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Anthony Ries, Jon Touryan, Patrick Connolly; Spatial and temporal features of the lambda response in fixation-related potentials . Journal of Vision 2016;16(12):108. doi: 10.1167/16.12.108.
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Combining simultaneous recordings of electroencephalography (EEG) and eye-tracking provides a powerful method to evaluate the neural mechanisms of vision by isolating fixation-related potentials (FRPs), evoked EEG activity during periods of eye fixation. This approach provides a means to evaluate visual information processing without imposing the constraint of central eye fixation commonly required in many event-related potential (ERP) studies. The earliest and most prominent brain potential following fixation onset is commonly referred to as the lambda response and reflects the afferent flow of visual information at fixation to visual cortex. The FRP-based lambda response is affected by low level visual features similar to the P1 ERP; however, when evoked by the same stimulus, the lambda response generally peaks earlier and has a larger amplitude compared to the P1 suggesting a difference in the underlying mechanisms. While many studies have evaluated the spatial and temporal properties of the P1 ERP, few studies have investigated these properties in the lambda response. Here we utilized independent component analysis (ICA) to separate the neural sources underlying the fixation-related lambda response obtained during a guided visual search task. We found that the lambda response in the FRP consists of both early and late source components with central occipital and lateral occipital topology respectively. These results suggest that the lambda potential may be generated by independent but temporally overlapping sources in visual cortex.
Meeting abstract presented at VSS 2016
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