Neurolinguistics and Cortex Imaging

Aphasia and Hearing People

If language is disrupted because of damage to specific neural regions and pathways specialized for these functions, it often results in a group of disorders termed aphasia. These impairments usually result from an ischemic or hemorrhagic event in the middle cerebral artery, but they can have a number of other etiologies. A number of types of aphasia affect comprehension, repetition, and expression of language processes, as well as produce related deficits in reading (i.e., alexia) and/or writing (i.e., agraphia). Current conceptualizations of aphasia acknowledge the multimodal aspects of the disorder and describe aphasia types as fluent (typical speech production with difficulties comprehending spoken speech and/or repeating spoken language), nonfluent (difficulties articulating/producing spoken language with intact comprehension of spoken speech and the ability to repeat spoken language), or pure (isolated difficulties with recognizing or naming words). Fluent aphasia often occurs as a result of damage to the inferior frontal gyrus and related pathways (also known as Broca’s area or Brodmann areas 44 and 45. Nonfluent aphasia typically results from damage to the superior temporal gyrus and related pathways (also known as Wernicke’s area or Brodmann area 22). The left-sided language system also relies on the following neuroanatomical regions and pathways: ventral portions of the postcentral and precentral gyri, the supramarginal gyrus, the angular gyrus, and the medial temporal gyrus. Occasionally, the damage to this left hemisphere system is so pervasive that most language functions are disrupted (global aphasia); these individuals have difficulties comprehending, repeating, and/or producing language. These findings were originally identified in [Page 713]hearing individuals who used speech as their primary means of communication.

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