Hamamé Carlos M, Vidal Juan R, Perrone-Bertolotti Marcela, Ossandón Tomas, Jerbi Karim, Kahane Philippe, Bertrand Olivier, Lachaux Jean-Philippe
Lyon Neuroscience Research Center, Brain Dynamics and Cognition Team, INSERM U1028, CNRS UMR5292, Lyon, France; University Lyon 1, Lyon, France; Laboratoire de Psychologie Cognitive, CNRS UMR6146, Aix-Marseille Université, Marseille, France.
Lyon Neuroscience Research Center, Brain Dynamics and Cognition Team, INSERM U1028, CNRS UMR5292, Lyon, France; University Lyon 1, Lyon, France.
Neuroimage. 2014 Jul 15;95:276-86. doi: 10.1016/j.neuroimage.2014.03.025. Epub 2014 Mar 18.
Eye movements are a constant and essential component of natural vision, yet, most of our knowledge about the human visual system comes from experiments that restrict them. This experimental constraint is mostly in place to control visual stimuli presentation and to avoid artifacts in non-invasive measures of brain activity, however, this limitation can be overcome with intracranial EEG (iEEG) recorded from epilepsy patients. Moreover, the high-frequency components of the iEEG signal (between about 50 and 150Hz) can provide a proxy of population-level spiking activity in any cortical area during free-viewing. We combined iEEG with high precision eye-tracking to study fine temporal dynamics and functional specificity in the fusiform face (FFA) and visual word form area (VWFA) while patients inspected natural pictures containing faces and text. We defined the first local measure of visual (electrophysiological) responsiveness adapted to free-viewing in humans: amplitude modulations in the high-frequency activity range (50-150Hz) following fixations (fixation-related high-frequency response). We showed that despite the large size of receptive fields in the ventral occipito-temporal cortex, neural activity during natural vision of realistic cluttered scenes is mostly dependent upon the category of the foveated stimulus - suggesting that category-specificity is preserved during free-viewing and that attention mechanisms might filter out the influence of objects surrounding the fovea.
眼球运动是自然视觉中持续且必不可少的组成部分，然而，我们对人类视觉系统的大部分了解都来自于限制眼球运动的实验。这种实验限制主要是为了控制视觉刺激的呈现，并避免在脑活动的非侵入性测量中出现伪影，不过，这种限制可以通过对癫痫患者进行颅内脑电图（iEEG）记录来克服。此外，iEEG信号的高频成分（约50至150Hz之间）可以在自由观看期间提供任何皮质区域群体水平的尖峰活动的替代指标。我们将iEEG与高精度眼动追踪相结合，以研究梭状面孔区（FFA）和视觉词形区（VWFA）的精细时间动态和功能特异性，同时让患者查看包含面孔和文本的自然图片。我们定义了第一种适用于人类自由观看的视觉（电生理）反应性的局部测量方法：注视后高频活动范围内（50 - 150Hz）的幅度调制（注视相关高频反应）。我们发现，尽管枕颞叶腹侧皮质的感受野很大，但在自然观看杂乱场景时，神经活动主要取决于中央凹注视刺激的类别——这表明在自由观看期间类别特异性得以保留，并且注意力机制可能会滤除中央凹周围物体的影响。
