Fig. 4: Artificial reactivation of cold-sensitive engrams in the DG increases metabolism and thermogenesis genes.

a, Genetic strategy. b, Experimental timeline. c, Environmental temperature during the labelling window. d, Representative image of hippocampal slice with FOS⁺ cells (red) and eYFP⁺ cells (green). e, Time plot of oxygen consumption during artificial reactivation of cold-sensitive engrams. Blue bars indicate the time the laser was turned on. f–h, Comparison of oxygen consumption between the on (blue) and off (grey) epochs during the three stimulations. i, Comparison of oxygen consumption between the on (blue) and off (grey) epochs of cold-sensitive cells during all stimulations combined. j, Genetic strategy. k, Experimental timeline. l, Representative image of a hippocampal slice with FOS⁺ cells (red) and eYFP⁺ cells (green). m–o, Comparison of colabelled neurons between the cold-stimulated cohort (dark blue) and the no-cold-stimulated control cohort (grey) in the LHA (m), the MPO (n) and the LPO (o). p, Correlation between the percentage of colabelled/eYFP⁺ cells in the LHA and oxygen consumption after cold stimulation (blue) and no-cold stimulation (grey). q, Experimental timeline. r–v, Relative expression of lipolysis and thermogenesis genes (Ucp1 (r), Cpt1a (s), Hsl (t), Atgl (u) and Ppargc1a (v)) in the BAT of mice with cold-sensitive stimulated cells (blue) and no-cold control-stimulated cells (grey). e–i, Data are mean, n = 8–9 mice per group. m–p,r–v, Data are mean ± s.e.m., n = 5–7 mice per group. e–i, Paired t-test. m–o, Unpaired t-test. p, Simple linear regression. r–v, Unpaired t-test. *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001. ChR2, channelrhodopsin. Scale bars (d, l), 250 μm. Illustrations of the transgenic labelling systems (a,j), the behavioural timelines (b,k) and the tissue collection timeline (q) were created with BioRender (https://biorender.com).