Frequency tagging with infants: The visual oddball paradigm

The development of visual categorization based on high-level cues

This study investigated the development of rapid visual object categorization. N = 20 adults (Experiment 1), N = 21 five to six-year-old children (Experiment 2), and N = 140 four-, seven-, and eleven-month-old infants (Experiment 3; all predominantly White, 81 females, data collected in 2013-2020) participated in a fast periodic visual stimulation electroencephalographic task. Similar categorization of animal and furniture stimuli emerged in children and adults, with responses much reduced by phase-scrambling (R2  = .34-.73). Categorization was observed from 4 months, but only at 11 months, high-level cues enhanced performance (R2  = .11). Thus, first signs of rapid categorization were evident from 4 months, but similar categorization patterns as in adults were recorded only from 11 months on.

Communicative signals during joint attention promote neural processes of infants and caregivers

Communicative signals such as eye contact increase infants' brain activation to visual stimuli and promote joint attention. Our study assessed whether communicative signals during joint attention enhance infant-caregiver dyads' neural responses to objects, and their neural synchrony. To track mutual attention processes, we applied rhythmic visual stimulation (RVS), presenting images of objects to 12-month-old infants and their mothers (n = 37 dyads), while we recorded dyads' brain activity (i.e., steady-state visual evoked potentials, SSVEPs) with electroencephalography (EEG) hyperscanning. Within dyads, mothers either communicatively showed the images to their infant or watched the images without communicative engagement. Communicative cues increased infants' and mothers' SSVEPs at central-occipital-parietal, and central electrode sites, respectively. Infants showed significantly more gaze behaviour to images during communicative engagement. Dyadic neural synchrony (SSVEP amplitude envelope correlations, AECs) was not modulated by communicative cues. Taken together, maternal communicative cues in joint attention increase infants' neural responses to objects, and shape mothers' own attention processes. We show that communicative cues enhance cortical visual processing, thus play an essential role in social learning. Future studies need to elucidate the effect of communicative cues on neural synchrony during joint attention. Finally, our study introduces RVS to study infant-caregiver neural dynamics in social contexts.

Rhythmic visual stimulation as a window into early brain development: A systematic review

Rhythmic visual stimulation (RVS), the periodic presentation of visual stimuli to elicit a rhythmic brain response, is increasingly applied to reveal insights into early neurocognitive development. Our systematic review identified 69 studies applying RVS in 0- to 6-year-olds. RVS has long been used to study the development of the visual system and applications have more recently been expanded to uncover higher cognitive functions in the developing brain, including overt and covert attention, face and object perception, numeral cognition, and predictive processing. These insights are owed to the unique benefits of RVS, such as the targeted frequency and stimulus-specific neural responses, as well as a remarkable signal-to-noise ratio. Yet, neural mechanisms underlying the RVS response are still poorly understood. We discuss critical challenges and avenues for future research, and the unique potentials the method holds. With this review, we provide a resource for researchers interested in the breadth of developmental RVS research and hope to inspire the future use of this cutting-edge method in developmental cognitive neuroscience.

What determines the neural response to snakes in the infant brain? A systematic comparison of color and grayscale stimuli

Snakes and primates have coexisted for thousands of years. Given that snakes are the first of the major primate predators, natural selection may have favored primates whose snake detection abilities allowed for better defensive behavior. Aligning with this idea, we recently provided evidence for an inborn mechanism anchored in the human brain that promptly detects snakes, based on their characteristic visual features. What are the critical visual features driving human neural responses to snakes is an unresolved issue. While their prototypical curvilinear coiled shape seems of major importance, it remains possible that the brain responds to a blend of other visual features. Coloration, in particular, might be of major importance, as it has been shown to act as a powerful aposematic signal. Here, we specifically examine whether color impacts snake-specific responses in the naive, immature infant brain. For this purpose, we recorded the brain activity of 6-to 11-month-old infants using electroencephalography (EEG), while they watched sequences of color or grayscale animal pictures flickering at a periodic rate. We showed that glancing at colored and grayscale snakes generated specific neural responses in the occipital region of the brain. Color did not exert a major influence on the infant brain response but strongly increased the attention devoted to the visual streams. Remarkably, age predicted the strength of the snake-specific response. These results highlight that the expression of the brain-anchored reaction to coiled snakes bears on the refinement of the visual system.