A modern assessment of the basic forms of aphasia

A brief survey of the field of aphasia is presented. Many of the facts described in the neurological classics remain valid, but the interpretation of these facts must be altered. The basic principles of aphasia are reassessed in the light of neuropsychology. Neuropsychological analysis shows sensory (acoustico-gnostic) aphasia to be based upon an impairment in phonemic hearing. Motor aphasia breaks down into afferent (kinesthetic) and efferent (kinetic) aphasia. The former is based upon an impaired kinesthetic input into the speech functions, which results in a special type of oral apraxia. Efferent (kinetic) aphasia is based upon a breakdown in the kinetic organization of speech motor acts. Nominative (amnestic) aphasia consists of a number of forms, each based on either a weakness of visual or auditory analysis or difficulty in selection between evoked memory traces. “Transcortical motor aphasia” proves to be either perseverative aphasia, i.e., aphasia in which the dynamics of plasticity are impaired, or the result of the impairment of internal speech. The basic defect underlying “conduction” aphasia is beginning to be understood as a weakened acoustico-gnostic function or difficulties in retarding sideline associations.