Figure 6.

Theta activity. Topographic plots (spline-interpolated) of conventional, wavelet power (a,c) versus the P_episode of oscillations based on the BOSC method (b,d) comparing theta (6.73 Hz) activity for Young (a,b) and Older (c,d) participants. Colour scale denotes log(power) (a,c) or P_episode (b,d), but these are dimensionless, since the topographic patterns were normalized to unit vector-length for each participant prior to averaging. Scales are adjusted to the range of values for each panel separately, to best visualize the topographic patterns. Note that although sources of EEG signal are usually dipoles, because power and the BOSC method start by squaring voltage, a dipole appears not as a positive pole next to a negative pole, but like two positive poles.