The hippocampus in depth: a sublayer-specific perspective of entorhinal-hippocampal function.

Understanding how the brain represents events is a fundamental question in neuroscience. The entorhinal-hippocampal system is central to such representations, which are severely compromised in some neurological diseases. In spite of much progress, a comprehensive, integrated view of spatial, temporal and other aspects of episodic representation remains elusive. Here, we review recent data on the role of cell-type specific entorhinal inputs which excite deep and superficial CA1 pyramidal cells by direct and indirect pathways. We discuss how an entorhinal dialogue with deep-superficial CA1 cells can multiplex neuronal activity along theta phases and how their reactivation may be segregated during sharp-wave ripples. Thus, deep and superficial CA1 sublayers provide substrate for general hippocampal function.