W11 - Atypical Vision Flashcards
(49 cards)
What are the two main visual differences explored?
- Global motion perception 2. Visual stress/discomfort
What terminology is encouraged for inclusivity in discussing conditions?
Use “condition” over “disorder”, use both person-first and identity-first language, avoid deficit framing (describe as “higher thresholds” rather than “worse performance”).
What does the motion coherence task measure?
The ability to detect the direction of motion from moving dots—harder with lower coherence.
What does elevated motion coherence threshold mean?
The person needs more dots moving in the same direction to perceive motion accurately.
Which conditions show elevated motion coherence thresholds?
Autism, dyslexia, Williams syndrome, schizophrenia, hemiplegia, Fragile X, congenital cataract.
What do these condtions imply about mostion processing?
Motion processing difficulties are not condition-specific.
What characterises dyslexia?
Difficulties with reading and spelling, with multiple contributing factors.
What is the magnocellular hypothesis?
Dyslexia may stem from impaired magnocellular processing, affecting high temporal frequency and motion perception.
Evidence for the magnocellular hypothesis?
Livingstone et al. (1991): smaller LGN magnocellular neurons; Benassi et al. (2010) meta-analysis supports motion difficulty in dyslexia.
What are the limitations of the magnocellular hypothesis?
Only ~30% of dyslexic individuals show motion issues; many studies lack tasks isolating magnocellular function; alternative theory: dorsal-stream dysfunction.
How does the DSM-5 (2013) define autism?
- Social communication/interaction differences 2. Restricted/repetitive behaviours or interests, including sensory processing.
How does autism affect motion perception?
Elevated thresholds, likely due to reduced integration, internal noise, or poor noise exclusion.
What does Weak Central Coherence theory propose?
Autistic people focus on local details, struggle to integrate into a global whole, may pool motion over fewer dots.
What is the neural basis of WCC?
Reduced long-range connectivity and reduced top-down modulation.
How do illusions support WCC?
Autistic individuals are less influenced by visual illusions (e.g., Ebbinghaus), suggesting strong local focus.
What three mechanisms are proposed?
Reduced sampling; increased internal noise; reduced noise exclusion.
What tasks were used (Manning et al., 2015)?
- Motion Coherence Task 2. Direction Integration Task (equivalent noise paradigm).
What is equivalent noise modelling?
A method to separate sampling efficiency from internal noise levels.
Who were the participants (Manning et al., 2015)?
66 children (33 autistic, 33 typically developing), ages 6–13, matched on age and performance IQ.
What did autistic children show (Manning et al., 2015)?
Greater sampling, no improvement in motion coherence (poor signal–noise segregation), slight increase in internal noise.
What do the results of manning et al. support?
Weak Central Coherence—enhanced local integration, impaired filtering of irrelevant motion.
What two condition-specific theories have been proposed?
- Dyslexia → magnocellular/dorsal-stream dysfunction 2. Autism → Weak Central Coherence.
What broader insight arises from motion coherence findings?
Elevated thresholds occur across many conditions, suggesting need for more general theories of motion processing differences.
What are the dorsal and ventral visual streams responsible for?
Dorsal: “Where/how” (motion, spatial); Ventral: “What” (form, identity, colour).
