Selective deficits in human audition: evidence from lesion studies

The human auditory cortex is the gateway to the most powerful and complex communication systems and yet relatively little is known about its functional organization as compared to the visual system. Several lines of evidence, predominantly from recent studies, indicate that sound recognition and sound localization are processed in two at least partially independent networks. Evidence from human studies on selective auditory deficits following brain lesions has indicated that auditory processing after brain damage relies on alternative neural networks. This paper is a report on the performance of five brain-damaged patients and six normal subjects in sound localization and sound recognition aptitudes, as assessed by the number of correct replies and reaction times on auditory tasks. Based on the results, brain-damaged patients can have slower reaction times for specific functions, reflecting most probably processing within alternative networks. In our study three out of five patients presented deficits in auditory spatial tasks or in sound identification and sound motion, confirming previous findings of such dissociations. Our data indicated that response times were significantly slower, as compared to normal subjects, in deficient domains. Each of the three patients had at least one domain in which normal performance in terms of correct replies was associated with response times within the normal range, speaking against a general slowness. The results of this research and the general approach presented in this paper are relevant to the evaluation of potential plasticity.