Asymmetry of waking electroencephalography (EEG)
alpha power in frontal regions has been correlated with
waking emotional reactivity and the emotional content of
dream reports. Little is known regarding alpha asymmetry
during sleep. The present study was performed to compare
alpha power and alpha power asymmetry in various brain
regions across states of sleep and wakefulness. Waking
and sleep EEG were recorded in a group of patients undergoing
polysomnographic evaluation for possible sleep disorders.
Alpha EEG asymmetry in frontal and temporal regions was
significantly correlated in waking versus sleep, particularly
during rapid eye movement (REM) sleep. These results suggest
that patterns of frontal alpha asymmetry are stable across
sleep and waking and may be related to emotional reactivity
during dreaming. During sleep, alpha power was highest
during slow-wave sleep and lowest during REM sleep. Implications
of these data for understanding the functional significance
of alpha power during waking and sleeping are considered.