Facial recognition in patients with Williams syndrome-an MEG study-

我们使用脑磁图（MEG）来评估威廉姆斯综合征（WMS）患者对直立和倒置面部刺激的反应。该患者对正脸和倒立脸均有明显的面部感知特异性MEG成分2M，但其对倒立脸的峰值潜伏期短于对正脸的峰值潜伏期。这一发现与健康受试者有很大的不同，健康受试者对倒立脸的潜伏期通常比正立脸的潜伏期长2M，这就是“倒立脸效应”。在本例WMS患者中，“人脸倒立效应”不存在，即倒立面部刺激的2M峰值潜伏期并不比直立面部刺激的2M峰值潜伏期延长。直立面部的峰值潜伏期与健康受试者无显著差异。在每次刺激过程中，估计到的2M分量的偶极子源位于下颞叶和枕叶后部，与健康受试者的结果一致。这些结果表明，该患者直立面部感知的神经生理过程至少在面部感知特异性MEG成分2M上与健康受试者没有差异，而倒置面部的神经生理过程在潜伏期上与健康受试者不同，说明倒置效应不存在。这种现象可能表明局部加工在患者中占主导地位，因为局部加工被认为是处理倒立脸的必要条件。

We examined face perception processing in a patient with Williams syndrome(WMS) using magnetoencephalography(MEG) by evaluating responses to the upright and inverted face stimuli. The face-perception-specific MEG component, 2M, was clearly identified in response to both upright and inverted face images in this patient, but its peak latency to the inverted face was shorter than that to the upright face. This finding was much different from that in healthy subjects, who usually showed a longer latency of 2M for the inverted face than for the upright face, which is the "face inversion effect". In the present patient with WMS, the "face inversion effect" was absent, meaning the peak latency of the 2M for the inverted face stimuli was not prolonged than that for the face upright stimuli. The peak latency for the upright face was not different from that of the healthy subjects. In each stimulus session, the locations of the dipole sources of the 2M component were estimated in the inferior temporal lobe and posterior part of the occipital lobe, which were consistent with those obtained in healthy subjects.These findings indicate that neurophysiological process of upright face perception in this patient is not different from those of healthy subjects at least concerning the face-perception-specific MEG component 2M, whereas, that of the inverted faces was different from those in healthy subjects in terms of latency, indicating the absence of inversion effects. The phenomenon may indicate a predominance of local processing in the patient, since local processing is considered to be necessary in the processing of inverted faces.