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The Neurological Turn: Top-Down or Bottom-Up? (April 2023): Bottom-up Reductionism

By Heidi Storl

Bottom-up Reductionism

The magnitude of empirical data generated by the neurosciences remains unquestioned. The enormity of facts is evident in the large number of databases dedicated to integrating this evidence into a coherent format that is readily accessible. As an example, consider NIF: Neuroscience Information Framework, which announces itself as “bring[ing] together 16 NIH institutes, centers and offices that support neuroscience research into a collaborative framework to coordinate their ongoing efforts and to plan new cross-cutting initiatives.” The creators of NIF “recognized that a framework for identifying, locating, relating, accessing, integrating, and analyzing information from the neuroscience research enterprise is critical to enhancing cooperative activities in the neurosciences.” Thus was born the initiative known as the Neuroscience Information Framework. The default framework underlying most of these databases and the work that is represented therein is largely representative of a “bottom-up” approach. In other words, if the neural processes for facial recognition, memory loss, anxiety, empathy, and, ultimately, consciousness can be identified, then these diverse and often-complex experiences can be successfully “reduced” to a more basic form. Although it is widely recognized that necessary and sufficient conditions are unlikely to surface for such experiences, reliable probabilistic causes are not beyond discovery. 

Evidence for this reductive framework is readily found in the relatively brief history of neuroscience. As early as the mid-1800s, Paul Broca and Carl Wernicke discovered the location of two key speech-related areas of the brain. Similarly, Wilder Penfield’s famous localization of conscious experiences associated with different senses and bodily movement serves as a now-classic example of the reductionist, or bottom-up, strategy. Most recently, Sara Manning Peskin’s A Molecule away from Madness and Guy Leschziner’s The Man Who Tasted Words provide accessible insight into the neurochemical, neuroanatomical, and neurophysiological basis of reductionist approaches. Peskin, a practicing neurologist, encourages her reader to imagine “molecular villains” that are “nimble in hijacking” normal brain functions in such common maladies as Alzheimer’s disease and other forms of dementia. The hard science that underlies the work of Peskin is nicely captured in Karl Herrup’s How Not to Study a Disease: The Story of Alzheimer’s. Herrup, a neurobiologist, offers keen insight into the successes and failures of common research programs and protocols, and suggests a new direction for future research into this affliction. More generally, the structural, functional, and computational components of the brain and its processes are admirably captured by Edmund Rolls in Brain Computations: What and How and in MIT Press’s monthly peer-reviewed journals Neural Computation and Network Neuroscience. Each of these sources offers deep insight into the reductionist, bottom-up approach to the nature of sensation, perception, emotion, and cognition. The new interdisciplinary and multidisciplinary NeuroPhilosophy: An Interdisciplinary Journal of Neuroscience and Philosophy is also worth notice. Edited by Patricia Churchland, author of Neurophilosophy: Toward a Unified Science of the Mind-Brain, and Sultan Tarlaci, author of Neuroquantology: Quantum Physics in the Brain, NeuroPhilosophy aims to provide critical analysis and original research related to many topics at the intersection of theoretical and practical inquiry in neuroscience and philosophy. 

Each of the aforementioned processes—sensation, perception, emotion, and cognition—plays a central role in human behavior. Emergent behaviors are the subject of several noteworthy, reductionist or quasi-reductionist works. Whereas discussion of behavior invites consideration of the “up” of bottom-up approaches, the framework continues to account for behavior in physicalist terms. Hagai Bergman’s The Hidden Life of the Basal Ganglia: At the Base of Brain and Mind is a good example of this. Bergman demonstrates how the basal ganglia and associated mechanisms inform various disease-based behaviors, such those associated with Parkinson’s disease, but also offers insight into such deeply philosophical questions as free will and human responsibility. An equally interesting foray into the emergence of human behaviors is Giorgio Vallortigara’s Born Knowing. Since before Descartes, philosophers and scientists have wrestled with the question of whether there are inherent forms of knowing, or innate knowledge. In his famous Meditations on First Philosophy (first published in Latin in 1641), Descartes committed to the idea of content “perceived by the mind alone.” Defenses of such a priori forms of knowledge came under swift attack by early (and later) empiricists such as John Locke, who proposed that the mind was a tabula rasa, a blank slate, on which only direct experience made a mark. Vallortigara joins this longstanding debate by arguing that the mind/brain is not a Lockean blank slate. According to Vallortigara, early behaviors are biologically predisposed, instinctive, innate. It is our history as a species that informs our very first behaviors, not our individual experiences.

To conclude discussion of bottom-up orientations to the ongoing, rapid accumulation of neuroscientific findings—as well as the ongoing pesky questions involving nature of mind, self, and other—several works offer more general overviews. A quick introduction is available in Zoltan Torey’s The Conscious Mind. In this text, Torey enriches work from his earlier The Crucible of Consciousness: An Integrated Theory of Mind and Brain to conclude that the mind “is an exclusively human neural system, first instantiated when, empowered by the motor-wiring of the speech-areas, the brain gained access to itself” (from chapter 9). For a more comprehensive overview, the work of Paul Thagard, well known for his thoroughgoing naturalist approach to perceptions, intentions, emotions, and other “mental states,” is highly recommended. Thagard’s approach to the fundamental characteristics of consciousness is captured in a series of three stand- alone but interrelated texts: Brain-Mind: From Neurons to Consciousness and Creativity; Mind-Society: From Brains to Social Sciences and Professions; and Natural Philosophy: From Social Brains to Knowledge, Reality, Morality, and Beauty. In the preface to Brain-Mind Thagard writes that he “presents a unified, brain-based theory of cognition and emotion with applications to the most complex kinds of thinking, right up to consciousness and creativity.” Mind-Society offers neuropsychological descriptions and explanations of central phenomena discussed in such diverse disciplines as sociology, politics, economics, medicine, law, and education. And, as suggested by its title, Natural Philosophy connects naturalism to some larger philosophical themes. In so doing, Thagard also incorporates key insights from psychology, cognitive science, the computational theory of mind, and, of course, neuroscience. Intriguingly, though Thagard moves in a bottom-up direction—from neurons to most facets of human being—he characterizes his goal in this trilogy as one that harmonizes “the cognitive sciences, social sciences, professions and humanities as a coherent system, not to reduce one to the other.” The method that enables this approach is based in large part on the work of Chris Eliasmith’s Semantic Pointer Architecture, in which a semantic pointer is understood as a neurocomputational process that, Thagard writes, “explains how mental representations might operate in the brain.” Thagard’s trilogy is a go-to for anyone interested in a provocative and engaging introduction to a neuroscientifically based account of who we are, what we do, and perhaps why we have evolved as we have. 

Works Cited