Figure 3

Percent signal change by ROI for the contrast of stimuli predicting Reward vs. No Reward. Unadjusted mean values across dogs by run and by modality (blue = visual, red = olfactory, green = verbal). Error bars denote the standard error of the mean across dogs for each modality and run. Lines denote second-order polynomial trend lines across all runs for each modality and ROI. Consistent with studies of reward learning, there were main effects of [Reward-No Reward] across all ROIs (p < 0.001), which was only marginally significantly different by modality (p = 0.045). There was a significant interaction between [Reward—No Reward] and ROI (p = 0.014), suggesting the magnitude of the effect was different in each region. All ROIs showed evidence of varying time course (p = 0.018), which differed by modality (p = 0.006), consistent with different rates of learning and habituation by modality. (A) Averaged beta values in the caudate show marked learning curves for visual and olfactory stimuli. (B) Averaged beta values in the amygdala show learning curves across all stimulus modalities, but verbal stimuli peak later than visual and verbal stimuli. (C) Averaged beta values in the parietotemporal area show weak learning effects for all modalities. (D) Comparison of initial learning rates for each modality for Run 1. Bars denote the temporal derivative (d/dt) of the polynomial fit for [Reward—No Reward] by modality and ROI. Across all three ROIs, percent signal change to visual and olfactory stimuli occur at a faster rate than verbal stimuli, and is evident in the first few exposures.