A sorted single unit on microelectrode recording. This figure demonstrates a sorted single unit. The expectation-maximization algorithm was applied to raw signal (white) for getting isolated unit waveforms (green) from noise signal (yellow). Top, raw spiking activity; middle left, unit waveforms (green) and isolated form noise (yellow); middle right, isolated unit and noise on a principle component plot (x-axis, PC1;y-axis, PC2); bottom, raster trace of unit events (green) and noise events (yellow) over a selected time period.