Cortical states Flashcards
What are the most important external cues for the circadian cycle?
Levels of light and darkness.
What will happen to the duration of the circadian cycle if shifted by abnormal external cues?
Nothing, 24 hrs length persists.
Is our internal biological clock following the circadian cycle stopping in the absence of external cues?
No, operates even in the absence of external information.
What is our internal clock synchronized with the circadian cycle principally regulated by? How so?
Environmental illumination makes the photo-sensitive ganglion cells of the retina signal to the hypothalamus.
Where is the suprachiasmatic nucleus found?
In the hypothalamus.
Describe the pathway that leads to melatonin secretion.
Photosensitive ganglion cells (expressing melanopsin) fire when in the dark → fire to suprachiasmatic nucleus “master clock” via the retinohypothalamic tract →paraventricular nucleus →spinal cord intermediolateral cells →superior cervical ganglion →melatonin synthesized in pineal gland.
When is melatonin most secreted during the circadian cycle?
During the deepest phase of sleep.
Circadian effects can affect learning and mood in two ways. What are they? Hint: one direct and one indirect.
Direct: shift of circadian ryhthm (e.g. less light in winter) might enhance the risks of depression and disturb sleep schedule
Indirect: light also signals to PHB nucleus →projecting to limbic system to modulate mood-related areas in the cortex
True or false: sleep dept affects mood and can even produce hallucinations, but can’t impair judgement.
False: also impairs judgement.
Name three functions of sleep in humans.
- Energy conservation
- Memory consolidation
- Clearance of brain metabolic waste with CSF
What are the three non-REM stages according to the AASM terminology? Provide the principal characteristic of each stage.
N1: drowsiness
N2: sleep spindles
N3: delta waves (deepest phase of sleep)
True or false: REM sleep stage is the deepest sleep stage of the night.
False: N3 is the deepest sleep phase.
True or false: duration of sleep stage N3 stays the same during the night while REM periods get longer.
False: N3 gets shorter during the night and REM periods get longer.
Rapid ballistic eye movements are a characteristic of which sleep stage?
REM
Name three differences between REM and non-REM dreams.
REM:
- REM dreams do not immediatly connect with everyday life of dreamer
- Longer
- Primarily visual
Non-REM:
- Non-REM dreams usually relate more to current life of dreamer
- Shorter
- Less visual
What happens to the general duration of a night of sleep as we get older? What happens to the proportion of REM sleep?
- Less and less overall sleep
- Less and less REM sleep (but proportion of REM sleep stabilizes at early adulthood)
Neural circuits underlying sleep involve three principal structures, what are they?
Brainstem, thalamus and cortex
Name and define the three neural circuits activated during REM sleep.
- REM saccades regulated in the brainstem
- PGO (pontine-geniculate-occipital) waves go with REM saccades: phasic bursts of action potentials occuring throughout the forebrain
- Hyperpolarization of spinal cord motor neurons via pontine inhibitory area
Acetylcholine induces _____. Serotoninergic neurons induce _____.
Place the followings:
- non-REM sleep
- REM sleep
Acetylcholine induces REM sleep. Serotoninergic neurons induce non-REM sleep.
What are the cerebral structures in which there is an increase of activity during REM sleep? Structures in which there is a decrease of activity?
- Increased activity in:
- Amygdala
- Para hippocampus
- Pontine tegmentum
- Anterior cingulate cortex (lymbic system)
- Decreased activity in:
- Dorsolateral prefrontal cortex
- Posterior cingulate cortex
Where is the reticular activation system located? What are its three type of nuclei?
In the brainstem.
Cholinergic nuclei, Locus coeruleus and Raphe nuclei.
True of false: the three nuclei of the reticular activation system have the ability to induce wakefulness.
True.
Where are found the noradrenergic neurons? The serotoninergic neurons? The histaminic neurons?
Locus coeruleus of brainstem.
Raphe nulcei of brainstem.
Tuberomammillary nucleus of hypothalamus.
How does histamine increase wakefulness?
Excites histaminic neurons of tuberomamillary nucleus of thalamus ->activates either (or both) noradrenergic neurons of Locus coeruleus or serotoninergic neurons of Raphe nuclei -> more inhibition on thalamocortical cell (in thalamocortical feedback loop) -> less excitation on cortical pyramidal cell (in thalamocortical feedback loop) ->less excitation on reticular cell (in thalamocortical feedback loop) ->less inhibition on thalamocortical cell (in thalamocortical feedback loop) -> sensory information will reach the cortex ->provoking wakefulness.
How are the nuclei of the reticular activation system inhibited?
VLPO nucleus of hypothalamus → INDUCE STATE OF SLEEP → inhibit reticulary activation system = closes hypothalamus gate.
How does arise the intrinsic bursting state in the cortex during sleep?
Thalamus does not transmit sensory information during sleep (nuclei of reticular activation system in the brainstem are inhibited by VPLO) → synchronization of neuronal activity (can be measured by EEG) = intrinsic bursting state.
What are the three components to the global workspace model of consciousness?
- Conscious activation network
- Preconscious activation network
- Subliminal activation network
True or false: we are aware of most of our neural processes.
False.
Consciousness is closer to awareness or to wakefulness?
Awareness.
Concerning the cortex, how are semi-conscious comatose and vegetative states differentiating?
In a vegetative state, there can’t be any cortex activation.
In a semi-conscious comatose state, there can be activation of cortex, but no motor command can signal that.
How are the default mode network and the central executive network correlating?
They are anticorrelated: when one is activated the other is deactivated.
