Dorsalstream motion processing deficits persist into adulthood in Williams syndrome

1
Dorsal-stream motion processing deficits persist
into adulthood in Williams syndrome

• Atkinson et al. (2006) Neuropsychologia, 44,
  828-833

2
Milner Goodale (1995)
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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 lt ventral

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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.

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Motion and Form coherence in WS

• Atkinson et al. (1997)
• Participants WS N15, CA 4-14 (mean 9.7
  years).
• Controls N30, CA 4-20 (mean 8.1 years)
• Results No stats
• Control threshold lt 0.4
• WS form 3/15 gt 0.4 motion 7/15 gt 0.4

• Atkinson et al. (2003)
• Participants WS N45, CA 48 to 154 (mean
  95 years)
• Controls Ngt100, 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 gt motion. Similar to TD
  controls aged 4 to 5 years.

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Atkinson et al. (2006)

• Participants WS N45, CA 16-47 (mean 28.3)
• Controls N19, CA 18-41 (mean 27.5)
• Results
• Group Threshold, WSgtTD
• Group by task greater group diff for motion than
  form
• WS standard scores threshold, motion gt form
• Large variability in motion coherence thresholds
  in WS
• Performance not related to CA for WS or controls.

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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.

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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)