UNIT 1 - TOPIC 3

Continuum of arousal

the operating of a low level of arousal through a high level of arousal. From coma → general anaesthesia → deep sleep → light sleep → drowsiness → awake and alert → excitement → hyperarousal

Attention

relates to the internal and external information that we are actively processing, either consciously or unconsciously. It can be selected or divided.

Selective attention

the process of focusing on one particular object in the environment for a period of time while simultaneously ignoring or filtering out the other irrelevant stimuli in the environment. It is used for controlled processes as a person must actively focus attention to successfully complete a task..

Divided attention

the capacity to attend to and perform two or more activities at the same time (multitasking). It allows us to simultaneously process different information from various sources and to successfully complete multiple tasks at the same time. If a task requires little mental effort and attention (automatic processes), we can often engage in other tasks at the same time.

Circadian rhythm

a biological rhythm that occurs approximately once every 24 hours.

Sleep-wake cycle

It is a regular cycle that is an example of circadian rhythm. It is determined by an internal body clock called the suprachiasmatic nucleus (SCN). It includes two stages of sleep: rapid eye movement (REM) and non-rapid eye mobement (NREM).

Suprachiasmatic nucleus (SCN)

It is located in the hypothalamus and regulates sleep by signalling the pineal gland to release melatonin when environmental light is low (at night) and also to stop the release when environmental light is high. The optic nerves detect light and send a message to the SCN to send to the pineal gland to do this.

Melatonin

A hormone that is produced by the pineal gland. It plays a crucial role in regulating sleep.

What does daylight do to melatonin levels?

It suppresses melatonin release. This means that people do not fall asleep easily in the daytime, unless they are drowsy in the middle of the afternoon.

How does the reticular formation and cortex focus conscious attention on a particular target?

The reticular formation extends into the thalamus and cerebral cortex, sending signals that influence which sensory information reaches conscious awareness. It filters input based on saliency (importance), reducing repetitive signals and allowing novel or important stimuli to pass through. In doing so, it adjusts cortical activity to maintain arousal and direct attention. The cortex, particularly the prefrontal and parietal regions, then applies top-down control to focus on chosen targets and suppress distractions. This interaction of bottom-up input from the reticular formation and top-down control from the cortex allows us to consciously attend to a particular stimulus.

How does the thalamus focus conscious attention?

It focuses attention on important visual and auditory information, and relays this information to the cerebral cortex where it is interpreted. It also inhibits unnecessary background information. It plays a key role in regulating arousal and alertness.

What hormone is responsible for alertness?

cortisol (higher levels indicate greater alertness). It is thought to play a role in initiating wakefulness.

techniques used to measure consciousness

electroencephalography (EEG), electromyography (EMG), and electrooculography (EOG).

electroencephalography (EEG)

It detects, amplifies and records electrical activity in the brain in the form brainwaves on the outside of the skull during sleep. The patterns of the waves can help determine the stage of consciousness a person is in or when they are drowsy or alert.

electroography (EOG)

It detects, amplifies and records electrical activity in the muscles around the eyes during sleep. It can help determine whether a person is in rapid eye movement (REM) (dreaming) or non-rapid eye movement (NREM) (non-dreaming) sleep.

electromyography (EMG)

It detects, amplifies and records electrical activity in the other muscles of the body (movement and tension). It helps us determine whether a person is awake or asleep and also if they are in REM or NREM sleep.

How many stages does NREM have and how are they predominantly measured?

3 stages, lasting about 80 percent of our total sleep. There used to be a 4th stage, however it is now part of the 3rd stage. It is predominantly measured through brainwave patterns.

NREM sleep

Characterised by a progressive reduction in physiological activity. It is thought that our body repairs itself during NREM sleep.

How is Stage 1 NREM sleep entered?

We enter a relaxed state known as a hypnogogic state. We can experience hallucinations like flashing lights and vivid images. Also hypnic jerks are common.

Stage 1 NREM (N1) sleep

Sometimes called the pre-sleep stage because it is very light sleep that drifts in and out from which people are easily awakened. It can last between 30 seconds to 10 minutes. It begins to reduce body temperature, brain activity and heart rate. If we are woken, we wouldn’t believe we were asleep.

Stage 2 NREM (N2) sleep

Light sleep, but deeper than N1 sleep. It can last between 10 to 25 minutes per sleep cycle (gradually increases per cycle). Humans spend most of their sleep at this stage. If we are woken, we wouldn’t believe we were asleep.

Stage 3 NREM (N3) sleep

Referred to as the “slow-wave sleep” due to reduced brain activity. It is the deepest sleeping stage. It typically lasts between 20 to 40 minutes per sleep cycle (gradually decreases per cycle). It is extremely difficult to wake someone in this sleep stage.

