Investigating neuromagnetic brain responses against chromatic flickering stimuli by wavelet entropies

International Guidelines for Photosensitive Epilepsy: Gap Analysis and Recommendations

People with photosensitive epilepsy may have seizures caused by flashing lights, patterns, and video sequences. Because of this, there is increasing interest among researchers, developers, and companies toward making content safer. There are five major guidelines (from the U.K., Japan, ISO, ITU, and W3C) to limit risk in different technology domains that have been created since the mid-1990s. All address similar risk factors, but they are not fully harmonized and can be confusing. Furthermore, there have been significant changes in technology since the guidelines were introduced. This article compares and clarifies the guidelines, describes risk factors that have changed (such as the reduction of risk due to display technology), gaps in our knowledge, the coverage of new technology, and new characteristics (such as the duration and synchronicity of individual flash transitions) that may need to be accounted for. The authors suggest working values for new thresholds and propose updated guidelines.

Decoding the coupling between the brain and skin reactions in auditory stimulation by information-based analysis of EEG and GSR signals

BACKGROUND

The analysis of brain activity in different conditions is an important research area in neuroscience.

OBJECTIVE

This paper analyzed the correlation between the brain and skin activities in rest and stimulations by information-based analysis of electroencephalogram (EEG) and galvanic skin resistance (GSR) signals.

METHODS

We recorded EEG and GSR signals of eleven subjects during rest and auditory stimulations using three pieces of music that were differentiated based on their complexity. Then, we calculated the Shannon entropy of these signals to quantify their information contents.

RESULTS

The results showed that music with greater complexity has a more significant effect on altering the information contents of EEG and GSR signals. We also found a strong correlation (r= 0.9682) among the variations of the information contents of EEG and GSR signals. Therefore, the activities of the skin and brain are correlated in different conditions.

CONCLUSION

This analysis technique can be utilized to evaluate the correlation among the activities of various organs versus brain activity in different conditions.

The effects of visual discomfort and chromaticity separation on neural processing during a visual task

Visual stimuli that are uncomfortable to look at evoke a large neural response suggesting altered processing. While there is some evidence linking uncomfortable achromatic stimuli to impaired visual processing, the effect of uncomfortable chromatic patterns on visual cognition has yet to be explored. Large differences in chromaticity separation (e.g. red and blue) elicit visual discomfort, larger metabolic responses, larger visual evoked potentials, and greater alpha suppression compared to small chromaticity separations (e.g. pink and purple). We investigated the impact of stimuli that varied in their chromaticity separation (calculated in perceptual color space) on a visual task and their effect on neural responses across the cortex. Thirty participants completed a continuous pairs task (letters changed at 3 Hz) while grating patterns that differed in their chromaticity separation alternated with a grey screen at 5 Hz. The different temporal frequencies allowed for steady-state visual evoked potentials (SSVEPs) to the two stimulus-types to be measured simultaneously using electroencephalography (EEG). A subset of participants rated the gratings on a 9-point scale of discomfort. We observed greater ratings of discomfort and increased power at 5 Hz with the larger chromaticity separations. The increase in 5 Hz power with greater chromaticity separation was evident across the cortex. However, there was no significant effect of chromaticity separation on power at 3 Hz, or on reaction times, and no consistent effect on behavioral accuracy. Despite eliciting heightened neural responses across the cortex, short term exposure to uncomfortable chromatic stimuli does not adversely impact visual task performance.