Fig. 2.

Cells display distinct spike frequency accommodation (SFA) patterns, which help to distinguish DGCs from interneurons. A: representative traces of firing pattern in response to a depolarizing step (500 ms). A₁: strong accommodation (n = 21). A₂: weak accommodation (n = 11). A₃: no accommodation (n = 6). A₄: low firing [did not fire more than 3 action potentials (APs) in a spike train at the highest level of stimulation]. For such cells (n = 11), SFA index could not be calculated. Scale bar: 200 ms, 25 mV. B: plot of SFA index vs AP interval. Strongly accommodating cells reached an SFA index value of at least 3 by the end of the spike train, while the value for weakly accommodating cells never exceeded 2.5, and the value for nonaccommodating cells never exceeded 1.2. Values are means ± SE. C: distribution of SFA types among DGCs in the GCL, DGCs cells in the hilus, and cells that do not fit physiological characterization of DGCs (putative interneurons). There was no significant difference in the distribution of firing patterns between DGCs in the hilus or the GCL (P = 0.75, Fisher's exact test).