Virtual dyscalculia induced by parietal-lobe TMS impairs automatic magnitude processing.
People suffering from developmental dyscalculia encounter difficulties in automatically accessing numerical magnitudes [1-3]. For example, when instructed to attend to the physical size of a number while ignoring its numerical value, dyscalculic subjects, unlike healthy participants, fail to process the irrelevant dimension automatically and subsequently show a smaller size-congruity effect (difference in reaction time between incongruent [e.g., a physically large 2 and a physically small 4] and congruent [e.g., a physically small 2 and a physically large 4] conditions), and no facilitation (neutral [e.g., a physically small 2 and a physically large 2] versus congruent) [3]. Previous imaging studies determined the intraparietal sulcus (IPS) as a central area for numerical processing [4-11]. A few studies tried to identify the brain dysfunction underlying developmental dyscalculia but yielded mixed results regarding the involvement of the left [12] or the right [13] IPS. Here we applied fMRI-guided TMS neuronavigation to disrupt left- or right-IPS activation clusters in order to induce dyscalculic-like behavioral deficits in healthy volunteers. Automatic magnitude processing was impaired only during disruption of right-IPS activity. When using the identical paradigm with dyscalculic participants, we reproduced a result pattern similar to that obtained with nondyscalculic volunteers during right-IPS disruption. These findings provide direct evidence for the functional role of right IPS in automatic magnitude processing.
Cohen Kadosh
Roi
R
Department of Behavioral Sciences and Zlotowski Center for Neuroscience, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel. r.cohenkadosh@ucl.ac.uk
Cohen Kadosh
Kathrin
K
Schuhmann
Teresa
T
Kaas
Amanda
A
Goebel
Rainer
R
Henik
Avishai
A
Sack
Alexander T
AT
D000328:Adult; D001931:Brain Mapping; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008433:Mathematics; D010296:Parietal Lobe / Q000502:physiology*; D011930:Reaction Time; D050781:Transcranial Magnetic Stimulation