听觉皮层优势半球及频率分布的功能MRI研究

目的 研究正常人调幅音刺激任务时听觉皮层的优势半球及不同频率任务刺激时初级及次级听觉皮层的激活情况.方法 对25名健康受试者采用事件相关Sparse设计、正弦调幅音任务下的EPI序列fMRI数据采集,实验刺激声音分别为0.5、2、4 kHz纯音经8 Hz正弦调幅,双耳同时呈现,利用SPM2软件进行数据分析,观察听觉皮层激活的优势半球及不同载波频率调幅音的激活部位、体积和强度.结果 25名受试者中9名由于EPI采集时头动超过最大限度而失败.余16名受试者主要表现为初级听觉皮层激活,且左侧激活的强度和体积均高于右侧.双侧初级听觉皮层的激活体积和强度均随刺激频率的增高而减小;其中6名左侧、7名右侧初级听觉皮层激活的部位表现出清晰的高频偏内,低频偏外的频率响应分布特点.在其他个体,这种分布不明显.次级听觉皮层的激活无明显规律.结论 正常人对调幅音的响应以左侧大脑半球为优势半球;随着刺激频率的增加,初级听觉皮层激活的强度和体积下降,fMRI激活部位的频率分布特点表现为高频偏内,低频偏外.

Dominant hemisphere and tonotoplc organization of auditory functional MRI in Chinese

Objective Functional MRI (fMRI) was measured in responses to stimulations of different frequencies to investigate dominant hemisphere and tonotopic organization in primary and secondary auditory cortex. Methods 25 healthy subjects with normal hearing were examined using tones of 0. 5,2 or4 kHz that were amplitude modulated (AM) sinusoidally at 8 Hz. The AM signals were presented at 96 dB SPL Event-related design was combined with a sparse clustered volume acquisitioning paradigm for data collection in the attempt to reduce the influence of acoustic scanner noise. SPM2 software was used for offline data analyzing. Results Data from 9 subjects were discarded due to a large head movement during recording. In the rest of 16 subjects, activation was found mainly in the primary auditory cortex. In most of these cases, the activation area and intensity by BOLD were find to be decreased with increasing signal frequency. In a great portion of cases (6 left and 7 right hemispheres) , a lateral-medial preference for low-to-high frequency response shift was clearly demonstrated in the primary auditory cortex. However, this was not clear in all other cases. No significant rule could be found in secondary auditory cortex activation. Conclusion The responses to AM signals showed a clear lateralization to left cerebral hemisphere. The activated area and response intensity decreased with increasing frequency of stimulation. The activation is related to the signal frequency with high frequency AM activating more medially.