BASAL GANGLIA - WordPress.com · Damage to the Basal Ganglia esp. Caudate Circuit Timing and...
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BASAL GANGLIA
Dr. Ayisha QureshiProfessor
MBBS, MPhil
We have completed three levels of the motor system hierarchy: 1. Spinal cord,
2. Brainstem, and the3. Motor cortex,
Both Basal Ganglia & Cerebellum, can be considered as “side loops” in the motor hierarchy.
They influence the processing of motor control and modulate the outputof the descending pathways without directly causing motor output.
Because the most obvious clinical signs of damage to these areas are a wide variety of motor impairments, they are still generally considered to
be motor structures.
BASAL GANGLIA
Also called the Basal Nuclei, it consists of several masses of gray matter located deep within the
cerebral white matter.
CEREBRAL CORTEX
THALAMUS BASAL GANGLIA
It consists of the following nuclei:
1. caudate nucleus, 2. putamen,3. globus pallidus, 4. substantia nigra, and 5. subthalamicnucleus.
One of the principal roles of Basal Ganglia is to function in association with the
corticospinal system to control complex patterns of motor activity.
BASAL GANGLIA
Executing Motor Activity
Putamen Circuit
Cognitive control of Motor Activities
Caudate Circuit
Has 2 major circuits
PUTAMEN CIRCUIT(Executing learned patterns of
movements)
• Writing • Cutting with scissors • Hammering nails • Shooting a basketball• Passing a football• Talking • Controlled eye movements.
CAUDATE CIRCUIT(cognitive control of sequences of
motor patterns)
• Role of cognition and cognitive control of motor activity (motor actions as a consequence of thought)
• Sequential pattern of movements requiring thought and planning and then execution.
• E.g: seeing a lion, turning away from the lion, beginning to run and even climbing a tree.
PUTAMEN CIRCUIT (subconscious execution of learned
patterns of movement)
CAUDATE CIRCUIT(cognitive planning of
sequential & parallel motor patterns)
DISORDER OF THE PUTAMEN CIRCUIT leads to hemiballismus (injury to subthalamus
causing flailing of an entire limb), athetosis (injury to GP causing writhing movement of a hand, an arm
or face) and chorea (injury of putamen causing flicking movements in hands, face and other parts of
the body).
Damage to the Basal Ganglia esp. Caudate Circuit
Timing and scaling is a function of the caudate cognitive motor control circuit working in
association with the association areas of the cerebral cortex.
E.g. How large the writing should be and whether it should be written slowly or rapidly.
Because Basal Ganglia works in combination with Parietal Posterior Cortex (most association areas),
damage to this area leads to 2 conditions: 1. Agnosia- inability to accurately perceive
objects through normally functioning sensory mecahnisms.
2. Personal Neglect Syndrome in which the patient fails to use or clean or be aware of the side
of the body opposite to the side of the damaged posterior cortex.
(Note in the figure that the ability of the person to copy the left side of the drawing is severely
impaired.)
GABA & Dopamine make Negative Feedback Loops, thus, acting as stabilizers to the motor control systems.
PARKINSON’S DISEASE Also known as paralysis agitans, it results
from widespread destruction of the portion of the substantia nigra that sends dopamine-
secreting nerve fibers to the caudate nucleus & putamen.
TREATMENT
• L-DOPA • MAO inhibitors (L-DEPRENYL) • Transplanted Fetal Dopamine Cell• Destroying part of Feedback circuitry in the
Basal Ganglia
Huntington’s Disease (Huntington’s Chorea)
It is an autosomal dominant hereditary disorder, characterized by flicking movements in individual muscles & progressive severe distortional movements of entire body.
(dementia & motor dysfunction is also seen)
CAUSE: Loss of GABA secreting & Ach secreting neurons in many parts of the brain.
Gene involved: Huntingtin
Question: Summarize the integration of the many parts
of the total motor control of the body.