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Dawn Senathi-Raja

Following a right hemisphere stroke that involved small portions of the secondary association cortex, MR displayed a variety of cognitive and perceptual auditory deficits. MR's deficits appear to relate exclusively to the non-verbal auditory domain, providing support for Peretz's broad distinction between verbal and nonverbal sounds (Dalla Bella & Peretz, 1999; Peretz et al., 1994). Within the nonverbal domain, while the hypothesis that MR would reveal disordered recognition of musical and environmental sounds was supported by the results, there was no support for the prediction that MR would exhibit impaired recognition of speech prosody. Thus, although MR's voice recognition was not assessed, MR can be classified within Peretz's taxonomy as a case example of circumscribed music and environmental agnosia.

Orthogonal to distinctions among auditory domains is the division between associative and apperceptive types of agnosia (Peretz, 1993a). MR's impaired recognition of non-verbal sounds relative to verbal sounds is disproportionate. This would be interpreted as indicative of associative agnosia according to Peretz's approach (Peretz et al., 1994). The present study investigated a possible elementary perceptual basis for MR's emergent higher cognitive deficits. As expected, MR revealed pitch perception and auditory scene analysis deficits. In the following discussion, the explanatory power of Peretz's higher-level cognitive approach will be compared with accounts of MR's auditory agnosias and musical illusions based on both pitch perception and auditory scene analysis.

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