In my dissertation, I examine the historical development from the seventeenth to the nineteenth century of the notion of the neural subject, or the scientific and philosophical identification of subjectivity with the states and processes of the brain alone. I do so by focusing specifically on the brain itself, by looking at the ways the concept of the brain has been thought to situate different and historically changing conceptions of subjectivity. Instead of regarding the brain as an anatomical organ whose biology naturally gives way to mental and affective properties, I approach the brain more broadly as a conceptual and formal site that, in one way or another, historically encapsulated scientific and philosophical formulations of the human subject. In this sense, I examine the concept of the brain in terms of the ways in which it has been topologized, or abstractly spatialized as the location of the subject, often according to complex, even paradoxical relations of proximity, envelopment, and interiority/exteriority that belied, to a degree, strictly physical or physiological descriptions of brain matter.
Modern formulations of the brain and the nervous system have relied upon complex and abstract spatial schematizations in order to define the intricate operations and objectives of neurophysiology. These often implicit topologies indexed not only the brain's biological complexity, but its conceptual overextension as a space that had to circumscribe and embody numerous anatomical and conceptual possibilities and even divergent ontologies. Even the most concrete formulations of the space of the brain as a localizable topography, or map, of biological structures with corresponding psychological functions often hid more complex topological configurations which could not in themselves be expressed in coherent or tangible material terms. The brain not only encapsulated the conditions of subjectivity, but it defined the contours of the most intricate physical, cognitive, social, and even ethical convergences. In this way, more than resolving the question of how the brain could localize the cognitive and affective dimensions of the subject, this dissertation shows how the brain actually demarcated the very problem of spatializing the subject in any way other than according to the most complex topological formulations -- that the brain was itself only ever a formal problem of space.
In the dissertation, I closely examine three different historical conceptions of the brain as an abstract space of subjectivity. In each, the brain assumed a complex topological formation that encapsulated a number of different anatomical, organizational and even ontological conditions. I first look at René Descartes' formative neuroanatomy and specifically his controversial doctrine of the pineal gland. The pineal gland constituted the space that could properly stage the ontological conjoining of body and soul into a distinctly human subject. The gland was no ordinary anatomical region, but had to take on an ontologically transitive and ecstatic dimensionality, a topological configuration that could not entirely cohere with a Cartesian conception of matter. The second conception I examine was prevalent from the end of the seventeenth century to the early-to-mid eighteenth century. During this period, the brain underwent a kind of conceptual retreat and was defined either directly according to a relatively diffuse definition of living matter, or indirectly through an increased emphasis on the pervasive functionality of the nervous system. The brain was conceptually and materially dispersed, and this dispersion was embodied in the concept of the sensorium commune, or the abstract space of organizational unity. Many notable neurophysiologists, including Albrecht von Haller and Robert Whytt imagined that the brain materially unified and substantiated the theoretical unity of the subject by constituting the space not only in which sensory perceptions were unified, but where the vital, mental and even social properties of the subject were all brought together and "rendered common," so to speak. In the final chapter, I examine how, throughout the early-to-late nineteenth century, the nervous system was abstractly spatialized as a hierarchy of vertical levels of neurological organization and complexity. The vertical spatialization of the nervous system was described by a variety of biologists, neurologists and philosophers during the period, including Franz Gall, Herbert Spencer, and John Hughlings Jackson. But this vertical paradigm actually concealed a more challenging micro-topological problem within the spaces that separated one level from another. These abstract, though relatively buried spaces at the lowest levels of the nervous system demarcated a fundamental material complexity, where physical abstractions implicitly led to the most incipient psychical emergences.
The episodes I outline mark a trajectory representing a gradual change in the notion of neurobiological matter, a change defined as a move towards a state of greater abstraction. The materiality of the brain and nervous system, particularly by the end of the nineteenth century, began to acquire extra-material or non-corporeal properties and slowly embodied a physicality that could be defined only in more and more abstract, topological terms. I end the dissertation by showing how these new conceptions of neurobiological matter did not necessarily constitute an impasse for neuroscience but were incorporated into new theorizations of the brain itself.