7. Brain States Flashcards
Brain activity during sleep is important for _____ and _______
Brain health and solidifying memories
Sleep deprived people are at increased risk for…
Diabetes, stress, obesity, high BP, anxiety, cognitive impairment, depression
SWS
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
REM
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.
Periods of SWS and REM sleep alternate in…
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.
To study sleep, _______ are used. However…
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
Wakefulness is maintained by…
Arousal systems, which each regulate different aspects of the awake state.
Many arousal systems are in the __________, where neurons connecting with the ________ use __________, __________, __________, and _________ to stay awake
Upper brainstem, forebrain, acetylcholine, norepinephrine, serotonin, glutamate
Orexin-producing neurons
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
Balance of ________ and _________ can affect whether we’re awake (_________) or in ____ (_________)
Balance of acetylcholine and norepinephrine can affect whether we’re awake (high levels) or in SWS (low levels).
During REM, _____________ is _____ while ____________ is _____, activating _______ and ______ enough for __________
During REM, norepinephrine is low while acetylcholine is high, activating thalamus and neocortex enough for dreaming.
Dreams are produced by…
Forebrain excitation without external stimuli. Forebrain is excited by signals from REM sleep generator (special neurons in brainstem)
During SWS, arousal systems are suppressed by…
Ventrolateral preoptic nucleus, a group of cells in the hypothalamus. Releases inhibitory neurotransmitters galanin and GABA. Damage to this area causes irreversible insomnia
Two cycles that drive the need for sleep
Circadian system (time of day) and homeostatic system (how long you’ve been awake)
Circadian and homeostatic system act…
Independently
Circadian system
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.
Homeostatic system
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.
How does caffeine act as a stimulant?
By blocking adenosine receptors
Insomnia
Difficulty falling asleep or staying asleep
Sleep apnea
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.
REM sleep behaviour disorder
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)
Narcolepsy
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)
During arousal, specific neurons release multiple neurotransmitters such as…
Dopamine (movement), norepinephrine (alertness), serotonin (emotion), acetylcholine, histamine
Role of thalamus in arousal
Sorts sensory input, which can stimulate arousal. Regulates arousal
Reticular activating system
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
Sexual arousal
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.
Two types of attention
Voluntary (endogenous) and involuntary (exogenous)
Voluntary attention
Choose what to focus on. Frontal and parietal cortices active
Involuntary attention
Something in the environment grabs your attention. Ventral frontoparietal network in right hemisphere processes distractions
4 attention disorders
ADHD, schizophrenia, prosopagnosia, hemineglect syndrome
Prosopagnosia
Face blindness
Hemineglect syndrome
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
_______________ more active during rest
Default mode network
Activity of ___________ decreases when _______
Activity of default mode network decreases when doing or thinking of doing a demanding task
Default mode network
Made up of frontal brain regions (ventromedial PFC, dorsomedial PFC, anterior cingulate cortex), posterior cingulate cortex, lateral parietal cortex, and precuneus.
Ventromedial PFC
Activity related to how anxious a subject feels. Suggests that DMN may play a role in regulating emotion and mood
Dorsomedial PFC
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
Posterior brain regions (in DMN)
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
