Acquired impairment of language following brain injury or disease. A diagnostic label can encompass multiple deficits and lesion patterns; behavioral components must be measured rather than inferred solely from the label.
Improvement in language function following acquired impairment. Residual tissue, network reorganisation, task practice and rehabilitation can contribute; recovery should be assessed across useful functions and time.
A clinical syndrome with progressive language impairment as the principal initial problem. Detailed profiles distinguish loss of word meaning, motor speech difficulty, agrammatism and phonological-memory demands; a syndrome label is not a unique anatomical lesion or molecular pathology.
A PPA pattern involving word-finding pauses and impaired repetition, with phonological-memory limitations often important. Sentence length and syntactic complexity should be varied independently when testing comprehension.
A PPA pattern prominently affecting word and conceptual meaning. Failure to understand a sentence can arise from missing word knowledge even if some grammatical operations remain available.
A PPA pattern characterised by effortful or agrammatic language, often with apraxia of speech. Motor speech and syntactic comprehension should be measured separately; neither is established merely by slow output.
A disproportionate naming difficulty for visually presented objects despite evidence of recognition. Nonverbal knowledge and naming through other input routes help distinguish it from visual agnosia.
A pattern of impaired semantic processing often investigated after stroke, in which regulating the use of knowledge can be especially difficult. The label does not imply that every patient has the same brain lesion or precisely the same mechanism.
Difficulty retrieving names. A naming failure can reflect lexical access, phonological output or degraded semantic knowledge, so naming alone does not diagnose failed object recognition.
An unintended substitution or alteration in speech, involving sounds or words. Fluent output can contain many such errors and therefore need not convey accurate information.
An aphasic presentation dominated by difficulty understanding language. This descriptive dimension does not identify one necessary brain lesion or exclude production deficits.
A fluent aphasic syndrome in which comprehension, repetition and informative speech can all be impaired. Acoustic–phonological analysis, semantic representations and semantic control must be distinguished; receptive difficulty does not imply preserved production.[ref]
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