The relative isolation from the world of biological psychiatry, specifically, the fields of neurochemistry and neurophysiology has been a cogent criticism of classical psychoanalytic theory and practice. It is important to remember that until the early 1950s' psychoanalysis could not be justifiably reproached for this deficiency as the state of the art did not allow for convincingly alternative modes of scientific or empirical explanation. Though the advances in the second half of the 20th century in the biological realm have been enormous, not enough is really known to explain fully and adequately the nature and meaning of mental phenomena. Its promise has yet to be fulfilled. However, though the end point of ultimate scientific knowledge has not been reached, it remains our responsibility to explain the phenomena of nature as best we can, given the knowledge that is already available.

A significant advance in the field of neurophysiology was the serendipitous discovery in 1953 by Aserinsky and Kleitman of the