Sleep deprivation and memory
It has been found that sleep plays an important role in memory both before and after learning a new task. The process of sleep, learning and memory is a complex one that, though not entirely understood, needs more investigation.
Sleep helps learning and memory in two distinct ways – firstly, a sleep deprived person cannot focus optimally and, therefore, cannot learn efficiently and secondly, sleep itself has a role in the consolidation of memory, which is necessary for learning new information.
The process of memory and learning is divisible into three stages – 1. Acquisition refers the introduction of new information into the brain, 2. Consolidation is the process, by which a memory becomes stable and 3. Recall is an ability to access the information after it has been stored. All the three steps are necessary for the memory to function. The stages of acquisition and recall occur only during wakefulness, whereas the stage of consolidation takes place during sleep. Though it is not clearly understood how it takes place, the researchers think that specific brainwaves during different stages of sleep are associated with the formation of particular type of memory.
Types of memories and stages of sleep –
Basically, there are five stages of sleep –
Stage 1 – It is a light sleep from which one can be awakened easily.
Stage 2 – Brainwaves become slower but there occur an occasional burst of brainwaves.
Stage 3 – There occur extremely slow brainwaves called delta waves, interspersed with smaller and faster waves.
Stage 4 – There occur delta waves exclusively.
Stages 3 and 4 are referred to as deep sleep or delta sleep.
REM sleep – It occurs in the second half of sleep cycle. In REM sleep, breathing becomes more rapid, irregular and shallow, eyes jerk rapidly and limb muscles are temporarily paralyzed. Brain waves during this stage increase to levels experienced when a person is awake. This is the time when most dreams occur, and, if awoken during REM sleep, a person can remember the dreams. Most people experience three to five intervals of REM sleep each night.
Basically, there are two types of memory -
Declarative memory – It includes the knowledge of fact based information, for example, the capital of the USA. The scientists have hypothesized that stage of REM (rapid eye movement) sleep, in which dreaming occurs most frequently, seems to be involved in declarative memory processes if the information is complex and emotionally charged. If the information is simple and emotionally neutral, probably REM sleep is not involved. Slow wave sleep (SWS), which is deep and restorative sleep, is also associated with the processing and consolidation of declarative memory that is newly acquired. But this area also requires more research.
Procedural memory – It includes the knowledge of how to do something, for example, riding a bicycle or playing a piano. REM sleep seems to play a critical role in the consolidation of procedural memory. Motor learning, which is a process of improving motor skills through practice with lasting changes of responses, seems to depend on the amounts of lighter stages of sleep. Certain types of visual learning seem to depend on the amount and timing of both deep slow wave sleep (SWS) and REM sleep.
Impact of sleep deprivation on memory -
With sleep deprivation, our focus, attention and vigilance drift, thus making it more difficult to receive information. Moreover, the overworked neurons of the brain can no longer co-ordinate information properly and, therefore, we lose our ability to access previously learned information.
As a result, we cannot interpret and assess the situations properly and, therefore, are not able to make sound decisions. Our judgment becomes impaired. Being chronically tired to the extent of exhaustion means that the neurons do not fire optimally, muscles are not rested and body’s systems are not synchronized.
Sleep requirements -
A healthy adult requires 7 to 9 hours of sound sleep per 24 hours but children have more requirements depending on their age. For instance, a youngster of 10 to 17 years will require 8.30 to 9.30 hours of sound sleep, whereas a child of 1 to 3 years requires 12 to 14 hours of sleep per 24 hours. But there is no optimal number of sleep hours that applies to all adults and all kids. Sleep requirements are probably influenced by growth rates, stress, disease, pregnancy, and other aspects of physical condition. They may also be influenced by genes of an individual.
Some tips for sleep hygiene -
Since the sleep deprivation has far reaching ill effects on our memory, it will not be out of context to mention here something basic about sleep hygiene.
- Go to bed and wake up at the same time every day.
- Avoid naps if possible because naps may cause sleep fragmentation and difficulty initiating sleep.
- If stressed, don’t stay in bed awake for more than 10 to 15 minutes. Get out of bed and sit in a chair in dark to relax till you are sleepy again. Then return to bed.
- Don’t watch TV or read in bed, which should be reserved only for sleep and sex.
- There should be no TV, computer or any other electronic gadget in the bedroom, which are, in fact, ubiquitously found in the bedrooms these days. Screen time or any other media use before bedtime hinders initiation of sleep.
- Don’t drink caffeine after noon because its effects can last for several hours. Caffeine can fragment sleep and cause difficulty initiating sleep. Remember that soda and tea also contain caffeine.
- Cigarettes, alcohol, and over-the-counter medications may cause fragmented sleep.
- Exercise regularly before 2 pm every day as it promotes continuous sleep.
- Keep a comfortable temperature in your bedroom. Generally, a little cooler is better than a little warmer. The bedroom should be dark. Background white noise like a fan is OK.
- Eat your dinner, which should be lightest of all the three meals, at least two hours before going to sleep so as to avoid its disturbance.
- A ritual of relaxation like a warm bath or shower, listening to soft soothing music, or meditation just before going to sleep will help induce sleep quicker.
The bottom line –
Sleep plays an important role in our memory before and after learning a new task, and that is why, it becomes essential for all of us to have adequate sound sleep daily. In fact, sleep deprivation has such a profound effect on our memory that it makes more difficult for us to receive new information and, at the same time, it hampers our ability to access the previously learned information. Sleep deprivation impairs our judgmental power, thus raising our chances of making wrong decisions.