Neuronal mechanisms of bilateral hearing in hearing impaired human subjects

Saberi和Takahashi（2002）在猫头鹰耳蜗核进行了单单位记录。我们发现，适当的输入声时间差可引起耳蜗神经元的兴奋，而不同的时间序列则可引起较小的兴奋。声音到达差的信息被传导到上级丘，并检测声源的方向。然而，鲜为人知的是，在听力受损的主题这样的机制。在前期研究中，我们对一只耳朵植入人工耳蜗（CI），另一只耳朵佩戴助听器（HA）的受试者的双耳听力机制进行了研究（Iwaki和Kubo，2000）。噪声中听力测试（HINT）是由Nilsson和Soli（1994）开发的，在美国被广泛用于测试安静和噪声环境下的言语检测能力。我们在Soli的合作下使用日语进行了该测试（HINT-J：Shiroma等人，2002年）。用HINT-J测试安静和噪声条件下的言语知觉能力。安静条件下，单独CI和HA+CI条件下的言语知觉无显著差异。但在噪声条件下，这两种情况之间的差异显着。虽然输入声音的特性应该是不同的两个耳朵（CI与HA），额外的影响是在我们的听力受损的受试者检测。

Single unit recording in the cochlear nucleus of owl have been done by Saberi and Takahashi (2002). We found that an appropriate time difference of input sound caused the excitation of cochlear neurons, but less excitation was resulted by different time sequences. Information of sound arrival difference was conducted into the superior colliculus and direction of sound source was detected.The benefit of binaural hearing has been extensively investigated in human subjects. However, little is known for such mechanisms in hearing impaired subjects. In the preliminary study, we examined the binaural hearing mechanisms in subjects who weared cochlear implant (CI) in one ear and the hearing aid (HA) on the other side (Iwaki and Kubo, 2000).Hearing in Noise Test (HINT), which was developed by Nilsson and Soli (1994), has been widely used in USA to examine the speech detection ability under quiet and noisy circumstances. We made this test using Japanese language with the cooperation of Soli (HINT-J: Shiroma et al., 2002). Using HINT-J the speech perception ability was examined under the quiet and noisy conditions. There was no significant difference in speech perception under quiet condition when CI alone and HA+CI conditions were compared. But a significant difference was found under noisy condition between these two conditions. Although characteristics of input sound should be different between two ears (CI vs HA), the additional effects was detected in our hearing impaired subjects.