Figure 3.
Gradual Emergence of Replay between P17 and P32
(A) Significant linear trajectory events in POST-sleep at different ages (four examples per age). For each event, top panel shows time-by-position probability posterior derived from Bayesian decoding of position, based on event spiking. False colors show decoded probability, and white lines indicate the band of the best linear fit. Summed probability within fit lines (p) and speed of event (speed) are indicated above the posteriors. Bottom panel shows spike raster of complex spike cell activity during replay events. Cells are ordered by the position of their spatial peak firing on the track. Linear trajectories are predominantly stationary at younger ages, with replay emerging gradually in older animals.
(B) Percentages (±95% confidence interval) of events with a significant linear trajectory during PRE- and POST-sleep sessions across development. Dotted line represents 95% confidence threshold. In all age groups, significantly more events than expected by chance showed a significant linear trajectory in POST sessions (binomial test; p < 0.001 for all groups).
(C and D) Mean characteristics of significant linear trajectory events in each POST-sleep session. For all plots, each data point represents mean (±SEM) of all significant linear events in one experimental session (one rat/day). Adult data represent overall mean across all sessions. For each measure, r2 and p values of linear regression over age are indicated above plots (adult data are always excluded from regression analysis). Distance covered (C) and speed of decoded trajectories (D) are shown.
(E and F) Cumulative distributions of the distance covered (E) and the speed (F) of all significant linear trajectory events in the age groups P17–P20, P21–P24, P25–P32, and in adult animals.
See also Figures S1, S2, and S3.