Extended Data Fig. 6: Intrinsic activity in murine primary cultures resembles organoids after shuffling.

a, Raster plot visualization of single-unit spiking (blue dots) measured across a 2D murine primary culture from ref. ²⁸ (Pr1) recorded on a high-density microelectrode array. The population firing rate is shown by the red solid line. Population bursts are marked by sharp increases in the population rate. Burst peak events are denoted by local maxima (black dots) that exceed 4× r.m.s. fluctuations in the population rate. The shaded gray regions denote the burst duration window as defined by the time interval in which the population rate remains above 10% of its peak value in the burst. b, The instantaneous firing rate of single-unit activity from a after reordering. The backbone units are plotted above the dashed line, while non-rigid units are plotted below the dashed line. In each category, units are ordered based on their median firing rate peak time relative to the burst peak, considered over all bursts in the recording. c, The average burst peak-centered firing rate measured across all burst events for the example recording of which part is shown in a. The burst peak is indicated by the dotted line. The unit order is the same as b. Please note that the progressive increase in the firing rate peak time relative to the burst peak, as well as a spread in the active duration for units having their peak activity later in the burst are not present in the murine primary recording, similar to the organoid data after shuffling as shown in Extended Data Fig. 5. The average firing rate is normalized per unit to aid in visual clarity.