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I want to design a project for EEG signal processing. In my research I found the concept of SSVEP. SSVEPs represent the electrical activity of the brain as measured via EEG, and are evoked by visual stimuli with low frequency applied to the eye.

My question is whether it is known how the electric activity of brain will change? And a second thing, does it mean that each frequency applied to the eye has a fixed reaction for the brain?

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Explained perfectly in pubmedcentral.nih.gov/articlerender.fcgi?artid=1880883 –  Devashish Das Jul 19 '14 at 19:03
    
I corrected your title since the SSVEP is the pattern in the EEG activity and is not the stimulus for it. –  jonsca Jul 20 '14 at 1:44
    
I slightly modified question wording. Feel free to roll back. –  AliceD May 22 at 0:24

1 Answer 1

Short answer
SSVEP frequency corresponds to stimulus frequency and SSVEP amplitude decreases with stimulus frequency.

Background
The simplest form of steady state visual-evoked potentials (SSVEPs) are those to flash stimuli. Herrmann (2001) studied the SSVEP by recording the EEG from the visual cortex at various flash frequencies. He found that SSVEPs occurred at a frequency corresponding to the flicker stimulus. Amplitudes decreased steadily with frequency and SSVEPs could be recorded up to ~90 Hz flicker frequencies. The shape and frequency following of SSVEPs are shown in Fig. 1.

SSVEPs
Fig. 1. SSVEPs and FFT spectra at various frequencies. Source: Herrmann (2001)

Interestingly, SSVEPs in response to some frequencies showed resonance phenomena, indicating a selective frequency preference of the neural oscillators. Specifically, SSVEPs at around 10, 20, 40 and 80 Hz resulted in higher amplitudes than stimuli flickering at adjacent frequencies (Fig. 2).

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Fig. 2. SSVEPs showing resonance at 80 Hz. Source: Herrmann (2001)

Reference
Herrmann, Exp Brain Res (2001); 137: 346–353

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