The Auditory Agnosias

Auditory agnosia refers to the defective recognition of auditory stimuli in the context of preserved hearing. There has been considerable interest in this topic for over a hundred years despite the apparent rarity of the disorder and potential diagnostic confusion with deafness or even Alzheimer's disease (Mendez and Rosenberg, 1991—see Case P593 below). Following Lissauer's (1890) distinction between 'apperceptive' and 'associative' forms of visual object agno-sia, disorders of sound recognition have been divided between impaired perception of the acoustic structure of a stimulus, and inability to associate a successfully perceived auditory representation with its semantic meaning (Vignolo, 1982). Much research has centred on the 'apperceptive' form of auditory agnosia, although the study of such disorders has not been aided by terminological differences in the literature. Some authors have used the term 'auditory agnosia' to refer to a generalized disorder affecting the perception of all types of auditory stimuli, from non-verbal sounds to speech and music (e.g., Miceli, 1982). Others have employed separate names to highlight specific deficits, using 'auditory agnosia' to refer to impairment of non-verbal, environmental sounds (Albert et al., 1972—see Case P565 below), 'amusia' to escribe deficits in the processing of melodies (e.g., Peretz et al., 1994—see Case P601 below), and 'pure' word deafness for disorders of speech recognition (e. P605 and P569 below). While 'pure' word deafness is perhaps the most commonly used label, it has been noted for some time that the disorder is rarely pure—in the majority of cases there is some concomitant impairment of non-verbal sound processing (Hemphill and Stengel, 1940—see Case P583 below; Nielsen, 1946; Wohlfart et al., 1952—see Case P613 below). Furthermore, many cases are not even free of aphasia (as implied by the original use of the term 'pure': Auerbach et al., 1982—see Case P567 below; Vignolo, 1982). Analysis of impaired speech perception in word deafness suggests that certain speech sounds may be affected more than others (Saffran et al., 1976—see Case P605 below). Auditory comprehension can be improved by lipreading (Shindo et al., 1991—see Case P606 below) and context (Saffran et al., 1976). While impaired speech recognition normally occurs in the presence of generalized auditory agnosia, some patients have been described with an apparently language-specific disorder (Auerbach et al., 1982). Franklin (1989—see Case P574 below) highlighted five different levels of language-specific impairment that might give rise to poor spoken comprehension. One of these, word meaning deafness, is a form of …