Hit the Books or Hit the Sack*?
Many students have pulled
"all-nighters" trying to cram for an exam the next day. They risk the loss of
one night's sleep in hopes of earning a better grade by cramming for the exam.
But how useful is this? Would getting a good night's sleep
the night before be better? Actually, a student needs both study and sleep to
succeed on the test. This holds true for ongoing learning as well. In fact,
study without sleep may be a complete waste (Fackelmann, 2000).
How much sleep do we really need? Experts recommend at least eight hours of
sleep a night for the average adult - and at least that much for teens (Neergaard,
1999). How much sleep does a student need to do well on tests involving memory?
In order to have new information truly integrated into memory, one should sleep after learning the new material. According to research, one needs at least six hours of sleep within thirty hours of the study period to show any signs of memory improvement (Conner, 2000). In a study led by Harvard professor Robert Stickgold, volunteers were trained to press buttons in response to symbols on a computer screen. Although this learning task involved implicit (unconscious) and procedural (muscle) memory, Stickgold speculated that the results could also apply to other memorization. The researchers noted each student's correct response times. The students tested the same later that day. Students who slept six hours or less after training showed no improvement in their results. Those with more than six hours of sleep improved in speed and accuracy. Students who had slept eight hours showed the most improvement (Blakeslee, March 2000).
Why is so much sleep needed? Memory consolidation is an all-night process, involving the interaction between two stages of sleep. Slow-wave sleep (SWS), which occurs mostly early in the night, and rapid eye movement (REM) sleep, which typically occurs later in the night, each contribute to the processing of memory traces (Butcher, 2000). In one study, those who had mostly slow-wave sleep after learning sessions significantly improved at the task. Those who were trained during the night and then allowed to finish their sleep, which cycled into REM sleep, did not improve (Butcher, 2000). Those with both SWS and REM sleep improved the most. Once SWS initiates the process, REM sleep can enhance memory.
Researchers used to believe that little brain activity occurs during deep sleep (Blakeslee, November 2000). Recent research argues otherwise. Scientists have discovered signals being sent among brain tissue cells of sleeping cats during SWS. At sleep onset, the thalamus, a relay station for the brain, stimulates cells in the higher cortex. These cells fire repeatedly, possibly reviewing what has been learned during the day. The hippocampus, another region, that encodes and stores short-term memory, relays learned information to the cortex in a rhythmic fashion at only one to four cycles per second. During the next four hours, Stickgold theorizes, the brain distributes this new information into relating networks (Blakeslee, March 2000). Once the hippocampus ceases its firing completely, cortical cells send out neurotransmitters - chemicals that help carry information - in miniature synaptic events, or minis (Blakeslee, November 2000). Cells most active during the day will release the most nighttime minis. As soon as a cell has released enough minis to reach a certain threshold, it fires a burst of signals, activating synapses on all the cells with which it had been in contact during the day. The specific cells that had been marked by the stimulation of neurotransmitters earlier in the day during an event are again reactivated. In this heightened state, signals turn on genes to synthesize proteins, strengthening the connections between nerve cells involved in that memory. Later in the day, when we are awake, if a few of these same cells are stimulated, the links are activated and an entire memory is recalled.
The last two hours of sleep are spent in REM sleep, during which the cortex goes into an active dreaming state (Blakeslee, March 2000). Recent findings strongly support scientists' theories that REM sleep plays a role in memory consolidation. Researchers identified four specific brain regions in volunteers who were trained to perform a visual discrimination task that become more active both during learning and during REM sleep (Larkin, 2000). These areas, identified using positron emission tomography (PET) scanning technology, were significantly more active in learners than in controls, who had not been trained at all.
Circadian rhythms and sleep cycles vary across age groups. For this reason, there are good biological arguments favoring later school starting times if society wants teenaged students to remember what they are trying to learn in school. In order for teens to get enough sleep to be attentive during the presentation of new material and for memory consolidation to occur during their nightly sleep, these youth need to sleep more than they do, probably at least ten hours a night!
Is it possible to make up for lost hours of sleep? Probably not. Individuals who were deprived of the first night of sleep after training were then allowed to sleep as much as they liked the following two nights. When tested on the fourth day, those who tried to "catch up" showed no improvement whereas those who got sleep all three nights did (Fackelmann, 2000).
Many students and workers in today's busy society to survive (get by/ make do) with less than five hours a night during the week, then catch-up on the weekends. Much of the information learned during a sleep-deprived week will not be well-integrated into memory circuits. Facts thought to have been memorized fade away and details are forgotten. If you want to keep the memorization at which you worked so hard, experts recommend you sleep on it!
* Hit the books = to study hard. Hit the sack = to go to bed for sleep.
