Sleep, Dreams and Consciousness Flashcards
What is sleep?
A readily reversible state of reduced responsiveness to, and interaction with, the environment.
What suggests sleep universal?
Fruit fly, drosophila, sleeps.
What sort of rhythms are associated with alertness and waking, or dreaming?
High F, low A.
What sort of rhythms are associated with non-dreaming sleep states, certain drugged states, or coma?
Low F, high A.
What suggests that sleep is restorative?
Homeostatically regulated. Sleep loss promotes proportional increases in tendency to sleep (sleep drive).
Adenosine sleep-promoting factor, levels based on rundown of adenosine triphosphate ATP stores in awake period.
What study showed that rat functional muscle recovery was impaired following myotoxic injury in sleep deprived?
Schwarz et al (2013).
What suggests sleep is not restorative?
If was would expect direct correlation between MR and sleep duration. But not case. Low MR bats 18h high MR horses 3h.
What suggests (REM) sleep important for memory consolidation?
Karni et al (1994). Selective disruption of REM sleep resulted in no performance gain on visual discrimination task.
What suggests (REM) sleep is not important for memory consolidation?
Selective REM deprivation no effect on behaviour. MAOIs no obvious impairments after years or months.
Also no evidence dolphins or wales have REM yet have good memory, capable of recognising signature whistles of former companions after separations exceeding 20 years.
What suggests that it is nREM>REM that is important for memory consolidation?
Wilson and McNaughton (1994), ensembles of hippocampal place cells repeat waking activity during subsequent episodes of SWS.
Marshall et al (2006), transcranial application of 0.75Hz potentials during early nREM enhances declarative memory retention. Stimulation also caused immediate increase in SWS.
Huber et al (2004), motor task, SWS induced in circumscribed regions active during learning. Local plastic changes.
What suggests that REM is important?
When sleep deprived REM rebound, Randy Gardener, 264 hours slept for 15.
Where is the SCN?
Located in the hypothalamus on either side of the midline, bordering the third ventricle.
What evidence shows the importance of the SCN for circadian rhythms?
Edgar et al (1993), bilateral removal abolishes rhythmicity of physical activity, sleeping and feeding.
Lehman et al (1987), implantations of fetal SCN re-establishes rhythms of locomotor activity in adult hamsters previously made arhythmic by lesions.
IPRGCs synapse directly onto neurons. How are they photosensitive?
Express melanopsin, large dendritic spines.
What shows that APs not necessary for SCN cells to maintain rhythm?
What shows rhythms internally generated by SCN cells?
When TTX removed, APs fire in same schedule.
Yamaguchi et al (2003). 100 SCN neurons maintained in tissue culture, FR, glucose utilisation, protein synthesis still varied ina. 24 cycle.
Same thing happens when animal deprived of zeitgebers.
How do SCN cells maintain rhythm internally?
Modulation of gene expression via a negative feedback mechanism.
Describe the mechanism behind how SCN cells maintain internal rhythm.
CG transcribed to produce mRNA which is translated into proteins. After a delay, proteins send feedback to transcription mechanism, decrease in CG expression, less protein, CG increases.
What did Takahashi et al show?
Clock genes produce proteins that inhibit further transcription. Gene transcription and the FR of individual SCN neurons cycles up and down over 24h.
What causes delayed sleep phase syndrome?
Mutations in clock genes, make timing longer.
When cells from liver, kidney, lung are grown in isolation, what do they exhibit?
Circadian rhythm of their own.
Why are older people afflicted with insomnia?
Pineal gland calcifies.
What suggests melatonin important for sleep?
Old people insomnia, treats jet lag and insomnia.
Other than the pineal gland, where does the SCN output to, and what is the function of this?
ANS and andrenal gland. Alters CBT, cortisol, and neural circuits controlling feeding and metabolism.
What is the influence of the SCN on core body temperature?
Drops by 1 degree each night. Pulse of cooling ensures clocks remain set to cycles of dark and light.
Why are SCN clocks resistant to temperature changes?
Ensures it is not destabilised by its own signals.
What did Moruzzi and Magnoun show?
Brainstem RF critically important for stim. and maintenance of waking, since lesions resulted in coma in animals and humans.
Where does the RAS project? What does this mean?
To thalamus, in turn giving rise to widespread diffuse projections across cortex. Means it can stimulate widespread and long-lasting cortical activation.
What can modulatory systems in the brainstem do?
Modulate activity of RAS.
What do NA neurons in locus coeruleus do to RAS? What evidence is there for this?
Increase RAS activity, and prevent REM sleep (explains MAOIs).
Carter et al (2010), optogenetic activation of these neurons during SWS led to immediate cortical activation, behavioural arousal and locomotion in mice.
What do dopaminergic neurons do the RAS? What evidence?
Increase activity.
Amphetamine prolonged increase, releases catecholamines.
Jones et al (1977), NA LC lesions did not alter prolonged wakefulness caused, highlights role of DA neurons of the SN and VTA.
What does ACh do to sleep/wake? Evidence?
Promotes wakefulness, but also seemingly plays a role in REM sleep. May be why activity much like waking.
Also inhibits motor neurons during REM. (Sleep also involves activity in descending pathways of diffuse M systems).
AChR agonists such as carbachol into the pontine RF during SWS elicited REM sleep and muscle atonia.
What is the effect of adenosine on DMSs?
Inhibits ACh, NE and 5-HT.
Explains why caffeine [romotes wakefulness.
Although sleep was once considered to be a passive deactivation of the CNS, …
It has been found to involve an active process of inhibition of the multiple arousal circuits.
Where is the ventrolateral preoptic area?
Hypothalamus.
What do VPLO neurons do>
Inhibit activity of orexinergic neurons which excite arousal centres (raphe nuclei, locus coeruleus).
What is the effect of the SCN on orexin neurons?
Modulates so that they are more active during the circadian day than circadian night.
In what sense do glucose levels mediate orexin levels?
Low G, high O, food seeking.
What is sufficient to produce narcolepsy? Evidence?
Deficient orexinergic transmission.
Animal models with dysregulated orexin signalling exhibit narcolepsy-like phenotype.
What does the flip/flop switch hypothesis argue?
That sleeping is a continual fight between the VLPO and RAS, both which act as a switch, mutually inhibiting each other.
