Neuropsychiatry and neurophilosophy.

The objective of neuropsychiatry is to understand the diseased brain so that it can be healed. The seemingly loftier purpose of neurophilosophy is to understand the human mind and indeed consciousness on the basis of brain function. The two disciplines concur that we do not need to look beyond brain science to understand the mind. The ghost in Gilbert Ryle’s machine has been securely laid to rest. Modern philosophers have, moreover, gone beyond the indulgence of armchair examinations of their own thinking to understand consciousness and have armed themselves with neuroscientific knowledge with increasing sophistication. In this climate of ever-dissolving interdisciplinary boundaries then, how might neuropsychiatry contribute to the understanding of mind and consciousness? The time-honored approach of neuropsychiatry has been to attempt to delineate the consequences of part impairment of the brain. The neuropsychiatrist observes the consequent disturbance in behavior, emotion or cognition, and relates it to neurophysiological disturbance. Implicit in this is the realization that mind and consciousness are not unitary concepts, and disturbances in them are not categorical in nature. Indeed, the neuropsychiatrist does not venture to define the mind’ or consciousness’, recognizing that philosophers’ attempts to do so have generally imposed a limitation on their conceptualization, and in fact colored the concepts with the tint of their own spectacles. Furthermore, the neuropsychiatrist is not mesmerized by how easy’ or hard’ a problem is. His/her concern is with the empiricism of the problem and whether the scientific method is applicable. Many philosophers may not appreciate the salient contributions neuropsychiatry has made to the neurophilosophical debates. The work of Broca and Wernicke in the 19th century firmly put the study of higher brain functions on the agenda and began the challenge to the prevalent mind–brain dualism. The brain was now seen as an information processing machine capable of generating the mental functions that were hitherto mysterious and beyond scientific inquiry. The development of psychosurgery in the 1930s was a clear announcement of the neurophysiology of the mind, and while it suffered many attacks from psychodynamically oriented psychiatry, it had opened the mind to scientific dissection (1). The introduction of psychotropic drugs in the 1950s, and their rapid acceptance by the medical community, announced the physical basis of many mental phenomena and moved the debate to the ultrastructural level. While these developments made mind and consciousness legitimate areas for scientific inquiry, the study of consciousness continued to be dominated by philosophical debates uninformed by science. This changed with the work on the split brain by Sperry and et al. (2), which showed that consciousness depended upon the anatomical connections in the brain, and each hemisphere could be described as having its own integrated awareness. It also became clear that the brain processed a great deal of information unconsciously – a kind of non-Freudian unconscious that of course begged the question about the elements that brought some of these brain processes to conscious awareness. The split brain studies, helped by the evidence for the lateralization of language, spawned an abundance of literature on the specialization of the cerebral hemispheres. It has even been conjectured that this lateralization of mental functions may be the essence of being human and has placed a massive distance between us and the ape (3). Miller (4) explores this through the paradigm of binocular rivalry, which elegantly shows the brain’s ability to switch between hemispheres and to disambiguate overlapping objects. Neuropsychiatry provided the model of examining the effects of brain lesions on mental functioning. There have been some outstanding stories that emerged from this approach. The famous case of H.M., an epileptic man who had bilateral temporal lobe surgery, informed us a great deal about the neuroanatomical basis of episodic memory (5). Phineas Gage, a 25-year-old construction worker