Figure 1.
a, Extracellular action potential waveforms (negative up) of five well-defined clusters, C1–C5. Gray waveforms (C0) are unclustered spikes. The four signals recorded from each wire of the tetrode (T1–T4) are drawn next to each other, separated by vertical black lines. Waveforms were stored 250 μs before the upward threshold crossing and 1.75 ms afterward. b, Different 2-D slices of the clusters in feature-space. T1-peak is defined as the peak voltage on wire 1 (see Materials and Methods). T1-V(0.181) is a user-defined feature defined as the voltage on wire 1 at time 181 μs of the stored waveform. T3-V(0.307) is the voltage on wire 3 at 307 μs. These features were selected by an expert user to optimize waveform isolation, as reflected in the well-separated clusters. Only the five best clusters found are highlighted here. Voltage is in units of millivolts. c, Top, IsoIBG of the five clusters shown in b. Bottom, IsoINN of the five clusters.