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62 Cards in this Set

  • Front
  • Back
What is consciousness?
-Awareness of self/environment
-Subjective experience
-Globally available information
-Integrated information
What is consciousness not?
What are the 2 dimensions of consciousness?
What is the highest level of consciousness? What is just below it?
Conscious wakefullness
What dimension of consciousness is altered in sleepwalking and vegetative states?
Awareness is low but wakefulness is high
What is the lowest level of awareness and wakefulness?
What 4 structures of the brain are necessary for consciousness?
1. Rostral pontine tegmentum
2. Midbrain tegmentum
3. Diencephalon (intralaminar thalamic nuclei)
4. Medial hemispheric wall (cortex and subcortex)
What is not necessary for consciousness?
-Spinal cord
-Medulla (if you maintain artificial resp and BP)
-Caudal half of pons
-Entire basis pontis
-CN motor nuclei
-Basal ganglia
How much of the cerebral cortex is needed for consciousness?
Only one hemisphere
What is the ARAS?
The ascending reticular activating system
What does the ARAS do?
Enables the conscious state
What are the 4 levels/components of the ARAS?
1. Medulla
2. Pons
3. Midbrain
4. Thalamus
What happens if you transect the spinal cord at C1?
The normal sleep-wake cycle is preserved
What happens if you transect the brainstem between the diencephalon and mesencephalon?
A permanent state of sleep results.
Does the waking state require constant sensory input?
What happens when you electrically stimulate the reticular formation in a sleeping animal? if you lesion?
Stimulation - It wakes it up
Lesion - It sleeps
What do we know innervates the reticular core?
Ascending sensory pathways
What happens when we're awake and sensing things?
Ascending sensory systems give input via collateral branches to the ARAS which produces nonspecific cortical activation
What else gives input from the spinal cord to ARAS?
Somatic activation
What is the result of descending activation by the ARAS and somatic output from ARAS?
Physiologic regulation
What 2 types of input does the cortex give to the ARAS?
1. Positive feedback - Arousal during daydreaming
2. Negative feedback - Inhibitory during boring lectures
What pathway is the source of active sleep?
Medularry Reticular Negative Feedback
What will result from a lesion of the frontal forebrain projection from the ARAS to cortex?
Akinetic mutism
What will result from a lesion of the dorsal forebrain pathway from the ARAS?
What will happen if you lesion the ARAS at the level of the dorsal tegmentum?
What happens if you lesion the ventral tegmentum?
Locked in syndrome
What 4 important systems in the brain give input to the ARAS?
What are their nuclei?
-Dopaminergic (Subst nigra pc)
-Serotonergic (Raphe)
-Cholinergic (septal / basalis)
-Noradrenergic (Locus ceruleus)
What is Sleep?
An altered state of consciousness - not unconsciousness.
What are 2 hypothesized functions of sleep?
-Cell regeneration
-Memory consolidation
What causes the regionally specific changes in dreaming?
Prefrontal deactivation
What controls the switch between wakefulness and sleep?
The thalamus
What is the nature of thalamic neuron firing during wakefulness?
Single spikes at a steady rate
What is the nature of thalamic neuron firing during slow wave sleep?
What is the level of Aminergic and Cholinergic tone during:
-REM sleep
-NREM sleep
Why? What is Rem-on and -off?
Waking: both high
REM: Aminergic low, Cholinergic high (latter are Rem-on!)
NREM: both low (Aminergic are REM-off)
What nucleus in the thalamus regulates our state of awakeness or sleep? How?
NRT - nucleus reticularis of the thalamus (intralaminar);
Interacts with Thalamocortical cells reciprocally.
What type of cells are in the NRT? (what do they release)

When does slow-wave sleep occur?

SWS = during Nonrem sleep
What are the GABAergic cells of the NRT in reciprocal relationship with?
Glutamatergic Thalamocortical TC Relay cells
What does the NRT receive its input from?
Cholinergic ascending collaterals from the brainstem and forebrain, and Cholinergic desc collaterals from cortex.
What do the asc/desc collaterals release and how does it affect the NRT?
They release acetylcholine during wakefulness and REM sleep, which inhibits the NTS
What does the NRT do when it is NOT inhibited?
NRT releases gaba on the TC cells, which hyperpolarizes them and opens low-threshold Ca channels.
What happens when Ca channels open in the TC cells?
Sodium activated Action Potentials occur in bursts
When do we see bursts of APs in the thalamus?
During slow wave sleep
What causes the bursts to cease in the TC cells?
Opening of Ca-activated K channels
So the result of NRT inhibition of TC cells is:
Slow wave sleep
Can slow wave sleep occur during wakefulness? Why not?
No; because cholinergic neurons from the cortex and brainstem inhibit the NRT from releasing GABA.
How many stages of sleep do we have?
What happens to sleep as the night goes on?
It gets less deep
How is consciousness split up in the brain?
Each hemisphere has awareness of its own but only the left is reportable.
What happens when a person has a split brain?
Confabulatory interpretation - the left brain tries to make sense of things.
Couple things more about sleep
What are REM-on cells?
What are REM-off cells?
Do TC cells have anything to do with REM-on and REM-off cells? Why/why not?
No - TC cells are GLUTAmatergic
So the 4 cell types and NTs we're talking about here are:
1. Rem on - Cholinergic
2. Rem off - Aminergic (dopa)
3. TC cells - Glutamatergic
4. NRT cells - GABAergic
What nuclei in the brain cortex and brainstem release Acetylcholine?
-Nucleus basalis
-Nucleus parabrachialis
What does Acetylcholine from the brain and brainstem do?
Inhibits the NTS during wakefulness
What are off-REM cells?
What do they release?
In what state are they during Wake, NREM, and REM states?
-Release dopamine
-On during wake
-Turning off during NREM
-Off during REM
What are REM-on cells?
What do they release?
In what state are they during Wake, NREM, and REM states?
-Release ACh
-Off during wake
-Off during NREM
-On during REM
When are Beta waves seen on the EEG?
During awake
When are Alpha waves seen on the EEG?
When eyes are closed and resting
When are Theta waves seen on the EEG?
During sleep
When are Gamma waves seen?
During deep sleep