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Author Notes:

Corresponding Author: Hsiao-Wei Tu, Yerkes National Primate Research Center, Emory University, 954 Gatewood Road, Atlanta, GA 30329, Phone: 404-727-9619, Fax: 404-727-8088, hsiaowei.tu@emory.edu

Author contributions: R.R.H. and E.A.M. designed research; R.R.H. performed research; H.-W.T. analyzed data; H.-W.T. wrote the paper.

Acknowledgements: We thank Sparky Zivin for assistance with testing animals and animal care; Rick Duntz for assistance in surgery; and Jeanette Black and Renee Hill of the NIH In Vivo Nuclear Magnetic Resonance Research Center for technical assistance.


Research Funding:

This work was supported by the Intramural Research Program of the National Institute of Mental Health (NIMH). Additional support was provided by NIMH Grant R01MH082819, National Science Foundation Grant 0745573, and Yerkes Center Base Grant RR-00165, which was awarded by the Animal Resources Program of the National Institutes of Health.


  • habit
  • recognition memory
  • process dissociation
  • implicit
  • explicit
  • amnesia
  • interference

Perirhinal Cortex Removal Dissociates Two Memory Systems in Matching-to-Sample Performance in Rhesus Monkeys


Journal Title:

Journal of Neuroscience Nursing


Volume 31, Number 45


, Pages 16336-16343

Type of Work:

Article | Post-print: After Peer Review


Dissociations of memory systems are typically made using independent cognitive tests. For example, in monkeys habits have been inferred from performance in object discrimination tests, while nonmatching-to-sample tests are thought to measure familiarity resulting from single exposures. Such tests cannot measure individual memory processes accurately when more than one memory process contributes to performance. In process dissociation procedures (PDPs) two memory processes cooperate and compete in the performance of a single cognitive task, allowing quantitative estimates of the contributions of each process. We used PDP to measure the contributions of habits and one-trial memory to visual matching-to-sample performance. Sets of test images were shown only once in each daily testing session but were repeated day after day. To produce habits, high-frequency images were correct more frequently than other images across days. Habits were manifest in the extent to which choices in the test phase of matching-to-sample trials were made to the high-frequency images, irrespective of which image had been presented as the sample. One-trial memory was measured by the extent to which choices at test were made to the image that had appeared as the sample on that trial, irrespective of habit. Perirhinal cortex removal reduced the contribution of one-trial memory to matching performance, but left both habits and the ability to discriminate images intact. PDP can be applied in monkeys in a way that parallels its use in humans, providing a new tool for investigating the neurobiology of memory in nonhuman animals and for comparing memory across species.

Copyright information:

© 2011 the authors

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