SOUND LATERALIZATION IN PATIENTS WITH LESIONS INCLUDING THE AUDITORY-CORTEX - COMPARISON OF INTERAURAL TIME DIFFERENCE (ITD) DISCRIMINATIONAND INTERAURAL INTENSITY DIFFERENCE (IID) DISCRIMINATION

We examined sound lateralization using dichotic presentation of noises in 15 patients with left unilateral (12 patients) or bilateral (3 pat ients) temporal lobe lesions, that included the auditory cortex, and e valuated their abilities to discriminate interaural time and intensity difference (ITD, IID) separately. On the ITD discrimination test, dis crimination thresholds in patients with left unilateral lesions were s ignificantly higher than those in normal subjects, but all patients wi th left unilateral lesions could detect ITD. However, none of 3 patien ts with bilateral lesions could detect ITD. On the IID discrimination test, all patients with either unilateral or bilateral lesions could d etect IID. IID discrimination thresholds in these patients were signif icantly higher than those in normal subjects. The auditory cortex play s an important role in discriminating both cues, but appears to be nec essary for discriminating ITD.