EMG reactivity to viewed facial expressions was modulated in an emotion- and muscle-specific manner in healthy controls (F(2.20,43.94) = 5.03, p = 0.009) and the participant cohort as a whole (chi2(8) = 80.05, p < 0.001). There was further evidence that this interaction between emotion and muscle reactivity varied between participant groups (interaction of group, emotion and muscle: (chi2(32) = 143.91, p < 0.001). After the generation of a muscle contrast reactivity measure for each trial, ANOVA revealed significant main effects of participant group (F(4) = 10.84, p < 0.001), emotion (F(4) = 3.40, p = 0.009) and the interaction of group and emotion (F(16) = 2.79, p < 0.001; Table 2). In post hoc T-tests comparing participant groups (with Bonferroni correction), overall EMG reactivity across the five emotions was significantly reduced in the bvFTD group relative to the healthy control group (pbonf < 0.001), the svPPA group (pbonf < 0.001) and the nfvPPA group (pbonf = 0.042); and significantly reduced in the rtvFTD group relative to the healthy control group (pbonf = 0.001) and the svPPA group (pbonf = 0.005).