X-Message-Number: 12451 Date: Wed, 22 Sep 1999 19:47:43 -0400 From: Jan Coetzee <> Subject: Pulling the plug on the hippocampus Pulling the plug on the hippocampus The hippocampus is intimately involved in the formation of memories. But details of its involvement are difficult to ascertain. The complexity of memory is one reason. Memories require mechanisms for encoding, storage, consolidation, and retrieval. It would be very useful to have some way of turning the hippocampus on and off at will during a memory test. That is now possible with the development of a novel technique that uses a drug to block glutamate receptors in the hippocampus. Early application of the approach indicates that the hippocampus plays a key role in the encoding and retrieval of spatial memory. Nature Neuroscience October 1999 Volume 2 Number 10 pp 898 - 905 Reversible neural inactivation reveals hippocampal participation in several memory processes G. Riedel1, 2, 6, J. Micheau3, 6, A.G.M. Lam4, E.v.L. Roloff1, 2, S.J. Martin1, H. Bridge1, 5, L. de Hoz1, B. Poeschel1, J. McCulloch4 & R.G.M. Morris1 1. Department and Centre for Neuroscience, University of Edinburgh Medical School, Crichton Street, Edinburgh EH8 9LE, UK 2. Department of Biomedical Sciences, University of Aberdeen, Aberdeen AB25 2ZD, UK 3. Laboratoire de Neurosciences Comportementales et Cognitives, CNRS UMR 5807, Universit de Bordeaux I, Avenue des Facult s, 33405 Talence Cedex, France 4. Department of Neuroscience, Wellcome Surgical Institute, University of Glasgow, Garscube Estate, Glasgow G61 1QH, UK 5. Present address: Department of Experimental Psychology, University of Oxford, Oxford OX1 3UD, UK 6. The first two authors contributed equally to this work. Correspondence should be addressed to R G M Morris. e-mail: Studies of patients and animals with brain lesions have implicated the hippocampal formation in spatial, declarative/relational and episodic types of memory. These and other types of memory consist of a series of interdependent but potentially dissociable memory processes encoding, storage, consolidation and retrieval. To identify whether hippocampal activity contributes to these processes independently, we used a novel method of inactivating synaptic transmission using a water-soluble antagonist of AMPA/kainate glutamate receptors. Once calibrated using electrophysiological and two-deoxyglucose techniques in vivo, drug or vehicle was infused chronically or acutely into the dorsal hippocampus of rats at appropriate times during or after training in a water maze. Our findings indicate that hippocampal neural activity is necessary for both encoding and retrieval of spatial memory and for either trace consolidation or long-term storage. Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=12451