Title: Psychology 393 Cognitive Neurology
1Psychology 393Cognitive Neurology
- Motor Systems Apraxia
- January 30, 2007
2Subcortical Motor Control
- Two primary structures
- Cerebellum
- Basal Ganglia
3Subcortical Structures Cerebellum
- 3 Divisions
- Vermis
- Intermediate zone
- Lateral zone
- 3 Nuclei
- Fastigial nucleus
- Interpositus nucleus
- Dentate nucleus
4Subcortical Structures Basal Ganglia
- Striatum
- Putamen
- Caudate
- Nucleus Accumbens
- ( Major input zones into Basal Ganglia)
- Globus Pallidus
- Internal section
- External section
- (Output from BG to Thalamus)
- Substantia Nigra
- Subthalamic Nucleus
5Subcortical Structures Basal Ganglia
- Important for
- the accomplishment of movements that may take
some time to initiate or stop - Two major modulatory roles
- Facilitating/sustaining ongoing action
- Suppressing unwanted action
6Subcortical Structures Basal Ganglia
- Caudate/Putamen (BG input) connects to Globus
Pallidus (BG output) by two routes - Direct Pathway
- Activation of Caudate/Putamen inhibits internal
GP (iGP). - iGPs normal inhibition of thalamus (motor
nuclei) is inhibited excitation of thalamic
motor nuclei - Excitation of thalamic motor nuclei
facilitation / maintenance of ongoing behaviour
7Subcortical Structures Basal Ganglia
- Caudate/Putamen (BG input) connects to Globus
Pallidus (BG output) by two routes - Indirect Pathway
- Activation of Caudate/Putamen inhibits external
GP (eGP). - eGPs normal inhibition of subthalamic nucleus
(STN) is inhibited excitation of STN - STN in turn excites the inhibitory connections of
iGP to thalamus. - Inhibition of thalamic motor nuclei stopping of
unwanted behaviour.
8Subcortical Structures Basal Ganglia
- Damage to Direct Pathway
- (hypokinetic disorders)
- Parkinsons Disease
- Lack of dopaminergic inputs from substantia nigra
to striatum - Akinesia (inability to initiate movement)
- Bradykinesia (motor slowing)
- Resting tremors
- Postural disturbances
- Once action is begun, difficult to stop
- Responses to external stimuli preserved
(internally guided / motivated movements
disturbed)
9Subcortical Structures Basal Ganglia
- Damage to Indirect Pathway
- (hyperkinetic disorders)
- Huntingtons Disease
- Damage to striatum giving rise to indirect
pathway - Choreaform movements (uncontrollable jerking /
twitching movements) - Athetosis (writhing movements)
- Unlike PD (inability to respond to internal
stimuli), HD patients may be unable to suppress
reactions to somatosensory / kinesthetic stimuli
10Cortical Motor Control
- Involved in externally guided movements those
requiring linkage between sensory inputs and
motor outputs - Key Structures
- Primary motor cortex
- Supplementary motor area
- Premotor cortex
- Anterior Cingulate
- Parietal lobes
11Cortical Structures Primary Motor Cortex
- Provides command signal to drive motor neurons to
make muscles move. - Damage
- weakness
- Imprecise fine motor movements
12Cortical Structures Premotor Cortex (PMC) /
Supplementary motor area (SMA)
- Premotor and SMA are involved motor programs
abstract representations of an intended movement
(a motor plan) - SMA involved in complicated motor action
sequencing - PMC involved in motor action selection (coding
for type of action necessary)
13Cortical Structures Anterior Cingulate Cortex
(ACC)
- ACC implicated in motor planning of novel or
cognitively demanding actions - A ? B (well rehearsed)
- A ? M (novel) anterior cingulate activation
- Topography for different motor functions
- Manual posterior regions
- Speech middle regions
- Ocular anterior regions
14Cortical Structures Parietal Cortex
- Twofold role
- Superior Parietal Lobule
- Integration between motor and sensory information
- Damage difficulty guiding limbs (overreaching)
- Inferior Parietal Lobule
- Contributes to the ability to produce complex,
well-learned acts - Damage difficulty with well-learned motor acts
(apraxia)
Need to know Table 5.2
15Cortical Motor Dysfunction Apraxia
- Oral vs. Limb Apraxia
- Oral apraxia
- associated with difficulties performing voluntary
movements with the muscles of the tongue, lips,
cheek, larynx
16Cortical Motor Dysfunction Apraxia
- Oral vs. Limb Apraxia
- Limb apraxia
- disrupts the ability to use limbs to manipulate
items such as screwdrivers, scissors or hammers. - Hand as object errors