The contribution of neurogenesis to hippocampal network computations and dentate dependent behavior.

SCHLENNER A; LEUTGEB S.; EWELL L.A.; CAMERON H.A.; PIATTI V.C.; AN Y; LEUTGEB J.K.

Buenos Aires

Congreso; 2nd Federation of Latin American and Caribbean Neuroscience Societies (FALAN) Congress; 2016

Newneurons are continuously integrated into the fully functional neural circuit ofthe dentate gyrus (DG) of the hippocampus. In the rat, there are approximatelyone million dentate granule cells (DGCs) and most of them are silent. So one mightquestion what the additions of new DGCs provide to the network. The highexcitability of the immature DGCs has leaded to the hypothesis that they playan essential role in DG network function and, as a consequence,dentate-dependent behavior. We tested this hypothesis in a transgenic rat model(GFAP-TK) in which neurogenesis (NG) can be selectively blocked by the oraladministration of valganciclovir (Snyder et al., 2016). We first tested therole of NG in a dentate-dependent spatial discrimination task (Morris et al., 2012).We found that rats without NG (N=9) performed at the same level as control rats(N=9), which suggests that immature neurons are not necessary to supportdentate-dependent spatial discrimination task. Next, we recorded single unitsin the DG and its target area, CA3, of GFAP-TK rats with (N = 7) orwithout NG (N= 7) while they foraged in similar novel spatial contexts. Ourdata showed that similar sensory inputs become less orthogonalized in the CA3network without NG. Altogether these results suggest that new DGCs may berequired for the spatial pattern separation when the inputs are novel however theybecame unnecessary for the spatial discrimination behavior task, in which thecontext is familiar.