Proceedings of the Annual Meeting of the Cognitive Science Society

With the recent ability to construct fault tolerant computer models using connectionist approaches, researchers are n o w able to investigate the effects of damage to these models. This has great appeal for cognitive science as it provides a further way to verify or falsify a computer model. Existing studies employ a concept of network "lesioning" that fails to have explanatory adequacy for neurobiology. While using anatomically plausible architectures for cognitive models, they nonetheless use biologically implausible methods for simulating neurological damage to these networks. This paper examines the different objects of computational networks and their analogical neurobiological counterparts, and suggests a taxonomy of connectionist network lesion methods. Finally, an existing visual system model is used as a testbed to study the differential effects of focal and diffuse lesions. Tlie exj)erimcnts with focal damage versus diffuse damage suggest that while the effects of focal brain injury m a y be due to the particular computations performed in some brain area, the effects of diffuse brain injury or degeneration may cause cognitive defici ts because of the inherent nature of the brain as a distributed computational device, and not through differential local effects