projections from striatum to pallidum.

Where does the medial pallidum (GPi) send its output?

To the thalamus via ansa lenticularis and lenticular fasciculus

What are the main outputs of the basal ganglia?

From medial pallidum (GPi) to thalamus.

Through what tracts do GPi outputs reach the thalamus?

Ansa lenticularis (ventral GPi) and lenticular fasciculus (dorsal GPi).

Where do basal ganglia outputs ultimately project?

Merge and project to premotor cortex → influences motor cortex & UMNs.

What is the role of the direct pathway in movement?

Disinhibits the thalamus to allow voluntary movement.

What is the role of the indirect pathway in movement?

Increases inhibition to suppress competing movements.

What are negative signs in basal ganglia disorders?

Loss or reduction of movement.

What are examples of negative signs?

Akinesia (difficulty initiating), bradykinesia (slowness), abnormal postural adjustments (dystonia).

What are positive signs in basal ganglia disorders?

Excess or unwanted movement.

What are examples of positive signs?

Dyskinesia: tremor, chorea, athetosis, ballismus, tics; rigidity (bidirectional stiffness).

What structure is affected in Parkinson’s disease (PD)?

Degeneration of dopamine neurons in substantia nigra pars compacta.

What are the motor symptoms of Parkinson’s disease?

Tremor (“pill-rolling”), rigidity, akinesia, bradykinesia, dystonia, stooped posture, shuffling gait, reduced arm swing.

What are speech symptoms in Parkinson’s disease?

Hypokinetic dysarthria: imprecise consonants, monopitch, monoloudness, short rushes of speech, reduced loudness.

What are treatments for Parkinson’s disease?

L-dopa medication and deep brain stimulation (DBS).

What causes Huntington’s disease (HD)?

Inherited dominant gene; degeneration of striatal neurons and cortex.

What are the motor symptoms of Huntington’s disease?

Chorea, athetosis, dementia.

What are speech symptoms in Huntington’s disease?

Hyperkinetic dysarthria: strained-harsh voice, breathiness, irregular articulation, variable rate, hypernasality.