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Appearances may not be deceiving: calculation deficits due to a brain structure abnormality in neurologically normal children.

Calculation is an essential function learned in childhood that humans use in everyday life for many purposes. Calculation deficits typically occur in adults after left parietal lobe lesions (Grafman et al ., 1982). Historical evidence suggested that, more specifically, the region of the left angular gyrus was crucial for the mediation of calculation, but more recent research using functional neuroimaging and patient studies indicates that the left intraparietal sulcus may be even more important for the representation of specific calculation processes (Levy et al ., 1999; Rickard et al ., 2000; Rueckert et al ., 1996). Regardless of the exact location in the parietal lobe(s) of the key cortical structures concerned with supporting the computational mechanisms needed for aspects of calculation, significant advances have occurred regarding our knowledge about the cognitive architecture of calculation over the last two decades (Grafman and Rickard, 1997). These advances have allowed for more precise mapping of cognitive processes to brain sectors.

Dyscalculia is as prevalent as literacy problems in very low birthweight pre-term children. In this issue of Brain , Isaacs and colleagues used a new analytic technique, voxel-based morphometry, to identify a local region in the left parietal cortex where there was less grey matter in very low birthweight children who had dyscalculia …