MRI Morphometry
Note …… in the sylvian fossa of the stutterer
Extra gyri
Gene locations
All stutterers: chr 9
Persistent only: chr 15
Males only: chr. 7
Females only: chr. 21
What might be transmitted?
Structural anomalies
Biochemical pathways
Brain processing
Motor skills
Temperament
Cerebral dominance Theory
Proposed stuttering was caused by a lack of cerebral dominance
Left and right hemispheres compete for control of speech movements
Asynchrony of neural impulses from both sides of the brain disrupts speech fluency
Auditory perceptual theory
- Stuttering was caused by defective auditory feedback
- The speaker expects to hear own speech sound earlier than their auditory system feeds it back
- The speaker waits (prolongs) or repeats trying to correct the delay
Brainstem reflexes: disorder of movement theory
Proposed stutterers have reduced tolerance for a range of oral movements
If the range is exceeded, brainstem reflex management is upset
Afferent and efferent signals of speech muscles conflict > so stuttering occurs
DIVA (Directions into Velocities of Articulators)
Stuttering is due to a disorder of sensorimotor speech control
PWS have unreliable feedforward systems; they rely excessively on controlling speech via feedback
Fluency is disrupted by attempts to adjust speech movements after commands have been issued
