The American psychiatrist Jonathan
Winson believes in a connection between the neurophysiological processes of
the brain (specifically, of the hippocampus) and the unconscious, which lends
Freud's psychoanalytical theories biological plausibility.
Winson details neuroanatomical evidence in favor of his theory. The neocortex processes sensory input and sends it to the hippocampus, that acts as a gateway to the limbic system. The limbic system mediates between sensory input and motor output. Initially, the hippocampus is needed to retrieve information stored in long-term memory, but, after about three years, the brain somehow learns how to access directly such information. During REM sleep, the time when we dream, the neocortex is working normally, except that movement in the body is inhibited. Most mammals, except for primates, exhibit a theta rhythm in the hippocampus (about 6 times per second) on two occasions: whenever they perform survival-critical behavior, and during REM sleep.
From this evidence, Winson deduces that REM sleep must be involved in survival-critical behavior. Early mammals had to perform all their "reasoning" on the spot ("on-line"). In particular they had to integrate new information (sensory data) with old information (memories) immediately to work out their strategies. Winson speculates that at some point in evolution brains invented a way to "postpone" processing sensory information by taking advantage of the hippocampus: REM sleep. Theta rhythm is the pace at which that ("off-line") processing is carried out. Instead of taking input from the sensory system, the brain takes input from memory. Instead of directing behavior, the brain inhibits movement. But the kind of processing during REM sleep is the same as during the waking state. Winson speculates that this off-line processing is merging new information with old memories to produre strategies for future behavior. Theta rhythm disappeared in primates, but REM sleep remained as a fundamental process of brains. In humans, therefore, REM sleep, i.e., dreams corresponds to an off-line process of integration of old information with new information. From an evolutionary point of view, REM sleep helped the brain "remembering" important facts without having to add cortical tissues. Dreaming is an accidental feature that let us "see" some of the processing, although only some: a dream is not a story but a more or less blind processing of the day's experience.
Winson goes as far as to suggest that all long-term memory may be constructed through this off-line process (i.e., during REM sleep). During sleep, the hippocampus would process the day's events and store important information in long-term memory.
There is a biologically relevant reason to dream: a dream is an ordered processing of memory which interprets experience that is precious for survival. Dreaming is essential to learning.
Winson relates this off-line process that operates during sleep with Freud's subconscious. Winson offers neurobiological support for the idea that dreams are the bridge between the conscious and the unconscious. The Freudian subconscious is the phylogenetically ancient mechanisms involving REM sleep, in which memories and strategies are formed in the prefrontal cortex.
The book's weakest part is the recapitulation of Freud's theory of the subconscious, which is completely redundant and unnecessary. Winson goes out of his way to reconcile his own impressive intuitions with an obsolete and unscientific theory. This part of the book only proves how powerful dogmas are. Winson could have as well proven that there is a neurobiological foundation for the ancient Greeks' view of the brain. The truth is that Freud was as far as anybody else from understanding what dreams are and how the brain works.