Chapter 4 States of consciousness BY: DR. UCHE AMAEFUNA (MD)

THERE ARE MORE TO LECTURES THAN JUST SLIDES……..

This area covers topics related to states of consciousness such as waking consciousness, sleep, dreams, and sleep deprivation.

Measurement of physiological responses

Measurement of physiological responses which can indicate different states of consciousness: electrical activity of the brain and other physiological responses, including heart rate, body temperature and galvanic skin response.

A state of consciousness cannot be observed or measured directly. However, psychologists use various tools to detect changes in levels of consciousness. The electroencephalograph (EEG) is used to measure the electrical activity of the brain.

Changes in brain wave patterns provide psychologists with information about a person's level of consciousness. The EEG has proven most useful in the identification of the different stages of sleep.

Measurement of heart rate The measurement of an individual's heart rate, body temperature and breathing rate can also provide psychologists with information about the individual's state of consciousness. Generally, an altered state of consciousness would reveal a decrease in heart rate and body temperature.

Psychologists also use the galvanic skin response (GSR) to make inferences about the changes in an individual's state of consciousness. The GSR measures changes in electrical conductivity in the skin by using two electrodes placed on the skin and passing a weak current between them.

These changes indicate arousal of the autonomic nervous system, as arousal causes sweating and the consequent damp skin increases its electrical conductivity.

The ways to study sleep: The ways to study sleep; (A) Electroencephalograph (EEG) (B) Electromyograph (EMG) (C) Electro-oculargram (eye movements) and (D) Sleep laboratories.

Researchers use many different devices to study sleep and gain information about particular stages of sleep. The most important apparatus of a sleep laboratory is the polygraph. This is a machine which records on paper the output of various devices that can be attached to the person being studied.

Sleep researchers use the following devices: The electroencephalograph (EEG) is used to measure the electrical activity of the brain through small metal discs pasted to the scalp. Changes in brain wave patterns provide psychologists with information about a person's level of consciousness and which stage of sleep they are in.

When a person is awake and alert, the output of the EEG reveals brain wave patterns which are high in frequency (15-30 cycles per second) and low in amplitude. These small, irregular waves are called beta waves. (Try to remember beta = busy, as the person is active and alert.)

Beta Waves.

When a person is relaxed and somewhat drowsy, the EEG recording shows a higher amplitude and lower frequency rhythm (8-12 cycles per second). These brain waves are called alpha waves. These waves are characteristic of someone falling asleep, entering stage 1 of sleep. (Try to remember alpha = almost asleep.)

Alpha Waves.

As sleep progresses; As sleep progresses and becomes deeper and deeper, the EEG recordings reveal brain waves which are slower in frequency and higher in amplitude. Stages three and four of sleep reveal these slow waves which are called delta waves.(3-5 cycles per second). (Try to remember delta = deep sleep.)

Delta Waves

An Electromyograph (EMG) is a device that measures electrical activity in the muscles through electrodes attached to the chin. This machine helps to establish if a person is in rapid eye movement (REM) sleep, as the output would show low activity due to relaxed muscles (atonia) in REM sleep.

The electro-oculargram (EOG) is used to measure eye movements by attaching electrodes to the skin around the eyes. It also assists in the recognition of REM sleep, as the EOG shows high activity due to rapid eye movements in REM sleep.

Most sleep research takes place in a sleep laboratory. As a person's sleep is affected by their surroundings, a sleep laboratory attempts to mimic a home. It contains one or more small bedrooms and furnishings and decorations are as homelike and comfortable as possible.

A subject may spend a couple of nights in the sleep laboratory before data is recorded from them, as it is expected that they may be unsettled for the first night or two because of the new environment. However, by the third night, sleep is essentially normal and from this point on, observations can be considered useful.

Characteristics and patterns of the stages of sleep; (1)Rapid eye movement sleep (REM sleep) and (2)Non-rapid eye movement sleep (NREM sleep).

When we are awake and alert the electroencephalograph (EEG) shows wave lengths which are low in amplitude and high in frequency called beta waves. As we relax the brain waves become alpha waves, which are higher in amplitude and lower in frequency.

During sleep, periods of rapid eye movement (REM) alternate with Non-REM (NREM) sleep. The sleep cycle consists of four stages. Stage one: This stage is characterised by small, irregular waves which are a combination of alpha and theta waves.

During this stage the individual is drowsy and is drifting off into a light sleep from which they can be easily awoken. The person's heart rate slows down and their muscles relax. Apart from the very first time the person enters stage one sleep, this stage is known as REM sleep.

Stage two: In this stage sleep spindles begin to occur. These are sharply pointed waves recorded by the EEG. The EEG also shows rapid bursts of electrical activity with irregular brain waves.

Stage three: This stage is characterised by the onset of slower delta waves. These brain waves are high in amplitude and low in frequency. At this stage, the person becomes harder to awaken, their breathing and pulse rate slow down and their temperature drops.

Stage four: This stage consists of pure delta waves and it is extremely difficult to rouse the sleeper. This is the stage when sleep walking, sleep talking and night terrors occur.

Once the sleeper reaches stage four (about an hour after sleep begins) they then travel back up through stages three, two and one. When stage one is reached for the second time, REM sleep begins and the sleeper engages in about ten minutes of dreaming.

Most dreams occur during this REM stage. The EEG reveals brain wave patterns that are very similar to beta waves when a person is awake, active and alert. For this reason, REM sleep has been called 'paradoxical sleep'.

It is also characterised by jerky movements of the eyes beneath the eyelids, hence the label, rapid eye movement. The person's heart rate also increases, their blood pressure rises and their breathing becomes faster and more irregular. Luckily for others, our muscles are paralysed, preventing us from acting out our dreams.

As the night progresses, the time spent in stages three and four decreases while REM sleep increases. The last stages or REM sleep can last up to one hour or so. The entire cycle of stages one through to four occurs approximately four to six times during an average eight hour period of sleep.