How neurons mean: A neurocomputational theory of representational content


Chris Eliasmith

Philosophy-Neuroscience-Psychology Program
Washington University in St. Louis, 2000

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Questions concerning the nature of representation and what representations are about have been a staple of Western philosophy since Aristotle. Recently, these same questions have begun to concern neuroscientists, who have developed new techniques and theories for understanding how the locus of neurobiological representation, the brain, operates. My dissertation draws on philosophy and neuroscience to develop a novel theory of representational content.

I begin by identifying what I call the problem of "neurosemantics" (i.e., how neurobiological representations have meaning). This, I argue, is simply an updated version of a problem historically addressed by philosophers. I outline three kinds of contemporary theory of representational content (i.e., causal, conceptual role, and two-factor theories) and discuss difficulties with each. I suggest that discovering a single factor that provides a unified explanation of the traditionally independent aspects of meaning will provide a means of avoiding the difficulties faced by current theories. My central purpose is to articulate and defend such a factor.

Before describing the factor itself, I summarize the necessary background for evaluating a solution to the problem of neurosemantics. The resulting analysis results in thirteen questions about representation. I provide a methodological critique of the traditional approach to answering these questions and argue for an alternative approach. I discuss evidence that suggests that this alternative provides a better means of characterizing representation.

After having established the nature of the problem and a preferred methodology, I briefly describe my theory of content. I then outline a neurobiologically motivated theory of neural computation that I and others have helped Charles H. Anderson develop. I use the computational theory show how to mathematically define the relations relevant to understanding representational content at various levels of analysis. I then show how this theory can be made philosophically respectable and integrated with the theory outlined earlier. I then answer each of the thirteen questions about representation.

In conclusion, I defend this theory from potential philosophical criticisms. This defense includes an explication of how concepts are to be accounted for on this theory, and a consideration of the problem of misrepresentation. I also show how this theory is immune to the standard critiques facing each of causal, conceptual role, and two-factor theories of content.