Neural Tuning for Face Wholes and Parts in Human Fusiform Gyrus Revealed

29 Although the right fusiform face area (FFA) is often linked to holistic processing, new data 30 suggest this region also encodes part-based face representations. We examined this question by 31 assessing the metric of neural similarity for faces using a continuous-carry over fMRI design. 32 Using faces varying along dimensions of eye and mouth identity, we tested whether these axes 33 are coded independently by separate part-tuned neural populations or conjointly by a single 34 population of holistically-tuned neurons. Consistent with prior results, we found a sub-additive 35 adaptation response in the right FFA, as predicted for holistic processing. However, when 36 holistic processing was disrupted by misaligning the halves of the face, the right FFA continued 37 to show significant adaptation, but in an additive pattern indicative of part-based neural tuning. 38 Thus, this region appears to contain neural populations capable of representing both individual 39 parts and their integration into a face gestalt. A third experiment, which varied the asymmetry of 40 changes in the eye and mouth identity dimensions, also demonstrated part-based tuning from the 41 right FFA. In contrast to the right FFA, the left FFA consistently showed a part-based pattern of 42 neural tuning across all experiments. Together, these data support the existence of both part43 based and holistic neural tuning within the right FFA, further suggesting that such tuning is 44 surprisingly flexible and dynamic. 45