The Japanese journal of neuropsychology

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ArticleTitle	Evaluation of central auditory function by dichotic tests in patients with unilateral brain damage
Language	J
AuthorList	Chie Yoshikawa¹⁾, Tsuneo Harashima²⁾, Akiyoshi Katada³⁾, Nobuo Sanjo⁴⁾, Takashi Matsumoto⁴⁾
Affiliation	1) Doctoral Program in Disability Sciences, University of Tsukuba 2) Department of Disability Sciences, University of Tsukuba 3) Kinjo University 4) Department of Neurology, Saitama General Rehabilitation Center
Publication	Japanese Journal of Neuropsychology: 17 (3), 192-200, 2001
Received	Aug 8, 2000
Accepted	Feb 23, 2001
Abstract	Dichotic tests were used to measure lateralized information processing in the two hemispheres of the brain and the central auditory dysfunction. The method most used is the dichotic listening test (DLT) introduced by Kimura (1961), which involves the presentation of different speech signals simultaneously to each ear, and recall. Another dichotic monitoring test (DMT), the one introduced by Geffen (1979) is presented simultaneously as DLT but the subject is instructed to press a button to a target. The previous investigation had used both these tests for the same testing, but it was not clear that these tests evaluated the same function of the brain. The present study addresses the brain damage effects on hearing in a dichotic situation in patients with unilateral brain damage by comparing several dichotic tests. Thirteen patients were tested; 7 left-brain damage (LBD) patients and 6 right-brain damage (RBD) patients. The results showed hemispheric difference. The same dominant ear direction was retained in RBD patients, but in LBD patients it varied. In the two dichotic tests the evaluations were not the same. For example, even though patients showed auditory extinction in DLT, no extinction resulted in DMT. In light of the above, a number of factors that influence performance in dichotic listening were examined. First, the reaction method was varied between dichotic tests; DLT required stimulus reproduction but DMT required reconfirmation. Second, it was suggested that each test required divided attention to the stimuli, while DMT also required sustained attention. For these reasons, it was proposed that it be considered attentional extinction rather than auditory extinction when patients showed auditory extinction only by DMT. We suggest that the problems in hearing of patient, with unilateral brain damage are able to be analyzed by using different tests in detail, since the results evaluated by a number of different dichotic tests show different functions.
Keywords	auditory extinction, dichotic listening, dichotic monitoring, unilateral brain damage, attentional extinction