PL10 Physiology of Sleep & EEG

State the EEG characteristic in wakefulness state.

Wakefulness is characterized by fast, low voltage EEG activity with both alpha and beta waves present. (desynchronized EEG).

Sleep-waking cycle involves two systems. Describe briefly the systems.

1. Activation of arousal system by stimulation of RAS: a. sensory receptors. b. midline reticular formation of brain stem. c. hypothalamus, locus ceruleus. d. raphe nuclei. 2. Activation of sleep system: a. removal of afferent stimuli. b. decrease activity of reticular activating system. c. stimulation of sleep zones

State the feature of each type of EEG waves.

1. Alpha rhythm: physical & mental rest, with eyes closed (in awake). 2. Beta rhythm: with the eyes open (awake) or with mental activity. 3. Theta rhythm : in a subject entering into light sleep. 4. Delta rhythm : during deep sleep.

State 4 physiological changes associated with slow wave sleep (SWS).

1. Decreased vascular tone - Heart rate, BP & Respiratory rate are reduced. 2. BMR is reduced. 3. Increased threshold of many reflexes, Muscle tone is reduced. 4. Increased secretion of growth hormone. 5. Decreased secretion of adrenal medullary catecholamines. 6. Pupillary constriction, eyeballs rolled up but stationary. 7. Dreams occur but on awakening the individual cannot recall them - no consolidation of dreams in memory, "dreamless sleep", dreams and sometimes even nightmares do occur.

Explain briefly the physiological basis of EEG.

1. EEG record of activity of rhythmically discharging cells in the superficial layers of cortical grey matter. 2. It is graded potential which are summated as postsynaptic potentials in brain neurons. 3. Electrical responses of the axon and the dendrites of a large cortical neuron. 4. Current flow to and from active synaptic knobs on the dendrites produces wave activity. 5. All-or-none action potentials are transmitted along the axon.

State 3 concomitants (associations) of REM sleep.

1. Generally report that they were dreaming. 2. Tooth-grinding (bruxism) associated with dreaming occurs in some individuals. 3. Snoring occurs in all stages of SWS and in REM sleep, Obstructive sleep apnea occurs in REM.

State the EEG feature in different types of epilepsy: 1. Grand mal epilepsy (generalized tonic-clonic seizure). 2. Petit mal epilepsy (absence seizure).

1. Grand mal epilepsy (generalized tonic-clonic seizure) - high voltage, slow waves preceded by spike. 2. Petit mal epilepsy (absence seizure) - spike & dome pattern.

State two clinical importance of recording EEG.

1. Localizing pathologic processes - collection of fluid/subdural hematomas, lesions in cerebral cortex. 2. Localizing epileptogenic foci & types of epilepsy.

State 3 basic theories of sleep.

1. Passive theory: due to fatigue of Reticular activating system (RAS). 2. Active inhibitory process: RAS inhibition. 3. Hormonal or chemical mechanism. + Increased other transmitters related to sleep - muramyl peptide & nonapeptide i.e., Hypotoxin, DSIP (delta-sleep inducing peptide), factor S (sleep promoting factor).

State the neural control of sleep-waking cycle.

1. Periods of sleep and being awake, alternates once a day. 2. Circadian rhythm (Biological clock) by Hypothalamic Suprachiasmatic nucleus (SCN).

State the characteristic features of Rapid Eye movement [REM] sleep / Paradoxical Sleep / Desynchronized sleep.

1. REM is characterized by bursts of rapid side to side movement of the eyeballs. 2. EEG: high frequency, low voltage rhythm (β-rhythm or desynchronized rhythm). + Adults spend about 20 - 25% of their sleep cycle in REM.

State the distribution of sleep stages in: 1. Slow wave sleep. 2. Rapid eye movement sleep.

1. Slow wave sleep - Stage I, II, III and IV (70-100 min). 2. Rapid eye movement sleep - REM sleep lasts for 5-30 min, this cycle is repeated at intervals of 90 min through out the night. 4-6 REM periods occur per night.

State two types of sleep.

