Dichotic simultaneous and time-staggered speech perception data from four patients with temporal lobectomies are compared to results from over 100 normals. In these tests, two different nonsense syllables are given in competition, one to each ear. The syllables are presented simultaneously, then with time separations ranging from 15 to 500 msec. With simultaneous onset, normals showed right ear superiority; with time separations of 30 to 90 msec, normals showed a "lag effect," ie, better scores for the trailing stimulus. In sharp contrast, temporal lobectomy patients showed poorer contralateral ear function than ipsilateral ear function, and no lag effect. Comparing preoperative and postoperative scores, we see that postoperatively there is additional degradation of contralateral ear scores and enhanced ipsilateral ear function in dichotic listening. Patients with both left and right temporal lobectomies behaved similarly in this respect.
Charles I. Berlin, Sena S. Lowe-Bell, Peter J. Jannetta, David G. Kline. Central Auditory Deficits After Temporal Lobectomy. Arch Otolaryngol. 1972;96(1):4–10. doi:10.1001/archotol.1972.00770090042003