FIGURE 1.

Example of waveforms from extracellular tetrode recordings in the hippocampus from different cell types and a putative axon: (A) pyramidal cell, interneuron, and short duration waveform. The pyramidal cell (red) has an average spike width of 500 μs with a long lasting hyperpolarization. The interneuron (green) has a shorter spike width of 250 μs with a shorter hyperpolarization period. The third example is of a short duration waveform that is triphasic, exhibiting a brief hyperpolarization period before and after a brief depolarization; (B) overlay of the three average waveforms; (C) average and standard error of peak-trough time for pyramidal cells (n = 53, 567 ± 8.68 μs), interneurons (n = 5, 241 ± 14.1 μs), and putative axons (n = 64, 176 ± 4.84 μs) recorded in the medial white matter (MWM), alveus, and pyramidal cell layer of the hippocampus; (D) Scatter plot of signal to noise ratios for individual units against peak-trough time for SDWs recorded in MWM, alveus, and CA1 of the hippocampus, as well as pyramidal cells (PYR) and interneurons (INT) in CA1 of the hippocampus. The SDWs, and pyramidal cells clearly cluster by peak-trough time while interneurons overlap with the longer SDWs.