Acquired AOS Flashcards
What is AOS?
an acquired disorder of learned volitional actions associated with breakdown in the planning or programming of the movements needed for speech
Is AOS developmental?
no
Does AOS affect reflexive movements?
no
Does AOS affect non-speech movements?
What is this known as?
no
oral apraxia or bucco-facial apraxia
breakdown is not in…
expressive or receptive language - aphasia, or oro-motor strength or sensation - dysarthria
what did the term apraxia initially describe?
problems moving limbs
What did Liepmann (1900a) describe as apraxia?
What was his theory about?
- a patient who was unable carry out movements, in the absence of any paralysis (weakness) or ataxia (incoordination).
- how our brain sends instructions to our limbs to carry out movements. When this process is disrupted – the result is an “apraxia”.
what parts of the body can apraixa affect?
- limb movements
- eye movements: ocular apraxia
- facial movements: oral/bucco-facial apraxia
- can affect the ability to carry out movements using objects- known as “ideational apraxia”.
kernel features of AOS
- Sound distortions (including distorted substitutions)
- Extended segment* durations
- Extended intersegment durations
- Prosodic deficits
substitutions
speaker has selected or accessed
incorrect phonemes and articulated these normally
(e.g in phonemic paraphasia)
distortions
correct phoneme was accessed, but articulated in an imprecise or unusual way (e.g. in AOS, dysarthria)
distorted substitutions
the impression that both
phoneme selection and articulatory accuracy are
incorrect – most common error type in AOS
most common distortions in AOS
length, voicing,
tongue placement
extended segment durations
- lengthened production of consonants and vowels
- rate of speech is perceived as slower overall
extended intersegment durations
may also be referred to as…?
may insert…?
- lengthened pauses between sounds and between words
- speech sounds segmented
- May also be referred to as “syllabification”
- May insert “intrusive schwa” in between segments
prosodic deficits
- restricted alteration of pitch, intonation, loudness (monotonous)
- slow rate
- equal lexical stress
- unnatural sounding (not like themselves)
- rare: foreign accent
non-discriminatory features
- Articulatory groping
- Perseverative errors
- Increasing errors with word length
- Speech initiation difficulties
- Awareness of errors
- Automatic speech > propositional
- Islands of error free speech
____ is not a feature of AOS
anticipatory errors
range of severity of AOS
- slightly slow, relatively fluent speech
- slow segmented speech with lots of sound errors and disturbed prosody
- complete inability to speak
AOS co-occurs with ___ in over ___% of cases
aphasia
90%
what other disorder does AOS sometimes co-occur with?
dysarthria
are cases of pure AOS rare?
yes: only a handful have been described
acute AOS can be caused by:
- Primarily caused by stroke – typically left hemisphere; most often frontal and parietal
lobes; most often larger strokes - TBI or a brain tumour/brain
surgery
Primary progressive AOS can be caused by neurodegenerative diseases such as:
- Cortico-basilar degeneration (CBD)
- Progressive supranuclear palsy (PSP)
- MND or ALS
Lesion sites proposed to be associated with AOS
- the left insula
- Broca’s area/left inferior frontal gyrus
- the pre-central gyrus and
post-central gyrus i.e. primary motor and somatosensory areas) - pre-motor cortex
why is it hard to say where AOS lesions occur?
Our current understanding is that speech is likely organised across a wide network of structures with different roles including:
parts of Broca’s area, precentral gyrus, postcentral gyrus, anterior insula, subcortical structures (basal ganglia, cerebellum)
Stroke/TBI can affect multiple areas of the brain
The organisation of speech in the brain may change after stroke/TBI due to neuroplasticity and cortical reorganisation
therefore we don’t know whether different structures have taken over different roles in the person with AOS
Moser (2016) reported on 2 people with similar cases of AOS who had very different brain damage locations when brain
imaging (MRI scan) was used suggesting there may not be one area specific to AOS
Research studies have often used differing diagnostic criteria to identify AOS (due to the controversies about diagnostic
symptoms) and this makes it hard to compare and collate results of different experiments
Models and theories of AOS?
- Van der Merwe 4-stage model
- DIVA/GODIVA model
Van der Merwe (1997) steps
Stage 1: Conceptual linguistic
Stage 2: Motor Planning
Stage 3: Motor programming
Stage 4: Execution
Conceptual-linguistic stage of Van der Merwe
Stage associated with what disorder?
- Pre-motor stage
- Intention to speak
- Message constructed: syntax,
semantics, morphology - Phonological plan (phonemes)
- aphasia
Motor planning stage of Van der Merwe
Associated with what disorder?
- Strategy of action
- Spatial specifications (place and manner)
- Temporal specifications (timing)
- Core motor plans = goals of
movement - AOS
Motor programming stage of Van der Merwe
- Muscle-specific programs selected and sequenced
- Spatial and temporal dimensions: tone, direction, force, rate
Execution stage of Van der Merwe is associated with what disorder?
dysarthria
Proposals for what goes wrong with motor planning in AOS?
- The brain mis-selects the incorrect motor programme for the intended production target
- The brain can no longer access stored programmes for the intended target, or the quality of these stored programmes has deteriorated
- There is interference in the brain between competing motor programmes
- The correct programme is selected, but the programme is applied to the wrong articulator
DIVA stands for
DIRECTIONS INTO VELOCITIES OF ARTICULATOR MODEL
What does DIVA model suggest?
- we have a “speech sound map” believed to be located in the left frontal cortex
- This “map” area is believed to be made up of “mirror neurons” (Hickock, 2012) which are activated both when a sound is produced and heard
- These neurons in this area are thought to be responsible for motor planning/programming by sending out “feedforward” commands to the articulators, and receiving “feedback” from
auditory and sensory routes
how has the DIVA model been tested?
with speech-generating computer software – when they disable this “map” area in the computer model- the result is
speech that replicates AOS i.e. sound distortions, prosodic disturbance
how does feedforward and feedback work in motor planning?
- A movement goal is identified (e.g. producing a syllable)
- A motor program or command for that movement is activated and initiated
- Simultaneously an efference copy of that command is generated, i.e. a prediction of the expected sensory feedback from the issued motor command
- As the movement unfolds, the actual sensory consequences are compared to the prediction
- If a mismatch is detected, error signals arise and corrective motor commands are
generated to modify the ongoing movement - The error signals are also used to update the “stored” motor programs, thereby improving the accuracy of future attempts to perform that motor task
- this is motor learning
non-discriminatory features of AOS
- Groping, effortful speech, difficulty initiating speech
- Awareness of errors and self-correction
- Variability of errors
- Increasing errors with word length
- Automatic speech better than propositional speech e.g. counting 1-10 easier than counting 10-1
- Islands of error free speech
what is groping in speech?
Gives the impression that the speaker searches for articulatory postures, recognizes
inaccurate postures, and attempts to self-correct
error location
whether an error occurs on the same target sound within a word across repeated trials
Dog
dod
Dog
dok
Dog
error type
whether the same error is made within the same location of a word across repeated trials
Dog
dok
Dog
dok
Dog
dok
why is error variability controversial?
- Historically, AOS was considered to be characterised by highly variable errors but not supported by recent studies
- Duffy (2013) suggested that individuals with AOS with more severe impairment demonstrate more consistent and predictable errors compared with those with milder deficits due to their more limited sound repertoire
why might PWAOS have increased errors with increasing word length?
- Multisyllabic words require motor planning of several phoneme and syllable units at a time, as well as variations in relative duration and amplitude of movements across adjacent units
to achieve the correct stress contrast - they require significantly increased motor
programming and thus are likely more challenging for people with AOS
