Mapping behaviourally induced immediate-early gene expression along the septotemporal axis of CA1

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Dube, Sutherland Theresa Ann
University of Lethbridge. Faculty of Arts and Science
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Lethbridge, Alta : University of Lethbridge, Dept. of Neuroscience
The longitudinal (or septotemporal) axis of the rodent hippocampus is generally described as being functionally segregated. However, the division between septal and temporal areas is not clearly delineated, and current anatomic, genetic, and physiological data propose varying gradients and domains that in large part do not coincide. In an attempt to clarify these issues, we mapped the behaviourally induced activity of neurons throughout the longitudinal axis of CA1 using immediate early genes (IEGs), which enable large-scale analysis of neuronal activity at the cellular level with a high degree of spatial resolution. Interestingly, the IEG data were not consistent with any of the proposed anatomical schemas or with the available single neuron recording data. The data suggest an alternative classification of hippocampal modules, with a functional domain in septal CA1 and a functional gradient through intermediate and temporal CA1. We suggest delineation between these two subdivisions of CA1 could correspond to amygdalar input to CA1. Further experiments could provide information on whether this input provides a basis for functional segregation at the level of neural activity dependent IEG expression.
blobs , CA1 , hippocampal longitudinal axis , Homer1a , immediate-early genes , intranuclear transcription foci