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Dorsal-stream motion processing deficits persist into adulthood in Williams syndrome

Dorsal-stream motion processing deficits persist into adulthood in Williams syndrome. Atkinson et al. (2006) Neuropsychologia, 44, 828-833. Milner & Goodale (1995). Williams syndrome. Ventral stream functions = relative strengths (e.g. face recognition)

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Dorsal-stream motion processing deficits persist into adulthood in Williams syndrome

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  1. Dorsal-stream motion processing deficits persist into adulthood in Williams syndrome Atkinson et al. (2006) Neuropsychologia, 44, 828-833

  2. Milner & Goodale (1995)

  3. Williams syndrome • Ventral stream functions = relative strengths (e.g. face recognition) • Dorsal stream functions = relative weakness (e.g. visuo-spatial manipulation) • Atkinson et al. (1997) • the mailbox task: dorsal < ventral

  4. Motion and Form coherence • Indicators of function within extrastriate visual areas in the two streams • Activate largely non-overlapping systems in posterior cortex • But – both involve occipital, parietal and temporal lobes (human vs. animal explanation)

  5. Motion and Form coherence: Tasks employed by Atkinson group • Motion coherence: Participants locate a target strip (1/3 of display, left or right of centre). Coherently moving dots oscillated in opposite phase to remainder of display. • Form coherence: Jittering line segments. Participants locate dots oriented to lie on concentric circles (left or right of centre). Coherence = signal dots / total dots.

  6. Motion and Form coherence in WS Atkinson et al. (1997) • Participants: WS: N=15, CA: 4-14 (mean: 9.7 years). Controls: N=30, CA: 4-20 (mean: 8.1 years) • Results: No stats • Control: threshold < 0.4 • WS form: 3/15 > 0.4; motion: 7/15 > 0.4 Atkinson et al. (2003) • Participants: WS: N=45, CA: 4;8 to 15;4 (mean: 9;5 years) Controls: N>100, CA: 4 to 10 years, and adults • Results • WS number above 90th %ile. Motion: 19/45, form: 18/45. • WS standard score: no significant difference (form vs. motion) • Subset of WS: form > motion. Similar to TD controls aged 4 to 5 years.

  7. Atkinson et al. (2006) • Participants: WS: N=45, CA: 16-47 (mean: 28.3) Controls: N=19, CA: 18-41 (mean: 27.5) • Results • Group: Threshold, WS>TD • Group by task: greater group diff for motion than form • WS standard scores: threshold, motion > form • Large variability in motion coherence thresholds in WS • Performance not related to CA for WS or controls.

  8. Quotes from paper • “These results extend into adulthood the findings that WS children show a problem in global motion processing” • “Variability: reflects efficiency of underlying mechanism or strategies employed.” • “Deficits in WS are dorsal (visuo-spatial construction), but further along the stream. Typical motion coherence can be accompanied by impaired visuo-spatial construction.”

  9. Discussion • Matched by CA • Motion-form discrepancy not consistent across individuals with WS • Are these measures of dorsal and ventral stream processing? • Dorsal vulnerability not specific to WS (autism, dyslexia, fragile X) • Some dorsal functions available in WS: • Point light walkers (Jordan et al., 2002) • Size transformation (Farran & Jarrold, 2004) • Reiss et al. (2004). • Motion coherence (which of two panels shows coherence?) and Biological motion: typical performance • Form from motion (like Atkinson task): poor performance. • Developmental delay and premature arrest. • Difficulty: segmenting object from background? (see Farran & Wilmut, 2006)

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