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. 2016 Jun 2;15(11):2387–2399. doi: 10.1016/j.celrep.2016.05.026

Figure 4.

Figure 4

Slow Depolarizing Fluctuations during Quiet Wakefulness Have an Earlier Onset in L5 Neurons

(A) Example slow depolarizing events (SDEs) from a dual L2/3 (red) and L5 (blue) whole-cell recording in an awake, resting mouse. Vm traces are aligned to the onset (left) and offset (right) of the SDE in the L2/3 neuron, and bottom traces show Vm averages. Note that L5 leads at the onset, but not the offset, of the SDEs. Horizontal lines indicate Vm (mV) for L2/3 and L5 (trial 1 onset, −69.3/−63.1 mV and offset, −47.7/−44.7 mV; trial 2 onset, −59.3/−59.1 mV and offset, −40.0/−37.7 mV; trial 3 onset, −60.9/−57.0 mV and offset, −31.8/−31.7 mV; trial 4 onset, −59.7/−56.4 mV and offset, −42.0/−37.7 mV; and trial 5 onset, −58.3/−55.7 mV and offset, −40.0/−30.1 mV). Average onset, −60.0/−52.6 mV and offset, −41.9/−37.0 mV. APs have been truncated.

(B) Plots of selected SDEs from seven dual whole-cell recordings. SDEs were aligned at threshold crossing at the onset (left) and offset (right) of the SDE in the L2/3 neuron and arranged by duration. Top boxes show L2/3 data, and bottom boxes show L5 with colors corresponding to the normalized Vm from minimum (blue) to maximum (red) values.

(C) Population distribution (top) and trial-by-trial measurements (bottom) of the subthreshold onset (left) and offset (right) times in L5 neurons relative to the onset and offset times in L2/3, respectively (n = 7 dual recordings). Onset and offset times were estimated by the 5% level of a sigmoidal fit to the Vm at onset and offset (see Supplemental Experimental Procedures for details).

(D) Population average of the normalized Vm SDEs in L2/3 and L5 relative to the threshold-crossing at onset and offset of the L2/3 neuron.

(E) Population peri-SDE time histogram of AP times from the dataset used in (D).

(F) Population analysis of onset and offset times relative to the L2/3 SDE shows a significantly earlier onset in L5 but similar offset times. To calculate the onset/offset timing difference, we first measured the time of SDE onset/offset relative to the time of threshold crossing of the L2/3 SDE. Then, we subtracted the population mean L2/3 onset/offset time from all values. Filled circles with error bars show mean ± SEM, and lines show data from individual pairs.

For all panels, ∗p < 0.05, ∗∗p < 0.01, and ∗∗∗p < 0.001. See also Figures S4 and S5.