Diesch E, Luce T
Institute of Medical Psychology and Neurobiology, University of Tübingen, Germany.
J Cogn Neurosci. 2000 Sep;12(5):878-93. doi: 10.1162/089892900562480.
The auditory-evoked neuromagnetic field elicited by single vowel formants and two-formant vowels was recorded under active listening conditions using a 37-channel magnetometer. There were three single formants with formant frequencies of 200, 400, and 800 Hz, another single formant with a formant frequency of 2600 Hz, and three vowels that were constructed by linear superimposition of the high- onto one of the low-frequency formants. P50 m and N100 m latency values were inversely correlated with the formant frequency of single formants. A strong effect of formant frequency on source location was obtained along the postero-anterior axis, which is orthogonal to the well-established latero-medial tonotopic gradient. Regardless of whether single formants or first formants of vowels were considered, N100 m sources were more anterior and sustained field sources were more posterior for higher-frequency than for lower-frequency formants. The velocity of the apparent posterior-to-anterior movement across cortical surface of N100 m sources first reported by Rogers et al. [Rogers, R. L., Papanicolaou, A. C., Baumann, S. B., Saydjari, C., & Eisenberg, H. M. (1990). Neuromagnetic evidence of a dynamic excitation pattern generating the N100 auditory response. Electroencephalography and Clinical Neurophysiology,77, 237-240] decreased as a function of latency. The amount of deceleration was positively correlated with formant frequency. Responses to the vowels were superadditive, indicating that the processes elicited by the constituents of composite stimuli interact at one or more stages of the afferent auditory pathway. Such interaction may account for the absence of a lateral-to-medial tonotopic mapping of first formant frequency. The source topography found may reflect activity in auditory fields adjacent to AI with the strength of the contribution varying with formant frequency. Alternatively, it may reflect sharpness-of-tuning and inhibitory response-area asymmetry gradients along isofrequency stripes within AI. Either alternative may be interpreted in terms of a spectral blurring mechanism that abstracts spectral envelope information from the details of spectral composition, an important step towards the formation of invariant phonetic percepts.
在主动聆听条件下，使用37通道磁力计记录了由单个元音共振峰和双共振峰元音诱发的听觉诱发神经磁场。有三个共振峰频率分别为200、400和800赫兹的单共振峰，另一个共振峰频率为2600赫兹的单共振峰，以及三个通过将高频共振峰线性叠加到低频共振峰之一上构建的元音。P50m和N100m潜伏期值与单共振峰的共振峰频率呈负相关。沿着与已确立的外侧-内侧音频拓扑梯度正交的前后轴，获得了共振峰频率对源位置的强烈影响。无论考虑的是单共振峰还是元音的第一共振峰，高频共振峰的N100m源比低频共振峰的更靠前，持续场源更靠后。Rogers等人首次报道的N100m源在皮质表面从后向前移动的速度[Rogers, R. L., Papanicolaou, A. C., Baumann, S. B., Saydjari, C., & Eisenberg, H. M. (1990). Neuromagnetic evidence of a dynamic excitation pattern generating the N100 auditory response. Electroencephalography and Clinical Neurophysiology,77, 237 - 240]随潜伏期而降低。减速量与共振峰频率呈正相关。对元音的反应是超相加的，表明复合刺激成分引发的过程在传入听觉通路的一个或多个阶段相互作用。这种相互作用可能解释了第一共振峰频率缺乏从外侧到内侧的音频拓扑映射。发现的源地形图可能反映了与AI相邻的听觉区域的活动，其贡献强度随共振峰频率而变化。或者，它可能反映了AI内等频率条纹上的调谐锐度和抑制反应区域不对称梯度。这两种可能性都可以根据一种频谱模糊机制来解释，该机制从频谱组成的细节中提取频谱包络信息，这是形成不变语音感知的重要一步。
