To further the understanding of how the brain operates at the most basic level of interest to human communication theorists, intrapersonal communication, this paper reviews the arguments against the hemispheric dominance theory and for a neurological processing style model of brain functions and then focuses on the impact of the corpus callosum (a thin band of fibers which coordinate the functions of the two hemispheres) as a feature of communication within the brain itself. Topics covered in the paper include the following: (1) the two competing perspectives on the brain--the simple left-brain right-brain view and MacLean's triune brain (reptilian, paleomammalian, and neomammalian); (2) assessment of the intrapersonal communication system by beginning at the preverbal stage; (3) the role of the brain in understanding intrapersonal communication processing; (4) modularity of brain function and intrapersonal communication; (5) interhemispheric cooperation; and (6) interhemispheric dissonance. The paper concludes that intrapersonal communication should not be regarded as either oxymoronic or all-inclusive, because the communication among brain modules--where modules may or may not interact, exert control over one another, compete, or cooperate--is indeed a form of intrapersonal communication. Seven pages of references, a table of brain functions and structures, and a diagram of the triune brain conclude the paper. (SKC)