When we sleep, we were essentially cut off from the sensory world. There is no auditory, gastatory, olfactory, or feeling sensations. We would not even see if our eyes were peeled open.
This is because when you are asleep, the following happens (or doesn't happen):
- Acetylcholine (ACh) system becomes inactive
- Sensory thalamus inhibited
- Reticular nucleus active
- Thalamocortical neurons in slow rhythm
- EEG synchornous
Also, during sleep the dorsal raphe nuclei (a cluster of serotonergic cells) and the locus ceruleus (a group of noradrenergic neurons) help to keep consciousness suppressed during dreaming. During REM sleep, only the eyes muscles twitch (hence Rapid Eye Movement) but the middle ear muscles also twitch, for an unknwon reason. This occurrs mostly because of the descending inhibition. Dreaming turns on a group of cells in the medulla that descend down the spinal cord and inhibit motor activity. Very specific lesions of these cells (a rare event) lead to a phenomenon called "violent sleeping", where the dream physically acts out his or her dreams. This is different from sleepwalking, as sleepwalking does not occur during REM sleep.
If there is any possibility of auditory perception during sleep, it would be because the auditory nerve carries it's signals all the way to the brainstem which synapses with the cochlear nucleus. From here, the auditory sense eventually reaches the medial geniculate nucleus and then into the auditory cortex. If this occurs, it is very incidental and very rare.
What to keep in mind is that, during slow wave sleep, neuron activity significantly slows down. Neurotransmittesr such as norephinephrine, serotonin, and histamine are at very low reproductive states. However, during REM, ACh fire rapidly, producing a dreaming state, but the monoamine cells stop firing altogether. Do not confuse this with what I said above; ACh does not fire during the first few stages of sleep, but only in REM period.
Proprioception occur's within the cerebellum, which is facilitates by monoamine cells. Since there is no production of monoamine cells within the period of dreaming, propriocetion is impossible. If there is any sense that you feel your body or are "aware" of it, it is most likely your memory recalling the sense. Primarily, your memory facilitates all that occur's within your dreaming states and your sensory perception - hence why you dream in a visual state.
If you woud like links to references I have used or experiments done to discover the senses activity during sleep, please just ask.
I hope I have been enlightening.
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