Science of Sleep Final Exam

Positron emission tomography (PET)

measures brain function

PET measures brain function by looking at

Blood flow, Metabolism (rate of glucose consumption), Radiolabeled drugs

1. inject a trace (Radioactive molecule)

2. Brain "utilizes" the tracer

3. Radioactive decay

4. Positron meets electron

5. Scanner detects gamma rays

6. 3D map of tracer concentration

How PET works

- Expose the brain to multiple magnetic fields

- Hydrogen protons respond by emitting electromagnetic signal

- Scanner receives signal, uses it to create high-res image of the brain

Functional MRI

Participants are advised to:

- lay still

- let their mind wander

- do not think of anything in particular

Pro: no task needed

Con: must rely on them to follow instructions

Resting State Functional MRI

High spatial resolution, can measure not only cortical but subcortical activities (activity in the thalamus and hippocampus)

fMRI

Great temporal resolution but limited to scalp surface

EEG

advantageous for improving both temporal and spatial resolutions and could provide greater specificity of neural activities compared to a single neuroimaging method

multimodal approach (combining fMRI and EEG)

- Obtaining complementary data in response to the same changes in spontaneous or evoked brain activity

- Having the same sensory environment for all measures

- Reducing total experiment duration

Advantages of simultaneous EEG-fMRI

- MR environment present difficulties for safely recording EEG

- Magnetic fields of the MRI scanner can be disrupted by the presence of the EEG system inside the scanner

Challenges of simultaneous EEG-fMRI

cannot image individual axons but can image bundles with…

diffusion MRI

diffusion MRI useful in studying

neurodegenerative diseases, stroke, aging, development...

Gray matter

diffusion is unrestricted (isotropic)

White matter

Diffusion is restricted (anisotropic)

Magnetic Resonance Spectroscopy (MRS)

provides a non-invasive ‘window’ on biochemical processes within the body

measurement of the magnetic field generated by the electrical activity of neurons

MEG

provides very accurate resolution of the timing of neuronal activity

MEG

high spatial and temporal resolution

MEG

What determines an individuals sleep behavior?

genes, brain structures/connectivity, circadian rhythm, physical health, mental health, beliefs, attitudes, priorities

lack of nutritious dietary options found in disadvantaged neighborhoods

food desert

higher prevalence of chronic conditions such as obesity, diabetes, and cardiovascular disease

Food desert consequence

(sleep deserts) Environments not conducive to adequate and good quality sleep may increase risk for:

cardiovascular disease, obesity, mental health problems, neurodegenerative disorders

(social ecological model of sleep)

- maintain regular bedtimes and waketimes in a week

- limit caffeine, alcohol, and other substances

- create a cool, dark, and quiet bedroom

- restrict digital media in the hour before bedtime

- allow adequate opportunity for sleep

- limit exposure to melatonin suppressing light from screens

individual behavior factors

(social ecological model of sleep)

- sleep and circadian health interventions

- in-person and web-based coaching

opportunities for intervention

(social ecological model of sleep)

- not being in supportive relationships

- loneliness

- stressful or discriminatory workplace interactions

- employment characteristics (number of hours worked, workplace culture, timing of work/school)

- sociodemographic factors such as race/ethnicity, education, religion

interpersonal factors associated with poor sleep health

(social ecological model of sleep)

- physical (buildings, roads, traffic patterns, trees) and ambient environment (noise, temperature, light pollution)

- neighborhood social environment factors (social cohesion, safety, crime, socioeconomic advantage) are associated with sleep health by influencing psychological and physiological stress responses

- interactions with the health care system (access to care, costs, inpatient sleep environment)

societal factors associated with poor sleep health

(social ecological model of sleep)

- cultural leadership (public health priorities and sleep health awareness campaigns) and public policy, regulations and incentives

opportunities for intervention

Patients with schizophrenia have specific reduction in…

sleep spindles

reduction in sleep spindles in schizophrenia patients correlates with…?

deficits sleep-dependent memory consolidation

sleep spindle deficit is a putative endophenotype of schizophrenia:

predates its onset, persists throughout course, not related to illness chronicity or antipsychotic medication, present in first-degree relatives, linked to cognitive function

medication to increase spindles

5 mg eszopiclone before bedtime (fails to improve memory)

spindles initiated by the

thalamic reticular nucleus (TRN)

spindles propagated to the

cortex

spindles synchronized via

thalamocortical feedback loops

Thalamus <--> Sensory-Motor cortex

hyperconnectivity

Thalamus <--> Prefrontal Cortex

hypoconnectivity

Link between two endophenotypes of schizophrenia suggests

a shared underlying pathophysiology, TRN dysfunction

- Initiate and propagate sleep spindles

- mediate sleep-dependent memory consolidation

TRN circuitry

- Act as gatekeeper of flow of sensory info from thalamus to cortex

- attenuates transmission of redundant sensory info to protect higher-order cognitive function from interference

- Sensory processing deficits seen in antipsychotic-naive early course patients and first degree relatives

Schizophrenia biomarkers

Schizophrenia is a neurodevelopmental disorder that unfolds over an extended timeframe

subtle signs in childhood, negative symptoms and positive symptoms may precede frank psychosis by months or years (prodromal phase), onset of psychosis typically in late adolescence/early adulthood

