Harvey Cushing and Sigmund Freud shaking hands How electrical brain stimulation became a psychoanalytic method to study the unconscious (1870–1955)

In the first half of the 1950s, psychoanalysts and neurosurgeons used electrical brain stimulation to explore hard-to-reach, unconscious psychological processes such as repressed memories, defence mechanisms and sexual identity. The development of evolutionary theory and neurophysiological methods and theory, together with the birth of psychoanalysis, were important precursors to these remarkable stimulation experiments. Experimental, theoretical and clinical antecedents of these stimulation experiments between the 1870s and the 1940s are discussed to show how smoothly the apparently opposing perspectives of psychoanalysis and neurophysiology merged. Two case studies are then briefly described. It is concluded that this striking and brief collaboration demonstrated a pragmatic and eclectic approach that integrated different theories and methods for a more holistic understanding and treatment of psychiatric disorders.