Modeling Double Dissociation using Widespread, Progressive Damage

Abstract

Introduction Recent work using connectionist models has demonstrated that double dissociations can arise in non-modular systems. For example, Farah and McClelland (1991) damaged perceptual or functional processing units in a network to produce category specific semantic impairments to biological kinds or artifacts, while Plaut (1995) damaged different banks of connections to produce selective impairments of either abstract or concrete nouns. Both of these models used localized damage to simulate behavioral patterns resulting from focal brain damage. A very different etiology, however, can also produce double dissociations. Gonnerman et al. (in press) reported two Alzheimer's subjects, one with a deficit for natural kinds, the other selectively impaired on artifacts. The present study examines whether a model of a single processing system without separable components can produce double dissociations even when the damage to the system is progressive and widespread, as it is in A