In contrast to Broca aphasia, the patient with Wernicke aphasia usually talks volubly, gestures freely, and appears strangely unaware of his deficit. Speech is produced mostly without effort; the phrases and sentences appear to be of normal length and are properly intoned and articulated. These attributes, in the context of aphasic disturbances, are referred to as “fluency” of speech (i.e., Wernicke aphasia is a fluent aphasia). Despite the fluency and normal prosody, the patient’s speech is remarkably devoid of meaning. The patient with Wernicke aphasia produces many nonsubstantive words, and the words themselves are often malformed or inappropriate, a disorder referred to as paraphasia. A phoneme (the minimal unit of sound recognizable as language) or a syllable may be substituted within a word (e.g., “The grass is greel”); this is called literal paraphasia. The substitution of one word for another (“The grass is blue”) is termed verbal paraphasia or semantic substitution and is even more characteristic of Wernicke’s aphasia. Neologisms, that is, syllables or words that are not part of the language, may also appear (“The grass is grumps”). In its extreme, the fluent, paraphasic speech of Wernicke’s aphasia may be entirely incomprehensible (gibberish or jargon aphasia). Fluency, however, is not an invariable feature of Wernicke’s aphasia. In some patients speech may be hesitant, in which case the block tends to occur in the part of the phrase that contains the central communicative (predicative) item, such as a key noun, verb, or descriptive phrase. The patient with such a disorder conveys the impression of constantly searching for the correct word and of having difficulty in finding it. Wernicke aphasia may also at times begin with complete mutism.
Although the motor apparatus required for the expression of language is intact, patients with severe Wernicke’s aphasia have difficulty functioning socially because they are deprived of the main means of communication. They cannot understand fully what is said to them; a few simple commands may still be executed, but there is failure to carry out complex ones. They cannot read aloud or silently with comprehension, tell others what they want or think, or write spontaneously. Written letters are often combined into meaningless words, but there may be a scattering of correct words. In trying to designate an object that is seen or felt, they cannot find the name, even though they can sometimes repeat it from dictation; nor can they write from dictation the very words that they can copy. Copying performance is notably slow and laborious and conforms to the contours of the model, including the examiner’s handwriting style. All these defects are present in varying degrees of severity and the mildest form consists of mild verbal and literal paraphasias and minimal difficulty with comprehension of grammatically complex material (“mini-Wernicke”). In general, the disturbances in reading, writing, naming, and repetition parallel the severity of impairment in comprehension. There are, however, exceptions in which either reading or the understanding of spoken language is disproportionately affected. Some aphasiologists thus speak of two Wernicke syndromes.
In terms of the idealized Broca-Wernicke schema, in Wernicke aphasia the motor language areas are no longer under control of the auditory and visual areas. The disconnection of the motor speech areas from the auditory and visual ones accounts for the impairment of repetition and the inability to read aloud. Reading may remain fluent, but with the same paraphasic errors that mar conversational language. The occurrence of dyslexia (impaired visual perception of letters and words) with lesions of the Wernicke area is ostensibly explained by the fact that most individuals learn to read by transforming the printed word into the auditory form before it can gain access to the integrative centers in the posterior perisylvian region. Only in the congenitally deaf is there thought to be a direct pathway between the visual and central integrative language centers.