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How and where does the brain produce words? Evidence from language disorders in patients with brain disease.
Authors:
Patterson, K.
Reference:
Proceedings of the 6th International Conference on Spoken Language Processing, Vol 2, Beijing. China,
Year of publication:
2000
CBU number:
4193
Abstract:
In recent years, neurolinguistic research has broadened from an exclusive focus on the study of acquired aphasia due to cerebrovascular accident (stroke) to include patterns of language disruption and preservation in patients with neurodegenerative diseases that have a relatively focal impact on brain systems. Two distinctly different patterns of language degeneration have been identified, labelled "fluent" and "nonfluent" to reflect the characteristics of the patients' spontaneous speech. This paper reviews some of the implications of these two forms of progressive aphasia for language representation in the brain, with a focus on speech production. Progressive fluent aphasia is observed in cases with focal atrophy of the anterior, inferior, lateral regions of the temporal lobes of the brain, typically bilateral but asymmetrical. Neuropsychological testing reveals progressive deterioration of semantic aspects of language, particularly a severe loss of receptive and especially expressive content-word vocabulary. Progressive nonfluent aphasia, of equal interest but as yet less well understood, is associated with atrophy of left perisylvian cortex. Some features are reminiscent of the Broca-type aphasia observed in cases of extensive left-hemisphere stroke; but our current research suggests that this condition is not a progressive equivalent of Broca's aphasia. Speech production at any level beyond single words or very simple phrases is profoundly effortful, especially in self-generated conversation but even in tasks like reading or repetition where the stimulus specifies the output. Progressive fluent aphasia is observed in cases with focal atrophy of the anterior, inferior, lateral regions of the temporal lobes of the brain, typically bilateral but asymmetrical. Neuropsychological testing reveals progressive deterioration of semantic aspects of language, particularly a severe loss of receptive and especially expressive content-word vocabulary. Progressive nonfluent aphasia, of equal interest but as yet less well understood, is associated with atrophy of left perisylvian cortex. Some features are reminiscent of the Broca-type aphasia observed in cases of extensive left-hemisphere stroke; but our current research suggests that this condition is not a progressive equivalent of Broca's aphasia. Speech production at any level beyond single words or very simple phrases is profoundly effortful, especially in self-generated conversation but even in tasks like reading or repetition where the stimulus specifies the output.
