Cortical States - Chapter 28 Flashcards
Cortical States
Sleep/Wakefulness
What is a circadian rhytm?
How is it programmed biologically?
Need external cues to distinguish day and night but they are regulated internally
Where is the central/master clock
Hypothalamus(Superchiasmatic nucleus)
Peripheral clock
Sensors in retina signals hypothalamus - SCN - Master clock
Physical activity
Signaled by increased temperature and metabolism (muscle tissue and other organs) - Peripheral Clock
How are hormones secreted
Hypothalamus connects to pituitary which sends signal to secrete a hormone, not associated to cognition, associated to autonomic function
Andrew Huberman
Focuses on achieving maximal cognitive performance, seeing low angles of light and working out. Seeing light in day is awesome. Using 2 best signals to regulate inner clock
When does core body temp reach it’s peak?
At night
Melatonin reaches peak when…
No light
When does cortisol peak?
When you wake up
Regulation of circadian rhythm through light
Intrinsically photosensitive ganglion cells - MELANOPSIN -> Superchiasmatic nucleus -> down spinal cord -> up to pineal gland
What is cortisol opposed to? What does it do? When does it peak?
Melatonin. Synchronize cells in body - immune system response - intense physical activity - psychological and emotional stress. 6am
Lack of light has an effect on…
Emotional neural circuits
Alternative pathway found that circadian rhythm affects mood…
thalamic perihabenular nucleus -> Nucleus Accumbens -> medial Prefrontal cortex
Sleep - Behaviourally
Reversible state of perceptual disengagement from and unresponsiveness to the environment
Sleep - Electrophysiologically
Brain wave criteria - patterns of electrical activity
Current view of sleep
Highly organized state generated by the cooperative interplay of many behavioral and neural components
What are the 4 theories for the purpose of sleep?
1) Energy conservation: Replenish brain glycogen levels - decreased metabolism
2) Evolutionary thing bc we can see stuff at night and its better to pause and avoid predators
3) Consolidation of memory: closes gate b/w short term and long term memory states
4) Clearance of metabolic waste: Cerebrospinal fluid
EEG - Stages of Sleep - Name the 5 waves
1) Gamma(30-100)
2) Beta(12-30)
3) Alpha (8-12)
4) Theta (4-7)
5) Delta (1-4Hz)
High frequency, low amplitude
Awake (Beta)
Low frequency, High amplitude
Drowsier (Alpha) More synchronized when sleep
Stage I sleep (Purves terminology)
Transition to sleep/drowsiness - waves start showing lower frequency, higher amplitude
Low arousal Threshold
When we sleep thalamus…
Closes gate, no more info from outside world
Stage II
Sleep spindles - bursts of activity 10-12HZ
Lower frequency, Higher amplitude
K-complexes
Stage III and IV
Slow-wave sleep
#of spindles decreases
Delta waves(0.5-4)
Highest arousal threshold(hard to wake person up)
Might disappear from later cycles
REM
EEG similar to wake
Rapid eye movement
Physiological variables increase
Pupils constrict
Paralysis of large muscle groups
Small ones twitch
Spontaneous penile erection
More dreaming
REM becomes longer across night
K-Complex
Some bit of external information reached the cortex - spike in activity
Parameters of sleep - 6 of them
1)Decrease in muscle tone
2)Body movements
3)Heart rate
4)Blood pressure
5)Metabolic rate
6)temperature
Dreaming in non-REM
Features of memory
non-emotional
short
less visual
Dreaming in REM
long
visual
emotional
bizarre
unrelated to what happened in the day
Percentage of Sensory Modalities in dreams
Visual: 100%
Auditory: 65%
Vestibular: 8%
Temp: 4%
Tactile, olfactory, gustatory: 1%
Emotional content of dreams
Anxiety: 14%
Surprise: 9%
Joy: 7%
Sadness: 5%
Shame: 2%
PENILE ERECTIONS
Men
Women get physiological counterparts of sexual arousal
REM sleep goes down throughout life
Infants have most dreams - REM sleep
Magoun and Morizzi - 1949
Stimulating midbrain-pons junction induces wakefulness and arousal (cats)
Walter Hess
low frequency pulses to thalamus induce slow-wave sleep
Reticular activating system
Patterned interaction b/w brainstem, thalamus and cortex
Three groups of nuclei in brainstem sending outputs to the cortex through thalamus
Noradrenaline
Seratonin
Acetylcoline
Thalamocortical interactions
Interactions b/w thalamus and brainstem
Tonically Active
Neurons depolarized by sensory stimuli(peripheral) - Wakefulness - “gate open”
Intrinsic Bursting State - OSCILLATORY STATE
- gate is closed - fires in oscillatory rate - “disconnected from outside world” (e.g asleep)
What determines if thalamus is open or closed? Whether you are in oscillatory state or tonically active state?
