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Jeffrey L Goldberg, Alexandra Yakovleva, Bethany Hung, Anthony Norcia; Dynamics of human ON and OFF Visual Pathways. Invest. Ophthalmol. Vis. Sci. 2018;59(9):5028. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Recent single unit physiology in cat (Jin et al., J Neurosci 2011, Komban et al., Neuron, 2014) and human psychophysical results (Komban et al J Neurosci., 2011 Neuron, 2014) suggest that the OFF-pathway has a faster temporal response. Here we sought an experimental model of this timing difference in human by using Steady-State Visual Evoked Potentials (SSVEPs).
Thirty-five adult participants (mean age 19.9, 17 males) with 20/20 or corrected to 20/20 vision participated. The visual stimulus comprised a matrix of small flickering hexagonal elements (probes) superimposed on top of larger, static hexagons (pedestals) whose size was scaled according to the cortical magnification factor. The size of the central pedestal ranged between 28 and 80 arc min, with the probes being 20% of the size of the pedestal. Probe contrast was modulated by a sawtooth-profile to create rapid increment (ON-favoring) or rapid decrement (OFF-favoring) stimuli. The temporal frequency was 2.75 Hz. 128-channel EEG data was collected over a 0.3 to 50 Hz bandwidth. Response waveforms were extracted using a spatial filtering procedure (Dmochowski et al., NeuroImage, 2015). Waveform differences were assessed by permutation tests.
OFF-favoring sawtooth stimuli elicited evoked responses that were 14 msec faster than ON-favoring stimuli. The OFF-related response was typically, but not always larger in amplitude. Response amplitudes were much larger in the lower visual field compared to the upper visual field.
An electrophysiogical correlate of faster OFF-pathway single-cell and psychophysical responses can be demonstrated with OFF- vs ON-favoring sawtooth stimulation.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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