Fig. 5.
Chronic MUA changes. (a) An example animal with an acute increase in tSR. Top panel shows the SR normalized to the maximum SR recorded by each specific channel throughout the experiment. Channel number portrays sequential electrode site order, remapped from the Neurolynx channel numbers. Channel 1 represents the electrode site nearest the pial surface, whereas channel 16 is the deepest electrode site. Middle panel is the tSR recorded by all 16 channels, summed across all channels. Bottom panel shows the SNR over time. (b) A representative animal with an acute decrease in tSR. Same as (a), panels show normalized SR of 16 channels, tSR, and SNR over time. (c) Total SR over time for all six implanted animals with long-term electrophysiological data. Data are averaged within monthly or quarterly time windows for better visualization of the trend of change. tSR started reducing 6 to 9 months postimplantation. After 12 months of implantation, electrodes almost completely failed to record spikes. (d) Number of channels recording more than 20 spikes in a recording session, which shows a similar trend to tSR. (e) Number of viable channels was determined by the quality of LFP and MUA (see Sec. 2 for criteria). Electrodes started to physically fail 9 to 12 months postimplantation, which is after the reduction in SR. (f) SNR remains stable for up to 12 months postimplantation. (g) Amplitude of noise, shown as one STD of the signal mean, started reducing 6 to 9 months postimplantation. (h) Change of amplitude of spikes, which, in line with noise amplitude, started decreasing from 6 to 9 months postimplantation. Data expressed as .