While at Laval University, he discovered that the slow oscillations of
NREM sleep arise when groups of
neurons fire together for a little while (so-called "on periods"), then fall silent for about a fraction of a second ("off periods"), and then resume their synchronized firing. This was one of the fundamental discoveries in sleep research. After his discovery, scientists have also discovered that in birds and mammals, the slow waves are large if preceded by a long period of wakefulness and become smaller as sleep goes on. The majority of his research was on
corticothalamic oscillations. He was among the first to study the dynamics of the
brain during sleep, and one of his key discoveries was determining the role of
thalamic reticular neurons as pacemakers in producing the
sleep spindle rhythm. He also discovered slow (<1 Hz) sleep rhythms associated with
intracortical activity. == Honors ==