Figure 3.

An example of multiple-unit recording with a tetrode isolated by an off-line sorter. A, Superimposed waveforms of 4 neurons (a, b, c, d) recorded by each electrode (E1-E4) from a tetrode corresponding to cluster analysis in B. B, Cluster analysis. The x- and y-axes represent peak values of signals in electrode 2 and 1 of the four tetrode electrodes, respectively. Each dot represents one neuronal spike that exceeded the defined threshold. Four encircled clusters (a, b, c, d) were identified. White clusters dispersed in the center and at left and right corners represent baseline noise and stimulation signals, respectively. Calibration: 0.8 ms, 0.5 mV.