Module 34 - Cortical states Flashcards
What are the two main tenants of the consciousness system?
- Content of consciousness
- Level of consciousness
What is the content of consciousness?
- The content of consciousness is systems mediating sensory, motor memory, and emotional functions
- Memory
- Emotion and drives
- Language
- Executive function
What is the level of consciousness?
- The three A’s
- Alertness
- Attention
- Awareness
What are the three A’s of level of consciousness?
(IMPORTANT QUESTION)
- Alertness
- Attention
- Awareness
How do we sustain the LEVEL of consciousness (arousal /alertness) and attention?
By consciousness system networks
By consciousness system networks
What are the four key brain areas of the consciousness system networks?
(IMPORTANT QUESTION)
Upper brainstem
Thalamus
Hypothalamus
Basal forebrain
What are the thalamus and hypothalamus often referred to?
The diencephalon
Where is the basal forebrain located?
Locate the structure on the image.
Important structure to produce acetylcholine
What is a key neurotransmitter for alertness?
Acetylcholine
Which structures mediate alertness, attention, and awareness?
- Upper brainstem
- Thalamus
- Hypothalamus
- Basal forebrain
What is the hierarchy of the consciousness system networks?
You need to be alert before you can attend to something; and you need to be attentive before you can be aware of something
- Alertness
- Attention
- Awareness
What is alertness?
In order to be alert, we need normal brainstem & diencephalic arousal circuits, and the cortex
What is attention?
Same circuits as alertness (In order to be alert, we need normal brainstem & diencephalic arousal circuits, and the cortex) + frontoparietal association cortex
*remember that our association cortices are these heteromodal areas of the brain where information from different sensory systems are coming in and being analyzed together
What is the heteromodal association cortices that are important for attention?
frontoparietal association cortex
What is awareness?
Ability to combine various higher-order forms of information from disparate regions into a unified and efficient summary of mental activity - which can be remembered at a later time.
Which of the 3 A’s is the highest level of consciousness?
Awareness
What does alertness depends on?
- Neuromodulatory systems in the brainstem
- Influence widespread cortical areas
- The cortical regions to which these neuromodulatory systems project
What is neuromodulatory systems sometimes referred to? Why does it makes sense that we call it that way?
- Subcortical arousal systems
- It makes sense because if we think about the four parts of the brain that are part of these conscious system networks we have the …
- The upper part of the brainstem → which is subcortical = it is below the cortex
- The hypothalamus and the thalamus → which is not part of the actual cortex
- The basal forebrain → although it is part of the cortex, it is considered as subcortical
What are the brainstem modulatory centers?
A bit like “dimmer switches” - turn overall activity up or down
Involved in learning, motivation, arousal, etc.
Is alertness a black or white, yes or no phenomenon? Why or why not?
It is not !!!
For example, you can be awake but not necessarily very alert → perhaps when you are listening to a lecture, you are awake but you might not be alert
Or you can be very alert, for example, if you were walking late at night in a dark ally in a foreign country you might be extremely alert.
What does it mean when we say that neuromodulatory systems in the brainstem influence widespread cortical areas?
- They are made up of cholinergic and non-cholinergic projections to :
- Thalamus → transfers inputs from the upper brainstem to cerebral cortex
- Hypothalamus
- Basal forebrain
- NOTICE WHERE THEY ARE IN THE DIAGRAM OF THE IMAGE
Describe the neuromodulatory system?
Think about a neuromodulatory system as a structure and a neurotransmitter = that together makes a system
There are a number of _________________ systems in the brainstem.
There are a number of neuromodulatory systems in the brainstem.
Each neuromodulatory system uses a different neurotransmitter, and is involved in…?
Alertness
Cognitive processes
What type of neurotransmitters are associated with each neuromodulatory/subcortical arousal (alertness) system? *(not as important to remember this by heart)
- Upper brainstem + reticular formation = Ach + glutamate
- Upper brainstem = NE, serotonin, dopamine
- Posterior hypothalamus = histamine, orexin
- Basal forebrain = Ach
- Medial/intralaminar thalamic nuclei = ?glutamate
For now, let’s treat these various neuromodulatory/subcortical arousal systems as a single unit, and ask: What activates these systems? (i.e. which brain regions provide input to the parts of the upper brain stem/reticular formation mediating alertness?)
(IMPORTANT QUESTION)
- AS AN EXAMPLE - one of the modulatory systems = upper brain stem
- There are 3 brain regions that provide input to the parts of the upper brain stem/reticular formation mediating alertness
- Ascending sensory inputs
- Anterolateral pathways
- Pain can increase alertness
- Frontopareital association and limbic cortices
- Cognitive and emotional processes can modulate alertness
- Hypothalamus
- Fight or flight
What characterizes a coma?
- Psychologically meaningful or purposeful responses mediated by the cortex are absent
- B- what you can see in the coma image = blue areas are severely depressed in function = the cortex, as well as the important alertness areas, are being severely depressed
What characterizes a vegetative state?
- No meaningful responses, speech or gestures
- IMAGE = There is still a severely depressed function throughout the cortex → in the higher processing brain areas. BUT, now you can see that the systems mediating alertness are only variably depressed
What do we use to assess the alertness state of a patient?
GCS = Glasgow coma scale
What characterizes a minimally conscious state?
- It can occur after the vegetative state OR as a primary state
- The appearance of visual tracking may be one of the earliest signs.
What type of assessment do we use for patients that are in a minimally conscious state?
- NeuroWestern stimulation profile
- Not just looking at arousal and attention anymore, we are looking at different responses to different sensory things
- For example, can the patient respond to audition? Do they have a visual response? Can you close and open your eyes to command?
What is a locked-in syndrome?
- The cortex, or higher levels of cognition, is extremely intact
- The upper brainstem, diencephalon, and basal forebrain are also totally intact
- The lesions are at the area where our motor system and pyramidal decussation occurs
- Locked-in syndrome (LIS), also known as pseudocoma, is a condition in which a patient is aware but cannot move or communicate verbally due to complete paralysis of nearly all voluntary muscles in the body except for vertical eye movements and blinking.
What is dopamine responsible for as a consciousness system NT? (IMPORTANT QUESTION)
- Alertness
- Memory
- Movements
- Initiative
IMAGE = You can see that all of these structures = thalamus, hypothalamus, basal forebrain and upper brainstem = which are all cholinergic projection systems are responsible for alertness and memory.
IMAGE
What happens if these brain systems (thalamus, hypothalamus, basal forebrain, and upper brainstem) are not sending acetylcholine to their respectful areas in the cortex?
If they are not really working, you can see how the higher levels of cognition can’t happen, if the part of the brain that makes us alert is now depressed, it makes it very difficult for the rest of the brain to work properly
