These are colloquially known as "wet dreams".The visual nature of dreams is generally highly phantasmagoric; that is, different locations and objects continuously blend into each other. The visuals (including locations, people, and objects) are generally reflective of a persons memories and experiences, but conversation can take on highly exaggerated and bizarre forms. Some dreams may even tell elaborate stories wherein the dreamer enters entirely new, complex worlds and awakes with ideas, thoughts and feelings never experienced prior to the dream. People who are blind from birth do not have visual dreams. Their dream contents are related to other senses like hearing, touch, smell and taste, whichever are present since birth. Neurophysiology
Dream study is popular with scientists exploring the mind–brain problem. Some "propose to reduce aspects of dream phenomenology to neurobiology." But current science cannot specify dream physiology in detail. Protocols in most nations restrict human brain research to non-invasive procedures. In the United States, invasive brain procedures with a human subject are allowed only when these are deemed necessary in surgical treatment to address medical needs of the same human subject. Non-invasive measures of brain activity like electroencephalogram (EEG) voltage averaging or cerebral blood flow cannot identify small but influential neuronal populations. Also, fMRI signals are too slow to explain how brains compute in real time.Scientists researching some brain functions can work around current restrictions by examining animal subjects. As stated by the Society for Neuroscience, "Because no adequate alternatives exist, much of this research must be done on animal subjects."
Etymology
The word "dysphagia" is derived from the Greek dys meaning bad or disordered, and the root phag- meaning "eat". See also
Aphagia
MEGF10
Pseudodysphagia, an irrational fear of swallowing or choking

References
External links
Dysphagia at Curlie