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The Journal of Neuroscience, November 22, 2006, 26(47):12186-12197; doi:10.1523/JNEUROSCI.2818-06.2006
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Behavioral/Systems/Cognitive
Why Does Brain Damage Impair Memory? A Connectionist Model of Object Recognition Memory in Perirhinal Cortex
Rosemary A. Cowell,1 Timothy J. Bussey,2,3 andLisa M. Saksida2,3 1Department of Experimental Psychology, University of Oxford, Oxford OX1 3UD, United Kingdom, 2Department of Experimental Psychology, University of Cambridge, Cambridge CB2 3EB, United Kingdom, and 3The Medical Research Council and Wellcome Trust Behavioural and Clinical Neuroscience Institute, University of Cambridge, Cambridge CB2 3EB, United Kingdom
Correspondence should be addressed to Rosemary A. Cowell, LEAD–CNRS (UMR 5022), Université de Bourgogne, Pôle AAFE, Esplanade Erasme, 21065 Dijon, France. Email: rosemary.cowell{at}u-bourgogne.fr
Object recognition is the canonical test of declarative memory, the type of memory putatively impaired after damage to the temporal lobes. Studies of object recognition memory have helped elucidate the anatomical structures involved in declarative memory, indicating a critical role for perirhinal cortex. We offer a mechanistic account of the effects of perirhinal cortex damage on object recognition memory, based on the assumption that perirhinal cortex stores representations of the conjunctions of visual features possessed by complex objects. Such representations are proposed to play an important role in memory when it is difficult to solve a task using representations of only individual visual features of stimuli, thought to be stored in regions of the ventral visual stream caudal to perirhinal cortex. The account is instantiated in a connectionist model, in which development of object representations with visual experience provides a mechanism for judgment of previous occurrence. We present simulations addressing the following empirical findings: (1) that impairments after damage to perirhinal cortex (modeled by removing the "perirhinal cortex" layer of the network) are exacerbated by lengthening the delay between presentation of to-be-remembered items and test, (2) that such impairments are also exacerbated by lengthening the list of to-be-remembered items, and (3) that impairments are revealed only when stimuli are trial unique rather than repeatedly presented. This study shows that it may be possible to account for object recognition impairments after damage to perirhinal cortex within a hierarchical, representational framework, in which complex conjunctive representations in perirhinal cortex play a critical role.
Key words: inferotemporal cortex; configural; hippocampus; visual perception; medial temporal lobe; ventral visual stream; interference
Received July 3, 2006; revised Oct. 2, 2006; accepted Oct. 10, 2006.
Correspondence should be addressed to Rosemary A. Cowell, LEAD–CNRS (UMR 5022), Université de Bourgogne, Pôle AAFE, Esplanade Erasme, 21065 Dijon, France. Email: rosemary.cowell{at}u-bourgogne.fr
This article has been cited by other articles:
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[Abstract] [Full Text] [PDF]
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