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. Author manuscript; available in PMC: 2019 Apr 5.
Published in final edited form as: Behav Brain Res. 2011 Jul 23;227(2):470–479. doi: 10.1016/j.bbr.2011.07.012

Figure 2. Optogenetic approach to clarify the timing for functional involvement of adult-born DGCs.

Figure 2.

Top, Optical manipulation of neuronal activity with light-sensitive rhodopsins: Blue light (470 nm wavelength)-induced neuronal activation by channelrhodopsin-2 (ChR2), a cation channel (left). Yellow light (589 nm)-induced neuronal suppression by halorhodopsin (NpHR), a chloride pump, derived from Natronomonas pharaonis (right). GCL: granule cell layer. Bottom, Hippocampal circuitry and afferent connections from the entorhinal cortex (EC). Granule cells of the dentate gyrus (DG) project their axons, mossy fibers (MF), to the pyramidal cells of CA3. CA3 neurons target CA1 pyramidal neurons via the Schaffer collateral pathway (S/C). CA1 neurons also project back to the EC. The EC sends cortical information and hippocampal feedback to the DG through the medial perforant pathway (mPP), to CA3 through lateral the perforant pathway (LPP) and directly to CA1 through the temporoammonic pathway (TA). Some memories appear to have a temporary dependence on the hippocampus before cortical structures are capable of mediating the long-term maintenance of the memory trace.