PSY290 - Biorhythms, Sleep and Dreaming

rhythm

cyclic variation in a process over time

circadian

24 hours

infradian

24h to a year, r reproductive cycle

ultradian

less than 24h rs

free running rhythms

endogenous rhythms that don’t involve time cues

• sleep-wake cycle 25 hours w/o clues

• persistent even in the absence of cues like in plants

endogenous rhythms in animals

observation of hamster and house sparrow in constant light and darkness showed that even in the darkness there is still some rhythm

what gene controls the circadian clock?

PER and CRY

what happens when PER is modified to PER2?

familial advanced sleep phase disorder

what happens when CRY is modified to CRY1

delayed sleep phase disorder

where are the rhythmic cells located?

in the suprachiasmatic nucleus

what is the importance of the SCN in rhythms>

activity associated with circadian rhythms

how are rhythms created?

the retinal ganglion cells in the eye express melanopsin

melanopsin

light sensitive pigment

what are the modulatory signals?

SCN and melatonin

melatonin

created physiological pressure for sleep by targeting SCN and M1 + M2 receptors

electronic devices

emit light which suppresses melatonin release so when used at night its associated with poor sleep quality and mental health

what compounds affect arousal?

melatonin and adenosine

adenosine

levels increase throughout the day but decrease while sleeping by acting on neural targets to increase sleep pleasure

what weakness adenosine and melatonin signaling?

caffeine

when do cortisol levels rise?

before waking up

how does exercise modulate sleep phases?

doing it later in the day gives you more energy later at night delaying your regular sleep cycle

morningness

associated with better academic performance, agreeableness and conscientiousness

eveningness

associated with greater cognitive ability, neuroticism and sensation-seeking

chronotype

natural predisposition for wakefulness at certain times

sleep tendencies in adolescence

later sleep times

zeitgebers

time givers/cues that modify rhythms

entrainment

setting a rhythm

shat would our sleep cycle be entrained to?

light cues

what causes disruption in sleep rhythms?

jet lag, light population, device use and night shift

what causes people to sleep later?

exercising and waking up later (opposite for sleeping earlier)

what are the implications of rhythm disruptions?

• altered drug responses

• risk for metabolic disorders

• risk for cancer

• risk for mental health events

short term lack of sleep consequences

• stress

• somatic problems

• psychosocial issues

long term consequences

• cardiovascular disease

• obesity

• T2Dm

• Cancer

• Death

reticular activating system

• sensitive to sensory input

• connected to the basal forebrain

• stimulates reticular formation

why is connection of RAS to the basal forebrain important?

provides cholinergic stimulation to the rest of the brain

what occurs when the reticular formation is stimulated?

arousal

what could happen is RAS is damaged?

comatose

why is sleep important?

• maintains brain by clearing waste and restoration of injured/damaged tissue

• ontogenetic development of the brain

• maintenance of learning and memory processes

• energy

• dreams

what genes are associated with less sleep?

DEC2 and ADRB1 mutations

what exemplifies brain activity in sleep>

EEG

electroencephalograph

measures electrical activity in specific brain regions

what frequency is associated NREM1?

alpha and theta waves

NREM1

light sleep and lower frequency activity

what frequency is associated with NREM2?

theta waves

NREM2

lower frequency activity with sleep spindles and k complexes

what frequency is associated with NREM3/4?

delta waves

NREM3/4

deep sleep that is very low frequency and some spindles

• where we spend most of our time during sleep

REM

dream stage, high frequency activity that is similar to eyes open wakefulness

what sleep trends do we see in the elderly?

greater sleep latency and more arousal periods

• less REM and NREM3 and overall less sleep

atonia

lack of muscle tone during REM

REM rebound

when deprived of REM you enter REM stage sooner and spend more time in that state

what is lack of REM associated with?

reduced hippocampal neurogenesis, immune dysfunction, and mood disruption

• might be considered a preparatory stage for wakefulness

memory consolidation

process where memory is converted into long term form

replay

reactivation of the memory trace

• might occur in waking states as well as sleep states

• also hippocampus changes migh be key

what happens after spatial learning?

cells involved in the task will be linked during NREM sleep

• neurons involved in executing an implicit motor tasks might be active again during sleep

what is the correlation between GPA and dim-light melatonin onset?

negative

REM dreams

emotional, illogical and have sudden plot shifts

• makes up 80% of dreams

NREM dreams

thought-like, repetitive and centered around daily tasks

• makes up 20% of dreams

dream protection theory

sexual and aggressive instincts are transformed into symbols that represent wish fulfillment, interpretation required

evolutionary theory

dreams about threats to reproductive success, plan solutions

activation synthesis theory

dreams are an attempt by the brain to interpret random activity

sleep deprivation

effects on cognitive function brain (prefrontal cortex structure and function) and health

when does sleep deprivation tend to last longer?

during adolescence

insomnia

difficulty falling asleep or staying asleep

• acute or chronic

• primary (10%), secondary (90%)

what is comorbid with insomnia?

neuropsychiatric disorders like depression and anxiety

cataplexy

atonia without loss of consciousness triggered by arousing stimuli

narcolepsy

extreme daytime sleepiness with frequent episodes of dozing where rapid descent into REM is common

orexin expressing neurons

involved in the atonia circuit in the lateral hypothalamus by inhibiting neuros to limit atonia in the right situations

what happens when we loss orexin neurons?

dishibits special neurons which causes stronger inhibition of motor neurons

REM behavioral disorder

tendency to act out dreams due to loss of atonia during REM

• loss of inhibition to spinal motor neurons

Somnambulism

sleepwalking, person leaves the bed and moves around while still asleep

• more common in children