Disentangling dyscalculia & dyslexia Co ‐occurrence of numeracy and literacy Co‐occurrence of numeracy and literacy learning disabilities in adults Anna J. Wilson Educational Studies and Human Development College of Education, University of Canterbury

Acknowledgements Postdoctoral supervisor Karen Waldie Collaborators Stanislas Dehaene Philippe Pinel Research assistants, students Stuart Andrewes Veema Lodhia Rajna Bogdanovic Lucy Patston Helena Struthers Phil Light Funding provided by: The University of Auckland (FDRF Project Grant to Karen Waldie) University of Canterbury 

Specific learning disabilities • Severe difficulty learning in particular domain,  unexplained by general cognitive ability, or by education. – Mathematical disability (MD) or dyscalculia – Reading disability (RD) or dyslexia • Prevalence: around 6% for both • Underlying impairment in brain function • Strong genetic influence • Dyscalculia understudied compared to dyslexia • May be subtypes of both dyslexia and dyscalculia

Brain bases of dyscalculia

Dyscalculic children ‐ less grey matter in IPS  (Rotzer et al., 2008)

Dyscalculic adults born pre‐term – less gray matter in IPS (Isaacs, Edmonds & Lucas, 2001) Controls

Superimposed images of sulci Turner subjects

Dyscalculic children – less activation in IPS  during magnitude tasks (Kucian et al., 2006) Molko, Cachia and Riviere (2004) Turners subjects ‐ structural and functional alternations in IPS.

Number sense Using number sense activates the intraparietal sulcus (IPS): (Same area is involved in representing space, time, movement)

x = - 48

Right hemisphere

Axial slice

Left hemisphere z = 44

z = 49

x = 39

50 %

HIPS

22 % Dehaene, Piazza, Pinel, & Cohen (2003)

Mathematical tasks which activate this region:  Comparison of numbers  Subtraction  Approximation  Estimation e.g. comparison  Non‐symbolic tasks Automatically activated by viewing numbers

Causes of dyscalculia "Access" hypothesis : Deficit in link between number sense and symbols (Rouselle & Nöel, 2007)

left hemisphere

quantity

verbal "six"

  visual 6

"Core deficit" hypothesis: Deficit in number sense (Butterworth, 1999; Gersten & Chard, 1999; Wilson & Dehaene, 2007)

right hemisphere

quantity

 visual 6

Dehaene, S. (1992). Cognition, 44, 1-42. Dehaene, S., & Cohen, L. (1995). Mathematical Cognition, 1, 83-120.

Comorbidity in learning disabilities Commonly co‐occurring with dyscalculia (MD): • Dyslexia (RD), prevalence ≈50% • ADHD, prevalence ≈30% • Dyspraxia • Spatial difficulties

Dyscalculia & dyslexia comorbidity 1. Overlap in networks involved in mathematics and reading LH areas involved in reading, and implicated in dyslexia

Démonet, Taylor & Chaix (2004)

Dyscalculia & dyslexia comorbidity 1. Overlap in networks involved in mathematics and reading  Numerical comparison (1 digit) Exact subtraction > Comparison Exact subtraction > Multiplication Approximate addition Numerosity estimation Numerical distance effect (1 digits) Number subliminal perception Complex > Simple addition Numerical distance effect (2 digits) Multiplication > Comparison Multiplication > Subtraction Exact > Approximate calculation Subtraction ∩ Phoneme detection Simple addition > Complex addition Adapted from Dehaene et al. 2003

Dyscalculia & dyslexia comorbidity 1. Overlap in networks involved in mathematics and reading 

Non‐verbal Verbal Dehaene, Molko, Cohen & Wilson (2004)

Subtypes of dyscalculia? • Number sense / number sense access – Everything affected except counting, fact retrieval – May have difficulty with non‐symbolic tasks

• Verbal  – Difficulty with counting, fact retrieval, word problems – Associated with dyslexia?

• Executive  – Difficulty with fact retrieval, use of strategy/procedure – Associated with ADHD??

• Spatial  – Difficulty with subitizing, apprehension of non‐symbolic quantity… mental number line? Wilson & Dehaene (2007)

Dyscalculia & dyslexia comorbidity 1. Overlap in networks involved in mathematics and reading  Different neural impairments underlie dyscalculia in  presence/absence of comorbidity

Predictions:

Mathematics and reading disabilities (MDRD) → more impairment on verbal mathematical tasks Mathematics disability only (MD) → more impairment on non‐verbal mathematical tasks

Dyscalculia & dyslexia comorbidity 2. Diffuse neural impairment Same neural impairment underlies dyscalculia in  presence/absence of comorbidity Susceptibility genes for dyslexia (e.g. DYX1C1, DCDC2,  KIAA0319) involved in neural migration, and expressed  over wide areas of cortex. (Ramus, 2006) Predictions:

Mathematics and reading disabilities (MDRD) and  Mathematics disability only (MD) → either similar profiles across all mathematical tasks,  OR more impairment for MDRD across all tasks

Auckland comorbidity project Aims •Symptoms of dyscalculia in adults •Core deficit(s) in dyscalculia •Cause of co‐morbidity with dyslexia •Subtypes of dyscalculia and dyslexia Methods Four groups of subjects:

Control

Dyscalculia  only

Dyslexia only

Dyscalculia +  dyslexia

Control

MD

RD

MDRD

•Cognitive profiling (n=80) – battery of 14 tasks •fMRI (n=48) •Genetics (n=48)

Sample characteristics Total n = 49 n Average age (yrs) Female (%) Left handed (%) WJ word ID percentile WJ word attack percentile WRAT spelling percentile WRAT math percentile IQ – full IQ – verbal IQ – performance Education, yrs from age 6 Possible ADHD (Adult Self Rating Scale, ASRS, %) * p