REM sleep

Lighter than N3 sleep and characterised by rapid eye movements, increased brain activity and vivid dreaming. The first cycle of REM sleep lasts for about 10 to 60 minutes (starts at 10 minutes for first cycle then increases as night progresses). If we were woken in this stage, we would likely report that we were dreaming.

What physiological activity happens during REM sleep?

increases and fluctuations in heart rate, blood pressure and respiration. Body temperature tends to match the surrounding environment and there is no muscle tension.

What physiological changes determine stages of sleep?

brainwave patterns, muscle tension, eye movement, body temperature, heart rate, blood pressure, respiration and hormone release.

How does REM and NREM progress throughout the FIRST cycle?

N1 → N2 → N3 → N2 → REM. It lasts around 90 minutes.

Which type of sleep does dreaming usually occur?

REM sleep which lasts around 2 hours. For light sleepers or anxious people, dreaming can be experienced in NREM sleep.

Summary of physiological characteristics of each sleep stage

Evolutionary theories

It focuses on when and why different species sleep, with regards to increasing survival. Some propose that sleep contributes to increasing our chances of survival. This is because each species have adapted their sleep patterns to their environmental conditions over time and their chances of survival have increased.

Restoration theories

It focuses on why sleep is important for recharging, growing and recovering from physical and psychological work during the day.

How many hours of sleep do newborns have?

about 16 hours

How many hours of sleep does childhood have?

about 10 to 12 hours

How many hours of sleep do adolescents have?

about 9 to 10 hours

How many hours of sleep do early-middle adults have?

about 7 to 8 hours

How does REM and NREM progresses throughout the night?

The amount of time spent in REM sleep increases and NREM sleep decreases as the night progresses. This means that before we wake up, we are in REM sleep.

How does REM and NREM progress throughout the SECOND cycle?

N2 → N3 → N2 → REM

How does REM and NREM progress throughout the THIRD cycle?

excludes N3, includes a longer N2, and extends time spent in REM.

How does REM and NREM progress throughout the FOURTH TO SIXTH cycle?

rarely includes N3 and continues to show increased time in REM. We also tend to wake up briefly (usually without conscious awareness) and roll over before going back to sleep either before/after a period of REM sleep or directly after N2.

Typical hypnogram of one night’s sleep

Why does the adolescent sleep-wake shift occur?

The release of sleep–wake hormones like melatonin (which induces sleepiness) and cortisol (which promotes alertness) is delayed by about two hours in adolescents. As a result, they tend to fall asleep around 11 pm instead of the typical adult bedtime of 9

What are other reasons that can cause the adolescent sleep-wake shift

Busy schedules and stimulation from technology, schoolwork, part-time jobs, and social activities, leading to sleep deprivation. A sleep and wake schedule of 11 pm–7 am (typical during school days) creates a sleep debt of at least five hours per week, which can become chronic.

What is advanced sleep-wake phase disorder?

It is prevalent in older adults and it is when they feel sleepy earlier in the evening (around 6–9 pm) and wake very early in the morning (2–5 am). This also affects their ability to fall back asleep, causing interrupted or shorter sleep.

Why can delaying school times be beneficial for adolescents?

Studies have shown that it can help adolescents align better with their natural body clock, resulting in more sleep, improved focus, better grades, and fewer absences.

What factors affects how much sleep a person needs?

age, lifestyle and genetics

Partial sleep deprivation and its effect on concentration and mood

experienced when a person does not get the full amount of sleep they need (poor quantity sleep) or when a person is deprived of one particular stage of sleep (poor quality sleep). It has affective (mood), behavioural and cognitive (concentration) effects, as well as physiological effects.

Partial sleep deprivation effects

Affective include mood disturbances like amplified emotional responses, confusion and irritability, feelings of sadness. Behaviour include problems performing tasks, clumsiness, risk-taking behaviour, slowed performance. Cognitive include impaired creativity, memory problems, poor decision-making. Physical include droopy eyelids, headaches, slower physical reflexes.

Chronic sleep deprivation

occurs when partial sleep deprivation is ongoing over an extended period of time.

Total sleep deprivation and its effect on concentration and mood

when a person has no sleep in a 24-hour or longer period. Tasks requiring concentration (sustained attention) are seriously impaired. Mood can be irritable and confused.

Sleep deprivation psychosis

occurs when total sleep deprivation is ongoing over an extended period of time. It can increase difficulty in coping with others and the environment.

What stages of sleep are crucial for optimal functioning?

REM and Stage 3 NREM. REM is suggested to be more psychological well-being while Stage 3 NREM is for physiological well-being. But, some psychologists suggest otherwise.

