FIG. 6.

PSTHs produced by the [K⁺]_ext model (columns 2, 3, and 4) demonstrate rate adaptation not seen using an analogous model lacking the adaptation component (column 1). Three stimulus parameters are explored over the 18 PSTHs of columns 2, 3, and 4. The effects of stimulus pulse rate are contrasted by the upper set of PSTHs (A, 250 pulse/s) and the lower set (B, 5,000 pulse/s). Three electrode-to-fiber distances are examined across the three columns and the effect of changing stimulus level is demonstrated across the PSTHs within 1 column. While the no-adaptation model results (leftmost column) demonstrate an initial decrease in spike rate, it is attributed to refractoriness and no further decrements are evident. The current level (i) for each PSTH is expressed in microampere units. Each graph has two histograms, with the vertical bars representing 1 ms bin widths and filled circles representing long intervals. Onset rates are indicated and have units of spike/s.