Neurophilosophy, or the philosophy of neuroscience, is the interdisciplinary study of neuroscience and philosophy that explores the relevance of neuroscientific studies to the arguments traditionally categorized as philosophy of mind. Recent scientific discourse elucidates the distinction between "neurophilosophy" and "philosophy of neuroscience".
The term was coined by Patricia Churchland in her book, Neurophilosophy: Toward a Unified Science of the Mind–Brain, which was published in 1986 by the MIT Press. Churchland was driven by the mind-body problem, which asks a highly-debated question of how the mind, which drives intangible, nonphysical mental processes, is related to the brain, a physical organ. This problem extends to the understanding of other relatively unknown phenomena, such as decision making, learning, consciousness, existence of free will, as well as other related topics. Churchland originally theorized that the physical brain was clearly relevant and, more importantly, necessary to discovering the nonphysical mind and its related mental processes since the only thing that exists is the physical brain. These beliefs were initially met with contention from contemporary philosophers, who typically misinterpreted her argument. Instead of understanding her argument as "necessary," many philosophers often implied that Churchland argued that a neural underpinning was both "necessary" and "sufficient." This line of thought is not without historical context as many classical philosophers, such as Plato, Descartes, and Chalmers, argued that mind and brain have no connection. Contemporary philosophers often argue that the many undiscovered problems in neuroscience will never allow a mechanism into solving cognition. Churchland argues that proponents of this belief do not understand that the field of neuroscience is relatively young and is bound by the unknowns of chemistry and physics. The philosophy of neuroscience attempts to clarify neuroscientific methods and results using the conceptual rigor and methods of philosophy of science.
Specific issues Below is a list of specific issues important to philosophy of neuroscience: "The indirectness of studies of mind and brain" "Computational or representational analysis of brain processing" "Relations between psychological and neuroscientific inquiries" Modularity of mind What constitutes adequate explanation in neuroscience?Craver, "Explaining the Brain: Mechanisms and Mosaic Unity of Neuroscience" 2007, Oxford University Press, citation: preface vii "Location of cognitive function"Bickle, John, Mandik, Peter and Landreth, Anthony, "The Philosophy of Neuroscience", The Stanford Encyclopedia of Philosophy (Summer 2010 Edition), Edward N. Zalta (ed.), URL = <http://plato.stanford.edu/archives/sum2010/entries/neuroscience/ The binding problem, and the closely related boundary problem
Indirectness of studies of the mind and brain Many of the methods and techniques central to neuroscientific discovery rely on assumptions that can limit the interpretation of the data. Philosophers of neuroscience have discussed such assumptions in the use of functional magnetic resonance imaging (fMRI),Poldrack (2010). "Subtraction and Beyond" in Hanson and Bunzl, Human Brain Mapping. pp. 147–160Klein C. (2010) "Philosophical Issues in Neuroimaging" Philosophy Compass 5(2) pp. 186–198 dissociation in cognitive neuropsychology,Dunn (2003) "The Elusive Dissociation" cortex 39 no. 1 pp. 21–37Dunn and Kirsner. 2003. What can we infer from double dissociations? single unit recording,deCharms and Zandor (2000) "Neural Representation and the temporal code" Annual Review of Neuroscience 23: pp. 613–47 and computational neuroscience.Winsberg (2003). "Simulated Experiments: a Methodology for the Virtual World" Philosophy of Science.vol 70 no 1 105–125 Following are descriptions of many of the current controversies and debates about the methods employed in neuroscience.
fMRI Many fMRI studies rely heavily on the assumption of localization of functionHuettel, Song and McCarthy Functional Magnetic Resonance Imaging 2009 Sinauer Associates pp. 1 (same as functional specialization).
Localization of function means that many cognitive functions can be localized to specific brain regions. An example of functional localization comes from studies of the motor cortex.Passingham, R. E. Stephan, K. E. Kotter, R. "The anatomical basis of functional localization in the cortex" Nature Reviews Neuroscience. 2002, VOL 3; PART 8, pages 606–616 There seem to be different groups of cells in the motor cortex responsible for controlling different groups of muscles.
Many philosophers of neuroscience criticize fMRI for relying too heavily on this assumption. Michael Anderson points out that subtraction-method fMRI misses a lot of brain information that is important to the cognitive processes.Anderson.(2007) "The Massive Redeployment Hypothesis and Functional Topography of the Brain" Philosophical Psychology Vol20 no 2 pp.144–149 Subtraction fMRI only shows the differences between the task activation and the control activation, but many of the brain areas activated in the control are obviously important for the task as well.
