7. Brain States

Question 1

Brain activity during sleep is important for _____ and _______

Answer 1

Brain health and solidifying memories

Question 2

Sleep deprived people are at increased risk for…

Answer 2

Diabetes, stress, obesity, high BP, anxiety, cognitive impairment, depression

Question 3

SWS

Answer 3

Slow wave sleep. High amplitude, low frequency. High amplitude indicates that many cortical neurons are switching their activity in a synchronized way from depolarized to hyperpolarized and back. Important to sleep function, the longer a person stays awake, the more slow waves they experience. Become less frequent the longer a person is asleep. If awakened during SWS, most people only recall fragmented thoughts

Question 4

REM

Answer 4

Rapid eye movement sleep. Brain activity looks similar to that while awake. Lower amplitudes because neuron activity is less synchronized. Atonia (partial paralysis) occurs, only active muscles are those enabling breathing and eye movements.

Question 5

Periods of SWS and REM sleep alternate in…

Answer 5

90 minute cycles with 75-80 minutes of SWS followed by 10-15 minutes of REM sleep. Cycle repeats with deeper and longer REM periods towards morning.

Question 6

To study sleep, _______ are used. However…

Answer 6

Mice with sleep structures qualitatively similar to humans are used. However, rodents have shorter and more frequent sleep episodes lasting 3-30 minutes, and they sleep more during the day

Question 7

Wakefulness is maintained by…

Answer 7

Arousal systems, which each regulate different aspects of the awake state.

Question 8

Many arousal systems are in the __________, where neurons connecting with the ________ use __________, __________, __________, and _________ to stay awake

Answer 8

Upper brainstem, forebrain, acetylcholine, norepinephrine, serotonin, glutamate

Question 9

Orexin-producing neurons

Answer 9

Hypothalamus. Excitatory effects on other arousal systems. Increases metabolic rate. Production activated by low blood sugar. Loss causes narcolepsy. Also connect to hypothalamic neurons that contain histamine (neurotransmitter), which plays a role in staying awake

Question 10

Balance of ________ and _________ can affect whether we’re awake (_________) or in ____ (_________)

Answer 10

Balance of acetylcholine and norepinephrine can affect whether we’re awake (high levels) or in SWS (low levels).

Question 11

During REM, _____________ is _____ while ____________ is _____, activating _______ and ______ enough for __________

Answer 11

During REM, norepinephrine is low while acetylcholine is high, activating thalamus and neocortex enough for dreaming.

Question 12

Dreams are produced by…

Answer 12

Forebrain excitation without external stimuli. Forebrain is excited by signals from REM sleep generator (special neurons in brainstem)

Question 13

During SWS, arousal systems are suppressed by…

Answer 13

Ventrolateral preoptic nucleus, a group of cells in the hypothalamus. Releases inhibitory neurotransmitters galanin and GABA. Damage to this area causes irreversible insomnia

Question 14

Two cycles that drive the need for sleep

Answer 14

Circadian system (time of day) and homeostatic system (how long you’ve been awake)

Question 15

Circadian and homeostatic system act…

Answer 15

Independently

Question 16

Circadian system

Answer 16

Regulated by suprachiasmatic nucleus, a group of cells in the hypothalamus. Cells express clock proteins that go through a biochemical cycle of about 24 hours. Master clock neurons receive input directly from retina, so light can reset the master clock.

Question 17

Homeostatic system

Answer 17

Makes you feel sleepy. When awake for a long time, adenosine in the brain increases and binds to receptors in arousal centres to slow cellular activity and reduce arousal. Adenosine increases the number of slow waves during SWS.

Question 18

How does caffeine act as a stimulant?

