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Rick Gilmore, Stephen Mattes, Adam Christensen; Stability of SSVEP responses to optic flow. Journal of Vision 2008;8(6):26. doi: 10.1167/8.6.26.
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© ARVO (1962-2015); The Authors (2016-present)
Adults have distinct patterns of neural activation in response to specific patterns of optic flow. The stability of the VEP response has not been investigated, but is crucial for understanding changes across time such as those that occur during development. Two adult participants (1 female) participated in 4 VEP data sessions across a period of several weeks. During each session, the participants observed random dot patterns of optic flow consisting of translational motion, rotational motion, and expansion/contraction. The displays reversed direction at 1 Hz. EEG was measured with a standard 5-channel electrode array over positions PO7, O1, OZ, O2, and PO8. The EEG waveform was analyzed by amplitude at harmonics 1F1–5F1 of the fundamental frequency. Stability was assessed by Spearman-Brown correlations of phase-locked amplitude across sessions and a Spearman rho test of the rank-ordered harmonic amplitudes. Consistent with previous research, translational displays evoked the highest phase-averaged amplitudes at 2F1 and 4F1. Midline (O1, Oz, O2) channels showed the highest between-session stability for the translation condition in both participants. For one participant, these same channels showed high stability for the expansion display, but only modest stability for rotation. The other participant showed higher stability for rotation than expansion. The results suggest that there is moderate stability in ssVEPs to some patterns of optic flow, that there are individual differences in the stability of the response depending on display type, and that lateral channels show less stable responses overall.
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