The angular gyrus is a cortical area involved in cross-modal association among somatosensory (body-knowledge) information, auditory information, and visual information. Developmentally, the angular gyrus is one of the last to functionally and anatomically maturate. Classically, it has been assumed that the left angular gyrus participate in calculation abilities, reading/writing, naming, and some type of body-knowledge (somatognosis). The deficit associated to left angular lesion (or Gerstmann’s syndrome) includes acalculia, agraphia, right-left disorientation, and finger agnosia. Spatial knowledge mediated by the language has been proposed as a basic underlying deficit observed in cases of left angular gyrus damage, responsible for observed acalculia and so-called semantic aphasia. fMRI studies support the role of the angular gyrus in arithmetic abilities, but seemingly, the really most crucial area in number processing is the intraparietal sulcus. Interestingly, BA39 activation is observed in some reading-related tasks (e.g., understanding of the relationship among different characters), but no reports are readily available about its participation in writing, probably because writing may be more exactly associated with the superior parietal lobe and BA40 (apraxic agraphia in cases of parietal lobe damage). The right angular gyrus clearly participates in visuospatial processing, and damage to it results in severe hemi-spatial neglect. In addition, BA39 seems to also participate in an executive function brain circuitry, and it activates in tasks such as verbal creativity, inferential reasoning and processing sequences.
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