A possible physiological basis for the discontinuity of consciousness.

A comparison is made between the frequency of local minima in the analytic power (AP) of intracranial EEG (ECoG) from waking and unconscious human subjects and the frequency of putative frames of consciousness reported in earlier psychological literature. In ECoG from unconscious subjects, the frequency of deep minima in AP is found to be a linear function of bandwidth. In contrast, in ECoG from conscious subjects, the bandwidth/minima-frequency curve saturates or plateaus at minima frequencies similar to the frequencies of previously reported frames of consciousness.

EEG synchrony during a perceptual-cognitive task: widespread phase synchrony at all frequencies.

Objectives: (1) To examine the validity of comparing the phase of broad-band signals. (2) To measure phase synchrony over the whole head, at a variety of frequencies.

Methods: The concept of broad band phase is investigated (a) by visual comparison of the time series of two channels of filtered data with the time series of the spatial analytic phase difference (SAPD) between the two channels and (b) using artificial sinusoids.

Spatial resolution and the neural correlates of sensory experience.

Freeman and Baird [5; Freeman WJ, Baird B. Behav Neurosci 1987;101:393-408] recorded from the surface of the brain in waking rabbits and found spatial patterns of voltage that covaried with sensory experience. We simulate mathematically the electric fields produced by radial dipoles in cortical gyri and show that patterns with the spatial frequencies observed by Freeman and Baird could be produced by cortical dipoles spaced 3 mm apart.