Adult born neurons convey higher levels of associativity to information processing in the dentate gyrus of the hippocampus

MA. BELEN PARDI; LUCAS MONGIAT; ALEJANDRO F. SCHINDER; ANTONIA MARIN BURGIN

Florencia

Congreso; 8 IBRO World Congress of Nueorscience; 2011

IBRO

Adult neurogenesis provides a continuous pool of new granule cells (GCs) to the dentate gyrus (DG) of the hippocampus. During maturation, new GCs present higher excitability than mature GCs and require weaker inputs to be recruited in response to the activation of afferent inputs. These properties suggest that while mature GCs are presumably more selective in their responses, immature GCs could be recruited by several inputs, allowing associations to occur. To study differences in associativity between mature and immature GCs, we combined imaging and electrophysiological recordings from hippocampal slices obtained from adult mice after retroviral expression of RFP to identify immature GCs. GCs activity was monitored by loading the cells with the calcium dye OGB-AM1. Two electrodes were placed to stimulate independent medial perforant path inputs at different intensities. Under these conditions, the majority of mature GCs responded to only one of the two stimuli, however most immature GCs were equally recruited by both stimuli. This result indicates that independent inputs tend to recruit different populations of mature GCs, while recruiting the same population immature GCs, suggesting a higher ability of immature neurons to associate independent inputs. Blocking GABAergic inhibition incremented the level of associativity in the population of mature GCs, without modifying the properties of the immature GC population.  The increased associativity observed in immature GCs suggests that this neuronal population might serve to produce temporal associations in the DG .