Memory for Objects and Contexts Following Manipulation of Hippocampal Formation or Perirhinal Cortex Functions

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There will be two primary objectives: 1) To develop a new and improved methodology for testing object-recognition memory in rats, and to use it to clarify the effects of lesions of the hippocampal formation (HPC) and perirhinal cortex (PRh) on this ability. 2) To enhance the experience and training of students and other HQP through the support of collaborative projects with other laboratories. Much of our previous research employed a novelty-preference paradigm, which we used to assess object-recognition memory, as well as adaptations that we used to assess place-memory and context-memory. The novelty-preference paradigm has become popular among scientists as a method of testing memory, but certain observations in our studies have given rise to serious doubts about its internal validity as a memory test. There has been ongoing debate for many years concerning the extent to which the HPC and PRh are critically involved in the processes that underlie object-recognition memory. I believe the lack of clarity in the literature stems from inherent limitations of the novel-object preference test that was used in most of the relevant studies, and there is a great need for new procedures that can be used to reliably and accurately measure memory abilities in laboratory rats. During the past several months, my students and I have been working to establish a new protocol for assessing object-recognition in rats that will circumvent some of the interpretational limitations of the novelty-preference paradigm. We have discovered a few surprising pitfalls, but we have also had some success, and we are now confident that we have a reliable protocol that provides a good index of object-recognition memory in a relatively short period of time. We plan to amass normative data while manipulating key task parameters (the number of objects that must be remembered; duration of the retention interval) in order to determine the reliability and precision of our new methods. We will study the effects of surgical lesions involving the HPC and PRh on performance of our new object-recognition task.