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Yingxin Jia, Christopher Tyler; Brain responses elicited by saccadic fixations on natural images of faces. Journal of Vision 2017;17(10):1152. doi: 10.1167/17.10.1152.
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Introduction. In most previous electroencephalography (EEG) experiments, visual processing is examined with large eye movements precluded, making it difficult to determine the cortical mechanisms involved in the control of eye movements. A previous study (Jia & Tyler, 2016) validated the capability of simultaneous EEG and eye movement measurements with electrooculography (EOG) signals. The current study co-registered the EEG and EOG signals to reveal neural correlates of natural image processing while making fixational eye movements across images of faces. Methods. The fixation targets consisted of 18 white circles appearing in a window (29° by 22°) filled with a) a blank field, b) a white noise pattern, c) a natural image of a face, or d) only the facial features within the target circles with a noise pattern outside them. The targets were each presented for 2s in random order. Participants were required to saccade onto the presented stimulus and maintain fixation until the next stimulus appeared. EEG and EOG were measured simultaneously with a high-density EGI electrode net at a 500 Hz sampling rate. The resultant EEG signals were pre-processed and analyzed by Principal Component Analysis (PCA) to reveal visual fixation- and saccade-related potentials. Results. The analysis revealed a primary EOG eye movement component with a saccade-like waveform derived from the facial area around eyes. A slow anticipatory component was seen before the saccades. A transient Frontal Eye Field component accompanied the saccades. A posterior component with a single negative peak was found around the time of the saccade, interpretable as representing the neural substrate for saccadic suppression. Occipital components peaking 100-200 ms after the saccade were interpretable as the cortical responses to the targets. Conclusion. These findings show that local feature viewing of facial images elicits a range of saccadic control and visual cortical response components.
Meeting abstract presented at VSS 2017
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