Examination of differences in time–frequency power data between
recalled (R) and not-recalled (NR) items averaged across all electrodes
revealed two time–frequency clusters of significant EM effects in the
theta frequency range: an early effect for slow theta power which was
predominant from 2 to 4 Hz, and a later effect for fast theta power
which was predominant from 5 to 7.5 Hz (Fig. 3). On the basis of this
overall analysis, slow theta power data were collapsed from 2 to 4 Hz
and fast theta power data were collapsed from5 to 7.5 Hz for all further
analyses of EM effects.