纯音听觉优势半球--fMRI和脑磁图联合研究

目的 利用血氧水平依赖功能磁共振成像（BOLD-fMRI）和脑磁图（MEG）观察正常人在纯音刺激时听觉中枢的兴奋情况及两侧半球的差异。资料与方法 BOLD-fMRI研究对象为30名正常听力志愿者。BOLD-fMRI采用组块设计。声音刺激用140曲1kHz纯音，持续时间500in8，刺激间隔18，刺激施加频率1Hz。MEG检查共有10名正常受试者，采用90dB1kHz纯音刺激，持续时间8ms，刺激间期1s。用等电流偶极（ECD）描述皮质兴奋并将其与自身MRI图像叠加。结果 在BOLD-fMRI研究中，纯音刺激激活两侧听觉中枢和其周围邻近脑区，右侧半球听觉中枢的激活强度明显大于左侧。MEG检查中纯音刺激诱发的主要磁反应波为M100，M100 ECD位于初级听觉中枢预横回。右侧半球M100 ECD比左侧半球偏前、潜伏期短、强度高。结论 纯音刺激激活听觉中枢和周围脑区，右侧半球为纯音刺激时听觉的优势半球。

Predominant Hemisphere at Pure Tone Stimulus:A Study of fMRI Combined with MEG

Objective To observe responses evoked by pure auditory stimuli in healthy subjects with BOLD fMRI and MEG, and compare the differences of the activation of auditory cortex in left and right hemisphere.Materials and Methods There were 30 healthy subjects in BOLD fMRI study. In experimental tasks, every subject received stimuli of 1kHz pure tone bursts delivered to the bilateral ear with SPL 140dB, duration 500ms, interstimulus intervals 1s. 10 healthy subjects were included in MEG study. Every healthy subject received stimuli of 1kHz tone bursts delivered to the bilateral ear and SPL at 90dB, duration 8ms, interstimulus intervals 1s; The responses were described with ECDs that were overlapped to MRI.Results On BOLD fMRI, for healthy subjects to pure tone stimuli, significant activations were observed in bilateral auditory cortex and the surrounding areas, there was obvious activation in right hemisphere than that in left. On MEG, the most evident AEFs evoked with pure tone were M100, which located on the Heschl's gyrus. The location of ECD in right hemisphere was anterior to that in left. The M100 ECD in right hemisphere had stronger source strength and shorter latencies than that in left hemisphere.Conclusion The auditory cortex and the surrounding areas evoked by pure auditory stimuli, right hemisphere is predominance in healthy subjects.