James L. McClelland Walter Van Dyke Bingham Professor, Psychology and Computer Science (CMU), Adjunct Professor of Neuroscience and Center for Neuroscience(Pitt) Carnegie Mellon University Phone: (412) 268-3157 Fax: (412) 268-5060 Email: mcclelland@cmu.edu Individual Website: http://www.cnbc.cmu.edu/~jlm

Ph.D., University of Pennsylvania Research Interests My research addresses a broad range of cognitive neuroscience issues in learning, memory, language and cognitive development. I view cognitive functions as emerging from the parallel, distributed processing activity of neural populations, with learning occurring through the adaptation of connections among participating neurons. Research opportunities in my lab revolve around efforts to develop explicit computational models based on these ideas; to test, refine, and extend the principles embodied in the models; and then to apply the models to substantive research questions through behavioral experiment, computer simulation, functional brain imaging, and mathematical analysis. One line of research in my lab was inspired by the striking pattern of spared and impaired memory in patients with damage to the hippocampal region, suggesting that different parts of the brain play different, specialized roles in memory. With a neuroscience colleague and a student, we suggested that the hippocampus and neocortex may play complementary roles in learning and memory. The neocortex uses a very gradual learning procedure that allows it to exploit the structure in ensembles of inputs. The hippocampus is needed to complement the neocortex, providing a mechanism for rapid learning of the specific arbitrary aspects of particular items. The results of this rapid learning are gradually integrated into the neocortical system, accounting for the pattern of retrograde amnesia seen in many amnesic patients. We are now considering how the neocortex may learn and represent semantic knowledge, addressing children's acquisition of knowledge of living things and the deterioration of this knowledge in dementia. Developmental data suggest a progressive differentiation of concepts: We distinguish animals from plants before we distinguish birds from fish, or canaries from robins. In semantic dementia this trend reverses, so that the finer distinctions are lost before more general ones. These findings coexist with the fact that in some tasks, there appears to be a priority for accessing and naming concepts at an intermediate ("basic") level of specificity (e.g., bird is more accessible than animal or robin). Current work with a student in the lab addresses all these phenomena in a single model, where they reflect the interplay of frequency and concept similarity in determining the semantic representations of concepts and the ease with which distinct names may be assigned to them. Another project considers why the neocortical learning system in adults, clearly capable of learning in many cases, nevertheless shows some important failures. We focus on the failure of Japanese adults to learn the distinction between /r/ and /l/ as an example. Some approaches suggest this failure reflects a simple switching off of learning about speech sounds as a function of age or puberty. We suggest that it may reflect, at least in part, a characteristic of the neural mechanism that underlies learning, which may be based on Hebbian synaptic modification: when one neuron participates in firing another, the connection between them is strengthened. This form of learning can tend to strengthen a network's tendency to keep doing what it is already doing. Thus, Japanese adults' tendency to perceive /r/ and /l/ as the same may simply be strengthened each time they hear either sound. A model implemented by a student in my lab shows how these ideas, in conjunction with some other biologically motivated assumptions, can lead to failure to learn new phonemic distinctions in adulthood. The model suggests training methods that may allow adults to learn such distinctions. We are beginning to test the efficacy of these methods, with initially positive results. Recent Publications McClelland, J. L., Fiez, J.A. and McCandliss, B. D. (2002). Teaching the /r/-/l/ discrimination to Japanese adults: behavioral and neural aspects. Physiology & Behavior, 77, 657-62. McCandliss, B. D., Fiez, J. A., Protopapas, A., Conway, M., and McClelland, J. L. (2002). Success and failure in teaching the [r]-[l] contrast to Japanese adults: Predictions of a Hebbian model of plasticity and stabilization in spoken language perception. Cognitive, Affective and Behavioral Neuroscience. 2:2. 89-108. McClelland, J. L. and Rogers, T. T. (2003). The Parallel Distributed Processing Approach to Semantic Cognition. Nature Reviews Neuroscience, 4, 310-322. McClelland, J. L. and Patterson, K. (2002). Rules or Connections in Past-Tense inflections: What does the evidence rule out? Trends in Cognitive Sciences, 6, 465-472.