Fig. 6.

Quantitative electron microscope analysis of the cortical and thalamic innervation of individual direct and indirect MSNs. a Histograms show the average percentage (±SEM) of afferent synaptic terminals of second-order dendrites of neurobiotin-labelled MSNs that were VGluT1- and VGluT2-positive. On average, both, direct and indirect MSN dendrites receive significantly more cortical than thalamic synaptic input (two-way ANOVA with repeated measures; *P = 0.003). b VGluT1- and VGluT2-positive terminals preferentially target dendritic spines of both subtypes of MSNs. c The overall density of afferent synapses (t test *P = 0.014), and the density of both cortical and thalamic afferent synapses, was greater on direct pathway MSNs than indirect pathway MSNs (two-way ANOVA with repeated measures; *P = 0.014). Within the direct and indirect pathway MSN populations there is a greater cortical innervation when compared to thalamic and innervation from terminals negative for both of the VGluTs (two-way ANOVA with repeated measures; ^# P = 0.001)