Brainstem nuclei
Cortical state depend on which NT’s? What do they each do?
Noradrenaline: wakefulness
Cholinergic(acetylcholine): complex information processing and cognitive processes(present in both wakefulness and REM sleep)
Serotonin: “intermediate” NT. In high quantities linked with wakefulness, in minor quantities it’s linked to Non-REM sleep
Where to brainstem nuclei operating with distinct NT’s that project to?
thalamocortical neurons
Cholinergic nuclei
Reticular activation
Desynchronization of EEG
Wakefulness and REM sleep
Locus coeruleus
Noradrenergic neurons
Raphe Nuclei
Serotoninergic neurons
Noradrenergic neurons and serotoninergic neurons are _____ modulated by ______ nucleus of the hypothalamus (histhamine)
positively
tuberomamillary
Lateral Hypothalamus(orexin)
Activates noradrenergic neurons or serotoninergic neurons
2 substances that increase/activate noradrenergic neurons
1) Cocaine
2) Wellbatrine
Tubermomamillar nucleus
Keeps us awake
Ventrolateral preoptic nucleus (VPLO)
Inhibits noradrenaline, cholinergic and seroroninergic neurons
Valium
Causes wakefulness neurons to be inhibited by increasing GABAergic neurons of the VPLO - Ventrolateral Preoptic nucleus of the hypothalamus
REM-on cholinergic neurons
Acetylcholine - rem sleep
REM-off serotoninergic neurons
Serotonin - non rem sleep
High activation, external info, noradrenaline
Waking
High activation, internal info, acetylcholine
REM sleep
Medium activation, both internal and external source, serotonin minor quantities
Non-REM sleep
Increased activity regions in REM sleep
Amygdala, para hippocampus, pontine tegmentum, ACC(lymbic system - high emotionality)
Decreased activity regions in REM sleep
Dorsolateral prefrontal and posterior cingulate cortex
Why is there not a lot of inhibition of impulses when we are dreaming?
Because activity in PFC is decreased in REM sleep therefore resulting in less control of your actions and being less socially acceptable in your dreams.
What are the neural circuits that happen in REM sleep? 3of them
1) Hyperpolarization of spinal cord motor neurons:
- Inhibits movement in sleep
- Pontine inhibitory area - medulla - spine
2) REM Saccades
- Pons reticular formation -> eye movements
3) PGO (pontine-geniculate-occipital) waves
- Phasic bursts of AP occur throughout forebrain in association with rapid eye movements
What is the main ACTIVATING NT?
Noradrenaline - induces wakefulness
Does wakefulness equal consciousness?
wakefulness != consiousness
Awareness vs Self awareness
Consciousness as awareness
What operates with 3 distinct NT’s that promote wakefulness? What are the NT’s? What do these 3 NT’s determine?
A group of brainstem nuclei referred to as the RETICULAR ACTIVATION SYSTEM
1) Serotonin
2) Acetylcholine
3) Noradrenaline
These determine your cortical state.
Nuclei in hypothalamus that promote the action of brainstem nuclei
Tuberomamillar nuclei. Works with histhamine and wakes you up.
Nuclei in thalamus that decrease the action of brainstem nuclei
Ventrolateral preoptic nuclei. Works with GABA
Wakefulness (thalamus “gate” open) - What combination of NT’s?
