the demand for sleep

• Consciousness


  The awareness of your own internal mental processes, including your thoughts, feelings, sensations, and perceptions, and your awareness of the external world around you
• Consciousness


  • It includes the ever changing mental activities and processes going on in the mind at any given moment
  • Consciousness is not an 'all or nothing' phenomenon - you can experience variations in the degree of awareness you have at different times
• States of consciousness


  The different degrees or level of awareness of our internal state and external events
• Categories of states of consciousness

  • Normal waking consciousness (NWC)
  • Altered states of consciousness (ASC)
• Normal waking consciousness (NWC)


  A state associated with being aware of our internal and external environments, where we experience a regular level of awareness, can manage our attention and behaviour, and have organised and clear thoughts and perceptions
• Altered states of consciousness (ASC)

  Any state that differs in awareness from normal waking consciousness, where our levels of awareness are lower or higher than normal, and can show changes in brainwave patterns and a lowered ability to accurately perceive time passing
• Sleep


  A naturally occurring and reversible altered state of consciousness, characterised by a reduction in awareness and responsiveness to external surroundings
• Sleep


  • It is an ASC
  • It occurs regularly
  • It involves a lack of conscious awareness
  • It involves a reduced ability to control behaviour
  • It involves a reduction in the control we have over thoughts
  • It involves a less accurate understanding of the passage of time
• Psychological construct


  A concept, description or explanatory model that is constructed to describe psychological activity or a pattern of associated activities or processes, which can be verified via scientific processes but cannot be directly measured
• Sleep is considered a psychological construct
• Types of sleep


  • Non-rapid eye movement (NREM) sleep
  • Rapid eye movement (REM) sleep
• REM (rapid eye movement) sleep


  A type of sleep characterised by rapid eye movement, high levels of brain activity and low levels of physical activity
• NREM (non-rapid eye movement) sleep

  A type of sleep characterised by a lack of rapid eye movement, and is subdivided into three different stages
• Sleep episode


  The full duration of time spent asleep, made up of multiple repeated cycles of REM and NREM sleep, called sleep cycles
• Sleep cycle


  An approximately 90 minute period that repeats during a sleep episode in which an individual progresses through stages of REM and NREM sleep
• A sleep graph tracks the proportion of time spent in each stage of sleep, including awakenings, throughout a sleep episode
• NREM Stage 1


  The gradual transition from being awake to falling asleep, characterised by a feeling of falling, hypnic jerks, minimal body movement, slow eye movement, and a loss of awareness of self and surroundings
• NREM Stage 2


  A relatively light stage of sleep where people are still rather easy to wake up, muscles are very relaxed, eyes are still, and it lasts about 10 to 25 minutes
• NREM Stage 3


  The deepest stage of sleep, called slow-wave sleep due to the low frequency high amplitude brainwaves, where muscles are completely relaxed, eyes show virtually no movement, and a person is very difficult to wake
• REM stage


  The duration of REM sleep increases with each cycle, characterised by muscle paralysis, rapid eye movements, active brain activity, and most dreaming occurs during this stage
• Techniques for investigating and measuring sleep

  • Electroencephalography (EEG)
  • Electromyography (EMG)
  • Electro-oculography (EOG)
  • Sleep diaries
  • Video monitoring
• Electroencephalography (EEG)


  A technique that detects, amplifies and records the electrical activity of the brain, which can be used to determine the state of consciousness based on different brain wave patterns
• Brainwave characteristics


  • Frequency - the number of brain waves per second, with slower frequencies when tired/asleep and faster frequencies when awake/alert
  • Amplitude - the size of the peak and trough, with higher amplitude indicating synchronised activity in deep sleep and lower amplitude indicating different neuron groups working on different tasks in wakefulness and REM sleep
• Electromyography (EMG)


  A technique that detects, amplifies and records the electrical activity of the skeletal muscles, which may be used during a sleep study to measure muscle activity
• Frequency


  The number of brain waves per second
• Slower frequency waves


  • When we are tired, relaxed or asleep (increased wavelength)
• Faster frequency waves


  • When we are awake and alert (decrease wavelength)
• Amplitude


  The size of the peak and trough
• Higher amplitude


  • Indicates synchronised activity - evident in deep sleep
• Lower amplitude


  • Indicates groups of neurons are working on different tasks - evident in wakefulness and REM sleep
• Electromyography (EMG)


  A technique that detects, amplifies and records the electrical activity of the skeletal muscles
• Electromyogram during a sleep study


  1. Electrodes are attached to the surface of the skin, typically around the jaw and sometimes the legs or other body parts

  2. Used to measure muscle tension, which can indicate the stages and type of sleep the person is experiencing
• Electro-oculography (EOG)


  A technique that detects, amplifies and records the electrical activity of the muscles controlling the eyes
• Electro-oculogram during a sleep study


  1. Electrodes are attached to the surface of the skin around the sides of each eye

  2. Used to determine the onset of sleep as well as when the stages and types of sleep occur
• Eye movement during sleep


  • Decreases and slows down as you drift into deeper sleep
  • Increases when you experience REM sleep
• Physiological measures


  Measurements of physiological responses that enable researchers to obtain quantitative data on bodily processes and changes that occur as we fall asleep/are asleep
• Physiological measures


  • Objective as they can be precisely measured and are not subject to any personal opinion or interpretation of the researcher
  • Can be used to infer the stage of sleep an individual is in, but do not provide any information about the subjective experience of sleep
• Sleep diaries


  A subjective, self-report tool used by a person to track their own sleep and wake patterns
• Sleep diaries


  Record sleep onset, awakenings, wake up time, how they felt upon waking, caffeine intake, naps, exercise, etc
• Quantitative data in sleep diaries

  Number of hours of sleep or time taken to fall asleep