Neural basis of higher visual cognition by using brain models

结论：我们通过使用大脑模型研究了高级视觉认知的神经基础。以Alzheimer病（AD）和轻度认知功能障碍（MCI）患者为模型，采用低频重复经颅磁刺激（rTMS）在健康受试者脑内产生虚拟损伤。受试者被指示执行认知任务，如面部识别和连贯运动。在被试完成认知任务的同时进行心理物理和神经生理检查（视觉事件相关电位（ERPs）、脑磁图（MEG）和功能磁共振成像（fMRI））。首先，我们过滤掉原始灰度面部的低或高空间频率分量（宽带空间频率），从而制作出粗糙（低空间频率）和精细（高空间频率）面部。对于运动知觉，连贯的水平和光流刺激， ...更多信息 就业。第二，年龄对运动知觉有明显的影响。有趣的是，MCI和AD均显示运动阈值增加，MCI显示对光流运动的敏感性降低。第三，记录了ERPs到面部和运动感知的地形图。在面孔任务中，枕区P1对面孔的加工表现为整体加工。颞枕部的N170反映了面部识别。晚期慢成分（N250-400）对面部表情表现出明显的敏感性。首先区分正、负表达，然后实现负表达的区分。P200是光流觉的指示，并且在MCI患者中延迟或缺失。目前，我们正在记录面部和运动知觉的MEG和fMRI，以进一步研究神经机制。最后，低频rTMS应用于V1和V5在健康受试者，这导致增加的反应时间运动知觉，这种效果持续了40分钟。因此，rTMS是一种很有前途的方法，探索神经网络更高的视觉认知。少

OBJECTIVES : We studied the neural basis of higher visual cognitions by using brain models. Low-frequency repetitive transcranial magnetic stimulation (rTMS) was used to produce brain virtual lesion in healthy subjects while patients with Alzheimer disease (AD) and mild cognitive impairment (MCI) were considered as disease models. Subjects were instructed to perform cognitive tasks such as face recognition and coherent motion. Psychophysical and neurophysiological examinations (visual event-related potentials (ERPs), magnetoencehalography (MEG) and functional magnetic resonance imaging (fMRI)) were evaluated while the subjects performed cognitive tasks.RESULTS : Several new findings were observed. First, we filtered out either low or high spatial frequency components of the original grayscale faces (broadband spatial frequency) so that coarse (low spatial frequency) and fine (high spatial frequency) faces were made. For motion perception, coherent horizontal and optic flow stimuli were … More employed. Second, aging has a distinct effect on the motion perception. Interestingly, both MCI and AD showed increased motion thresholds and MCI revealed decreased sensitivity for optic flow motion. Third, topographical mapping of ERPs to face and motion perception was recorded. In the face tasks, P1 at the occipital site showed holistic processing of faces. N170 at the temporooccipital site reflects facial identification. Late slow components (N250-400) show distinct sensitivities for facial expressions. The difference between positive and negative expressions was first discriminated, then discrimination of negative expressions was achieved. P200 is indicative of optic flow perception and was delayed or absent in patients with MCI. Currently, we are recording MEG and fMRI during face and motion perception to further investigate the neural mechanisms. Finally, low-frequency rTMS was applied over V1 and V5 in healthy subjects, which resulted in increased reaction times for motion perception and this effect lasted for 40 min. Therefore, rTMS is a promising method for exploring the neural network for higher visual cognition. Less