Extended Data Fig. 1: Longitudinal tracking of single units in piriform cortex.
a, Chronic silicon probe implantation in anterior piriform cortex (green). Anatomical image and structure designations from the Allen Mouse Brain Atlas60 (http://www.brain-map.org). Inset, probe diagram with relative positions of the 32 recording electrodes; red, DiI marking probe position; black, cell bodies (NeuroTrace). Diagrams not to scale. b, Number of single units retained as a function of recording interval duration. Mean ± s.d. with individual data points; blue dotted line, linear regression; blue shading, 95% CI. ρ = −0.41, P = 1.2 × 10−3, n = 24 recordings across 8 days, n = 18 recordings across 16 days, n = 12 recordings across 24 days, n = 6 recordings across 32 days, all from 6 mice. c, Single-unit yield for single-day record sessions. Left, per recording session as a function of time since probe implantation. Blue dotted line, linear regression; blue shading, 95% CI. ρ = −0.12, P = 0.23. Right, single-unit yields across all single-day recording sessions (n = 97 recording sessions in 16 mice). d, Left, probability density of waveform similarities for all pairs of single units simultaneously recorded within each day. Red dashed line indicates inclusion criterion (0.93, the distribution’s 99th percentile) for rejection of candidate single units recorded across multiple days. Right, probability density of refractory period violations (refractory period is defined as an inter-spike interval <1.5 ms). e, Average waveforms for a representative single unit recorded at each of the recording sites of the silicon probe. Waveforms from all days (0–32) are superimposed with each day plotted as a separate colour (colour scheme maintained throughout). Inset e,i, mean waveforms for days 0, 8, 16, 24, and 32 for a subset of recording sites, indicated by the grey box. Inset e,ii, mean waveforms for days 0 to 32, superimposed for a single recording site (dashed grey box). f, Waveform correlations for each single unit across days 0 and 32 (red) and across all single units within-day (grey); within-unit, across-days versus within-day, across-units, P = 4.8 × 10−246, Wilcoxon rank-sum, n = 379 single units from 6 mice. The grey distribution is replotted from d (left). g, Single-unit waveform centroids across a 32-day interval from a representative mouse (centroid computed using spatial average across electrode positions weighted by the squared mean waveform amplitude at each electrode). Centroid for each single unit isolated on day 0 (blue circles) and days 8, 16, 24, and 32 (red circles, columns 1–4, respectively; days 0 versus 8, n = 100 single units; days 0 versus 16, n= 94 single units; days 0 versus 24, n = 84 single units; days 0 versus 32, n = 77 single units). Grey circles indicate the positions and sizes of the probe’s 32 electrode sites. h, Mean displacement of single-unit centroids from this mouse between day 0 (blue circle, defined at origin) and days 8, 16, 24, and 32 (red circles, columns 1–4, respectively). Grey contours indicate quintile boundaries of the distribution of centroid position displacement for the population. i, Top, cumulative distribution of within-unit centroid displacement (red) between day 0 and days 8, 16, 24, and 32 (columns 1–4, respectively) and across-unit centroid displacement within day (black) for this mouse. Median on day 0 versus 8 within-unit = 1.8 μm (Q1 = 1.1 μm, Q3 = 2.9 μm), across-unit = 63.5 μm (Q1 = 31.5 μm, Q3 = 107 μm); day 0 versus 16 within-unit = 2.1 μm (Q1 = 1.3 μm, Q3 = 3.2 μm), across-unit = 64.2 μm (Q1 = 32.0 μm, Q3 = 108 μm); day 0 versus 24 within-unit = 2.6 μm (Q1 = 1.5 μm, Q3 = 3.5 μm), across-unit = 64.4 μm (Q1 = 32.2 μm, Q3 = 108 μm); day 0 versus 32 within-unit = 2.8 μm (Q1 = 2.2 μm, Q3 = 4.2 μm), across-unit = 64.5 μm (Q1 = 32.1 μm, Q3 = 108 μm); for all comparisons P < 9.5 × 10−51, Wilcoxon rank-sum, n as in g. Inset at bottom, x-axis 0 to 10 μm.
