Lecture 13- Sleep

Question 1

Beta 12-30:
Alpha 8-12:
Theta 4-8:
Delta <4:

Answer 1

Beta activity: 12-30 Hz, arousal state and reflects desynchronous neural activity.
Alpha activity: 8-12 Hz , awake person in a state of relaxation
Theta activity: 4-8 Hz, intermittent in drowsy people, early sleep stages
Delta activity: <4 Hz, during deepest stages of slow wave sleep. Reflects synchronized low frequency, large amplitude brain activity

Question 2

Rapid eye movement (REM),
Rem deprivation:

Answer 2

desynchronized eeg activity, dreaming, muscle paralysis/inactive, cerebral blood flow and oxygen consumption increases.

when deprived, animals can stand or sit while asleep, but muscles will go limp during rem

Question 3

why is sleep is critical for survival?

Answer 3

-you will feel tired, and your mind will deteriorate, exhibit delayed reaction times and poor judgment.
-increased stress hormones, mood swings, impulsive behavior
-exhibit worse learning and memory
-increased propensity for weight gain, migraines, hallucinations, dementia…
-sleep disruptions preceded mental illness

Question 4

Predatory animals vs prey:

Answer 4

Predatory animals indulge in long, uninterrupted sleep

Preyed on will sleep in short intervals, maybe less than a couple minutes

Question 5

Metabolic rate and sleep connectedness:

Answer 5

Large animals have low metabolic rate per cell and long life span, they’re sleep is not frequent but is long.
Means sleep is critical for restorative process, and depends on the animals distribution of networks

Question 6

3 theories to sleep

Answer 6

1.To recover from physical or mental exertion: amount of time exercising and thinking should correlate with total sleep time.

2. Brain processing: (learning and memory) sleep gives the brain an opportunity to reorganize data and archive memories, not done efficiently when awake. Synaptic modifications occur during sleep
   Learning and memory are impacted, slow wave and rem sleep correlates with improvement in procedural memory.
   The brain actively processes information and transfers it between different areas.
3. Waste removal: as sleep time correlates with body size, it is critical for a process that benefits from economies of scale
   The concentration of many proteins in the brain increases across periods of wakefulness and decreases across periods of sleep.
   Clearance of waste products does not happen when awake.

Question 7

When animals sleep, what happens to glial cells?
What is the usage of the glymphatic system?

Answer 7

glial cells in the brain lose water and shrink in size. This promotes diffusion of cerebrospinal fluid through the brain, clearing waste.

clears away cellular waste, removes excess proteins and waste from interstitial space of the brain (at night).

Question 8

Circadian rhythms are the daily change in behavior and physiological processes follow a cycle 24hrs,
provide examples of how it does so

Answer 8

-controlled by internal biological ticks, daily variation in light keeps us adjusted.
-if rats shift their cycle by a couple of hours, the body will adapt.
-if light is constantly dim, rat finds its own source of rhythm

Question 9

Suprachiasmatic nucleus (SCN):
What do lesions do to it?

Answer 9

of the hypothalamus regulates sleep- cycles, receiving input from the retina.

lesions of scn alter circadian rhythm, and alter length and timing of sleep wake cycle

Question 10

Biological clocks:

Answer 10

Circadian rhythm is maintained by production of several genes and interlocking feedback loops. When the expression of one protein gets high enough, it inhibits production and expression of different proteins.

Question 11

Advanced sleep phase syndrome:
Delayed sleep phase syndrome:

Answer 11

Advanced sleep phase syndrome: mutation of gene called per2, causes 4 hr advance in the biological clock, strong desire to sleep at 7 am and wake at 4 am. (early-early)
Delayed sleep phase syndrome: mutation of gene per3, causes 4 hour delay in rhythm of sleep and temperature cycles. Sleep at 2 am, wake at 11 am. (late-late)

Question 12

Sleep molecule hypothesis:

Answer 12

-build up of molecules in interstitial fluid of the brain during wake hours, these molecules promote drowsiness and sleep at high concentrations.
-adenosine levels rise during wake and accumulate with sleep deprivation and fall during sleep.
-Drowsiness and duration of sleep are modulated by adenosine receptors, caffeine is an adenosine receptor antagonist.
-Adenosine is one of the many sleep inducing molecules in the brain, underlies animals’ need for sleep.

Question 13

Neural circuits regulate arousal; influenced by scn neurons and sleep promoting molecules.

Answer 13

-Serotonin (hindbrain)
-Norepinephrine (hindbrain)
-Acetylcholine (throughout the brain)
-Orexin (hypothalamus)
-Histamine (hypothalamus)

Question 14

norepinephrine neuron activity:
Serotonin neuron activity:

Answer 14

Norepinephrine neuron activity: correlates with focus and attention

Serotonin neuron activity: correlates with cortical arousal

Question 15

“flip flop circuit”, both regions can be active at the same time and the switch is fast:

Answer 15

Neurons in the Ventral lateral preoptic area of the hypothalamus promote sleep.
-Electrical stimulation causes drowsiness and immediate sleep, lesions cause insomnia
-vlPOA neurons inhibit wake promoting neurons.