Table 2.
Properties of the 12 neurons of Table 1 as recorded on the “closest” extracellular electrode
| <2·MAD | Thresholding Range Between 2 and 6·MAD |
||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Spike Amplitude, μV | SNR | Spikes | Spikes | Portion of spikes | Half-Width Ratio | ||||||||
| Neuron | MAD, μV | Nonburst | Burst | Nonburst | Other Deflections in Spike Range | Intra-to-Extra Peak Offset, ms | All | Nonburst | Burst | Nonburst | Burst | Mean burst spike number | Burst/nonburst |
| 1 | 14 | −267 (134) | −135 (124) | 19.24 | 36 | 0.30 | 37 | 28 | 269 | 0.01 | 0.27 | 4.7 (1.4) | 1.7 |
| 2 | 7 | −100 (24) | −79 (32) | 13.85 | 2,720 | 0.16 | 1 | 15 | 56 | 0.01 | 0.06 | 3.4 (1.0) | 1.2 |
| 3 | 8 | −91 (18) | −63 (16) | 11.71 | 766 | 0.07 | 0 | 1 | 1 | 0.00 | 0.07 | 2.0 (0.0) | 1.2 |
| 4 | 9 | −77 (12) | −54 (18) | 5.61 | 370 | 0.00 | 6 | 38 | 605 | 0.02 | 0.46 | 3.6 (1.8) | 1.4 |
| 5 | 9 | −82 (20) | −62 (27) | 9.09 | 8,441 | 0.04 | 58 | 110 | 926 | 0.02 | 0.23 | 3.4 (1.0) | 1.2 |
| 6 | 9 | −69 (15) | −65 (19) | 7.64 | 262 | 0.00 | 3 | 100 | 51 | 0.12 | 0.18 | 2.7 (1.0) | 1.0 |
| 7 | 13 | −68 (32) | −47 (37) | 5.23 | 37,073 | 0.03 | 141 | 1928 | 1141 | 0.64 | 0.70 | 3.2 (1.3) | 1.3 |
| 8 | 6 | −64 (10) | −56 (9) | 11.05 | 11 | 0.12 | 0 | 1 | 0 | 0.00 | 0.00 | 1.0 | |
| 9 | 6 | −60 (17) | −63 (9) | 9.80 | 1,725 | 0.03 | 2 | 10 | 1 | 0.05 | 0.17 | 1.2 | |
| 10 | 6 | −57 (8) | −41 (8) | 9.66 | 4 | 0.16 | 0 | 0 | 1 | 0.00 | 0.06 | 1.0 | |
| 11 | 8 | −53 (26) | −38 (31) | 6.26 | 20,807 | 0.03 | 86 | 682 | 657 | 0.38 | 0.55 | 3.2 (1.1) | 1.3 |
| 12 | 8 | −52 (17) | −52 (17) | 6.55 | 3,928 | 0.10 | 2 | 443 | 65 | 0.32 | 0.30 | 2.1 (0.4) | 1.2 |
MAD, median absolute deviation (see equation in materials and methods). Spike amplitude is denoted for both burst and nonburst spikes. Signal-to-noise ratio (SNR) is defined as the mean nonburst spike amplitude divided by MAD. Other deflections in spike range is a measurement of the noise and activity recorded from other neurons on the electrode that may confound spike detection and classification (for details of this calculation, see results). Intra-to-extra peak offset is the difference between the timing of the neuron’s spike as recorded by the extracellular electrode minus the timing of the same as recorded by the patch pipette, with details as follows: the timing of the maximum of the derivative of the mean patch-recorded spike waveform is defined as 0, and the reported offset is the time elapsed after 0 representing the maximum deflection of the mean extracellular spike waveform. We use a minimum spike detection threshold of 2·MAD and so report the number of spikes below it (as detected on the extracellular trace). To look at the number of spikes with amplitudes near or in the noise, we defined a noise range of between 2 and 6 times MAD, based on spike detection thresholds found in the spike sorting literature. (For most neurons, most extracellular spikes were greater in amplitude than 6·MAD.) Spikes in this range may be lost in the spike detection step of spike sorting. We report the number and portion of spikes, nonburst and burst, in this range, relative to the total number of nonburst and burst spikes, respectively. For some recordings burst spikes in particular are found in this range. Mean burst spike number (e.g., 2, 3, 4, …) is reported for the burst spikes in the 2–6·MAD range for each recording. Half-width ratio is the half-width of the mean burst spike divided by the half-width of the mean nonburst spike. When half-width ratio is 1, the mean burst and nonburst spikes have the same width; when half-width ratio is >1, the burst spike is longer than the nonburst spike. Mean values are reported as means (SD).