Describe the general organization of the arousal pathways in the brain. What is the role of orexin in sleep and waking?
What will be an ideal response?
There are brain stem arousal centers and forebrain arousal centers that both send projections to the prefrontal cortex, which in turn sends descending projections back to lower brain areas. The brain stem arousal centers have two ascending pathways that terminate in the prefrontal cortex, basal forebrain and hypothalamus: one involves the pedunculopontine and laterodorsal tegmental nuclei (PPT/LDT), which are most active during REM sleep and waking, and one that involves the locus coeruleus, raphe nuclei, tuberomammillary nucleus, and parabrachial nucleus. The PPT/LDT pathway also sends information to the thalamus. The forebrain arousal centers include the basal forebrain, which desynchronizes EEG and prompts wakefulness, and the lateral hypothalamus. Within the lateral hypothalamus, orexin-releasing neurons reduce REM sleep and prompt waking.
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Jones and Davis's theory of correspondent inferences specifies the conditions under which you are most likely to
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