Lack of REM sleep and the link with mood disturbances

REM sleep pauses the release of certain neurotransmitters like norepinephrine, which helps brain receptors recover and become more responsive, meaning they react better when the chemical is released again. If these chemicals don’t get their break, it can affect mood and learning like causing irritability, sadness, or grumpiness.

The effects of loss of NREM sleep

During NREM sleep, the body repairs itself and restores its tissues. One way it does this is by releasing growth hormones. If a person doesn’t get enough NREM sleep, especially stage 3, this repair process might not happen properly.

Common sleep disorders

narcolepsy, sleep-onset insomnia, sleep apnoea, and sleepwalking

Narcolepsy

a debilitating sleep disorder that causes sudden sleep attacks during the day. It does not matter how long the person has slept the night before, the sleep attacks still occur. Narcolepsy is thought to affect males and females equally.

Effects/symptoms of narcolepsy

• Sleepiness during the daytime

• Loss of muscle control

• REM hallucinations

• Can experience cataplexy

• Beginning nighttime sleep with REM

Causes of narcolepsy

• Can run in families

• Highly emotional events

• Could be triggered by medications or illnesses

Prevalence of narcolepsy

relatively rare compared to other sleep disorders, men and female is equally affected

Treatments for narcolepsy

• Maintaining a routine sleep schedule

• Regular exercise

• Healthy diet

• Scheduling naps during the day

• Avoiding alcohol and caffeine

Sleep-onset insomnia

trouble falling asleep at the beginning of the night (takes 30 minutes or more).

Effects/symptoms of sleep-onset insomnia

• Inability or excessive time to fall asleep at the start of the night

• Unsatisfactory sleep

• Excessive daytime sleepiness

• Fatigue

• Low energy

• Moodiness

Causes of sleep-onset insomnia

• Can run in families

• Stressful or highly emotional events

• Can be triggered by medications or illnesses

Prevalence of sleep-onset insomnia

10-30% in adults but more prevalent in females

Treatments for sleep-onset insomnia

• Cognitive behavioural therapy (CBT)

• Maintaining a sleep routine

• Relaxation techniques

• Learning to deal with negative thoughts and emotions

• Medical intervention

Sleep apnoea

It refers to the interruption of breathing during sleep. Breathing stops briefly, but repeatedly, for periods from 10 seconds to up to a minute or more. Typically, the person then wakes, gasping for breath, and resumes breathing.

Effects/symptoms of sleep apnoea

• Cessation of breathing for periods of the night

• Gasping for breath during the night

• Excessive daytime sleepiness

• Chronic snoring

• Can lead to hypertension, heart disease, mood and memory problems

Causes of sleep apnoea

• Obstructive sleep apnoea – caused by a physical obstruction to breathing (could be weight, or the inability of the airways to open)

• Central sleep apnoea – caused by the brain failing to adequately control breathing

Prevalence of sleep apnoea

2-3% in children and 6-17% in adults

Treatments for sleep apnoea

• CPAP device

• Diet changes

• Exercise

• Weight loss

• Avoiding alcohol

• Medication

Sleepwalking

The act of walking or completing routine activities while asleep.

Effects/symptoms of sleepwalking

• Walking during the night

• Completing routine acts during the night, e.g. brushing one’s teeth, going to the toilet

• Excessive daytime sleepiness

Causes of sleepwalking

• Triggered by a highly emotional event

• Stress

• Alcohol

• Medications

• Diet and lifestyle

Prevalence of sleepwalking

7% in children and 2% in adults

Treatments for sleepwalking

• Keeping a safe sleep environment

• Maintaining a sleep routine

• Avoiding alcohol

• Diet and lifestyle reviews

Cognitive behavioural therapy (CBT)

specific to insomnia. a form of psychotherapy that focuses on changing unhealthy thoughts (cognitions) and behaviours around sleep. It works on the idea that thoughts, feelings, and behaviours about sleep are connected. For example, poor sleep habits can lead to negative thinking about sleep, which in turn worsens sleep habits. CBT aims to break this unhealthy pattern of thinking and behaving and replacing them with positive habits and coping skills.

How does CBT work?

• Keeping a consistent sleep–wake schedule

• Avoiding long daytime naps

• Reducing caffeine and screen use before bed

• Improving sleep hygiene (e.g. a dark, quiet room, and no screens in bed)

Bright light therapy

specific for circadian phase disorders. used to advance or delay sleep and therefore treat circadian phase disorders by exposing a person to high-intensity light (2000–10,000 lux) at specific times of day. It acts as a zeitgeber, or external cue, that influences the suprachiasmatic nucleus, which controls circadian rhythms. This therapy adjusts melatonin production and helps regulate the sleep–wake cycle.

How many sleep cycles are there to complete the whole sleep-wake cycle process?

5 cycles