Fig. 4: Differences between periodic and random oddball paradigm responses.

A Schematic of a classical oddball sequence. It includes many repetitions of a standard tone (STD, light blue) and rare deviant tones (DEV, red) at a different frequency, with the STD immediately before each DEV shown in dark blue. B Schematic of a periodic oddball sequence. It uses repeating blocks of nine STDs followed by one DEV as a fixed frozen, ten-tone cycle over time; for illustration purposes only four STDs are shown. C Average PSTH of CSI-significant units recorded using multichannel probes from both CA1 (n = 5; 2 rats) and DG (n = 15; 3 rats), centered at the onset of deviant tones (0 ms, red). The plot includes the responses to the standard tones before and after a deviant (blue). Vertical bars indicate the duration of sounds. The response (mean ± SEM) during a random oddball sequence is shown with a continuous trace, while the mean response during a periodic oddball is displayed with a dashed trace. The shaded area along the lines represents the SEM error. Statistical significance for the comparison between random and periodic sequences is denoted by a thick black line above the X-axis. Note that the only statistical difference occurs during the presentation of the deviant tone (25–50 ms), marked by a circled D. D Bar plots representing the normalized spike counts for the 25–50 ms time window. E Bar plots representing the normalized spike counts for each experimental condition (red, deviant; blue, standard; green, control), using the analysis window (250-650 ms); no periodic/random difference is observed. Error bars indicate ± SEM. Asterisks indicate significance from a t-test with Holm–Bonferroni correction (**p < 0.01; ***p < 0.001). The underlying data for this Figure can be found in Supplementary Data 2.