September 2021
Volume 21, Issue 9
Open Access
Vision Sciences Society Annual Meeting Abstract  |   September 2021
Fixation-related potentials in total darkness
Author Affiliations
  • Olaf Dimigen
    Humboldt-Universit├Ąt zu Berlin
Journal of Vision September 2021, Vol.21, 2931. doi:https://doi.org/10.1167/jov.21.9.2931
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      Olaf Dimigen; Fixation-related potentials in total darkness. Journal of Vision 2021;21(9):2931. doi: https://doi.org/10.1167/jov.21.9.2931.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Although saccade- and fixation-related potentials (SRPs/FRPs) in the EEG are increasingly used as a tool in vision research, basic properties of these neural responses are still poorly understood. In particular, it is unclear to what degree nonvisual processes (e.g., from a corollary discharge) also contribute to eye movement-related activity measurable at the scalp. Likely due to technical and data-analytical limitations, older EEG studies on this issue have yielded inconsistent results, with the majority of papers reporting that SRPs/FRPs disappear entirely when the visual field is dark or featureless. The present work aimed to more systematically explore nonvisual contributions to the SRP and FRP waveforms generated by spontaneous saccades. EEG recordings were combined with long-wavelength infrared eye-tracking while participants searched for an occasionally appearing low-luminance target stimulus either in total darkness or while viewing natural scenes. Nonlinear deconvolution modelling (Dimigen & Ehinger, 2021) was used to control for overlapping potentials and to estimate responses in the time domain. As a key finding, we observed significant peri- and post-saccadic activity over visual cortex in total darkness, which peaked as a negative potential at occipital electrode Oz about 110 ms after saccade onset (or 70 ms after fixation onset). Topographically, this nonvisual response was polarity-reversed compared to the surface-positive postsaccadic lambda response (P1) seen with visual stimulation. This earlier nonvisual effect was followed by a positive potential peaking as late as 350 ms after saccade onset. Interestingly, nonvisual effects scaled nonlinearly with saccade size, suggesting that the well-established nonlinear relationship between saccade size and lambda response (P1) may be at least partially explained by nonvisual mechanisms. In summary, we observed clear modulating effects of saccade execution on early visual areas recordable in the scalp EEG. Frequency-domain and phase-locking analyses will be presented in an attempt to elucidate the functional relevance of these effects.

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