A Finnish study shows that individual circadian preference is associated with brain activity patterns during the night. Sleep spindles are bursts of oscillatory brain activity visible on an EEG (electroencephalogram) that occur mainly during stage 2 sleep. Sleep spindles are linked, for example, to sleep maintenance and strengthening of the memory traces during sleep. The … Continue reading “Morning Larks” Have Weaker Sleep Spindles During Night Than “Night Owls”