Answer 18

By blocking adenosine receptors

Question 19

Insomnia

Answer 19

Difficulty falling asleep or staying asleep

Question 20

Sleep apnea

Answer 20

When the airway muscles of throat relax during sleep to the point of collapse, closing the airway. Treatments focus on reducing airway collapse through lifestyle changes (losing weight, avoiding alcohol/drugs, avoiding sleeping on back). Most people still need breathing machines like a continuous positive airway pressure (CPAP), which uses a mask that fits over the nose to provide an airstream of pressure during sleep. Sometimes surgery is needed.

Question 21

REM sleep behaviour disorder

Answer 21

When nerve pathways in brain that prevent muscle movement during REM sleep don’t work. Cause unknown, but it’s more common in people with degenerative neural diseases such as Parkinson’s, stroke, or dementia. Can be treated with drugs for Parkinson’s or with clonazepam (a benzodiazepine), which enhances effects of GABA (inhibitory)

Question 22

Narcolepsy

Answer 22

Brain lacks neurons that help control sleep transition, resulting in sleep attacks during the day. Caused by loss of orexin neurons in lateral hypothalamus. Tend to enter REM sleep very quickly and may enter a dreaming state while still partially awake (hypnagogic hallucination). Some people have attacks in which they lose muscle tone while awake (cataplexy)

Question 23

During arousal, specific neurons release multiple neurotransmitters such as…

Answer 23

Dopamine (movement), norepinephrine (alertness), serotonin (emotion), acetylcholine, histamine

Question 24

Role of thalamus in arousal

Answer 24

Sorts sensory input, which can stimulate arousal. Regulates arousal

Question 25

Reticular activating system

Answer 25

In brainstem. Once brain is aroused, it coordinates signals that make sense of events and pass that information to the body. Controls autonomic nervous system

Question 26

Sexual arousal

Answer 26

Systems involved similar to those of general arousal (thalamus, reticular activating system). Distinguishing factor is that sexual arousal involves estrogen and testosterone, which activate neurons that release neurotransmitters of general arousal. Involves interactions between sex hormones and neurotransmitters (dopamine, serotonin, GABA, glutamate). Hypothalamus, amygdala, and hippocampus contain many receptors for sex hormones. Regions that mediate feelings of rewards (nucleus accumbens) and pleasure (amygdala) motivate sexual behaviours.

Question 27

Two types of attention

Answer 27

Voluntary (endogenous) and involuntary (exogenous)

Question 28

Voluntary attention

Answer 28

Choose what to focus on. Frontal and parietal cortices active

Question 29

Involuntary attention

Answer 29

Something in the environment grabs your attention. Ventral frontoparietal network in right hemisphere processes distractions

Question 30

4 attention disorders

Answer 30

ADHD, schizophrenia, prosopagnosia, hemineglect syndrome

Question 31

Prosopagnosia

Answer 31

Face blindness

Question 32

Hemineglect syndrome

Answer 32

Spatial/unilateral neglect. Caused by damage to right parietal cortex (common in sufferers of stroke). Ignore left side of visual field. Diagnosed by asking patient to draw a picture. Hemineglects only draw one side

Question 33

_______________ more active during rest

Answer 33

Default mode network

Question 34

Activity of ___________ decreases when _______

Answer 34

Activity of default mode network decreases when doing or thinking of doing a demanding task

Question 35

Default mode network

Answer 35

Made up of frontal brain regions (ventromedial PFC, dorsomedial PFC, anterior cingulate cortex), posterior cingulate cortex, lateral parietal cortex, and precuneus.

Question 36

Ventromedial PFC

Answer 36

Activity related to how anxious a subject feels. Suggests that DMN may play a role in regulating emotion and mood

Question 37

Dorsomedial PFC

Answer 37

Activity increases when a person is at rest and daydreaming. Involved in self-referential or introspective thoughts. Suggests that DMN may function in self-reflection

Question 38

Posterior brain regions (in DMN)

Answer 38

More active when remembering past experiences. Connected to hippocampus. Both hippocampus and DMN are more active when a person is at rest in evening and less active when waking up in morning. Indicates that DMN helps process and remember events of day