The Speech Motor Systems & Pathways
What is the starting point for any voluntary speech movement?
The desire to move
What is another name for the direct activation pathway?
Pyramidal tract
Which brainstem structures serve as attachment points for cranial nerves?
Cranial nerve nuclei
Why is sensation critical for speech motor control?
Speech is a sensorimotor process
Damage to upper motor neurons typically results in which type of dysarthria?
Spastic dysarthria
Which system is also called the lower motor neuron system?
Final Common Pathway (FCP)
What is the main function of the direct activation pathway?
Voluntary, fine motor control of speech
Which structure coordinates voluntary movements for precise speech timing and force?
Cerebellum
Which system supports reflexes, learning, and automaticity in speech production?
Reticular formation
Damage to lower motor neurons typically results in which type of dysarthria?
Flaccid dysarthria
Which cranial nerve controls jaw movement and sensation to the face?
Trigeminal (CN V)
Which tract of the UMN system connects the cortex to the brainstem?
Corticobulbar tract
Which structure is important for planning slow, continuous movements in speech?
Basal ganglia
Which system influences the emotional expression of speech?
Limbic system
Which artery, when damaged, is most often linked to apraxia of speech?
Left middle cerebral artery (MCA)
Damage to which cranial nerve affects resonance, phonation, and swallowing?
Vagus (CN X)
Which tract of the UMN system connects the cortex to the spinal cord?
Corticospinal tract
Which structure acts as a sensory “gatekeeper” to refine motor impulses before speech execution?
Thalamus
Which hemisphere contributes to prosody and pragmatic aspects of speech?
Right hemisphere
How does bilateral versus unilateral LMN damage to the vagus nerve differentially affect resonance, phonation, and articulation?
Unilateral damage primarily affects phonation and resonance mildly, while bilateral damage produces severe resonance, phonatory, prosodic, and articulatory impairments.
What happens at the neuromuscular junction in speech motor control?
LMN axons synapse with muscle fibers
What is the role of the indirect activation pathway in speech?
Postural support and automatic control for fine motor speech movements
*Bonus Question*
How does contralateral versus ipsilateral innervation of cranial nerves influence recovery potential after unilateral cortical lesions?
Contralateral innervation limits compensation, while bilateral innervation allows redundancy and greater recovery potential.
*Bonus Question*
What is the functional significance of the corticobulbar tract in motor speech disorders compared to the corticospinal tract?
Corticobulbar tract is critical for speech muscles (cranial nerves), while corticospinal primarily controls limb and trunk muscles.
Why does the direct activation pathway alone not account for smooth, coordinated speech, and what systems refine its output?
Because it generates raw voluntary impulses, refinement requires the basal ganglia, cerebellum, and thalamus.