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Nele Demeyere, Pia Rotshtein, Glyn Humphreys; Differentiating subitizing and counting: a voxel based correlational study. Journal of Vision 2011;11(11):175. doi: 10.1167/11.11.175.
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© ARVO (1962-2015); The Authors (2016-present)
There is an ongoing debate about whether the contrast between efficient visual enumeration of small number (subitizing) and the relatively inefficient enumeration of larger numbers (counting) is subserved by separable processes. All the neuropsychological evidence for distinct subitization and counting processes to date has emphasised behavioural differences between patients, and there is a paucity of data on the underlying neural correlates of any impairments. The present study provides a first lesion-based analysis of the relations of these different aspects of enumeration. We examined subitization and counting across a case series of brain lesioned patients with chronic deficits, correlating any behavioural deficits with data from whole-brain analyses of high resolution MRI scans. We related the range of behavioural performances on visual enumeration to a continuous measure of neural integrity using an observer independent voxel-based approach, separating out gray and white matter. Severe impairments in subitizing were associated with damage to the early visual areas and white matter in the occipito-parietal region, even with visual field defects accounted for in the modelling, while later visual areas were associated with less severe subitizing impairments. In contrast, impairments in counting efficiency were associated with damage to a larger fronto-parietal network, including the left angular gyrus as well as higher visual areas. The data support the argument for distinctive processes, and neural areas, supporting subitization and counting.
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