GLOSSARY

The basal ganglia are a group of grey matter nuclei deep in the cerebrum that connect with the cortex, thalamus, and brainstem in loops and play a part in selecting and initiating movement, suppressing unwanted movement, scaling movement intensity, habit learning, and motivation.

Components

• Striatum: the caudate nucleus and putamen, the main input.
• Globus pallidus: the main output (internal segment).
• Subthalamic nucleus.
• Substantia nigra: the source of dopamine for the striatum.

Mechanism

• Direct pathway: facilitates the desired movement (“release the brake”).
• Indirect pathway: suppresses competing and unwanted movements (“apply the brake”).
• Dopamine regulates the balance of these two pathways.

Clinical Application

• Parkinson’s disease: dopamine deficiency causing slowness of movement (bradykinesia), rigidity, resting tremor, and impaired balance.
• Huntington’s disease: degeneration of the striatum causing involuntary dance-like movements (chorea).
• Dystonia: involuntary contractions and abnormal postures, including focal dystonia in athletes.

Relevance to Sport

• Automating skill: with long practice, control of a skill shifts from the prefrontal cortex to the basal ganglia and the movement becomes automatic, freeing the athlete’s attention for tactics.
• The yips: a sudden disruption of learned precision movements (such as a golf putt or throwing in cricket and baseball); in some cases a form of focal dystonia linked to the basal ganglia, in others performance anxiety.
• Practical example: overthinking the details of an automated movement (such as a free throw) under pressure may cause choking; focusing on an external target rather than body movements helps.