Abstract
The role of visual experience in the development of face processing has long been debated. Deprivation studies in non-human primates and studies of adults with congenital blindness have yielded mixed results. Here we pursue a different angle on this question through a serendipitous study that can never be repeated. We rely on a classic fMRI repetition suppression design from adult cognitive neuroscience to study the representation of facial identity in infants. Namely, the adult fusiform face area (FFA) tends to show reduced neural activity when the identity of a face is repeated compared to when a novel identity is presented, suggesting that beyond responding to faces, FFA can tell identities apart. In our study, we showed awake infants short blocks of faces or scenes during fMRI. In half of face blocks, the same identity was repeated multiple times in a row (Repeat); in the other half of face blocks, a matching number of faces were presented but each a unique identity (Novel). As a natural experiment, we happened to collect part of our sample before the COVID-19 pandemic and the rest after the first lockdown in Connecticut was lifted. The resulting sample of 12 infants aged 9–23 months divided equally into pre- and post-lockdown groups that were age-matched and had similar data quantity and quality. The two groups had strikingly different neural responses: pre-lockdown infants showed repetition suppression (Novel > Repeat), whereas post-lockdown infants showed repetition enhancement (Repeat > Novel). This interaction was most pronounced in FFA and for human (vs. sheep) faces. Repetition enhancement in adult fMRI has been observed when repetitions provide an opportunity for additional learning. Thus, we tentatively interpret these findings as consistent with delayed development of neural selectivity to faces, and speculate that it may result from altered experience with faces during the pandemic.