Essential Sleep (Part 2)

The benefits of sleep include:

Feeling rested;

Being physically and mentally alert;

Having more energy;

Making fewer mistakes (including causing accidents);

Feeling psychologically and emotionally recovered;

and to experience:

Improved cognitive function;

Improved memory;

Higher stress tolerance and resilience;

Increased productivity;

Normal body balance;

Healthier weight;

Reduced risk of CVD, diabetes and cancer;

Living longer; and

Feeling healthier. 

during sleep the mind is cataloguing our memories and deciding what to keep and what to throw away it is making memories stronger. It also seems to be reorganizing and restructuring memories.

It’s not possible to learn something new when you sleep, like a foreign language, but you can reinforce something you already know.One study found that students learned to play a series of musical notes better after listening to them during a 90-minute nap. The research shows that memory is strengthened for something you’ve already learned. Rather than learning something new in your sleep.

A review of studies on sleep found that we tend to hold on to the most emotional parts of our memories.

Getting enough sleep is associated with energy, joy, optimistic thinking and coping with negative emotions. 

Stages of Sleep                                                                           

Sleep Stage

Brain Waves

Common Characteristics

Frequency

Type

 

 

Stage 1

NREM

 

 

4 to 8

 

 

Alpha

& Theta

 

Transition between sleep and wakefulness

Eyes begin to roll and close

Consists of mostly theta waves with some brief periods of alpha waves (similar to waves of wakefulness)

Stage lasts 5-10 mins

 

 

 

Stage 2

NREM

 

 

8 to 15

 

 

Theta, Spindles,

k-complexes

 

Brain wave peaks become higher

Spontaneous periods of muscle tone mixed with periods of muscle relaxation

Heart rate  and temperature decrease

Stage last 5-10 mins

 

 

Stage 3

NREM

 

2 to 4

 

Delta, Theta

 

Deep Sleep or Delta sleep

Very slow brain waves

 

 

Stage 4

NREM

 

0.5 to 2

 

Delta, Theta

 

The last of deep sleep before REM begins.

Consist mostly of Delta waves

 

 

 

Stage 5

 REM

 

 

 

≥ 12

 

 

 

Beta

 

Beta waves have a high frequency and occur when the brain is active when asleep and awake.

Frequent bursts of rapid eye movement (REM) and muscle twitches.

Increase in heart and breathing rate

Vivid dreaming occurs here.

(Cook and Nendick, 2007)

Circadian Cycle

When a person falls asleep and wakes up is largely determined by their circadian rhythm, a day-night cycle of about 24 hours. Circadian rhythms greatly influence the timing, amount and quality of sleep (Lockley et al. 1997).

Literally hundreds of circadian rhythms have been identified in mammals (Campbell 1993). Among the numerous systems and functions mediated by the circadian timing system are, hormonal output, core body temperature and metabolism. The circadian clock is believed to sit in the suprachiasmatic nucleus (SCN) located in the hypothalamus of the brain. It was thought that processes now linked with circadian timing e.g. sleep wake cycles, were due solely to environmental cues, for example solar activity, it is now recognised however that these biological rhythms are regulated by factors inherent to the organism (Campbell 1993). A circadian rhythm displays a 24 hour cycle of wakefulness and sleep synchronised with the world’s night/day clock (Mansuy et al, 2003).  Everyone’s cycle will vary depending on behavioural and psychological factors (Mansuy et al, 2003).  The most typical pattern will be low alertness in the mornings as we wake, to highly alert mid afternoon (Swain et al, 2007).

The natural circadian rhythm in the body, which maintains a regular sleep-wake cycle, makes important contributions to physiological processes and psychological health. The normal rhythm is reset daily by the influence of bright light in the morning. Shift-workers, who may work at night and sleep in the daytime, and blind people may have difficulty maintaining a normal sleep-wake cycle because the natural environmental cues are miss-timed (Morris 1999). Studies show that shift work is one the greatest influencing factor causing an alteration in an individual’s cycle along with sleeping disorders (Baulk, 2008).  Altering the circadian cycle can lead to periods of decreased alertness leaving people extremely vulnerable to accidents and injuries (Andersen et al, 2009).

Our sleep patterns appear to be polyphasic. In one experiment, subjects were exposed to 14 hours of darkness; then they remained in a state of quiet rest for about two hours before falling asleep.  They then slept for four hours, awakened from a dream, spent another two-hour period in quiet rest, and then fell asleep again for four hours more.  The subjects awoke at 6 a.m. each morning from their dream sleep and then spent two hours in quiet rest before arising at 8 a.m.  These subjects followed their own natural rhythms, sleeping for eight hours with blocks of time at quiet rest (Wehr, S.E, 1996).  This polyphasic sleep appears to be a pattern in many mammals.  We experience hypnagogic imagery – a state described as dreaming, drowsy, floating, wandering – every night just before we fall asleep.  Every night before we go to sleep we spend a few minutes in a state of relaxed wakefulness characterised by drifting thoughts and alpha brainwaves.

Another interesting method for lessening the impact of sleep deprivation was through a study that found there were certain hours better to sleep through the night. A new Stanford University study on the science of sleep deprivation suggests that early­ morning sleep is more restful than a middle‑of‑the‑night nap. In a study of two groups of men they found that early‑morning sleepers scored higher on wakefulness tests and on measures of sleep efficiency. (Stratton, 2003) Although this study shows that there may some advantages to when you get your sleep it is more an avoidance of the problem rather than a solution.

We are also influenced not just by sleep but also our perceptions of its quality. If we think we’ve had a wonderful sleep last night, we feel and perform better, even if our sleep was actually the same as usual. In this study researchers randomly told some people they’d had better sleep than others after they were hooked up to some placebo brain sensors). When they were given a cognitive test the next day, those who’d been told they slept the best also did the best in the test.

 

Part 3 and more coming