Zhang Yun-ting, Geng Zuo-jun, Zhang Quan, Li Wei, Zhang Jing
Department of Radiology, General Hospital of Tianjin Medical University, Tianjin 300052, China.
Chin Med J (Engl). 2006 Sep 20;119(18):1548-54.
Blood oxygen level dependent functional magnetic resonance imaging (fMRI) and magnetoencephalography are new techniques of brain functional imaging which can provide the information of excitation of neurons by measure the changes of hemodynamics and electrophysiological data of local brain tissue. The purpose of this study was to study functional brain areas evoked by pure tones in healthy and sensorineural hearing loss subjects with these techniques and to compare the differences between the two groups.
Thirty healthy and 30 sensorineural hearing loss subjects were included in this study. In fMRI, block-design paradigm was used. During the active epoch the participants listened to 1000 Hz, sound pressure level 140 dB pure tones at duration 500 ms, interstimulus interval 1000 ms, which presented continuously via a magnetic resonance-compatible audio system. None stimulus was executed in control epoch. In magnetoencephalography study, every subject received stimuli of 1000 Hz tone bursts delivered to the bilateral ear at duration 8 ms, interstimulus intervals 1000 ms. Sound pressure level in healthy subjects was 30 dB; in sensorineural hearing loss subjects was 20 dB above everyone's hearing threshold respectively. All subjects were examined with 306-channel whole-scalp neuromagnetometer.
In fMRI, all subjects showed significant activations in bilateral Heschl's gyri, anterior pole of planum temporale, planum temporale, precentral gyri, postcentral gyri, supramarginal gyri, superior temporal gyri, inferior frontal gyri, occipital lobes and cerebellums. The healthy subjects had more intensive activation in bilateral Heschl's gyri, anterior pole of planum temporale, inferior frontal gyri, left superior temporal gyri and right planum temporale than the hearing loss subjects. But in precentral gyri, postcentral gyri and occipital lobes, the activation is more intensive in the hearing loss subjects. In magnetoencephalography study, both in the hearing loss and the healthy subjects, the most evident audio evoked fields activated by pure tone were N100m, which located precisely on the Heschl's gyrus. Compared with the hearing loss subjects, N100m of the healthy subjects was stronger and had longer latencies in right hemisphere.
Under proper pure tone stimulus the activation of auditory cortex can be elicited both in the healthy and the sensorineural hearing loss subjects. Either at objective equivalent stimuli or at subjectively perceived equivalent stimuli, the auditory responses were more intensive in healthy subjects than hearing loss subjects. The tone stimuli were processed in a network in human brain and there was an intrinsic relation between the auditory and visual cortex. Blood oxygen level dependent fMRI and magnetoencephalography could reinforce each other.
血氧水平依赖性功能磁共振成像（fMRI）和脑磁图是脑功能成像的新技术，它们可以通过测量局部脑组织的血流动力学和电生理数据的变化来提供神经元兴奋的信息。本研究的目的是利用这些技术研究健康受试者和感音神经性听力损失受试者中纯音诱发的脑功能区，并比较两组之间的差异。
本研究纳入30名健康受试者和30名感音神经性听力损失受试者。在fMRI研究中，采用组块设计范式。在激活期，参与者通过磁共振兼容音频系统持续听1000Hz、声压级140dB、持续时间500ms、刺激间隔1000ms的纯音。在对照期不执行任何刺激。在脑磁图研究中，每个受试者接受双侧耳的1000Hz短音刺激，持续时间8ms，刺激间隔1000ms。健康受试者的声压级为30dB；感音神经性听力损失受试者的声压级分别比每个人的听力阈值高20dB。所有受试者均用306通道全头型神经磁强计进行检查。
在fMRI研究中，所有受试者双侧颞横回、颞平面前极、颞平面、中央前回、中央后回、缘上回、颞上回、额下回、枕叶和小脑均有明显激活。健康受试者双侧颞横回、颞平面前极、额下回、左侧颞上回和右侧颞平面的激活比听力损失受试者更强烈。但在中央前回、中央后回和枕叶，听力损失受试者的激活更强烈。在脑磁图研究中，听力损失受试者和健康受试者中，由纯音诱发的最明显的听觉诱发场均为N100m，其精确位于颞横回上。与听力损失受试者相比，健康受试者的N100m在右半球更强且潜伏期更长。
在适当的纯音刺激下，健康受试者和感音神经性听力损失受试者均可诱发听觉皮层的激活。无论是在客观等效刺激还是主观等效刺激下，健康受试者的听觉反应均比听力损失受试者更强烈。纯音刺激在人脑的一个网络中进行处理，听觉皮层和视觉皮层之间存在内在联系。血氧水平依赖性功能磁共振成像和脑磁图可以相互补充。
