Lecture 9: Consciousness Flashcards
What are the two main pathological mechanisms leading to coma? Which brain areas are involved?
Coma is the results of either (1) bilateral, severe cortical damage or (2) a focal lesion of the ARAS, either located in the brainstem (upper pons or midbrain) or in the diencephalon (thalamus, especially intralaminar nuclei).
Which brain areas are involved in cortical activation?
Basal forebrain, hypothalamus, thalamus and pontomesencephalic reticular formation.
Describe the ‘locked-in syndrome’, including its main cause.
The LIS is a result of brainstem lesions, affecting the corticospinal tract. Only the movement of the eyes is possible (cranial nerves preserved!). Patients are completely awake, as the ARAS is not affected.
Describe the ‘persistent vegetative state’.
The PVS looks like coma, but patients show a sleep-wake rhythm and normal EEG in general. Brain imaging studies show fMRI activity that is similar to non-patients when giving a mental imagery task, indicating that PVS might be an even more severe locked-in syndrome.
Differentiate between primary and extended consciousness. Which brain areas are mainly related to these types of consciousness?
Primary c. refers to a more or less binary state, being either awake or not. Extended c. refers more to the ‘higher’ features of consciousness (e.g. the content of consciousness).
Primary c. is associated with the ARAS (brainstem), whereas the extended c. is associated with the thalamocortical system.
In theory, after injecting acetylcholine, which sleep stage would you suspect to find a person in?
Acetylcholine induces REM sleep.
Llinas defined as specific oscillation pattern as marker for consciousness. What is their frequency?
40 Hz oscillations.
