Figure 5.

Intrinsic Excitability Determines Firing of GCs In Vivo during Spatial Navigation

(A) APs evoked by depolarizing current injection in an active GC. Depolarizing current amplitude varied from −100 to 150 pA in 50 pA steps. The inset shows the first AP in temporal expansion.

(B–F) Correlation analysis of possible determinants of AP frequency in GCs in vivo. Mean AP frequency in vivo is plotted on the abscissa on a log scale. Each data point represents a single GC recording. Lines represent results from linear regression: red line, correlation significant; gray line, correlation not significant. r, Pearson’s correlation coefficient; p, corresponding significance value. Relative AP threshold (absolute AP threshold − resting potential) (B), maximal rate of rise of AP ((dV/dt)_max) (C), AP peak amplitude (D), burstiness (E), and input resistance (F) are plotted against mean AP frequency. The relative AP threshold shows significant negative correlation with AP frequency, whereas both (dV/dt)_max and AP amplitude exhibit significant positive correlation with AP frequency.

(G) Parallel model of information processing in the dentate gyrus. Individual GCs receive similar excitatory synaptic input, probably conjunctive place-grid-tuned input, but convert it into output of a different frequency. The more complex dendritic tree and enhanced excitability suggest a higher degree of maturity of the active GCs.