M. Chirimuuta -- Heraclitean Brain Forthcoming in Massimi & McCoy (eds.) Understanding Perspectivism

The mainstream theory of the motor cortex is a computational and representational one, but it has been called into question because of an unresolved dispute over whether neurons in this region represent patterns of muscle activation or other movement parameters such as limb velocity. Some neuroscientists have recently argued that the representational theory should be replaced with a dynamical systems one. Here I argue that both of these scientific perspectives are responses to the challenge of constructing relatively simple models of the brain, a system which is extremely complex in the “Heraclitean” sense that its structure and functions are continually changing with experience and never precisely re-occur. Because each of these perspectives employs different assumptions in order to make the task of modeling the brain tractable, they result in different and apparently inconsistent “pictures” of what the brain/mind is like—either an information processor analogous to a computer or a non-representational dynamical system. I discuss proposals to reconcile these perspectives and consider whether any non-perspectival insights about the nature of the brain/mind can be derived from these models. 1. Perspectivism and the Demands of Simplification It is a frequently stated fact that the human brain is the most complicated object in the known universe; yet it is unclear whether or not this “fact” is a by-product of human vanity or hype drummed up by neuroscientists. To the neurologist Kurt Goldstein it was not obvious that an M. Chirimuuta -Heraclitean Brain Forthcoming in Massimi & McCoy (eds.) Understanding Perspectivism 2 invertebrate is more simple than a man, and for that reason he saw no obstacle to selecting the human being as his model organism (Goldstein 1939, 2). 1 The point is that, since everything in nature is in its own way complicated, claims for complexity need to be made specific. Here I will argue that an important respect in which the brain is complex is that it is Heraclitean. By this I mean that the brain, like the Heraclitean river, is the kind of thing that can only maintain its identity by undergoing continual change. John Dupré (2012) has argued that all living organisms should be characterized in this way, that is, as processes rather than entities. In addition, Peter Godfrey-Smith (2016) proposes that the Heraclitean nature of biological cells has important implications for how we understand cognition: it is the important difference between the nervous system and man-made computers. The fact that the brain is made of living tissue such as neurons (an electrically excitable type of biological cell), means that its constitution is constantly changing with metabolism. As Marder and Goaillard (2006, 563) describe, “each neuron is constantly rebuilding itself from its constituent proteins, using all of the molecular and biochemical machinery of the cell. ” Godfrey-Smith’s idea is that the inherent changeability of biological tissue was leveraged during the evolution of the nervous system, as a means for learning and coping with the challenge of staying alive in an unstable world, and is an important factor in making biological “computation” what it is. This, he argues, puts limits on the functional equivalence between brains and artificial computers. Looking outside the cranium, John Haugeland (1996) has argued that the fact that the brain is densely inter-connected with a mobile body, itself operating in an ever-changing environment, means that the mappings between “inner” neural states and “external” consequences may be 1 In the case of C. elegans, a tiny worm, it seems that Goldstein is vindicated by current neuroscience: “A counterintuitive finding in C. elegans is that there is no such thing as ‘simplicity’ despite the reduced connectome (302 neurons, 6963 synapses, 890 gap junctions), even at the earliest stage of sensory processing. ” (Frégnac 2017, 473) M. Chirimuuta -Heraclitean Brain Forthcoming in Massimi & McCoy (eds.) Understanding Perspectivism 3 constantly evolving. This is more contentious than the biological argument because, as we will see, the empirical evidence for the presence or lack of stable mappings is not conclusive. What is uncontroversial, however, is that science thrives when complex things can be made to seem simple. Various authors have made the case that complex systems, especially those studied in the biological and behavioral sciences, afford modeling from a variety of perspectives because no one set of theoretical or experimental practices gives the scientist access to all of the relevant phenomena in the domain of interest.2 Here I build on this work by emphasizing not only the way that scientific perspectives “passively” filter out details not relevant to their own theory and practice but also the way that they “actively” impose simplifying assumptions onto the target system.3 My case study in section 2 presents the ongoing controversy between two perspectives on the motor cortex as amounting to a difference in choice of methods selected to cope with the brain’s Heraclitean nature. The assumptions embedded in each modeling perspective are effective ways to simplify the brain, but they lead to views about the function of motor cortex that are apparently contradictory. In section 3 I discuss the philosophical implications of this clash of perspectives. Does it follow that there are non-perspectival truths about the motor cortex (and by extension, the primate brain) that are unknowable to science? In section 4 I voice some support for this Kantian conclusion by presenting a general framework for thinking about the operation of abstraction in