DPT 756- Basal ganglia

What are two major components of the Basal ganglia?

• Pyramidal

• Extrapyramidal

What type of impairments do we see with damage to the pyramidal component? (3)

• Spasticity/hypertonicity

• Clonus

• Paralysis

What impairments do we see with the damage to the extrapyramidal component? (3)

• Tremor and involuntary movement

• Changes in posture and muscle tone

• Poverty and slowness of movement without paralysis

What are functions of the basal ganglia? (6)

• Facilitate wanted movement

• Inhibit unwanted movement

• Enable flexibility and adaptation of movements to environmental demands

  • Adapting the postural set

• More involved in control of complex movements, sequenced movements

• More involved in internally generated movements

• Plays a roll in procedural memory

Whats the postural set?

Set of muscles needed for a posture

What are the paths of the motor loop?

Direct and indirect

Whats the ultimate result of the direct pathway?

disinhibition of the thalamus thereby facilitating willed, internally generated movement

What occurs due to activation of the direct pathway? (3)

• Results in more VA/VL activity

• Boosts the activity in the motor cortices

• Positive feedback circuit that serves to focus or funnel the activation of widespread cortical areas

Whats the ultimate result of the indirect pathway?

inhibition of thalamocortical neurons which inhibits movement

What occurs due to the activation of the indirect pathway? (3)

• Increased activity of the GPi which decreases VA/VL activity

• Assists in braking or possibly smoothing the movement (the direct pathway simultaneously facilitates the movement)

• Suppresses potential conflicting patterns (the direct pathway modulates voluntary movement by reinforcing the selected pattern)

What are the two disorders of the basal ganglia?

Parkinson’s and Huntingtons disease

Whats the overall result of Parkinson’s?

Increased inhibition of VA/VL

Whats the overall result of Huntington’s disease?

Dec inhibition of the VA/VL

What kind of disease is huntingtons disease?

Hereditary- autosomal dominant (fxn of huntingtin protein unclear)

Whats the outlook of huntingtons disease?

Progressive and lethal

Characteristics of Huntingtons disease?

• Hyperkinesias

• Dyskinesias (Chorea)

• Dementia

• Symptoms do not appear until adulthood

What’s the underlying cause of Huntingtons disease?

• Profound loss of neurons in the caudate nucleus, putamen, and GP

• Cortical degeneration

Whats ballism?

Violent, flinging movements of the extremities

What is hemiballism?

Same as ballism just to one region of the body (can be either UE, LE, or unilateral)

Whats the underlying causes of ballism? (2)

• Damage to the subthalamic nucleus usually from CVA

• Loss of excitatory input to neurons in the GP that project to VA/VL (underactivity in the indirect pathway)

What is Tourette syndrome? (4)

• Characterized by physical (motor) tics and at least one vocal (phonic) tic

• Coprolalia – inappropriate or derogatory remarks (rare)

• Does not affect intelligence or life expectancy

• Combination of genetic and environmental factors (mostly genetic)

What is dystonia

a neurological movement disorder characterized by involuntary muscle spasms and contractions, leading to repetitive and often awkward movements and postures

What causes dystonia?

Lesion or disease of the BG or putamen

Dystonia leads to what occuring?

• Reduction in the inhibitory control of motor circuits

• Failure of "surround inhibition," leading to unwanted muscle contractions and movements alongside the intended ones

Types of Dystonia?

Primary- Combination of genetic and environmental factors

Secondary- Drugs, CVA

What are some non-motor aspects of behavior that are affected due to injury of basal ganglia? (2)

• Associated w/ complex neuropsychiatric cognitive and behavioral disturbances

• Disorders Involve action rather than perception or sensation

  • Intensified action

  • Flattened affect

What neurotransmitters are important to depression?

Dopamine and serotonin