Brain rhythms: EEG, sleep and diurnal rhythms Flashcards
What is EEG and what is it used for?
Electroencephalogram (EEG): A technique that allows us to measure the electrical activity in the brain using electrodes. An EEG allows us to see if there are specific patterns or rhythms of electrical activity and whether those rhythms are what we would expect in a normal functioning brain or whether they indicate signs of pathology
What does normal electrical activity in the brain vary depending on?
Normal electrical activity in the brain varies depending on region and behaviour.
Which part of the brain does an EEG record?
EEG just records cortical activity - specifically the cortical pyramidal neurones.
How does an EEG work?
An EEG uses a whole network of individual electrodes placed over the head. The wires come off to the electrodes and go to a piece of equipment which can measure changes in electrical signals picked up by electrodes.
What are the advantages of EEG?
Benefits of EEG: It does not require anything invasive (no drugs or surgery) and it provides quick and painless recording.
What is actually being recorded by EEG?
The EEG picks up collective activity of many neurones that are close to it. The greater the activity in a group of neurones that are clumped together in the cortex, the bigger the signal the EEG electrode will pick up.
When do neurones fire synchronously normally?
Synchronous firing occurs in normal cognition (very fast synchronous oscillation) and during sleep.
What is synchronous firing in normal cognition?
Cognition involves our higher process and is all about our ability to process information and attach meaning to it. Synchronous firing can be indicative of high-level brain processing and attaching meaning to information and situations.
What is synchronous firing in sleep?
In sleep, EEG recordings show varying patterns. The height of the signal represents increased synchronisation, with beta waves indicating wakefulness and alpha, theta, and delta waves representing various stages of sleep.
What is REM sleep?
REM Sleep (rapid eye movement) shows beta rhythms that look indistinguishable from those present when a person is awake. However, there is a loss of muscle tone during REM sleep.
What differentiates REM sleep from the awake state?
There is a loss of muscle tone during REM sleep, preventing signals from leaving the brain to activate muscles.
What are the consequences if sleep is disturbed?
Impairment of cognitive performance, decreased mood, and altered physical health, including changes in metabolic processes and functioning of the immune system.
What rhythms does an EEG pick up when a person is awake?
When we are awake, we record alpha and beta rhythms, which are very asynchronous.
What is the awake state known as?
The awake state is known as arousal.
Is there an anatomical ‘sleep/wake’ centre?
Arousal (wakefulness) has long been associated with a part of the brain stem called the reticular activating system.
How is neural control of the awake state different from REM sleep?
In the awake state, sensory information is detected and channelled by the thalamus to the neocortex, while in REM sleep, only ACh neurones are active.
How is neural control of REM state different from the awake state?
In REM sleep, only ACh neurons are active, leading to lower aminergic activity and paralysis. This results in EEG patterns similar to wakefulness, but aminergic pathways are turned off, causing paralysis of skeletal muscle.
What is the significance of aminergic pathways in REM sleep?
The lack of activity in aminergic pathways differentiates wakefulness from sleep, resulting in paralysis that prevents motor signals from activating skeletal muscles.
What therapeutic drugs can impact sleep and wakefulness?
Therapeutic drugs can affect N-Ad, 5-Ht, and histamine, influencing sleep and wakefulness. For example, antihistamines can cause drowsiness by affecting aminergic pathways.
Is sleep just the absence of wakefulness?
No, sleep and wakefulness are two distinct states.
What characterizes neural control of non-REM sleep?
In non-REM sleep, there is decreased activity in cholinergic and aminergic pathways, resulting in a different EEG pattern and reduced stimulation of the thalamus.
What is the VLPO?
The VLPO (Ventrolateral preoptic nucleus) is a small nucleus in the hypothalamus that becomes more active during sleep.
What are the factors that can induce sleep?
Factors include waking time, physical activity, and circadian rhythm.
What is circadian rhythm?
Circadian rhythms are physical, mental, and behavioral changes that follow a 24-hour cycle.
