Human EEG responses to 1?100�Hz flicker: resonance phenomena in visual cortex and their potential correlation to cognitive phenomena

Abstract

The individual properties of visual objects, like form or color, are represented in different areas in our visual cortex. In order to perceive one coherent object, its features have to be bound together. This was found to be achieved in cat and monkey brains by temporal correlation of the firing rates of neurons which code the same object. This firing rate is predominantly observed in the gamma frequency range (approx. 30-80 Hz, mainly around 40 Hz). In addition, it has been shown in humans that stimuli which flicker at gamma frequencies are processed faster by our brains than when they flicker at different frequencies. These effects could be due to neural oscillators, which preferably oscillate at certain frequencies, so-called resonance frequencies. It is also known that neurons in visual cortex respond to flickering stimuli at the frequency of the flickering light. If neural oscillators exist with resonance frequencies, they should respond more strongly to stimulation with their resonance frequency. We performed an experiment, where ten human subjects were presented flickering light at frequencies from 1 to 100 Hz in 1-Hz steps. The event-related potentials exhibited steady-state oscillations at all frequencies up to at least 90 Hz. Interestingly, the steady-state potentials exhibited clear resonance phenomena around 10, 20, 40 and 80 Hz. This could be a potential neural basis for gamma oscillations in binding experiments. The pattern of results resembles that of multiunit activity and local field potentials in cat visual cortex.

MEG alpha activity decrease reflects destabilization of multistable percepts

“…Steady-state fields sessions 2 and 3 for which the percentual errors are Oscillatory visual stimulation results in so-called steadyindicated in parentheses as computed from the difference state responses of the visual cortex reflecting the frequency of presented to perceived reversals. Since in session 2 the of stimulation [17,60]. Fig.…”

Neural correlates of perceptual filling-in of an artificial scotoma in humans

“…Thus, it would not be expected to reveal activity associated with perceptual completion in neuronal populations that are not strongly driven by retinal input (16), such as those outside occipital cortex. Importantly, we found that target-specific responses were reduced but not eliminated during filling-in.…”

“…Data were band-pass filtered at 1-45 Hz (Butterworth) and from each of the time periods defined by subject responses, consecutive, nonoverlapping 500-ms epochs were extracted from the time series. Each epoch was extracted exactly at one of the trigger events, where the target changed from black to white, to ensure phase-locked averaging (16), with epochs starting 100 ms before the trigger and lasting until 400 ms after the trigger. Because epochs were nonoverlapping, not every trigger was used as a start point to extract data.…”

“…Topographies were produced by linearly interpolating sensor information at [14][15][16] Hz at the middle 20-ms time point onto sensor space. These were then smoothed by using a Gaussian kernel (FWHM 6 mm) and normalized to the mean of the power at 30-45 Hz.…”

Improving SSVEP-BCI performance using pre-trial normalization methods

“…SSVEPs are a phase-locked brain response triggered by fixing the user's gaze upon a repetitive visual stimulus (RVS) such as a flashing light [8], or a reversing pattern [9]. The SSVEP is produced by groups of neurons which output a repetitive signal matching the RVS frequency, maintained for the duration of the fixation period.…”