Vered Aharonson
Miriam Furst
Dept. of Elec. Eng.-Systems, Faculty of Eng., Tel Aviv Univ., Tel Aviv, Israel 69978
Amos D. Korczyn
Sackler School of Medicine, Tel Aviv Univ., Tel Aviv, Israel 69978
Most previous studies on MS patients' binaural performance reported similar performance according to intensity and time cues, or abnormality only for interaural time differences. In this study, combined lateralization and discrimination tests on both MS and CVA patients detected other phenomena. Lateralization and discrimination ability were measured during the same session for each patient, with clicks, high, and low narrow-band noises. Lateralization tests arbitrarily presented interaural time and intensity changes in 9 levels scale across the head. Adaptive 2I2AFC procedure determined jnd's. Ten CVA and 5 MS patients performed abnormally in some of the tests, and can be crudely divided into three groups: The first group performed normally in response to clicks and low frequencies, and failed only in high frequencies stimuli, in both lateralization and jnd. The second group performed abnormally in both tests and for all stimuli. The third group had normal jnd's for all stimuli. However, for some stimuli, those patients failed in the lateralization tasks, only in one of the interaural changes---either time or intensity. These results indicate that criteria used for jnd tasks are not applicable in lateralization and that time and level differences are estimated independently along the auditory pathways.