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

syndromesyndrome

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

833833

StreamStream Responsible for:Responsible for:

DorsalDorsal Action: spatial relationships relative to the observer, Action: spatial relationships relative to the observer, control of spatially directed actions (where and how), control of spatially directed actions (where and how), and sensitivity to motion and stereo info.and sensitivity to motion and stereo info.

VentralVentral Perception: recognition of objects and faces (what and Perception: recognition of objects and faces (what and who), and sensitivity to shape and colour info.who), and sensitivity to shape and colour info.

Milner & Goodale (1995)

Williams syndromeWilliams syndrome

Ventral stream functions = relative strengths Ventral stream functions = relative strengths (e.g. face recognition)(e.g. face recognition)

Dorsal stream functions = relative weakness (e.g. Dorsal stream functions = relative weakness (e.g. visuo-spatial manipulation)visuo-spatial manipulation)

Atkinson et al. (1997)Atkinson et al. (1997)• the mailbox task: dorsal < ventralthe mailbox task: dorsal < ventral

Motion and Form coherenceMotion and Form coherence

Indicators of function within extrastriate visual Indicators of function within extrastriate visual areas in the two streamsareas in the two streams

Activate largely non-overlapping systems in Activate largely non-overlapping systems in posterior cortexposterior cortex

• But – both involve occipital, parietal and But – both involve occipital, parietal and temporal lobes (human vs. animal temporal lobes (human vs. animal explanation)explanation)

Motion and Form coherence: Motion and Form coherence: Tasks employed by Atkinson groupTasks employed by Atkinson group

Motion coherence: Participants Motion coherence: Participants locate a target strip (1/3 of locate a target strip (1/3 of display, left or right of centre). display, left or right of centre). Coherently moving dots oscillated Coherently moving dots oscillated in opposite phase to remainder of in opposite phase to remainder of display. display.

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

Coherence = signal dots / total dots.Coherence = signal dots / total dots.

Motion and Form coherence in WSMotion and Form coherence in WSAtkinson et al. (1997)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 statsResults: 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)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 adultsControls: N>100, CA: 4 to 10 years, and adults ResultsResults

• WS number above 90WS number above 90thth %ile. Motion: 19/45, form: 18/45. %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 Subset of WS: form > motion. Similar to TD controls aged 4 to

5 years.5 years.

Atkinson et al. (2006)Atkinson et al. (2006) Participants: WS: N=45, CA: 16-47 (mean: 28.3)Participants: WS: N=45, CA: 16-47 (mean: 28.3)

Controls: N=19, CA: 18-41 (mean: 27.5)Controls: N=19, CA: 18-41 (mean: 27.5) ResultsResults

• Group: Threshold, WS>TD Group: 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 paperQuotes from paper

““These results extend into adulthood the findings These results extend into adulthood the findings that WS children show a problem in global motion that WS children show a problem in global motion processing”processing”

““Variability: reflects efficiency of underlying Variability: reflects efficiency of underlying mechanism or strategies employed.”mechanism or strategies employed.”

““Deficits in WS are dorsal (visuo-spatial Deficits in WS are dorsal (visuo-spatial construction), but further along the stream. construction), but further along the stream. Typical motion coherence can be accompanied by Typical motion coherence can be accompanied by impaired visuo-spatial construction.”impaired visuo-spatial construction.”

DiscussionDiscussion Matched by CAMatched by CA Motion-form discrepancy not consistent across individuals with Motion-form discrepancy not consistent across individuals with

WSWS 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 Dorsal vulnerability not specific to WS (autism, dyslexia, fragile

X)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?) Motion coherence (which of two panels shows coherence?)

and Biological motion: typical performanceand 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 & Difficulty: segmenting object from background? (see Farran &

Wilmut, 2006)Wilmut, 2006)