Organic Theories of Stuttering

Question 1

Orton-Travis Cerebral Dominance Theory (1930s)

Answer 1

• First formal organic theory
• AKA handedness theory
• stuttering is from a lack of cerebral dominance for the control of speech (neither is in control)
• thought motor nerve impulses from hemispheres needed to be synchronized for fluent speech; believed on dominated the timing

Question 2

Support/Rejection of Orton-Travis

Answer 2

Support:

• children who were shifted to right-handed or ambidextrous reportedly stuttered more often
• developed idea that language is in L hemisphere and should be lateralized

Rejected:

• large group of stutterers not distinguished by handedness
• forcing lateralization/a dominant hemisphere of stutterers was not successful

Question 3

Personality Theories

Answer 3

Followed popular theories of times (Freud)
- satisfy infantile needs/express agression

Anxiety
- stuttering= trait anxiety

Speech-Related Anxiety

• stutterers report higher speech anxiety
• not the case initially of stutterers

Question 4

Young study (Speech-Related Anxiety)

Answer 4

2 conditions

1: PWS warned there was a large audience, ended up being 1
2: PWS warned there would be 1 audience member, ended up being large group

Results: more dysfluencies in 1st condition

Question 5

Genetic Theories

Answer 5

Familial tendencies; no simple inheritance pattern

• more males than females
• neither polygenic nor single major locus
• 15% chance of stutterings if 1st degree relative stutters

Twin studies suggestive

• 70% concordance in monozygotic twins
• 10-15% concordance in dizygotic twins

Question 6

Neuroanatomical Abnormalities

Answer 6

Where stuttering research is going

White matter (information transmitter) abnormal in left superior longitudinal fasciculus and corpus callosum
LF = connects posterior language areas to high level motor acts
CC= connects hemispheres of brain

Question 7

Neuro differences (Sommer)

Answer 7

Differences in volume of white matter in left Rolandic operculum in PWS and fluent speakers
RO= close to motor strip near mouth control and near arcuate fasciculus (connects Broca’s and Wernicke’s areas)

Difference does NOT mean cause

Question 8

Neuro differences (Brown)

Answer 8

Meta-analyses of speech production studies using PET and fMRI studies (looking at function)

Found same areas were activated in PWS and fluent speakers but with different intensities

• increase in activation of lateral vocal-motor areas in R hemisphere mostly
• absence of activation in bilateral auditory areas (i.e. not monitoring speech)
• shift in activity in R hemisphere and reduction in L hemisphere
• Overactive cerebellum (i.e. coordination)

Differences does NOT mean cause: could be due to stuttering for years

Question 9

Studies with Children (Chang)

Answer 9

Measured grey and white matter in brains of 8 persistent stutterers, 7 recovered, 7 fluent controls

Results
- persistent and recovered had reduced grey matter
- persistent stutterers had reduced white matter compared to fluent controls
( in areas communicating with face and larynx)

Question 10

Studies with Children (Chang & Zhu)

Answer 10

27 PWS, 29 fluent controls: looked at white matter structure and resting structure

Results
- white matter connectivity in putamen (learning motor acts) and cortical and auditory regions was less sense in L hemisphere of PWS

Question 11

Speech motor control theories/models

Answer 11

• stutterings related to neuronal actions that initiate and regular muscle contraction for speech
• used by DCM to support their theory (low motor capacities)

Question 12

Before SMC theories were termed SMC…

Answer 12

• Did tongue strengthening

- Stimulated nerves of larynx (believed there was weakness)

Question 13

SMC Articulatory Dynamics

Answer 13

• how articulators work and move in speech
• speed and coordination is deficient in PWS
• found differences in PWS on their lip and jaw movement duration, displacement, and veolcity

Differences does NOT equal cause

Question 14

SMC Articulatory Dynamics Disproved

Answer 14

• movements of articulators in fluent speech and stuttered speech of PWS look similar to fluent speakers
• PWS do not have deficient articulators

Question 15

SMC Laryngeal Dynamics and Aerodynamics

Answer 15

Oral-laryngeal discoordination hypothesis: coordination between mouth and larynx don’t match

• research shows difference in voice onset time (could be compensatory strategy)
• differences between PWS and fluent speakers aren’t large