Varying Stimulus Duration Reveals Consistent Neural Activity and Behavior for Human Face Individuation

consistent relationships between neural activity and behavior is a challenge in human cognitive neuroscience research. We addressed this issue using variable time constraints in an oddball frequency-sweep design for visual discrimination of complex images (face exemplars). Sixteen participants viewed sequences of ascending presentation durations, from 25 to 333 ms (40-3 Hz stimulation rate) while their electroencephalogram (EEG) was recorded. Throughout each sequence, the same unfamiliar face picture was repeated with variable size and luminance changes while different unfamiliar facial identities appeared every 1 s (1 Hz). A neural face individuation response, tagged at 1 Hz and its unique harmonics, emerged over the occipito-temporal cortex at 50 ms stimulus duration (25-100 ms across individuals), with an optimal response reached at 170 ms stimulus duration. In a subsequent experiment, identity changes appeared non-periodically within fixed-frequency sequences while the same participants performed an explicit face individuation task. The behavioral face individuation response also emerged at 50 ms presentation time, and behavioral accuracy correlated with individual participants' neural response amplitude in a weighted middle stimulus duration range (50-125 ms). Moreover, the latency of the neural response peaking between 180 and 200 ms correlated strongly with individuals' behavioral accuracy in this middle duration range, as measured independently. These observa-tions point to the minimal (50 ms) and optimal (170 ms) stimulus durations for human face individuation and pro -vide novel evidence that inter-individual differences in the magnitude and latency of early, high-level neural responses are predictive of behavioral differences in performance at this function. (c) 2021 IBRO. Published by Else -vier Ltd. All rights reserved.

Automated summary

The study investigated the relationship between neural activity and behavioral performance in visual discrimination of complex images, finding that the optimal neural face individuation response emerged at 50 ms and 170 ms stimulus durations. Behavioral accuracy correlated with neural response amplitude in the 50-125 ms range, suggesting predictive value of early neural responses in predicting performance differences.