Quantitative estimation of convergence between input sources based on retrograde labeling patterns after injections in different Po subregions. a, Location of the retrograde tracer deposits. b, Percentage comparison of labeled cells sending putatively “driver” excitatory inputs to Po (L6 cells are not included). Cortical L5b (colored in white) versus subcortical structures (superior colliculus + sensory brainstem + spinal cord) shaded in gray. The total number of labeled cells counted in these structures in each experiment is indicated above. c, Percentage comparison of cells labeled among the four structures sending putatively inhibitory inputs to Po: anterior pretectal nucleus (APT, white), zona incerta (ZI, dash), reticular thalamic nucleus (TRN, gray shade) and substantia nigra pars reticulata (SNR, black). The asterisk used to indicate SNR labeling in some experiments probably reflects the involvement of the intralaminar nuclei and/or internal medullary lamina fibers. d, Percent comparison of L5b cells labeled in each cortical area over the total of putatively excitatory inputs (cortical + subcortical). e, Percent comparison of labeled cells in each subcortical structure over the total of putatively excitatory inputs (cortical + subcortical). Structures showing <2% of the total labeled cells were grouped as “others.” f, Correlation analysis between the absolute numbers of cells retrogradely labeled in subcortical structures providing Po long-range inhibitory inputs (APT + ZI + SNR) versus those labeled in subcortical structures providing putatively excitatory inputs. g, Correlation analysis between the absolute numbers of cells retrogradely labeled in subcortical structures providing long-range inhibitory inputs versus cells labeled in cortical L5b. h, Correlation analysis between the absolute numbers of cells retrogradely labeled in cortical L5b versus cells labeled in the trigeminal complex. i, Correlation analysis between the absolute numbers of cells retrogradely labeled cells in cortical L5b versus cells labeled in the spinal cord and DCN. Correlations between cases in Po are indicated by linear regression as well as by the coefficient of correlation (R²), data on VPM experiments are also shown for comparison. DCN: dorsal column nuclei; PrV: principal trigeminal complex; S1: primary somatosensory cortex; S2: secondary somatosensory cortex; SC: superior colliculus; SpV: spinal trigeminal complex; VC: vestibular complex.