Pure word deafness following bilateral lesions. A psychophysical analysis.

A detailed clinical and psychophysical study of a woman who had developed pure word deafness associated with amusia after bilateral temporoparietal destructions is reported. The patient had a defect in temporal resolution encompassing auditory, visual and somatosensory modalities, but the clinical defect was limited to the auditory sphere. Auditory comprehension did not improve even if she was spoken to slowly, although marked improvement of temporal resolution was observed as the duration of a nonlinguistic sound was extended. Also, she exhibited a supramodal defect in the perception and reproduction of rhythm, which was rate-dependent. These and other findings led to the following conclusions: the auditory modality is much more dependent on temporal resolution than other sensory modalities; for a full understanding of the mechanism of pure word deafness, not only the defect of temporal resolution but also many other factors, for example, defective discrimination of loudness, pitch or tone duration have to be taken into consideration; and rhythm sense strongly depends on a supramodal capacity of temporal resolution.