Fig. 5: Trisomy 21 alters the temporal pattern of the cerebellothalamic activation during locomotor activity.

A Schematic setup. An optic bundle consists of two optical fibers that connect the optical cannula implanted at the interposed nucleus (IPN) and ventrolateral nucleus of thalamus (VL) to the focal plane of the objective. A dichroic mirror separates excitation and detection pathways and selects the detected wavelength range with an emission filter. A complementary metal-oxide semiconductor (CMOS) camera sensor creates an image of the two-region fiber array. We used a 560-nm LED to excite RCaMP. Upper right: example video camera image of voluntary wheel running with simultaneous two-region fiber photometry recording. B Example trial recordings. Top to bottom: bulk RCaMP ΔF/F (VL), ΔF/F (CN), and velocity traces recorded simultaneously across two regions from an euploid mouse. Shaded area: running epochs. C Example peristimulus time histogram (PSTH) responses from two brain regions of an euploid mouse. Top: CN recordings, bottom: VL recordings. Heatmap colors in each row indicate ΔF/F amplitude of one running epoch. Dashed lines indicate running onset. D Average activity (area under z-scored responses) for euploid (n = 5) vs TcMAC21 (n = 6) during 10-min recordings. No significant differences, ANOVA followed by Sidak’s test. Data are mean ± SEM. E Locomotor state-dependent changes in mean response magnitude (maximum Z scored response averaged across behavior epochs). Individual mice shown, including mean ± SEM. *p < 0.05, ***p < 0.001, ****p < 0.0001 by two-way RM-ANOVA with Sidak’s multiple comparisons. F Multidimensional analysis using the eight temporal and amplitude bulk activity (z-scored ΔF/F) measurements from interposed nucleus and motor thalamus of TcMAC21 and euploid mice during locomotor state transitions. Each data point represents one mouse, mapped in principal component space. Neuronal responses during locomotor state transitions clustered according to genotype. G Pairwise Pearson’s correlations of bulk activity between motor thalamus and cerebellar nuclei recordings during each locomotor epoch for euploid (n = 5) and TcMAC21 (n = 6) mice. Data points represent correlation mean across epochs per mouse, including mean ± SEM. Euploids showed significantly increased correlation, while TcMAC21 mice showed significantly decreased correlation during the running phase. Significance found in CN-VL mean correlations: *p(Eu) = 0.019, **p (TcMAC21) = 0.007 by paired t-test. H Discrimination Index (DI) for quantifying the changes in neural synchrony between stationary versus running phases. DI was defined as the difference in mean pairwise Pearson’s correlations of bulk activity between motor thalamus and cerebellar nuclei recordings during each locomotor epoch, divided by the sum of standard deviations (see METHOD). Data are presented as the mean ± SEM. ***p < 0.001 by Unpaired t-test.