Figure 4.

Adaptation effects in the amygdala for the surprise-fear continuum. (A) Activation was extracted and averaged from left and right amygdala ROIs, shown here. These ROIs were specified using the MNI Automated Anatomical Labeling Template (Tzourio-Mazoyer et al., 2002). (B) Group level amygdala adaptation effects (mean and S.E.) for trial-to-trial transitions, as revealed by the categorical model. Significant adaptation of the right amygdala response (decrease in BOLD signal) was observed for transitions between 50/50 surprise/fear morphs and faces from the surprise end of the surprise-fear continuum (“50/50 <> surprise,” see Figure 2) *Group-level one sample t-test against zero, t₍₁₈₎ = −2.37, p <0.05. For transitions between 50/50 surprise/fear morphs and faces from the fear end of the surprise-fear continuum (“50/50 <> fear”), there was higher inter-individual variability and the group level adaptation effect did not reach significance. There was slight but non-significant release from adaptation for transitions between faces from one end of the continuum and the other (“surprise <> fear”). (C) “Adaptation bias” refers to the extent to which adaptation was greater for transitions between 50/50 morphs and fear end faces than between 50/50 morphs and surprise end faces (i.e., “50/50 <> fear”-“50/50 <> surprise”). This was significantly modulated by anxiety, r₍₁₇₎ = −0.44, p < 0.05. High trait anxious individuals showed greater adaptation (i.e., decrease) of the right amygdala BOLD response when 50/50 surprise/fear faces followed or preceded faces from the fear (vs. surprise) end of the continuum, this effect reversing in low trait anxious individuals.