Bursting and Oscillations in a Biophysical Model of Hippocampal Region CA3: Implications for Associative Memory and Epileptiform Activity
A detailed biophysical model of hippocampal region CA3 was used to show how septal cholinergic and GABAergic modulation, through three distinct mechanisms, interacts with intrinsic and synaptic conductances to influence population behavior. A dissection of each mechanism demonstrates a continuum of population firing activity ranging from fully-synchronized behavior to a mixture of repetitive bursting and oscillations in reduced subsets of neurons, ideal for forming accurate associations during a learning and recall task. Rhythmic modulation (GABAergic) is shown to play a role in the formation of place fields and the model’s capacity for learning sequence information. Such modulation is also shown to account for the phase precession of place units relative to the theta rhythm as an organism passes through the associated place field of the cell.
KeywordsPyramidal Cell Theta Rhythm Place Field Biophysical Model Perforant Path
Unable to display preview. Download preview PDF.
- Ault, B. and Nadler, J.V. (1982) Baclofen selectively inhibits transmission at synapses made by axons of CA3 pyramidal cells in the hippocampal slice. J. Pharmacol. Exp. Ther., 223: 291–297.Google Scholar
- Colbert, C.M. and Levy, W.B. (1992) Electrophysiological and pharmacological characterization of perforant path synapses in CAI: mediation by glutamate receptors. J. Neurophysiol., 63: 1–8.Google Scholar
- Doi, N., Carpenter, D.O. and Hori, N. (1990) Differential effects of baclofen and gamma-aminobutyric acid (GABA) on rat piriform cortex pyramidal neurons in vitro. Cell. Molec. Neurobiol., 10: 559–564.Google Scholar
- Dutar, P, Bassant, ME, Senut, MC and Lamour, Y, (1995) The septohippocampal pathway: Structure and function of a central cholinergie system. Physiol. Rev., 75: 393–427.Google Scholar
- Frotscher, M. and Leranth, C. (1985) Cholinergic innervation of the rat hippocampus as revealed by choline acetyltransferase immunocytochemistry: a combined light and electron microscopic study. J. Comp. Neurol., 239: 237–246.Google Scholar
- Man, D. (1971) Simple memory: A theory for archicortex. Phil. Trans. Roy. Soc. B, 262: 23–81.Google Scholar
- McNaughton, B.L., Bames, C.A. and O’Keefe, J. (1983) The contributions of position, direction and velocity to single unit activity in the hippocampus of freely-moving rats. Exp. Brain Res., 52: 41–49.Google Scholar
- Squire, L.R. (1992) Memory and the hippocampus - a synthesis from findings with rats, monkeys and humans. Psycho]. Rev., 99: 195–231.Google Scholar
- Zador, A., Koch, C. and Brown, T.H. (1990) Biophysical model of a Hebbian synapse. Proc. Natl. Acad. Sci., 87: 6718–6722.Google Scholar