Temporal Modulation of Steady-State Visual Evoked Potentials

Electroencephalographic responses to periodic stimulation are termed steady-state visual evoked potentials (SSVEP). Their characteristics in terms of amplitude, frequency and phase are commonly assumed to be stationary. In this work, we tested this assumption in 30 healthy participants submitted to 50 trials of 60[Formula: see text]s flicker stimulation at 15[Formula: see text]Hz frequency. We showed that the amplitude of the first and second harmonic frequency components of SSVEP signals were in general not stable over time. The power (squared amplitude) of the fundamental component was stationary only in 30% the subjects, while the power at the second harmonic frequency was stationary in 66.7% of the group. The phases of both SSVEP frequency components were more stable over time, but could exhibit small drifts. The observed temporal changes were heterogeneous across the subjects, implying that averaging results over participants should be performed carefully. These results may contribute to improved design and analysis of experiments employing prolonged visual stimulation. Our findings offer a novel characterization of the temporal changes of SSVEP that may help to identify their physiological basis.

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Color discrimination ellipses of trichromats measured with transient and steady state visual evoked potentials

Visual Neuroscience ◽

10.1017/s0952523808080383 ◽

2008 ◽

Vol 25 (3) ◽

pp. 333-339 ◽

Cited By ~ 6

Author(s):

BRUNO D. GOMES ◽

GIVAGO S. SOUZA ◽

MONICA G. LIMA ◽

ANDERSON R. RODRIGUES ◽

CÉZAR A. SAITO ◽

...

Keyword(s):

Steady State ◽

Evoked Potentials ◽

Fundamental Frequency ◽

Visual Evoked Potentials ◽

Second Harmonic ◽

Color Space ◽

Color Discrimination ◽

Pattern Reversal ◽

Different Color ◽

Visual Evoked

The purpose of this work is to investigate the use of different forms of visual evoked potentials (VEPs) to measure color discrimination thresholds and to plot color discrimination ellipses (MacAdam, 1942). Five normal trichromats (24.5 ± 2.6 years-old) were monocularly tested. Stimuli consisted of sinusoidal isoluminant chromatic gratings made from chromaticity pairs located along four different color directions radiating from one reference point of the CIE 1976 chromaticity diagram (u′ = 0.225; v′ = 0.415). Heterochromatic flicker photometry (HFP) was used to obtain the isoluminance condition for every subject and for all chromaticity pairs. VEPs were elicited using two cycles per degree grating stimuli at three different temporal configurations: transient, onset (300 ms)/offset (700 ms), 1 Hz fundamental frequency; steady-state, onset (50 ms)/offset (50 ms), 10 Hz fundamental frequency; and steady-state pattern reversal at 5 Hz fundamental frequency (10 Hz phase reversal). VEP amplitude was measured using transient VEP N1-P1 components and steady state VEP first (10 Hz) and second (20 Hz) harmonics. VEP amplitude was plotted as a function of chromatic distance in the CIE 1976 color space and the data points were extrapolated to zero amplitude level to obtain chromatic discrimination thresholds. The results were compared with psychophysical measurements performed using the same stimulus configurations and with the pseudoisochromatic method of Mollon-Reffin (one-way ANOVA). For all subjects and all stimulation methods, the ellipses showed small sizes, low ellipticities, and were vertically oriented. Despite some consistent differences in the results obtained with different procedures, there was no statistical difference between ellipses obtained electrophysiologically and psychophysically. For steady state VEPs, ellipses obtained from second harmonic amplitudes were larger and more elongated in the tritan direction than those obtained with first harmonic amplitudes.

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Selective lateralization of steady state visual evoked potentials at the second harmonic

Journal of Vision ◽

10.1167/8.6.1002 ◽

2010 ◽

Vol 8 (6) ◽

pp. 1002-1002

Author(s):

Y. J. Kim ◽

M. Grabowecky ◽

K. A. Paller ◽

S. Suzuki

Keyword(s):

Steady State ◽

Evoked Potentials ◽

Visual Evoked Potentials ◽

Second Harmonic ◽

Visual Evoked

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Differential Roles of Frequency-following and Frequency-doubling Visual Responses Revealed by Evoked Neural Harmonics

Journal of Cognitive Neuroscience ◽

10.1162/jocn.2010.21536 ◽

2011 ◽

Vol 23 (8) ◽

pp. 1875-1886 ◽

Cited By ~ 33

Author(s):

Yee-Joon Kim ◽

Marcia Grabowecky ◽

Ken A. Paller ◽

Satoru Suzuki

Keyword(s):

Steady State ◽

Evoked Potentials ◽

Visual Evoked Potentials ◽

Second Harmonic ◽

Frequency Doubling ◽

Cognitive State ◽

Visual Responses ◽

Visual Spatial ◽

Neural Populations ◽

Visual Evoked

Frequency-following and frequency-doubling neurons are ubiquitous in both striate and extrastriate visual areas. However, responses from these two types of neural populations have not been effectively compared in humans because previous EEG studies have not successfully dissociated responses from these populations. We devised a light–dark flicker stimulus that unambiguously distinguished these responses as reflected in the first and second harmonics in the steady-state visual evoked potentials. These harmonics revealed the spatial and functional segregation of frequency-following (the first harmonic) and frequency-doubling (the second harmonic) neural populations. Spatially, the first and second harmonics in steady-state visual evoked potentials exhibited divergent posterior scalp topographies for a broad range of EEG frequencies. The scalp maximum was medial for the first harmonic and contralateral for the second harmonic, a divergence not attributable to absolute response frequency. Functionally, voluntary visual–spatial attention strongly modulated the second harmonic but had negligible effects on the simultaneously elicited first harmonic. These dissociations suggest an intriguing possibility that frequency-following and frequency-doubling neural populations may contribute complementary functions to resolve the conflicting demands of attentional enhancement and signal fidelity—the frequency-doubling population may mediate substantial top–down signal modulation for attentional selection, whereas the frequency-following population may simultaneously preserve relatively undistorted sensory qualities regardless of the observer's cognitive state.

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