Frequency tagging reveals differential neural responses to overlapping faces and objects in infants and adults

• In Event: 2-104 - Infant Attention and Face Learning: Insights from Measures of Brain and Behavior

Integrative Statement

Previous research suggests that 3 months of experience hearing unfamiliar objects or faces labeled with individual-level labels, from 6- to 9-months of age, resulted in increased visual attention to and better discrimination of new objects within the same category (e.g., Scott & Monesson, 2009; Pickron et al., 2018). However, we currently do not know whether or how the neural mechanisms underlying attention to faces and objects during learning change from infancy to adulthood. In the current study, 6- to 12-month-old infants (n=30) and adults (n=27) completed an in-lab training during which novel objects were labeled with individual-level names over the course of a 5-minute learning period. Immediately before and immediately after the training, participants viewed concurrent novel exemplars of objects from within the trained category superimposed on neutral female faces. The faces and objects were sinusoidally modulated in contrast against a Brownian (naturalistic) noise background at a rate of 5Hz (objects) and 6 Hz (objects). Brownian noise changed in each trial and was used to minimize brain responses to low-level features. Continuous EEG was recorded throughout the task and steady state visual evoked potential (ssVEP) spectra were extracted from four 6-second trials. Attention to the overlapping stimuli was examined by comparing the magnitude of the signal to noise ratio (SNR) at each frequency across five posterior cortical regions.

The results revealed an overall greater SNR for pre-training compared to post-training (p = .02) and adults showed a greater SNR than infants (p = .01). There was also an interaction between training, condition and age group (p = .03), driven by infants exhibiting a greater SNR post-training compared to pre-training for objects (p = .03) but not for faces. Adults showed no change in SNR for objects, but an increased SNR to faces at pre-training compared to post-training (p < .001). One-sample t-tests comparing the SNR to 1 across posterior regions (see Figure 1) revealed that adults responded to objects across all posterior regions at pre- and post-test (all ps < .001) but the region with the maximal response shifted from medial occipital to right occipital after training. Adults responded to faces across all regions before training (all ps < .01) but only showed a significant response over the right occipitotemporal region after object training (p < .01). In contrast, infants only showed a significant SNR to objects over left, medial, and right occipital regions before training (all ps < .01) but showed a significant SNR across all posterior regions at post-test (all ps < .01). Infants did not show a significant SNR response to faces before or after training. Results reveal fundamental differences in infant’s ability to allocate attention during simultaneously presented faces and objects, relative to adults. In addition, topographic changes before and after a learning period suggest that neural responses to attended faces and/or objects change dynamically with individual-level label learning in both adults and infants.

Authors

• Ryan Barry-Anwar, University of Florida
  Presenting Author

• Ethan Kutlu, University of Florida
  Non-Presenting Author

• Gabriella Silva, University of Florida
  Non-Presenting Author

• Andreas Keil, University of Florida
  Non-Presenting Author

• Lisa S Scott, University of Florida
  Non-Presenting Author