3.2.4 brain waves, sleep & consciousness

What do Gamma brain waves represent?

Activated cortex, cross-modal sensory binding and active problem solving at 30-100Hz.

What do Beta brain waves represent?

Alert, attentive wakefulness at high-intensity desynchronised cortical processing 13-30Hz.

What do Alpha and Mu brain waves represent?

Relaxed wakefulness; alpha is predominant over occipital cortex and Mu over motor and somatosensory cortex at 7-13Hz.

What do Theta brain waves represent?

Drowsiness, meditation, and early Non-REM sleep stages 1 and 2 at 4-7Hz; involves hypnagogic hallucinations and hypnic jerks, hard to wake.

What do Delta brain waves represent?

High-amplitude, low-frequency synchronous waves during sleep stages 3 and 4 at < 4Hz; involve few eye and body movements, sleep slow waves, and sleep talking.

What are sleep spindles?

During sleep stage 2, a burst of rhythmic brain activity (high-frequency 8-14Hz) inhibits cognitive processes to maintain a tranquil state.

What are K-complex’s?

During sleep stage 2, sharp high-amplitude negative waves are followed by smaller, slower positive waves; memory consolidation.

What occurs during Non-REM sleep?

Parasympathetic activity, reduced metabolic rate and lowered body temperature, ~75% of total sleep.

What occurs during REM sleep?

Waking-like cortical activity, high oxygen consumption alongside skeletal muscle atonia, ~25% of total sleep.

How do the motor inhibition mechanisms work in REM sleep?

Brainstem glutamate neurons excite medullary neurons to release GABA and glycine onto spinal skeletal motor neurons.

What does an EEG measure?

Temporal summation of the synchronous activity of millions of cortical neurons that are spatially aligned.

What is the ascending reticular activating system and what does it do?

Brainstem nuclei in the midbrain and pons regulating wakefulness and sleep transitions.

What regions are involved in wakefulness?

The lateral hypothalamus releases orexin that coordinates activity in the ARAS system by exciting neurotransmitters.

What regions are involved in sleep?

The ventrolateral preoptic area and subset of neurons in the anterior hypothalamus release GABA whos binding to ARAS decreases firing.

What role does adenosine play in sleep and wakefulness?

Adenosine progressivvly increases during prolonged wakefulness inhibiting orexin from the lateral hypothalamus whilst exciting the ventrolateral preoptic area to release more GABA.

What is the main control of the circadian rhythm?

Suprachiasmatic nuclei synchronised by light and dark cycles (photic zeitgebers).

How is the suprachiasmatic nuclei modulated during wakefulness?

Light-sensitive ganglion cells that contain melanopsin send axons to the SCN, which excite orexin, inhibit VLPO, and inhibit melatonin release from the pineal body.

How is the suprachiasmatic nuclei modulated during darkness?

The suprachiasmatic nuclei inhibits lateral hypothalamus downregulating orexin, activates the VLPO increasing GABA and stimulates release of melatonin by pineal gland.

What tract does melanopsin travel to the SCN?

Retinohypothalamic.

What is melatonin synthesised from?

Tryptophan.

What occurs during narcolepsy?

Excessive daytime sleepiness, cataplexy, dream-like hallucinations, sleep paralysis. Caused by deficient orexin.

What occurs during insomnia?

Difficulty falling or staying asleep; affects 1/3 of the population; only 5% need treatment. Caused by stress, diet, and mental health conditions.

What occurs during sleep apnea?

Inability to breathe whilst sleeping (walls of throat close). Consequences include impaired concentration, daytime sleepiness, heart and cognitive impairment. Caused by obesity, genetics, old age, hormones, and deterioration of brain mechanisms that control breathing.

What occurs during sleepwalking?

During sleep stages 3 or 4, lasting a few seconds to 30 minutes as something triggers brain into arousal; 40% of children affected.

What occurs during night terrors?

Episodes of screaming, intense fear and flailing whilst asleep. Common ages 4-12, occurs during sleep stages 3 and 4, can last 30 seconds to 3 minutes.

What occurs during REM sleep behaviour disorder?

Paralysis normally seen in REM is absent, associated with dopamine deficiency and damage to pons which normally inhibit spinal neurons to reduce large muscle movement.