Hypoxia, Leptin and Hippocampal Neurons Firing Figure 1. Spontaneous activity of hippocampal primary cultures at different ages. A. Photograph of an hippocampal primary culture on DIV 11, plated over an array of planar microelectrodes (top). The photograph is a detail relative to 4 over the 60 recordings electrodes of the MEA. Representative spontaneous electrical activity recorded from three different channels of the same MEA, on DIV 11 (bottom). In the inset is visible a magnification of a single extracellularly recorded action potential, since single spike firing is the characterizing feature of young cultures. B. PLoS ONE | www.plosone.org 2 July 2012 | Volume 7 | Issue 7 | e41530