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

Stream Responsible for: Dorsal Action: spatial relationships relative to the observer, control of spatially directed actions (where and how), and sensitivity to motion and stereo info. Ventral Perception: recognition of objects and faces (what and who), and sensitivity to shape and colour info. Milner & Goodale (1995)

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

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

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. 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). Form coherence: Jittering line segments. Participants locate dots oriented to lie on concentric circles (left or right of centre). Coherence = signal dots / total dots.

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

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

Quotes from paper “These results extend into adulthood the findings that WS children show a problem in global motion processing” “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.” “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.” “Deficits in WS are dorsal (visuo-spatial construction), but further along the stream. Typical motion coherence can be accompanied by impaired visuo-spatial construction.”

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