Lecture 10 – Chapter 14Sleep

SLEEP •Circadian•Humans spend 1/3 of life sleeping (well over 175,000 hrs)•typically 8 hours/day…so - 3/day = extra 21 hrs/week 10,952 hrs/decade!!!

SLEEP•Amount of sleep changes with age – younger ages sleep more

Polyphasic vs monophasic

Part time sleepers….• unihemispheric

Dolphins sleep with only one half of their brain

Breathing is a conscious act…

Why DO WE SLEEP?

Do we need sleep? Repair & Rest

1965 – Randy Gardner

Science fair project…break world record of No sleep (260 hrs) 264 hr 12 min = 11 days!!!

“mind over matter”

First night: 15 hrsNext night: 9 hrs

Sleep deprivation (3 to 4 hrs)Humans

1. Increase in sleepiness2. Mood test3. Perform poorly on test of vigilance (ex: tones)

2 to 3 days (continuous sleep deprivation)“Microsleeps” (2 to 3 sec long)1. Eye lids droop2. Less responsive to stimuli3. Still standing

Performance on complex cognitive tasks?????Performance in motor tests???????

Animals….different story…Death (2 TO 3 WEEKS)

• Stop grooming• Loss ability to regulate temperature• Metabolic rate increases…eat…but never enough loss weight

- Is sleep a passive? NO!Many changes in our body during sleep

Sleep is a Behavior!

How do we measure this?

1. EEG (electrical activity)2. Biochemically (NT)3. Neuroanatomically

(brain structures)

1929, a German psychiatrist: Hans Berger,

Found the it was possible to record the feeble electric currents generated on the brain, without opening the skull, and to depict them graphically onto a strip of paper.

Berger named this new form of recording as the electroencephalogram (EEG, for short)

First EEG recorded by Hans Berger, circa 1928.

EEG (electroencephalograph) records electrical activity of the brain via electrodes attached to the scalp

•Gross measurement of neuronal activity takes an average of the whole population of cells in the area under the electrode

•Output of the electrodes are amplified and recorded

EEGs tell you whether a person is asleep, awake or excited

EEG lingo: Measurement of Brain Waves

Amplitude: index of voltage = larger the voltage the higher the amplitude (Height)

Frequency: index of waves across time, cycles per second (hertz, Hz) (how often they occur)

2 Basic EEG Patterns:

1. Desynchronized: neurons in the brain firing at many different times

produces EEG patterns of low amplitude & high frequency (wakefulness)

2 Basic EEG Patterns:

2. Synchronized: neurons are firing at the same time – produces well defined waves of low frequency high amplitude (characteristic of deep sleep)

EMG: Electromyogram - Leg

EOG: Electroculogram - Eye muscle

There are two divisions of sleep

1. non-rapid eye movement (NREM) 2. rapid eye movement (REM)

Non-Rapid Eye Movement SleepAbout 80% of adult sleep is NREM sleep. NREM sleep is divided into four stages:

•Stage 1—the drowsy transition from waking to sleeping •Stage 2—intermediate sleep, when arousal is more difficult •Stage 3—the beginning of "deep," or slow-wave, sleep •Stage 4—the deepest sleep, when there is little contact with external sensations During NREM: breathing, heart rates, body temperature, blood pressure decrease.

StageEEG Rate

(Frequency)EEG Size

(Amplitude)

Awake 8-25 Hz Low

1 6-8 Hz Low

24-7 Hz

Occasional "sleep spindles"Occasional "K" complexes

Medium

3 1-3 Hz High

4 Less than 2 Hz High

REM More than 10 Hz Low

Note that as sleep progresses from awake to sleep, brain activity becomes more synchronized (low frequency hi amplitude)

Resting quietlyEyes closed Arousal & awake

Transition btw wakefulness & sleep

Short burst of waves 2 to 5 tx a min 1-4 (aging)

Only here – pre to deltaSleeping soundly – but reportNot asleep at all!

REM sleep resembles stage 1

“Saw Tooth”

90 minutes to our first bout of REM – average of 5 cycles – REM lasts 10-20 min then we fall back to stage 2 and so on…

* somnambolism

REM SLEEP

PGO spiking : Pontine-Geniculate-OccipitalTriggers the onset of REM

1. Waves of neural activity first in the pons2. Then in the lateral geniculate3. Then in the occipital cortex

- Wave is synchronized with eye movement- At this time Pons is also sending inhibitory

messages to the spinal cord motor neurons

Neurochemistry: Pons releases ACh stimulate LGN(inject carbachol=Ach agonist=REM)

Locus Coeruleus: Noradrenergic neurons: destroy this area you get NO REM but SWS (stage 3 & 4)

Raphe Nucleus: Serontonergic neurons: destroy this area you get NO SLEEP = insomnia…agonist=increase in SWS

            

                              

Narcolepsy (hypersomnia):

- sleeping disorder (1 of 2000) characterized by periods of irresistible sleepiness (REM/hypnagogic hallucinations)

- "sleep attacks" happen without warning and can occur even after a good night's rest

- normally last about 20 minutes

- after waking up, the person feels refreshed, only to feel sleepy again a few hours later

- There is no known cause of this chronic sleep disorder

TX: Stimulants & Antidepressants (tend to suppress REM sleep)

So need more 5HT

Gene found in dogs…

PLAYING DEAD? A narcolepsy symptom called cataplexy causes some dogs to collapse when they get excited, as they have here during a tussle. The dogs have a genetic defect that affects a brain hormone that's missing in people with the sleep

disorder.Mignot/Stanford University

dog chromosome 6 Yanagisawa et al., (1998) University of Texas Southwestern

Med Cen discovered orexin