DIFFERENTIAL PROCESSING OF SPATIAL CONTENT ALONG THE DORSOVENTRAL CORNU AMMONIS

Spatial content differentiated into information related to overt landmarks (LM), or more subtle discrete local cues, is not encoded in a uniform manner by the dorsal hippocampal cornu ammonis (CA) (doi: 10.1002/hipo.22833). This may relate to information inputs to the hippocampus from dorsal and ventral streams that have been proposed to promote processing of 'what' information by distal CA1 (dCA1) and proximal CA3 (pCA3), and processing of 'where' information by pCA1 and dCA3 (doi: 10.1016/j.bbr.2013.04.048). Accordingly, learning about spatial locations of landmarks results in immediate early gene (IEG) expression in pCA3, whereas learning about locations of discrete local cues results in IEG expression in dCA1 and pCA3 (doi: 10.1002/hipo.22833).
Here, we examined whether CA subfield specialization for encoding the spatial information of LM, or discrete local cue, extends along the dorsoventral CA axis. Nuclear Homer1a mRNA was detected using fluorescence in situ hybridization 40min after exposing male rats to either a novel constellation of LM or of small objects hidden in holeboard holes (HBO).
Novel LM exposure significantly increased Homer1a expression in dorsal pCA3, ventral dCA1, pCA1, and pCA3, while intermediate CA was unaffected. Novel HBO exploration significantly increased Homer1a expression in dorsal dCA1, pCA3, and intermediate dCA1, but had no effect in ventral CA.
These findings support that a functional differentiation for the integration and encoding of “what” and “where” information exists along the dorsoventral axis of CA.
Supported by Deutsche Forschungsgemeinschaft grants to D-M.V. (SFB1280/A04, project number: 316803389; SPP2411-project number: 520284247). M.L. is a stipend recipient from Chinese-Scholarship-Council.