Overview: Motor Speech System & Motor Speech Disorders

MSS: Conceptual level

• psychological, intrinsic thoughts, emotions, experiences, memories

MSS: Linguistic Planning Level

• attaching lexical items to concepts (language)

MSS: Motor Planning & Programming

• transformation from phonological representation into speech movements in the correct sequence

MSS: Motor Control Circuits

• selectively enabling/suppressing competing motor programs (b.g.)

• motor learning and developing fine motor control over time (cerebellum)

• usually contralateral 

MSS: Direct Activation Pathway

• 2 neuron system to send the motor commands from cortex to periphery 

• efferent: info from cortex to peripheral nerves (baseline muscle tone)

MSS: Indirect Activation Pathway

• 3 or more neuron system involved in posture, muscle tone, and reflexes

MSS: Final Common Pathway

• functionaly describes role of LMNs

MSS: Ascending Sensory Pathway

• relays sensory information like touch, pressure, temp, proprioception acoustic feedback back to the brain/CNS from the periphery

Dysarthria (broad description)

• collectively, a group of neurological speech disorders that reflect abnormality in the strength, speed, range, steadiness, tone, or accuracy of movements required for respiratory, phonatory, articulatory, or prosodic aspects of speech production

Flaccid Dysarthria

• affects 1+ CNs —> issue w/final common pathway

• how it can go wrong:

  • facial nerve ittself ( CN/Peripheral N issue)

  • demyelination (MS)

  • muscle fibers impaired (MD)

  • Acetylcholine improperly bound to muscles (weak muscles)

Spastic Dysarthria

• bilateral UMN damage (indirect path impairment)

• higher levels of muscle activation at baseline 

Hypokinetic Dysarthria

• b.g. impairments (direct pathway - dopamine) - smaller speech movements

Hyperkinetic Dysarthria

• b.g. impairments (indirect) - extra and unwanted speech movements 

Ataxic Dysarthria 

• related to cerebellar dysfunction (degenerative, tumor, brainstem lesion)

Unilateral UMN Dysarthria 

• unilateral UMN lesion 

Mixed Dysarthria

• 2 or more of the other kinds

Apraxia of Speech: (broad description)

• impaired capacity to plan or program the sensorimotor commands necessary for directing movements for phonetically and prosodically typical speech 

• assume we are talking about acquired (degenerative or non-degenerative) in this class

• pathology: lesion in language dominant hemisphere (usually left) 

• often more than one area w/degeneration