Chapters 13 14 Single

The Movement System

Basal Ganglia „

Interconnected nuclei

Corpus striatum

… Caudate

… Caudate

… Putamen

… Putamen

… Globus

… Globus

pallidus … Nucleus accumbens … Olfactory tubercle „

„

Motor & non-

„

pallidus

Striatum … Caudate … Putamen

Striatum Caudate „ Putamen „ Globus pallidus „ Internal capsule „

Striatum „

Caudate … Head

bulges into lat. Ventricle … Degenerative diseases, aka Huntington’s, bulge is lost

Caudate Head – anterior horn „ Tail – inferior horn „

Striatum „

2 types of neurons … Spiny

– projection neurons

Silent at rest „ Discharge when stimulated „ Lost in Huntington’s Chorea „

…

i.e. lose output of striatum

… Aspiny

- interneurons

Spiny Neuron Inputs „

Cortical … Distal

„

dendrites

Local inputs … Proximal

dendrites

… Soma

„

Inputs nearer to cell body modulate far inputs.

Input to Striatum „

Direct … Corticostriate

projection „

…3

Almost all cortical areas

distinct zones „

Sensorimotor …

„

Associative …

„

Caudate

Limbic …

„

Putamen

Indirect

Nucleus accumbens

Output from Striatum Substantia Nigra „ Globus pallidus „ Nucleus accumbens „

Globus Pallidus & Substantia Nigra „

Globus pallidus … Arm

& leg representation

„

Substantia nigra … Head

& neck representation

„ „

Multipolar projection neurons 90% input from striatum

Striatopallidal Pathways „

Direct …

Striatum to internal segment of globus pallidus & substantia nigra pars reticulata … Disinhibits thalamus … Increase motor activity … Hyperkinesia – Huntington’s chorea „

Indirect …

Striatum to external globus pallidus to subthalamic nucleus to GPi & SNr … Inhibit thalamus … Decrease motor activity … Enhanced activation – Parkinson’s hypokinesia

GPi/SNr Output „

Major output … Thalamus „ „ „ „

Ventral anterior Ventral lateral Dorsomeidal Intralaminar

… Fields

„

of Forel

Minor output … S.C. … Habenular

nucleus … Reticular formation … Spinal cord

Subthalamic Nucleus „

Inputs … Cortex „

Motor, premotor, supplementary motor areas

… GPe … Thalamus … SNc … Dorsal

Nucleus of

Raphe „

Reticular input

Subthalamic Nucleus „

Outputs … GPe … GPi … SNr

„

Lesions … Ballism „

„

Violent, involuntary movements

Deep Brain Stim … Treatment

of Parkinson’s

Corticostriatothalamocortical Loops „

5 parallel loops … Motor … Oculomotor … Dorsolateral

prefrontal … Lateral orbitofrontal … Limbic „

Cortical area -> striatum -> globus pallidus -> thalamus -> back to cortical area

Motor Loop „

Putamen … Arm,

leg, face inputs … Target location … Limb kinematics … Muscle pattern

Oculomotor Loop Caudate nucleus „ Eye movements „

Dorsolateral Prefrontal Loop „

Caudate nucleus

„

DLPC – … Possibly

unique to

humans … Damage – schizophrenia … TMS – treat depression

Lateral Orbitofrontal Loop „

Caudate nucleus

„

Lateral orbitofrontal … Planning

complex behaviors … Personality

Limbic Loop Caudate, Putamen, Nucleus accumbens, olfactory tubercle „ Implicated in schizophrenia „

Split Circuitry „

Closed loops … Previous

„

loops

Open loops … Allows

for cross communication … Affects a cortical area that does not project to striatum

Basal Ganglia Functions „

Motor … Automatic

execution of learned motor plan … Preparation for movement … Cortically initiated … Damage – slower, less automatic, less accurate movements „

Presumably from cortical mechanism only

… Tics

& Tourette’s

Basal Ganglia Functions „

Gating Sensory Information for Motor Control … Hypokinesia „

– Parkinson’s

Decreased input of sensory information

… Hyperkinesia „

– Huntington’s

Increased access to sensory information

Basal Ganglia Functions „

Cognitive … Dorsolateral „

prefrontal loop

Deficits Spatial memory … Episodic memory … Semantic information …

Schizophrenia „ Huntington’s chorea – cognitive disturbances „ Parkinson’s disease – cognitive disturbances „

… Lateral

Orbitofrontal loop

Lesions „ Obsessive-compulsive disorder (OCD) „

Basal Ganglia Functions „

Emotional/Motivation … Limbic

loop

Schizophrenia „ Depression „

… Basal „

ganglia

Decrease in size in bipolar disorder

Basal Ganglia: Clinical Correlates „

Hyperkinetic Disorders … Chorea „

Milkmaid’s grip …

„

Cannot sustain tight hand grip

Trombone tongue Cannot maintain protruded tongue … Darts in and out …

Basal Ganglia: Clinical Correlates Huntington’s „ Atrophy of caudate (head) visible in lateral ventricle „

Basal Ganglia: Clinical Correlates „

Hyperkinetic disorders (continued) … Athetosis

Greek for ‘without position’ „ Slow, writhing, continuous, worm-like movements of the fingers. „ Lesion of putamen „

… Ballism

Greek for ‘jump’ „ Violent involuntary movements of the limbs „ Often one side of body „

…

hemiballismus

Basal Ganglia: Clinical Correlates „

Hyperkinetic disorders (continued) … Dystonia „ „

Greek for ‘bad tone’ Twisting, slow, contorting, involuntary movement …

„

Focal …

„

One body part, e.g. hand ƒ Writer’s cramp

Segmental …

„

Sustained and repetitive

2 or more adjacent body parts, e.g. head and neck ƒ Torticollis – involuntary turning/tilting of head

Generalized

Basal Ganglia: Clinical Correlates „

Hyperkinetic disorders (continued) … Tic

Brief, sudden, rapid, intermittent movements or sounds. „ Simple „

…

„

Contractions of only one group of muscles, e.g. eyeblinks

Complex …

Coordinated sequence of movements, e.g. eyeblink and shoulder shrug

Transient – days to weeks „ Chronic – months to years „ Prelude to Tourette’s „

Basal Ganglia: Clinical Correlates „

Hyperkinetic disorders (continued) … Tourette’s

Motor and verbal tics. „ Shrunken caudate „

Basal Ganglia: Clinical Correlates „

Hypokinetic Disorders … Parkinson’s

Tremor - rhythmic, recurring „ Cogwheel rigidity – resistance to passive movement of joint throughout range of motion „ Hypokinesia/akinesia – lessining/loss of associated movements, e.g. arm swinging when walking „ Dopamine depletion „

…

L-Dopa treatment