Department of Otolaryngology-Head and Neck Surgery, St. Vincent's Hospital, The Catholic University of Korea School of Medicine, Suwon, Korea.
Clin Exp Otorhinolaryngol. 2012 Sep;5(3):122-31. doi: 10.3342/ceo.2012.5.3.122. Epub 2012 Aug 27.
To investigate the electric-acoustic interactions within the inferior colliculus of guinea pigs and to observe how central masking appears in invasive neural recordings of the inferior colliculus (IC).
A platinum-iridium wire was inserted to scala tympani through cochleostomy with a depth no greater than 1 mm for intracochlear stimulation of electric pulse train. A 5 mm 100 µm, single-shank, thin-film, penetrating recording probe was inserted perpendicularly to the surface of the IC in the coronal plane at an angle of 30-40° off the parasagittal plane with a depth of 2.0-2.5 mm. The peripheral and central masking effects were compared using electric pulse trains to the left ear and acoustic noise to the left ear (ipsilateral) and to the right ear (contralateral). Binaural acoustic stimuli were presented with different time delays and compared with combined electric and acoustic stimuli. The averaged evoked potentials and total spike numbers were measured using thin-film electrodes inserted into the central nucleus of the IC.
Ipsilateral noise had more obvious effects on the electric response than did contralateral noise. Contralateral noise decreased slightly the response amplitude to the electric pulse train stimuli. Immediately after the onset of acoustic noise, the response pattern changed transiently with shorter response intervals. The effects of contralateral noise were evident at the beginning of the continuous noise. The total spike number decreased when the binaural stimuli reached the IC most simultaneously.
These results suggest that central masking is quite different from peripheral masking and occurs within the binaural auditory system, and this study showed that the effect of masking could be observed in the IC recording. These effects are more evident and consistent with the psychophysical data from spike number analyses than with the previously reported gross potential data.
研究豚鼠下丘内的电声相互作用，并观察中央掩蔽如何出现在下丘（IC）的侵入性神经记录中。
通过鼓室切开术将铂铱丝插入鼓阶，深度不超过 1 毫米，用于电脉冲串的耳蜗内刺激。将一个 5 毫米长 100 µm 的单叉、薄型、穿透性记录探针以 30-40°的角度垂直插入 IC 表面，在冠状平面上与矢状面偏离 2.0-2.5 毫米的深度。使用电脉冲串对左耳和左耳（同侧）和右耳（对侧）的声学噪声比较外周和中央掩蔽效应。双耳声学刺激以不同的时间延迟呈现，并与电声联合刺激进行比较。使用插入 IC 中央核的薄膜电极测量平均诱发电位和总尖峰数。
同侧噪声对电反应的影响比对侧噪声更明显。对侧噪声略微降低了对电脉冲串刺激的响应幅度。在声学噪声开始后立即，响应模式会发生短暂变化，响应间隔变短。在连续噪声开始时，对侧噪声的影响明显。当双耳刺激同时到达 IC 时，总尖峰数减少。
这些结果表明，中央掩蔽与外周掩蔽非常不同，并且发生在双耳听觉系统中，本研究表明可以在下丘记录中观察到掩蔽效应。这些效应与来自尖峰数分析的心理物理数据比以前报道的总潜力数据更明显和一致。
