Objectives

Basal ganglia

5 parts??

Basal ganglia

•Feedback loop between subcortical nuclei, thalamus, brainstem, and cerebral cortex

• Control of ____ motor movements (action selection)

• ____ of movement

• ___-___ of motor and premotor outputs

• Smoothly switch between behaviors

Caudate nucleus

•3 parts: ___, ___, __

• Head is continuous with the ____

• Tail terminates in the ___
Follows curvature of lateral ventricles

•Dopaminergic inputs from ____ ___

Putamen

•____ portion of the basal ganglia

•Continuous with ___ nucleus

• Connected by ___ ___ (fiber tract)

•Caudate + Putamen = ___ ____

Striatal afferents (inputs)

•____ fibers: excitatory inputs from PFC, premotor area, and primary motor cortex

•_____ fibers: inputs from intralaminar nuclei

•____ fibers: dopaminergic input from nigra

•_____ fibers: limbic system input

Striatal neurons

•___ ___ neurons:
• Principal neurons of the striatum (95% of striatum)

Express ___ receptors

Output neurons
• ____ (inhibitory)

*These cells fire in ___ of movement

Globus pallidus

•Internal (GPi) and external (GPe)
segments

• Separated by ___ ___ ____

•Putamen + globus pallidus (GPe and GPi)
= ___ nucleus

Globus pallidus

•Inputs from ____

•Sends outputs to the ___

•GABAergic

• Tonically active to ___
unwanted movement at rest

• Disinhibited by ___ ___
neurons

Important for regulation of
voluntary movement

Subthalamic nucleus

•Located ventral to the ____

•Inputs from ___

•Outputs to ___ ___
• Glutamatergic (___)

•Action selection

Substantia nigra

•Substantia nigra ("black substance") - dark appearance due to presence of ___

Pars compacta (SNc):
• Releases ___
• Fine motor control
•Axonal degeneration of SNc neurons = ___ disease

Pars reticulata (SNr):
• Releases ___
• ___ inhibition of motor outputs

Substantia nigra

•Inputs: ____

•Outputs:
• SNr sends ____ outputs to the thalamus and brainstem

• Primary output of basal ganglia for
___ movements

• SNc sends dopaminergic outputs to the striatum

• DI receptors: ____
• D2 receptors: ____

• Fine motor control and ____ processing

Direct pathway

Motor circuit for __-___ of muscle
activity

• Motor cortex (sends excitatory output to
___ in striatum)

• Striatum (sends inhibitory output to ___ & ___)

• Globus pallidus internal (becomes _____, so stops inhibiting thalamus)

• SNr (sends inhibitory output to ____)

• Thalamus (sends ___ output back to motor cortex)

Indirect pathway

• Motor circuit to prevent ____ muscle contractions from competing with voluntary movements

Motor cortex (sends excitatory outputs to ___)

Striatum (sends inhibitory outputs to __)

Globus pallidus external (becomes ____ so stop inhibiting subthalamic nucleus)

Subthalamic nucleus (sends excitatory outputs to ___)

___ of the inputs that GPi gets via the direct pathway

Thalamus (sends ___ ___ outputs to motor cortex)

Integration of the pathways

Cortical activity signals onset of movement

___ pathway inhibits GPi and
increases thalamic output
(facilitation of cortically initiated movement)

___ pathway excites GPi
and ___ thalamic output
(suppression of antagonistic
muscles/decreasing competing
movements).

**BOTH pathways are active at the __ time

Parkinson's disease

•Loss of ____ cells in SNc

•Reciprocal input between SNc and
striatum lost

•Subthalamic nucleus becomes ____ (b/c GPe inhibition of STN is completely removed)

•Increased excitatory outputs to __

•Greater inhibitory output from GPi
to ____

•Thalamic output to the cortex is
____

Parkinson's disease

•Loss of SNc dopaminergic neurons may be due to lesion, environmental toxin, or genetic causes

•Rigidity may be caused by decreased control of ___ neurons that control motor neurons. Impaired ability to prevent ___ muscle activity.

•____: reduced ability to initiate
voluntary movement

•____: involuntary movements (tremors, tics)

Deep brain stimulation

____ implantation of electrode into basal ganglia structures:

• subthalamic nucleus (STN)

• Internal segment of globus
pallidus (GPi)

•Levodopa-___ Parkinsons's
symptoms