Sleep and Memory Flashcards
When is memory consolidated?
during sleep, emotionally significant memories especially
EGG waves are summation of what?
synchronous postsynaptic potentials (EPSP’s & IPSP’s) in large populations of neurons
The ______ the synchrony the _____ the amplitude
greater, larger
Sleep oscillates between _____ stages every _____ minutes (also name the two stages)
2 stages every 90 mins
REM & non-REM (slow-wave)
How are sleep stages distinguished?
distinguished by EEG
When do you see non-REM sleep? What happens to the EEG waves? When do you see slow wave sleep?
as sleep depends (stages 1-4)
EEG waves increase in amplitude & decrease in frequency
4th stage, however is curtailed through the night
What is REM sleeps EEG similar to? What is the frequency and amplitude of the EEG waves like?
waking
EEGs are low amplitude & high frequency
The first half of nocturnal sleep is dominated by _____ whereas the second half is dominated by _______.
SWS, REM
Do you spend more or less time in deep sleep as you age?
LESS; in early adulthood the amount of SWS begins to decline, elderly adults typically have relatively short periods of slow-wave sleep & fewer of them
The reticular pathways are for what and project to where?
for wakefulness/arousal; is initiated & maintained by them and project to the thalamus & cortex
Pathways that activate the THALAMUS facilitiate what and what is the pathway?
facilitate transmission of information from thalamus to cortex
cholinergic pontine pathways (pedunculopontine & lateral dorsal tegmental nuclei)
When is the cholinergie pontine pathway most active?
during waking & REM sleep; less active in non-REM sleep
Pathways that activate the CORTEX faciliate what and what are the pathways?
facilitate processing of input from thalamus
- monoaminergic pathway: NE from locus ceruleus, serotonin from raphe nucleus, dopamine from periaqueductal grey
- cholinergic pathway from basal forebrain nucleus
- orexin/hypocretin pathway from lateral hypothalamus
What part of the brain regulates sleep?
hypothalamus specifically the VLPO (ventrolateral preoptic) nucleus; it inhibits (via GABA & galanin) all hypothalamic & brain stem nuclei that participate in arousal, induces drowsiness, discharges selectively throughout non-REM sleep
What does the suprachiasmatic nucleus respond to?
ambient light & dark cycles
What does the SCN project?
light-dark phases to supraventricular zone (SPZ) & dorsal medial nuclei of hypothalamus (DMH)
What does the DMH inhibit & what input does it need first?
with light DMH promotes wakefulness by inhiting VLPO via GABA neurons & stimulating orexin neurons via glutamate neurons
What do cytokines do in relation to circadian control of sleep?
disrupt circadian sleep cycle during illness= sleep during the day so can recover
How many sleep-wake phases are generated by different sets of reticular nuclei?
THREE
Cortical arousal and processing of sensory info is maintained by excitation of what three things?
cholinergric neurons from LDT, PPT
NE neurons
serotonin-5HT
What do cholinergic neurons from LDT, PPT activate?
thalamic processing of sensory information and activate cortex via nucleus basalis
NE neurons directly activate what?
cortex; NE comes from locus ceruleus
Serotonin-5HT directly activates what?
cortex; serotonin comes from dorsal raphe nuclei
Memory consolidation occurs first in ________ and final consolidation of memory occurs in __________. What stage (SWS or REM) is each dominated by?
early nocturnal sleep: dominated by SWS stages 2, 3, 4
late nocturnal sleep: dominated by REM
What is early nocturnal sleep good for?
consolidation of memory & procedural memory
What is late nocturnal sleep good for?
final consolidation of memory
In relation to causing wakefulness, what do neurons in the posterolateral hypothalamus do to the brainstem?
excites brainstem neurotransmitter system; it sends excitatory signals via forebrain & thalamus to the cortex & inhibits sleep-active neurons in the ventrolateral preoptic area
Is SWS or NREM sleep inhibition or activation of cholinergic & adrenergic pathways? It is associated with synchronous activity b/w what parts of the brain?
