Steady-State Visual Evoked Potentials: Distributed Local Sources and Wave-Like Dynamics Are Sensitive to Flicker Frequency

Abstract

Steady-state visual evoked potentials (SSVEPs) are used in cognitive and clinical studies of brain function because of excellent signal-to-noise ratios and relative immunity to artifacts. SSVEPs also provide a means to characterize preferred frequencies of neocortical dynamic processes. In this study, SSVEPs were recorded with 110 electrodes while subjects viewed random dot patterns flickered between 3 and 30 Hz. Peaks in SSVEP power were observed at delta (3 Hz), lower alpha (7 and 8 Hz), and upper alpha band (12 and 13 Hz) frequencies; the spatial distribution of SSVEP power is also strongly dependent on the input frequency suggesting cortical resonances. We characterized the cortical sources that generate SSVEPs at different input frequencies by applying surface Laplacians and spatial spectral analysis. Laplacian SSVEPs recorded are sensitive to small changes (1-2 Hz) in the input frequency at occipital and parietal electrodes indicating distinct local sources. At 10 Hz, local source activity occurs in multiple cortical regions; Laplacian SSVEPs are also observed in lateral frontal electrodes. Laplacian SSVEPs are negligible at many frontal electrodes that elicit strong potential SSVEPs at delta, lower alpha, and upper alpha bands. One-dimensional (anteriorposterior) spatial spectra indicate that distinct large-scale source distributions contribute SSVEP power in these frequency bands. In the upper alpha band, spatial spectra indicate the presence of long-wavelength (> 15 cm) traveling waves propagating from occipital to prefrontal electrodes. In the delta and lower alpha band, spatial spectra indicate that long-wavelength source distributions over posterior and anterior regions form standing-wave patterns. These results suggest that the SSVEP is generated by both (relatively stationary) localized sources and distributed sources that exhibit characteristics of wave phenomena.

Intense pain influences the cortical processing of visual stimuli projected onto the sensitized skin

“…Twenty-six participants took part in the experiment (18 women, 8 men, median age 23, range [19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37]. Participants were recruited among students and staff of the university and were naïve to the aims of the study.…”

Nociceptive Steady-State Evoked Potentials Elicited by Rapid Periodic Thermal Stimulation of Cutaneous Nociceptors

“…SS-EPs elicited by visual, auditory, and vibrotactile stimuli have been shown to originate mainly from the corresponding primary sensory cortices (Snyder, 1992;Pantev et al, 1996;Kelly et al, 1997;Kelly and Folger, 1999;Srinivasan et al, 2006;Giabbiconi et al, 2007). Hence, it may be hypothesized that nociceptive SS-EPs reflect the entrainment of neurons that are at least partly involved in early, modality-specific, nociceptive processing.…”

“…These steady-state responses are thought to result from an entrainment or resonance of a population of neurons responding to the stimulus at the frequency of stimulation (Herrmann, 2001;Muller et al, 2001;Vialatte et al, 2010). A large number of studies have used this approach to explore the cortical activity involved in processing other sensory modalities and have shown that this technique is effective to capture neural activity related to sensory processing, originating mainly from primary sensory cortices (Snyder, 1992;Pantev et al, 1996;Kelly and Folger, 1999;Tobimatsu et al, 1999;Plourde, 2006;Srinivasan et al, 2006;Giabbiconi et al, 2007;Vialatte et al, 2010).…”

Techniques and devices to restore cognition

“…Steady-state visual stimuli may be used to probe EEG responses: recent work comparing EEG and fMRI of human participants exposed to flickering light found that medial frontal cortex metabolic activity depended on the temporal frequency of visual input implying that during visual stimulation, input frequency can be used to activate distinct functional networks [146]. Indeed the use of visual flicker to purposefully modify cortical activity in order to improve memory has been explicitly tested [169,170].…”