title: Neural Decoding and "Inner" Psychophysics: A Distance-to-Bound Approach for Linking Mind, Brain, and Behavior.
abstract: A fundamental challenge for cognitive neuroscience is characterizing how the primitives of psychological theory are neurally implemented. Attempts to meet this challenge are a manifestation of what Fechner called "inner" psychophysics: the theory of the precise mapping between mental quantities and the brain. In his own time, inner psychophysics remained an unrealized ambition for Fechner. We suggest that, today, multivariate pattern analysis (MVPA), or neural "decoding," methods provide a promising starting point for developing an inner psychophysics. A cornerstone of these methods are simple linear classifiers applied to neural activity in high-dimensional activation spaces. We describe an approach to inner psychophysics based on the shared architecture of linear classifiers and observers under decision boundary models such as signal detection theory. Under this approach, distance from a decision boundary through activation space, as estimated by linear classifiers, can be used to predict reaction time in accordance with signal detection theory, and distance-to-bound models of reaction time. Our "neural distance-to-bound" approach is potentially quite general, and simple to implement. Furthermore, our recent work on visual object recognition suggests it is empirically viable. We believe the approach constitutes an important step along the path to an inner psychophysics that links mind, brain, and behavior.
authors.affiliation: Laboratory of Biological Psychology, Brain and Cognition Unit, KU LeuvenLeuven, Belgium; Department of Philosophy, University of MarylandCollege Park, MD, USA.
authors.forename: J Brendan
authors.initials: JB
authors.lastname: Ritchie
authors.affiliation: Perception in Action Research Centre, Department of Cognitive Science, Macquarie UniversitySydney, NSW, Australia; ARC Centre of Excellence in Cognition and its Disorders, Macquarie UniversitySydney, NSW, Australia.
authors.forename: Thomas A
authors.initials: TA
authors.lastname: Carlson
keywords: MVPA; inner psychophysics; reaction times; signal detection theory; visual object categorization