INHIBITION
b/w the cortex & thalamus (SWs)
During SWS/NREM sleep what neurons inhibit all the ascending arousal system? What are the parts of the ascending arousal system?
ventrolateral preoptic neurons inhibit.
includes: serotonin from the dorsal raphe nucleus; acetyl choline from laterodorsal tegmental & pedunculopontine areas LDT/PPT; NE from locus coeruleus
What are the characteristics of SWS/NREM sleep?
- decrease in afferent neural input into cortex
- decrease in muscle tone, HR, breathing, BP & metabolic rate (can still be tossing & turning/sleep walking w/o dreaming); inactive mind in an active body
REM sleep is excitation of what neurons from where? What do they stimulate?
cholinergic neurons from LDT/PPT
stimulate thalamo-cortical activity, rapid eye movement, & PGO waves in visual cortex
What is inhibited in REM sleep?
serotonergric neurons in raphe
What is REM characterized by?
- high brain activity
- transient paralysis
What are the two distinct types of REM?
- phasic REM
- tonic REM
What is phasic REM?
extensive rapid eye movements, high activity in several areas of the brain, external sounds (are suppressed)
What is tonic REM?
absence of eye movements, increased reactivity to outside stimuli, increased activity in auditory cortex
What is disinhibited in REM and what does this allow?
disinhibit cholinergic LDT/PPT neurons which activate thalamic structure and produce cortical desyncrhonisation
medial medullary nuclei produce atonia
What are the characteristics of REM in general?
- rapid eye movements
- paralysis of lg muscles
- increased BP, HR & metabolism
- dreaming, visual hallucinations
- active mind in an inactive body
What are some physiological functions that correlate w/REM stage?
- eye movements
- heart rate
- respiration rate
- penile erection
What do LDT/PPT cholinergic neurons do to REM activity?
STIMULATE IT!
What do NE & serotonergic neurons do?
locally inhibit LDT/PPT neurons
Feedback activity b/w LDT/PPT and NE & serotonergic neurons does what?
determines the length of REM & NREM sleep periods
Declarative memories encoded by the ______ are _________ during SWS & thereby consolidated in several cortical areas for ________ storage.
hippocampus; reactivated; consolidated
What neurotransmitter regulates the activation of memory traces in the hippocampus?
acetyl choline (from the nucleus basalis, septum & pontine nuclei)
What does increased Ach do?
increases sensory input & encoding w/in the hippocampus
What does decreased Ach do during SWS?
increases reactivation of memories in hippocampus & their transfer to neocortex
During sleep what are reactivated and consolidated and where?
memories (especially emotional memories)
in the cortex
Why don’t you form declarative memories as well during waking?
B/c they are labile & easily disrupted by interference of other sensory inputs
Does reactivation during wakefulness have the same or opposite effect as reactivation during SWS? aka do you stabilize memories during wakefulness?
opposite effect, memories labile & easily susceptible to modest modification
Memories consolidated during REM enable __________.
insight= discovery of hidden correlations across multiple episodes not just from one
What do consolidated memories provide that facilitates learning & storage of new information of the same kind?
A SCHEMA
What does the septum regulate? What does it underlie?
memory encoding in hippocampus
underlies theta rhythm
What does the theta rhythm of the septum do?
separates encoding of current stimuli & retrieval or episodic memory cued by current stimuli–> so don’t get interference b/w simultaneous encoding & retrieval
Where does the nucleus basalis (meynert) project to? To do what? What disease affects it?
Neocortex
to facilitate memory consolidation
degenerates w/Alzheimer’s
What are the characteristics of Alzheimer’s disease?
- degeneration of cortex, cholinergic & other neuromodulatory tracts
- amyloid plaques (extracellular)
- neurfibrillary tangles (intracellular)
- inability to consolidate short term into long term memories
What is the other disease which causes loss of memory consolidation?
Korsakoff’s syndrome; also causes cofabulation.
due to degeneration of thalamic nuclei & mammillary bodies from alcoholism.
bilateal hippocampectomy & loss of cholinergic septal input.
only long term memory present.
What is the Papez circuit?
circular route which connects hippocampus/amygdala to cingulate & prefrontal cortex via mediodorsal thalamus
