a) A representative comparison of recorded action potential waveforms, before and after the sixth and eleventh lesions (top, Monkey H; bottom, Monkey U). The location of the lesion electrodes on the arrays’ spatial layout are marked by black dots. Good quality signal was observed in the recording sessions immediately before and after lesioning (left, right). An action potential detection rate was determined from periods of task engagement (gray-scale shading, capped at 15Hz for visualization). b) As a proxy for neuron loss, a relative turnover in daily recorded neurons was determined by pairwise comparisons of action potential waveforms within three groups: pre-lesion days (pre-pre), pre-lesion versus post-lesion days (pre-post; up to three days post-lesion), and post-lesion days (post-post; four to nine days after a lesion). An inter-quartile range is shaded in grey for the set of 10 consecutive days leading up to lesion 11, the first in Monkey U. The median from this healthy control group was subtracted from all other pairwise comparisons to directly quantify a change in turnover. This pre-lesion group was then combined with the other pre-pre comparisons and tested against the pre-post and post-post groups. The change in the percentage of matching neurons dropped significantly after a lesion (Median test; * < 0.003, ** < 0.0003, corresponding to corrected significance levels of 0.01 and 0.001 for the three comparisons). Note, lesions 11-14 in Monkey U were well-spaced out over three months and considered as independent samples.