Human brain imaging during controlled and natural viewing

Assorted technologies such as; EEG, MEG, fMRI, BEM, MRI, TMS and BCI are being integrated to understand how human visual cortical areas interact during controlled laboratory and natural viewing conditions. Our focus is on the problem of separating signals from the spatially close early visual areas. The solution involves taking advantage of known functional anatomy to guide stimulus selection and employing principles of spatial and temporal response properties that simplify analysis. The method also unifies MEG and EEG recordings and provides a means for improving existing boundary element head models. In going beyond carefully controlled stimuli, in natural viewing with scanning eye movements, assessing brain states with BCI is a most challenging task. Frequent eye movements contribute artifacts to the recordings. A linear regression method is introduced that is shown to effectively characterize these frequent artifacts and could be used to remove them. In free viewing, saccadic landings initiate visual processing epochs and could be used to trigger strictly time based analysis methods. However, temporal instabilities indicate frequency based analysis would be an important adjunct. The class of Cauchy filter functions is introduced that have narrow time and frequency properties well matched to the EEG/MEG spectrum for avoiding channel leakage.