Fig. 2: Brain activation patterns during REM sleep.

A GLM analysis was used to demonstrate the activated networks during REM sleep by examining the REM > NREM contrast. The pigeon-specific hemodynamic response function²⁰ was used to optimize the modeled BOLD responses. The left panel shows the activation pattern of group-averaged data from 15 pigeons (29 sessions) in the axial view (group analysis using a nonparametric permutation-based test, “randomise”, 5000 permutations, with Threshold-Free Cluster Enhancement and a family-wise error correction, corrected for multiple comparison across the whole brain and significance at a threshould of p < 0.05). Functional maps were overlaid on the high-resolution anatomical data at the different levels of an ex-vivo pigeon brain (in greyscale). The right panel represents the same activation pattern during REM sleep in the sagittal views. The activation significance is demonstrated by the color scale. Anatomical borders (black and white lines) are based on the contrast difference in the ex-vivo Budapest pigeon brain, the pigeon brain atlas⁶², and the telencephalic connectome of the pigeon forebrain⁸¹. The corresponding abbreviations of delineated ROIs are listed in Supplementary Table 1. Frontal and sagittal slice coordinates are defined based on the Budapest pigeon’s brain anatomy (Supplementary Fig. 4). TFCE Threshold-Free Cluster Enhancement, FEW family-wise error.