Sensory info in speech motor control comes from which modalities?
- audition
- vision
- somatosenses: touch, proprioception, and pain
Describe the thalamus
- Primary sensory relay (except olfaction)
- Functions in: attention, memory and learning, abstract thinking and goal-oriented behaviours, consciousness and emotion
- Generating movements
Describe the ventral anterior (VA) and ventral lateral (VL) nuclei of the thalamus
- facilitate movement, associated with BG & cerebellum
- send info to motor cortex
Describe the ventroposterolateral (VPL) nuclei of the thalamus
- somatosensory relay
- send sensory info to somatosensory cortex
PCA hemorrhage involving the VPL and VPM results in what?
contralateral hemianasthesia
VA/VL damage results in what?
movement disorders reminiscent of cerebellar damage (ataxia and intention tremor) and BG damage (involuntary movements)
What are the two control circuits involved in speech?
basal ganglia
cerebellum
The BG and cerebellar control circuits are directly connected to the ________ and ________
motor cortex
thalamus
List the components of the basal ganglia
- striatum (caudate nucleus + putamen)
- globus pallidus (intenral and external)
- subthalamic nucleus
- substantia nigra
the direct loop of the BG control circuit is responsible for what?
stimulating/facilitating movement
the indirect loop of the BG control circuit is responsible for what?
inhibiting movement
Describe the steps in the direct BG loop
association cortex – striatum – inhibits GPi – excites thalamus – motor cortex
Describe the steps in the indirect BG loop
association cortex – striatum –> inhibits GPe – excites STN – excites GPi – inhibits thalamus – motor cortex
When active, the GPI inhibits which structure?
thalamus
When active, GPE inhibits which structure?
subthalamic nucleus
What are the basal ganglia functions
- facilitates or inhibits motor activity
- performs temporal sequencing of movements
- assists in motor learning (with supp motor cortex)
- Cognitive role in memory
Parkinsons involves a reduction of dopamine in the brain and damage to the ________ loop. Describe the damage
- direct
- GPI not inhibited properly, so it continues inhibiting the thalamus
What % of parkinson patients have dysarthria?
90%
Describe the motor abnormalities associated with parkinsons
- hypokinesia
- bradikinesia
- rigidity
- tremor at rest
- shuffling gait
- dysarthria
T or F: treatment for PD patients typically improves speech
False
Describe dyskinesias
- damage to the indirect loop of BG
- involves decreased output of BG to thalamus leading to hyperkineticity
- involuntary movements including chorea, ballism, dystonia, tics etc.
Huntington’s disease involves damage to what brain area.
striatum is damaged, leading to increased activity of GPE
T or F: dystonia always affect speech
False - they may or may not affect speech
What is a dystonia
- a persistent posture of a body part which can result in grotesque movements and distorted postures of the body
- involves co-contractions of agonist and antagonists
