SOUND LOCALIZATION IN HEMISPHERECTOMIZED PATIENTS

In order to precisely evaluate the consequences of cortical damage on free-field sound localization in humans, the present study examined re sponse accuracy to auditory targets in three hemispherectomized patien ts and IQ-matched controls. Listeners reported sound location by point ing with their dominant hand to the apparent sound location in an anec hoic chamber. Two conditions were tested: (i) localization of a fixed- sound source and (ii) localization of the beginning and the end of a s imulated moving stimulus. In both conditions, the responses of the pat ients were less accurate than those of the controls in the hemifield c ontralateral to their removed hemisphere. Moreover, the single-case an alyses revealed that the performances obtained with fixed sources were generally more precise than those obtained with moving sources. This result is discussed in terms of a differential involvement of cortical and subcortical pathways in the processing of stationary and moving s ounds. Finally, the age at surgery and the post-surgical interval were related with the magnitude of the deficits, suggesting the possible i nfluences of functional reorganization and cerebral plasticity.