Motor Control

•      Cerebellum

•      Basal Ganglia

•      Motor Cortices

Cerebellum

•      General principles

–    formation of loops

–    modulatory

–    ipsilateral

–    midline versus lateral

Cerebellum

•      Contains two hemispheres

•      three divisions

–    vermis

–    intermediate zone

–    lateral zone

Cerebellum

•      Vermis - fastigial nucleus

•      intermediate zone - interpositus nucleus

•      lateral zone - dentate nucleus

Vermis

•      Receives somatosensory information and kinesthetic information

•      Postural adjustments

•      Lesion:  fall toward ipsilateral side.

Intermediate Zone

•      Receives info from red nucleus and somatosensory info from spinal cord

•      Lesion:  ridigity, difficulty in moving limbs.

•      Lesion:  action (intention tremor)

Lateral zone

•      Input from motor and association cortices through pons.

•      Lesion:  ballistic movement.

•      Lesion:  coordination of multijoint movements (decomposition of movement)

Lateral Zone

•      Learning new movements

•      Cognitive functions (simple, but precise time tapping movements)

•      Cognitive - judgments about time (central timing mechanism).

Basal Ganglia

•      Caudate nucleus and putamen are known collectively as the striatum

•      receive all input

Basal Ganglia

•      Globus pallidus (pallidum)

•      main output pathway that connects with thalamus

•      motor/nonmotor regions:  dorsolateral, orbitofrontal

Basal Ganglia

•      Movements that take time to initiate or stop.

–    Setting the motor system with regard to posture

–    preparing nervous system

–    motor planning and learning

Basal Ganglia

•      Substantia nigra

•      subthalamic nucleus

Basal Ganglia

•      Striatum connects to globus pallidus by two routes.

–    Direct

•    sustaining/facilitating ongoing action

–    Indirect

•    surpresses unwanted movement

 

Lesions to Basal Ganglia

•      Akinesia

•      bradykinesia

•      tremors

–    rhythmic, oscillating.

•      Parkinsons

–    damage to substantia nigra

•    no input to direct pathway

•    indirect pathway becomes overactive

Lesions to Basal Ganglia

•      Striatum damaged

–    indirect pathway from striatum to globus pallidus is underactive

•    hyperkinesis

•    chorea

•    athetosis

 

•      This is what happens in Huntington’s disease!

Motor Cortices

•      Motor program

–    abstract representation of an intended movement

–    outside motor cortex

•    supplementary motor

•    anterior cingulate

•    frontal eye fields

•    parietal regions

Supplementary Motor Area (SMA)

•      Often called premotor

•      Projections

–    ipsilateral, contralateral, and contralateral SMA

•      Lesion

–    difficulty in bimanual coordination

•      Imaging

–    active when asked to imagine movement

 

 

Anterior Cingulate

•      Cognitive control of movement

•      Novel and unrehearsed movements

•      PET study

–    manual movements

•    caudal

–    oculomotor

•    rostral

–    speech

•    in between

Frontal Eye Fields

•      Voluntary eye movements

•      Synapse on brain-stem

–    3rd, 4th, 6th cranial nerves

•      Frontal eyefields have precedence over superior colliculi

•      Lesion:  can’t inhibit automatic eye movements

 

 

Frontal Eye Fields

•      Right frontal eye field

–    leftward direction

•      Left frontal eye field

–    rightward direction

Parietal Lobes

•      Control of movements in space.

–    Superior regions

•      Contributes to ability to produce complex, well learned motor acts.

–    Inferior regions.

Parietal Lobes

•      Proprioceptive information

•      feedback from motor and premotor areas

Parietal Lobes

•      Lesions

–    superior parietal region

•    lose ability to guide limbs/misreach

–    Inferior parietal region

•    loss of ability to perform complex acts (apraxia)

•    well executed, but incorrect movements

 

Parietal Lobe

•      Lateralization

–    left inferior parietal lobe

•    apraxia

Subcortical Motor Disorders

•      Parkinson’s Disease

•      Huntington’s Disease

•      Tourette’s Syndrome

•      Tardive Dyskinesia

Parkinson’s Disease

•      Damage to substantia nigra (dopamine)

–    60% nerve cells

–    80% dopamine

•      Tremors

•      Cogwheel rigidity

•      akinesia

–    masked face

•      postural disturbance

–    shuffling, festinating gait

Parkinson’s Disease

•      Treatment

–    L-dopa

–    grafting

Parkinson’s Disease

•      Masked face

Parkinson’s Disease

•      Gait

–    bradykinesia

–    akinesia

Parkinson’s Disease

•      Gait

Parkinson’s Disease

•      Gait

–    dyskinesia

Parkinson’s Disease

•      Gait

Parkinson’s Disease

•      Hand Tremor

Huntington’s Disease

•      Inherited

–    30-45 years of age

–    death within 10-15 years

–    50/50 chance

•      Chromosome 4

•      MRI

–    atrophy of caudate

•    slowing

•    eye-movements

•    cognitive impairment

 

•      Chorea

–    jerky movements

–    involuntary

–    well coordinated

•      bradykinesia

•      eye-tracking

 

 

Tourette’s Syndrome

•      Motor tics

–    simple motor tics

•    eyeblinks

–    complex motor tics

•    touching, hitting,jumping

•      Vocal tics

–    cries/vocalizations

•    echolalia

•    coprolalia

 

•      Runs in families

•      Linked to chromosome 18

•      Associated problems

–    OCD

–    LD

–    ADHD

•      Treatment

–    haloperidol

 

Cortical Motor Disorders

•      Alien limb syndrome

–    distal limbs

–    stroke

–    SMA

Apraxia

•      Inability to perform skilled, purposeful movements.

–    No muscle weakness

–    No abnormal posture

•      Observed after LH damage

 

•      Classification Schemes

–    body part

–    complexity of movement

–    objects vs no objects

Body Parts

•      Oral (buccofacial) apraxia

–    left frontotemporal

•      Limb apraxia

–    left parietal/parietotemporal

Complexity of Movement

•      Ideational Apraxia

–    form “idea” of movement

–    sequence of movement

•    light candle

•      Ideomotor Apraxia

–    disconnection between idea of movement and its execution

–    can’t perform simple movements

Spatial “apraxia” (RH)

•      Constructional apraxia

•      Dressing apraxia

Callosal apraxia

•      Disconnection syndrome

–    can’t manipulate objects in left hand in response to verbal commands

Object recognition

•      Ventral stream

–    “what”

•      Dorsal stream

–    “where”

Ventral stream

•      Occipital

•      Occipitotemporal

•      Temporal

•      Devoted to processing visual information.

•      Single-cell recordings.

Ventral stream

•      Simple = posterior (occipital)

•      Complex = anterior (temporal)

•      V2:  color, texture, length

•      Inferotemporal

–    hands or faces

•      Inferotemporal

–    changes in retinal position

 

 

Ventral stream

•      Receptive field

–    larger for anterior regions than for posterior regions.

•      Sensitive to color

–    figure-ground separation

Visual agnosia

•      Impaired recognition of visual object

–    no basic visual processing deficit

–    no pervasive memory disorder

–    modality specific

Apperceptive agnosia

•      Can’t bind visual info together to perceive a meaningful whole.

•      Basic visual processing intact (lines, light/dark)

•      Posterior right hemisphere

Associative agnosia

•      Perception cannot be linked to stored knowledge.

•      Bilateral at occipitotemporal border.

Major differences

•      Detail

–    “pig” example