1. Slow wave sleep or non-REM sleep (SWS/NREM) - restful sleep, brain waves are strong & low frequency. 75%. 2. Rapid eye movement sleep (REM) - non restful sleep associated with vivid dreaming, recurs about every 90 minutes. 25%. + Throughout an eight-hours sleep cycle, a normal adult alternates two different sleep states

Define these sleep disorders: 1. Somnambulism. 2. Insomnia. 3. Narcolepsy.

1. Somnambulism - sleep walking. 2. Insomnia - unable to sleep; occurs in anxiety, psychosomatic & psychiatric disorders, systemic disorders. 3. Narcolepsy - uncontrolled urge to sleep during day time activities.

State 4 physiological changes associated with REM sleep.

1. Threshold for arousal is markedly elevated - difficult to arouse by sensory stimuli than SWS but persons wake up in the morning during REM sleep. 2. Extreme reduction in muscle tone throughout the body, but irregular muscle movements do occur including periodic eyelid fluttering. 3. Threshold of many reflexes elevated. 4. Irregular breathing, heart rate and BP. 5. Most dreams occur during REM sleep. 6. During REM sleep, brain blocks signals to the muscles to remain immobile so dreams will not be acted out. 6. REM sleep is called "paradoxical" sleep because brain wave activity is similar to an awakened state.

State the hormonal or chemical mechanism of sleep and waking cycle in: 1. Waking state. 2. NREM sleep. 3. REM sleep.

1. Waking state: a. Increased NE, Serotonin & Decreased ACh from RAS. b. Decreased GABA & Increased Histamine from hypothalamus. 2. NREM sleep: a. Increased GABA & Decreased Histamine from hypothalamus. 3. REM sleep: a. Decreased NE, Serotonin & Increased ACh from RAS.

Name 4 types of EEG waves. State the wave with: 1. Highest amplitude. 2. Highest frequency.

4 types of EEG waves: Alpha, Beta, Delta, Theta. 1. Highest amplitude: Delta wave (δ). 2. Highest frequency: Beta wave (β).

This EEG wave result from spontaneous feedback oscillation between diffuse thalamocortical system & reticular activating system in the brain stem.

Alpha waves - physical & mental rest, with eyes closed (in awake).

Describe briefly the behavioral observation & EEG changes in REM sleep.

Deepest sleep - rapid eye movement, ponto-geniculo-occipital (PGO) spikes, dreaming. EEG change - resemble awake state (rapid, low voltage, irregular desynchronized (β) waves.

Slow wave sleep is also known as "dreamless sleep". Why?

Dreams occur but on awakening the individual cannot recall them (no consolidation of dreams in memory).

Rapid eye movement (REM) sleep is called "paradoxical sleep". Why?

REM sleep is called "paradoxical" sleep because brain wave activity is similar to an awakened state (beta rhythm).

What is electroencephalogram (EEG)?

Record of electrical activity of brain (cortical neural units in a volume conductor). 1. Recorded by placing 2 electrodes on scalp - Amplifier - CRO. 2. Also recorded directly on the surface of cerebral cortex. + EEG was first introduced by German psychiatrist - Hans Berger.

State the factors influencing sleep.

Reduction in sensory input. 1. Darkened room. 2. Relaxed musculature. 3. Comfortable warm surroundings. 4. Silence.

State the cause of Schizophrenia.

Schizophrenia occurs due to lose of responsiveness to glutamate or excessive secretion of dopamine. + Rx: chlorpromazine, haloperidol, and thiothixene decrease secretion of dopamine. + Parkinson patients develop schizophrenic-like symptoms when treated with L-dopa.

Define sleep.

Sleep is a periodic reversible physiological state of loss of consciousness from which the person can be aroused by sensory or other stimuli. + Physical and mental resting state, relatively inactive and unaware of the environment.

Describe briefly the behavioral observation & EEG changes in 4 stages of slow wave sleep.

Stage I - Light sleep, Alpha waves. Stage II - True sleep, Sleep spindles. Stage III - Sleep deepens, Theta waves. Stage IV - Deep sleep, Delta waves.