1. Chapter 34 Electroencephalogram (EEG), Wakefulness and Sleep

2. I.Electroencephalogram (EEG)

3. I. Brain Waves and EEG Normal brain function involves continuous electrical activity Brain Wave – The undulations in the recorded electrical potentials – Change with age, sensory stimuli, brain disease, and the psychoses An electroencephalogram (EEG) – The entire record of the brain wave – be used to diagnose and localize brain lesions, tumors, infarcts, infections, abscesses, and epileptic lesions – A flat EEG (no electrical activity) is clinical evidence of death

4. The EEG be recorded with Scalp electrodes through the unopened skull or with electrodes on or in the brain. A normal EEG

5. EEG Patterns Alpha: low-amplitude, slow, synchronous waves indicating an “idling” brain – Recorded from occipital, parietal and frontal regions. Person is awake, relaxed, with eyes closed. –8-13 Hz –20 ~100  V.

6. Beta: high-frequency but low amplitude waves seen in deep sleep or person’s attention is directed to some specific type of mental activity –Strongest from parietal and frontal lobes Produced by visual stimuli and mental activity. –14-30 Hz –5-20  V

7. Alpha Block: Replacement of the alpha rhythm by an asynchronous, low-voltage beta rhythm when opening the eyes.

8. Theta : more irregular than alpha waves –Emitted from temporal and parietal lobes. Common in newborn and sleep in adult. Adult indicates severe emotional stress. –4-7 Hz –100-150  V.

9. Delta: high- amplitude waves; Emitted from temporal and occipital lobes. Common during sleep and awake infant. In awake adult indicate brain damage. –0.5-3 Hz –20 – 200  V

10. SPONTANEOUS CORTICAL ELECTRICAL POTENTIALS: THE EEG

11. the electrical responses of the axon and the dendrites of a large cortical neuron. 2. Mechanism of EEG Current flow to and from active synaptic knobs on the dendrites produces wave activity, while AP are transmitted along the axon.

12. Mechanism of EEG Continuous graph of changing voltage fields at scalp surface resulting from ongoing synaptic activity in underlying cortex Inputs from subcortical structures – Thalamus – Brainstem reticular formation EEG signals generated by cortex Currents in extracellular space generated by summation of EPSPs and IPSPs

13. 3. EEG Records During Epileptic Seizure Epilepsy is characterized by uncontrolled excessive activity of either a part or all of the central nervous system. Grand mal epilepsy: characterized by extreme neuronal discharges in all areas of the brain, last from a few seconds to 3 to 4 minutes. Petit mal epilepsy: Characterized by 3 to 30 seconds of unconsciousness or diminished consciousness during which the person has several twitch-like contractions of the muscle. Psychomotor seizure often associated with temporal lobe disease and characterized by complex sensory, motor, and psychic symptoms such as impaired consciousness with amnesia, emotional outbursts, automatic behavior, and abnormal acts.

14. II Wakefulness and Sleep

15. Sleep Sleep is a behavior and an altered state of consciousness – Sleep is associated with an urge to lie down for several hours in a quiet environment Few movement occur during sleep (eye movements) – The nature of consciousness is changed during sleep We experience some dreaming during sleep We may recall very little of the mental activity that occurred during sleep We spend about a third of our lives in sleep

16. Two Types of Sleep Non-rapid eye movement (NREM) Rapid eye movement (REM)

17. Non-REM Sleep Alpha, delta, theta activity are present in the EEG record – Stages 1 and 2: Alpha waves – Stages 3 and 4: delta activity (synchronized) Termed slow-wave sleep (SWS) Light, even respiration Muscle control is present (toss and turn) Dreaming (not vivid, rational) – Difficult to rouse from stage 4 SWS (resting brain?)

18. Types and Stages of Sleep: NREM Stage 1 – – eyes are closed and relaxation begins – the EEG shows alpha waves – one can be easily aroused Stage 2 – – EEG pattern is irregular with sleep spindles and K complex (combination of delta and theta) – arousal is more difficult

19. Stage 3 – sleep deepens theta and delta waves appear vital signs decline dreaming is common Stage 4 – EEG pattern is dominated by delta waves skeletal muscles are relaxed arousal is difficult

20. REM Sleep Presence of beta activity (desynchronized EEG pattern) Physiological arousal threshold increases Heart-rate quickens Breathing more irregular and rapid Brainwave activity resembles wakefulness Genital arousal Loss of muscle tone (paralysis) Vivid, emotional dreams May be involved in memory consolidation

21. Sleep Stage Cycles  A typical sleep pattern alternates between REM and NREM sleep  SWS precedes REM sleep  REM sleep lengthens over the night  Basic sleep cycle = 90 minutes  The suprachiasmatic and preoptic nuclei of the hypothalamus regulate the sleep cycle

22. Importance of Sleep Sleep is necessary – for survival – for our nervous systems to work properly During the SWS – growth hormone secretion increase – important for infants growth physical restorative process of adult During REM – brain blood flow and protein synthesis increase – important for mental development of infants long-term memory and mental restoration in adults Daily sleep requirements decline with age

23. What Happens if We are Deprived of Sleep? Lack of alertness Fatigue Memory problems Irritability Depression Lack of motivation Accidents Fibro Myalgia

24. Tips for Getting a Good Night ’ s Sleep Avoid caffeine and alcohol after dinner Keep a routine Don’t go to bed hungry or right after eating Exercise Stop smoking

25. Rules for Optimal Sleep Get an adequate amount of sleep every night Establish a regular sleep schedule Get continuous sleep Make up for lost sleep

26. REM Dreaming NREM Dreaming “ vivid and exciting ” ~3 per night Longer, more detailed Fantasy world “ just thinking ” Shorter, less active Midst of nowhere Logical, realistic

27. Frightening dream episodes Occur in the REM stages Last about 20 minutes Can be result of taking drugs that affect neurotransmitter action or from drug withdrawal Severe cases can be treated with medication – Diazepam ( 安定） (tranquilizer) Nightmares

28. Brain Mechanisms of Wakefulness and Sleep The Control of Wakefulness – Two cholinergic pathways originate in the medulla Dorsal path: RF--> to medial thalamus --> cortex Ventral path: RF --> to lateral hypothalamus, basal ganglia, and the forebrain – Activity in locus coeruleus ( 蓝斑核） and raphe nuclei （中缝核团） The Initiation and Control of NREM Sleep – First segment of sleep is NREM – Locus coeruleus and raphe nuclei reduce activity – Thalamus synchronizes cortical activity

29. Brain Mechanisms of Wakefulness and Sleep （ cont. ） The Initiation and Control of REM Sleep – REM-on areas in pons – Locus coeruleus and raphe nuclei become silent Reactivation of locus coeruleus and raphe nuclei leads to either wakefulness or another segment of NREM sleep

30. Key Structures Involved With Wakefulness, NREM, and REM

31. PGO Waves Accompany REM Sleep

32. Pontine-geniculate-occipital (PGO) wave A synchronized burst of electrical activity that originates in the pons and like a wave it activates the lateral geniculate nucleus and then the occipital lobe, specifically in the visual cortex PGO waves appear seconds before and during REM sleep.

33. The Biochemistry of Wakefulness and Sleep Acetylcholine: High during wakefulness and REM Histamine – High during wakefulness – Lower during REM and NREM Norepinephrine and Serotonin （ 5-HT ） – High during wakefulness – Lower during NREM – No activity during REM Adenosine （腺苷） – Builds up during wakefulness – Gradually drops during sleep