Lütkenhöner B, Steinsträter O
Institute of Experimental Audiology, University of Münster, Germany.
Audiol Neurootol. 1998 Mar-Jun;3(2-3):191-213. doi: 10.1159/000013790.
Previous studies have proven that a dipole source analysis of the auditory evoked field is capable of providing evidence of the tonotopic organization of the human auditory cortex. To explore the nature of the estimated dipoles in greater detail, a single subject was extensively studied, and the estimated sources were registered in a three-dimensional reconstruction of the cortical surface derived from magnetic resonance images. The stimuli were 500-ms tone bursts with frequencies of 250, 500, 1,000, and 2,000 Hz (mean intensity of 60 dB SL). The total number of stimuli presented per condition was about 3,600 (36 independent experiments spread over 4 days). Using special postprocessing techniques, the relative localization accuracy could be enhanced to such an extent that differences in the dipole locations of 1 mm could be clearly distinguished. The results suggest that peak N1m (latency around 100 ms) arises from the planum temporale, whereas peak P2m (latency around 170 ms) appears to correspond to a center of activity in (or close to) Heschl's gyrus. The tonotopic organization found for the generator of N1m was consistent with earlier studies ("the higher the frequency the deeper the source"). However, additional findings (time dependence of the estimated sources; slightly different tonotopy obtained for field change; dependence of the estimated sources on the estimation technique) indicate that multiple areas are involved in the generation of N1m. Evidence of a frequency-dependent source location was found also for P2m.
先前的研究已经证明，听觉诱发电场的偶极子源分析能够提供人类听觉皮层音调组织的证据。为了更详细地探究估计偶极子的性质，对一名受试者进行了广泛研究，并将估计的源记录在从磁共振图像获得的皮质表面三维重建中。刺激为频率为250、500、1000和2000 Hz的500毫秒纯音脉冲串（平均强度为60 dB SL）。每种条件下呈现的刺激总数约为3600个（36个独立实验分布在4天内）。使用特殊的后处理技术，相对定位精度可以提高到能够清晰区分1毫米偶极子位置差异的程度。结果表明，N1m峰（潜伏期约100毫秒）起源于颞平面，而P2m峰（潜伏期约170毫秒）似乎对应于颞横回（或其附近）的一个活动中心。在N1m发生器中发现的音调组织与早期研究一致（“频率越高，源越深”）。然而，其他发现（估计源的时间依赖性；场变化获得的略有不同的音调定位；估计源对估计技术的依赖性）表明，多个区域参与了N1m的产生。在P2m中也发现了频率依赖性源位置的证据。
