Sleep (see more on sleep earlier in this volume)

. Sleep is important for the brain. We spend about 1/3 of our time asleep. The body possesses a series of internal biological clocks that are controlled by the brain. Part of the hypothalamus called the suprachiasmatic nucleus is involved.

. The brain is in constant tension between wanting to sleep (homeostatic sleep drive ‐ maintains the duration and intensity of sleep) and wanting to keep awake (circadian arousal system ‐ the tendency and timing of the need to go to sleep). Linked with this is chronotype and the nap zone. Chronotype refers to when you are most alert, eg early chronotype (morning) and late chronotype (evening). Need to match individual preferences with work schedules.

. When asleep, the neurons of brain show vigorous rhythmical activity. The reasons for this are not fully understood but it is thought that it is working on memory.

. Different people need different amounts of sleep and when they prefer to get it. There are varying amounts of required sleep depending on an individual's state, eg age, gender, moods, etc. For example, teenage students have a temporary shift in sleep/awake patterns to favour late chronotypes. The asleep hormones, like melatone are at their maximum level in the teenage brain. As we age, we need less sleep

. There is a biological drive for an afternoon nap. It is felt that a long night's sleep plus a short afternoon nap is the most natural. The afternoon nap has been shown to provide a significant improvement in performance (including visual texture discrimination, motor adaptations and motoring sequencing)

. Loss of sleep hurts learning by impacting negatively on attention, executive function, working memory, mood, quantitative skills, logical reasoning and motor dexterity