Figure 8.

Quality of neuronal recordings after inserting the 15-µm-thick, 32-channel silicon probe with the slowest (0.002 mm/s) and the fastest (1 mm/s) speed. (a) Schematic of the tip section of the silicon probe comprising 32 electrodes (white and black squares), with the electrode–channel relationship indicated (red text; Ch, channel). Representative three-second-long multi-unit activity (MUA) traces recorded after slow (b) and after fast (c) insertion on eight electrodes (colored black in panel (a)). Traces on the left show MUA shortly after probe insertion (1^st min), while traces on the right were obtained 45 minutes after implantation (45^th min). The same voltage scale was used on all the traces. Color maps constructed from three-second-long data recorded on all channels after slow (d) and after fast (e) insertion. Color maps on the left show MUA shortly after probe insertion (1^st min), while color maps on the right were constructed from data recorded 45 minutes after implantation (45^th min). Before plotting the color maps, the absolute value of the MUA was calculated, then a 30 Hz low-pass filter was applied on the data to obtain the envelope of the MUA (au; arbitrary unit). Black traces below the color maps show the instantaneous population activity recorded by the probe at each sample point of the three seconds, which was obtained by summing the values on all of the channels.