不同强度纯音刺激引起听觉中枢兴奋的磁源成像研究

目的 利用磁源成像(magnetic source imaging,MSI)观察正常人在不同强度纯音刺激时脑听觉中枢的兴奋差异.方法 受试者为10名医学生(19～24岁,平均21岁).采用强度为30、90dB的1 000Hz纯音刺激.利用Vectoview 306通道全头型生物磁仪记录声音刺激诱发的脑磁图(magnetoencephlography,MEG)信号,用等电流偶极(equivalent current dipole,ECD)描述皮质兴奋并将其与MRI图像叠加.结果 纯音刺激诱发的主要磁反应波为M100,ECD位于初级听觉中枢颞横回.90dB纯音比30dB纯音的M100 ECD的潜伏期缩短、强度增高,两种刺激时ECD的位置无明显变化.结论 纯音刺激激活初级听觉中枢颞横回,随着SPL增加初级听觉中枢反应的潜伏期缩短、兴奋强度增加.

Magnetic source imaging study of responses in auditory cortex evoked by pure tone stimuli at variable sound pressure level

Objective To observe responses evoked by pure auditory stimuli in healthy subjects with MSI.To compare the differences of the AEFs in healthy subjects at variable sound pressure level.Methods 10 healthy medical student subjects were included in this study.Every healthy subject received stimuli of 1 kHz tone bursts delivered to the bilateral ear at sound pressure level (SPL) 30dB and 90dB;All subjects examined with 306-channel whole-scalp MEG and the responses were described with ECDs that were overlapped to MRI.Results The most evident AEFs evoked with pure tone was M100,which located precisely on the Heschl's gyrus.When compare the AEFs evoked with 30dB and 90dB pure tone,we found that the M100 of 90dB tones had shorter latencies and stronger strength than that of 30dB.But there was no significantly different from the location of ECD in 30dB and 90dB tones.Conclusion The pure tone can evoke M100 on the primary auditory cortex-Heschl's gyrus in normal-hearing subjects.As the SPL increases the auditory cortex show stronger magnitude of activation and shorter latency.