Is there a neural basis for borderline splitting?

It is proposed here that borderline splitting and borderline pathology may have a neural basis. For the infant who splits its emotional and cognitive constitution of its mother during separation-individuation, the "good mother"--"bad mother" engram may be lateralized in the brain in a different way than for an infant who does not use this defense. The infant may be developmentally vulnerable to the effects of splitting during separation-individuation (18 to 36 months) because interhemispheric communication necessary for mental unity is not possible at this time, since neurons connecting left and right hemispheres are not totally myelinated and because the infant has not yet fully acquired language, a prerequisite for an integrated psychological reality. Two separate, unintegrated--and alternating--mental systems may come into being. Later, as myelination is completed, the infant's split emotional and cognitive constitutions of mother and of self may create a neural "template" for splitting all further experience and behavior through the two separate, alternating mental systems. The possibility that emotional trauma occurring later than separation-individuation, and involving other issues, may be the occasion for splitting is considered, as well as the possibility that a congenital abnormality in brain structure or function may be a primary factor in borderline pathology. Ways to test the hypothesis that borderline splitting has a neural basis are suggested.