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

我们使用脑磁图(MEG)检测了一名威廉姆斯综合征(WMS)患者的面部知觉加工，通过评估对直立和倒立的面部刺激的反应。在这例患者中，直立和倒立两种面孔图像都能清晰地识别出面部知觉特异性成分2M，但倒立面孔的峰值潜伏期比直立面孔的短。这一发现与健康受试者有很大不同，后者通常表现出倒脸的潜伏期比直立的潜伏期长2M，这就是“倒脸效应”。本组WMS患者无“翻脸效应”，即倒脸刺激的2M峰潜伏期不比直立脸刺激延长。直立面孔的峰潜伏期与健康人无明显差异。在每一次刺激中，我们估计了2M分量的偶极源在颞叶下部和枕叶后部的位置，这与正常人的结果一致。这些结果表明，该患者的直立面孔知觉的神经生理过程至少在面孔知觉特异性的脑磁图成分2M方面与健康受试者没有不同，而倒立面孔的潜伏期与健康受试者不同，表明没有倒置效应。这一现象可能表明局部加工在患者中占优势，因为局部加工被认为在处理倒脸过程中是必要的。

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.