Rejections of fMRI Some philosophers entirely reject any notion of localization of function and thus believe fMRI studies to be profoundly misguided.The Massive Redeployment Hypothesis and Functional Topography of the Brain" Philosophical Psychology Vol20 no 2 pp.149–152 These philosophers maintain that brain processing acts holistically, that large sections of the brain are involved in processing most cognitive tasks (see holism in neurology and the modularity section below). One way to understand their objection to the idea of localization of function is the radio repairman thought experiment.Bunzel, Hanson, and Poldrack "An Exchange about Localization of Function" Human Brain Mapping. pp.50 In this thought experiment, a radio repairman opens up a radio and rips out a tube. The radio begins whistling loudly and the radio repairman declares that he must have ripped out the anti-whistling tube. There is no anti-whistling tube in the radio and the radio repairman has confounded function with effect. This criticism was originally targeted at the logic used by neuropsychological brain lesion experiments, but the criticism is still applicable to neuroimaging. These considerations are similar to Van Orden's and Paap's criticism of circularity in neuroimaging logic.VanOrden, G and Paap, K "Functional Neuroimaging fails to discover Pieces of the Mind" Philosophy of science. 64 pp. S85-S94 According to them, neuroimagers assume that their theory of cognitive component parcellation is correct and that these components divide cleanly into feed-forward modules. These assumptions are necessary to justify their inference of brain localization. The logic is circular if the researcher then uses the appearance of brain region activation as proof of the correctness of their cognitive theories.
Reverse inference A different problematic methodological assumption within fMRI research is the use of reverse inference.Poldrack (2006). "Can Cognitive Processes be inferred from Neuroimaging Data"Trends in Cognitive Sciences. vol 10 no 2 A reverse inference is when the activation of a brain region is used to infer the presence of a given cognitive process. Poldrack points out that the strength of this inference depends critically on the likelihood that a given task employs a given cognitive process and the likelihood of that pattern of brain activation given that cognitive process. In other words, the strength of reverse inference is based upon the selectivity of the task used as well as the selectivity of the brain region activation.
A 2011 article published in the New York Times has been heavily criticized for misusing reverse inference.Hayden, B "Do you Really love Your iPhone that Way" http://www.psychologytoday.com/blog/the-decision-tree/201110/do-you-really-love-your-iphone-way In the study, participants were shown pictures of their iPhones and the researchers measured activation of the insula. The researchers took insula activation as evidence of feelings of love and concluded that people loved their iPhones. Critics were quick to point out that the insula is not a very selective piece of cortex, and therefore not amenable to reverse inference.
The neuropsychologist Max Coltheart took the problems with reverse inference a step further and challenged neuroimagers to give one instance in which neuroimaging had informed psychological theory.Coltheart, M(2006b), "What Has Functional Neuroimaging Told Us about the Mind (So Far)?", Cortex 42: 323–331. Coltheart takes the burden of proof to be an instance where the brain imaging data is consistent with one theory but inconsistent with another theory.
Roskies maintains that Coltheart's ultra cognitive position makes his challenge unwinnable.Rooskies, A. (2009). "Brain-Mind and Structure-Function Relations: A methodological Response to Coltheart" Philosophy of Science. vol 76 Since Coltheart maintains that the implementation of a cognitive state has no bearing on the function of that cognitive state, then it is impossible to find neuroimaging data that will be able to comment on psychological theories in the way Coltheart demands. Neuroimaging data will always be relegated to the lower level of implementation and be unable to selectively determine one or another cognitive theory.
In a 2006 article, Richard Henson suggests that forward inference can be used to infer dissociation of function at the psychological level.Henson, R (2006). "Forward Inference Using Functional Neuroimaging: Dissociations vs Associations" Trends in Cognitive Sciences vol 10 no 2 He suggests that these kinds of inferences can be made when there is crossing activations between two task types in two brain regions and there is no change in activation in a mutual control region.
Pure insertion One final assumption is the assumption of pure insertion in fMRI.Poldrack "Subtraction and Beyond" in Hanson and Bunzl Human Brain Mapping pp. 147–160 The assumption of pure insertion is the assumption that a single cognitive process can be inserted into another set of cognitive processes without affecting the functioning of the rest. For example, to find the reading comprehension area of the brain, researchers might scan participants while they were presented with a word and while they were presented with a non-word (e.g. "Floob"). If the researchers then infer that the resulting difference in brain pattern represents the regions of the brain involved in reading comprehension, they have assumed that these changes are not reflective of changes in task difficulty or differential recruitment between tasks. The term pure insertion was coined by Donders as a criticism of reaction time methods.
Resting-state functional-connectivity MRI Recently, researchers have begun using a new functional imaging technique called resting-state functional-connectivity MRI.Wig, Schlaggar, and Peterson (2011) "Concepts and Principals in the Analysis of Brain Networks" Annals of the New York Academy of Sciences 1224 Subjects' brains are scanned while the subject sits idly in the scanner. By looking at the natural fluctuations in the blood-oxygen-level-dependent (BOLD) pattern while the subject is at rest, the researchers can see which brain regions co-vary in activation together. Afterward, they can use the patterns of covariance to construct maps of functionally-linked brain areas.
The name "functional-connectivity" is somewhat misleading since the data only indicates co-variation. Still, this is a powerful method for studying large networks throughout the brain.
Methodological issues