Functional Neuroimaging and its Implications for Cognitive Science: Beyond Phrenology and Localization

Functional Neuroimaging and its Implications for Cognitive Science: Beyond Phrenology and Localization Ahmad Sohrabi (asohrabi@connect.carleton.ca) Institute of Cognitive Science, Carleton University, 1125 Colonel By Drive, Ottawa, ON K1S 5B6 Canada Andrew Brook (abrook@ccs.carleton.ca) Institute of Cognitive Science, Carleton University, 1125 Colonel By Drive, Ottawa, ON K1S 5B6 Canada Abstract The localization approach in neuroimaging is an attempt to find where a cognitive function is located in a specific area of the brain, which seems to be similar to an old effort, called phrenology, to relate the skull bumps to specific mental faculties. Using neuroimaging just to find “where” a function occurs doesn’t tell us much about “what” that function is and “how” it happens. The localizationist view has been criticized especially because of the dynamic nature of mind, the difficulty in definition and decomposition of cognitive functions, and the distribution of brain areas involved in most cognitive processes. In the present article, we are pointing out some problems with localizationist approach and trying to show the proper use of functional neuroimaging, especially fMRI, in the study of neural correlates of cognition. We discuss the application of functional neuroimaging as a part of interdisciplinary methods in cognitive science. Keywords: Neuroimaging; fMRI; localization; methodology Introduction [T]o state it [mind—brain relation] in elementary form one must reduce it to its lowest terms and know which mental fact and which cerebral fact are, so to speak, in immediate juxtaposition (James 1890, p. 177). In their quest for mind-brain relation, researchers have long employed various neuropsychological and neurophysiol- ogical methods such as lesion studies, electrical and magnetic recording, and direct stimulation of the brain. However, only recently has a relatively reliable measure- ment of the neural correlates of cognitive processes been possible. Despite some controversies in its success, a new neuroscientific method known as functional neuroimaging has attracted much attention among researchers interested in taking into account the brain activation in studying cognition. The most used functional neuroimaging methods are those based on the energy consumption of the brain While subjects are performing cognitive tasks. The increase in energy consumption of the brain elevates the regional Cerebral Blood Flow (rCBF) which is used in the Positron Emission Tomography (PET) and Single Photon Emission Computed Tomography (SPECT). The PET and SPECT are based on the injected radiotracers that make them invasive and limited but still powerful in some cases. A more recent method that is noninvasive is the fimctional Magnetic Resonance Imaging (fMRl). There are many fMRI methods with special applications but the most popular one is based on the Blood Oxygenation Level—Dependent (BOLD) 2044 response. The BOLD response is a function of the rCBF, blood volume, and especially deoxygenation of hemoglobin. Decrease in deoxyhemoglobin, which is paramagnetic, leads to the inhomogeneity of the local magnetic field in a way that can be measured by the receiver of the MRI scanner to create a map of the brain activation. Since the first functional neuroimaging studies using PET and fMRI in the 1980s and 1990s, respectively, many scientists have looked at the brain areas involved in a wide range of the mental functions, from word and face recogn- ition to morality and religion. Apparently, the simple applications of these methods have been the search for specific areas activated by cognitive tasks. Using these techniques to find the locations of cognitive processes is similar, to some extent, to the old effort of localization that has long been tried in neuroscience and psychology. In this article, we review some problems with the localizationist approach and then discuss the possibility of using neuroima- ging, especially the fl\/[RI in conjunction with the cognitive theories, to go beyond simple localization by looking for the complex and dynamic neural correlates of cognition. Localization and Phrenology The assumption in localization approach is that cognitive fimctions are modularly located in the specific areas of the brain. One of the first localizationist methods was phrenology proposed by Gall at the end of 18”‘ century (c.f., Hubbard, 2003; Uttal, 2001). Gall as the leader of phrenology claimed that the mental faculties are located in the specific brain areas and are detectable by looking at the skull bumps (e.g., Gall and Spurzheim 1806/1967). This approach finally turned out to be false but other forms of localization still continue nowadays. Issues related to the localization view are very important for cognitive science (c.f., Hubbard, 2003; van Gelder, 1999) especially because they are related to the age old debates on the mind-brain (or the fimction-structure) relations. It seems that there are two extremist views related to localization. The scientists with the first view argue for the existence of modular and encapsulated domains in the mind (Fodor, 1983), regardless of their neural bases. This classical functionalist theory of cognition is called “the fimctionalism Without identity” by Bechtel (2002). In this sense, understanding of a function is possible without knowing the related structure. Another extremist approach, but using neuroscientific methods especially functional

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