How we assess CHR symptoms

semi-structured clinical interview, Self-report screening questionnaires

- intricate plot

- fleeting thought or sensation

- could be based entirely on real memories

- very disconnected/fragmented/absurd

- aware of it

- remember it all

- can occur during REM and NREM

define a dream

Hypnagogic hallucinations

fleeting perceptual experiences occur during transitions from wakefulness to sleep

hypnopompic hallucinations

Fleeting perceptual experiences occur during transitions from sleep to wakefulness

multisensory experiences (simultaneous visual and somatic perceptions) are common in ______, but are rare in ______, which commonly occur in a single modality or different modalities in a sequence

sleep-related perceptions, hallucinations

when people have _____ they generally recognize them as hallucinations instead of real

hypnagogic hallucinations

sleep-related perceptions rarely affect or change the persons sense of self, personal narrative or beliefs. People living with _____ typically have paranoid or delusional beliefs and disordered thoughts associated with the hallucinations

schizophrenia

people are more likely to forget about their _____ while people with ____ may maintain memories of hallucinations for extended periods of time

hypnagogic hallucinations, schizophrenia

Rapid firing of brainstem neurons during REM sleep can activate primary sensory and motor cortex, dreams are a synthesis of these random activations

Activation-Synthesis Model

Sleep mentation

remembering any mental activity that occurred prior to waking up

Lesion-to-function mapping

one of the oldest and most robust methods of understanding brain function

havent been able to consistently link damage to a brain region with loss of …

dream mentation

Lesions of the brainstem regions responsible for REM-related activation do not lead to

loss of dreaming

lesions in the frontal or parietal cortices lead to

loss of dreaming

sleep mentation is generated by a single set of processes regardless of physiological differences between REM and NREM sleep

One-Generator model

qualitatively different generators produce cognitive activity in REM and NREM

Two-generator model

participants awakened throughout the night and asked to report if they were experiencing anything prior to awakenings

responses categorized as:

- no experience (NE)

- dreaming experience without recall of content (DEWR)

- dreaming experience (DE)

(describe content, rate on scale of thought like to exclusively perceptual, duration)

serial awakening model

lucid dreaming

becoming aware that ones dreaming while dreaming

vivid dreams definition

dreams that the individual can recall clearly upon awakening ; detailed descriptions of sensory experiences and emotions

what is sleep paralysis?

temporary inability to move or speak when the person is awake but is still experiencing REM atonia

reality testing

checking environment several times a day to see whether or not youre dreaming

waking up after five hours, staying awake for short period, going back to sleep in order to enter REM sleep period

Wake Back to Bed (WBTB)

waking after five hours of sleep and then repeatedly focusing your attention on visual, auditory, and physical sensations for 20 seconds each before going back to sleep

Senses Initiated Lucid Dream (SSILD)

increase in central alpha, increase in posterior alpha, increase in parietal beta, increase in frontolateral gamma, reduction in frotocentral delta

comparing lucid REM sleep to non-lucid REM sleep

Lucid dreamers structural brain differences

increased gray matter volume in frontal pole, right anterior cingulate cortex, left supplementary motor area, and bilateral hippocampus

Lucid dreamers functional brain differences

high freq LDers (>3 times a week) vs low freq LDers (once a year or less)

transcranial direct current stimulation (tDCS) and transcranial alternating current stimulation (tACS) resulted in

increases in some measure of dream content but dont appear to have increases in number of LDs in the traditional sense

narcolepsy patients expererience

longer more complex and vivid dreams and more freq nightmares and LDs

physiological studies conducted 50 to 100 years ago in dogs, rabbit, and rats indicated that prolonged sleep deprivation (SD) eventually results in death

puppies: 4-6 days, adult dogs: 9-17 days, adult rabbits: 7-31 days

Randy Gardner Sleep Deprivation Experiment (December 1963)

awake 11 days, describes experience like late stage alzheimers, physically fine but cognitive decline and emotionally irritable, slept over 14 hours at end, developed severe insomnia in late 50s, everything upset him (moody)

consequences of SD using the Bergmann-Rechtschaffen method

Weight loss, reduced resistance to infectious disease, endocrine abnormalities

habitual short sleep duration is associated with

excessive sleepiness, accidents, cognitive deficits, increased obesity risk, diabetes, hypertension, and all-cause mortality

_____ % of US population chronically restrict their sleep to less than 7 hours on weekday night primarily for lifestyle reasons

35-40

Multiple Sleep Latency Test (MSLT)

full-day test that consists of five scheduled naps, after the first nap trial, each nap should begin 2 hours after start of prior nap, during each nap lie quietly in bed and try to sleep, test will measure how long it takes for you to fall asleep, awakened 15 mins after you fall asleep, nap trial ends if you dont fall asleep in 20 mins

experimental SD in humans falls into one of three categories

total sleep deprivation, sleep restriction, sleep fragmentation

SD produces psychomotor impairments equivalent to those

due to alcohol consumption above the legal limit

SD cognitive reliable changes include

lapses of sustained attention, response disinhibition, prevention of sleep-dependent memory consolidation

Cognitive performance and SD most sensitive measures are

EEG, fMRI, behavioral measures of sustained attention

experimental quantification of cognitive effects of sleep loss is very challenging

SD increases variability within subjects (state instability) and between subjects (differential vulnerability)

Psychomotor Vigilance Test (PVT)

test of behavioral alertness, not confounded by aptitude or learning effect and sensitive to sleep loss

reliable, valid and sensitive measure of SD regardless of the reason for deprivation

PVT

has ecological validity

PVT