Noradrenerigic + cholinergic + serotoninergic
What NT has to be absent to be asleep? Thalamus “gate” closes
Noradrenergic
REM sleep combo of NT’s?
Low Noradrenaline + Acetylcoline
Non-REM sleep combo of NT’s?
low noradrenaline, low CHOLINERGIC + Serotonin pulses
When brainstem(Reticular activation formation) sends inputs to thalamus the gate is ____ and it is in a _____ state
Open
Tonically Active State
When there is no input from the brainstem to the thalamus it goes into ______ state, the gate is _______, EEG is ______, higher ________, lower ________
Intrinsic bursting state
Closed
More Synchronized
Amplitude
Frequency
What regulates the brainstem? Which specific 3 nuclei?
Lateral Hypothalamus (orexin) - Activates brainstem - Wakefulness
Tuberomammillary nucleus (histamine) - Activates brainstem - Wakefulness
Ventrolateral Preoptic nucleus (GABA) - Inhibits brainstem - Sleep
Brainstem nuclei
Cholinergic nuclei: Wakefulness and REM
Locus Coeruleus(Noradrenaline): Wakefulness
Raphe Nuclei(Serotonin): Wakefulness and NREM
Parasomnias (Sleep walking, sleep talking, confusional arousals, night terrors, REM behavior disorder)
Happen during stages 3 and 4 of sleep - delta wave or deep sleep
When short episodes the EEG doesn’t change
When they are longer, the EEG pattern changes to an “active” (awake or REM) pattern
REM behavior disorder
Descending inhibition of motor neurons is impaired
William James
Definition of Attention
Attention as a filter - selective processing - Who said this?
Allocation of neural resources at to the analysis of particular info “at the expense of resources that might have been allocated to other concurrent information”
Colin Cherry, 1950
- presented diff dialogues to each ear at same time, subjects would report accurately the content of the attended channel but barely the other
Anne Treisman
“a filtering system that could attenuate the inputs from concurrent channels in a flexible manner”
Consciousness and Attention
Attended info reaches threshold to enter into consciousness
Focusing neural resources according to the contingencies of the moment
Influence of perceptual load - more stimulus makes it harder to bring everything to conscious attention
Endogenous Attention - Top -down attention
Based on prior knwoledge, willful plans and current goals
300ms to few seconds
Consciously direct attention to particular thing when told to
Michael Posner - Late 1970’s
Visual fixation on central point
Arrow appears in middle pointing left or right
Indicates where upcoming target stimulus will most likely be
When target appears, subject must perform a discrimination task such as indicating whether the target is a circle or an oval.
In most of the trials the target is presented at the cued
location, but sometimes it is presented at another location.
- Subjects respond faster to targets appearing at the cued location (“valid”) than those appearing away from the cued location (“invalid”).
An advantage of this and related paradigms is quantification of attentional effects.
Exogenous(involuntary) Attention - Bottom-up attention
Unexpected stimuli (noise, flash of light) causes shift in focus trumping whatever else a person was attending at that moment.
In conjunction with that shift in attention, the unexpected stimulus also facilitates the processing of info in that region, at the same time diminishing the efficacy of processing elsewhere
75ms to a few hundred ms
After 400ms, “inhibition of return”
3 differences b/w endogenous and exogenous attention
Time courses of their influence on target processing.
Exogenous is faster.
endogenous has predictive value, exogenous does not
Endogenous spatial vs non-spatial
Spatial - Cue in a spot task
Non-spatial - Color word in a diff visual color
Inhibition of Return - IDK LEARN IT
Overt Attention - Who? What?
Alfred Yarbus
Orienting head and eyes to a stimulus, aligning visual and auditory processing and improving perception
Covert Attention
Alfred Yarbus
Directing attention without moving head or eyes.
How did Alfred Yarbus track eye movement of the subjects on the paintings?
Quantified overt attention by measuring subjects’ patterns of gaze in response to viewing paintings and sculptures, using an ingenious system of small mirrors glued to the eyes of participants which redirected light to photo-tracing paper.
