Okusa M, Shiraishi T, Kubo T, Nageishi Y
Department of Otolaryngology, Osaka University Medical School, Yamadaoka Suita City, Japan.
Otolaryngol Head Neck Surg. 1999 Nov;121(5):610-5. doi: 10.1016/S0194-5998(99)70067-7.
Cognitive event-related brain potentials (ERPs) recorded during a 2-tone discrimination (oddball) task were examined in 8 patients with cochlear implants. The aim of this study is to investigate the effects of discrimination difficulty formed by 4 conditions of stimulus contrast: the target stimuli were set at 2000, 1500, 1200, or 1100 Hz, and nontarget stimuli were set at 1000 Hz throughout. The averaged ERPs recorded after the target stimuli revealed N100, P200, N200, and P300 peaks, whereas those after the nontarget stimuli showed only N100 and P200 peaks. The peak latencies of the ERP components of early information processings (N100 and P200) were not significantly increased among the 4 conditions. In contrast, the latencies of late cognitive components (N2b and P300, whose peak latencies were longer than 250 msec) and reaction times were significantly increased as target discriminability decreased. In conclusion, early information processings were not delayed by the discrimination difficulty, but cognitive processings were delayed in patients with cochlear implants. Because the N2b amplitude, which is considered to be associated with controlled processings, was much larger than that previously reported from subjects with normal hearing, it is suggested that patients with cochlear implants make a considerable effort to process their poor auditory information.
对8名接受人工耳蜗植入的患者在双音辨别（异常球）任务期间记录的认知事件相关脑电位（ERP）进行了检测。本研究的目的是调查由4种刺激对比度条件形成的辨别难度的影响：目标刺激分别设置为2000、1500、1200或1100赫兹，非目标刺激始终设置为1000赫兹。目标刺激后记录的平均ERP显示出N100、P200、N200和P300波峰，而非目标刺激后的平均ERP仅显示N100和P200波峰。早期信息处理（N100和P200）的ERP成分的波峰潜伏期在这4种条件下没有显著增加。相比之下，随着目标可辨别性降低，晚期认知成分（N2b和P300，其波峰潜伏期超过250毫秒）的潜伏期和反应时间显著增加。总之，早期信息处理没有因辨别难度而延迟，但人工耳蜗植入患者的认知处理出现了延迟。由于被认为与控制处理相关的N2b波幅比之前正常听力受试者报告的波幅大得多，因此表明人工耳蜗植入患者在处理其较差的听觉信息时付出了相当大的努力。
