In an ophthalmological setting, visual function is typically assessed using “subjective” (i.e., psychophysical) measures that are critically dependent on the patient's ability to reliably report their perception. In cases of cognitive impairment or in pediatric populations, responses are often unreliable, highlighting the need for more objective assessment methods. Current objective approaches primarily rely on low-level visual evoked potentials (VEPs), recorded using frequency-tagging (FT) paradigms, which provide robust and rapid measures of pre-cortical visual pathway integrity and associated estimates of visual acuity (VA). Unlike conventional VEPs, the P300 component of the event-related potential reflects higher-level cognitive processes, such as stimulus recognition and discrimination and allows for the use of a wide variety of stimuli, including optotypes. Our recent work has progressively refined P300-based visual acuity estimation. We first established its relationship with psychophysical measures of VA and characterized attentional influence as a potential confound. Building on this, we validated P300-based VA estimation in amblyopia by directly comparing it with both psychophysical and VEP-derived measures, thereby addressing disease-specific acuity overestimation inherent to VEP-based approaches. We further demonstrated that reliable estimates can be obtained with rapid stimulation (~4.6 Hz) using an FT-based paradigm, making the approach more viable for clinical routine. Together, these findings highlight the translational potential of the P300 as an objective tool for quantifying visual and visuo-cognitive functions across a wide range of populations, including children and cognitively impaired patients. Both VEP- and P300-based measures of VA might serve as screening tools in studies of higher-level visual performance.

Early learning experiences relate to infants’ ability to detect commonalities among objects in their environment. Assessing fast categorization in infants may, thus, enable us to understand risks of early cognitive development. As part of the Bremer Initiative to Foster Early Childhood Development (BRISE), we investigated ERP familiarization and frequency tagging (FT) responses to frequent (A) and infrequent (B) artificial categories in N = 314 infants from a high-risk sample (M = 8.5 months, SD = 38 days). In the ERP paradigm, 50 images of the frequent category were presented for 1,000 ms each. In the FT oddball paradigm, 6 images were presented per second (6 Hz), with categorical changes at every 5^th image (AAAABAAAABA…, corresponding to 1.2 Hz) while recording EEG.

As expected, the Negative central (Nc) component showed a strong decrease of attention during familiarization (subsample N = 249), p < .001. In the FT paradigm (subsample N = 161), a strong and significant visual categorization response was observed in most participants (81.08%). Compared to a non-risk sample (N = 120 7-month-olds), a lower base response (6 Hz and harmonics) was detected, p < .01, reflecting decreased general visual responses. This response was correlated with paternal employment status, r = .16, p < .05. The categorization response (1.2 and harmonics) did not differ between groups, but increased variability was recorded in the high-risk sample, p < .05. Together, these data reveal an early attentional disadvantage associated with increased variability of cognitive functions in infants at-risk.

Developmental changes in functional neuronal networks are sensitive to environmental influences. This EEG study from the Bremen Initiative to Foster Early Childhood Development (BRISE) examined how family background influences infants’ neuronal responses to auditory stimuli. A total of 255 infants (M = 8.3 months, SD = 1.4 months) participated in a passive auditory oddball paradigm (200 standards, 48 deviants). Additionally, resting-state EEG data was collected to extract the individual alpha frequency (IAF) for the sample. Socioeconomic status (SES) was assessed via parental education and migration background.

Results revealed an immature N2-P3a complex. The N2 was diminished for deviant processing in infants from families with both low parental education and migration background, suggesting a cumulative impact of SES factors. These group differences were also reflected in event-related spectral perturbation (ERSP) and inter-trial coherence (ITC) around the infants’ IAF of 5.3 Hz for the N2 time-window of deviant processing. Increased developmental risks may delay the emergence of faster spontaneous oscillations that the infant N2 emerges concurrently with. Our results may be an indication that the N2 component is immature in infancy and sensitive to environmental influences.

Together, these findings highlight that early differences in the neuronal response to deviating stimuli - reflected in both ERP and oscillatory dynamics - are shaped by the intersection of environmental stressors and neurodevelopmental stages. These neuronal markers may serve as early indicators of altered attentional development, later becoming evident in behaviour, and underscore the importance of inclusive developmental research and early prevention efforts.

Research shows that the theta rhythm in infant electroencephalogram indexes learning processes and is a promising candidate for a marker of early cognitive development. However, a scarcity of studies investigating the stability of individual differences in theta activity in infancy, and a large variability in analytical approaches in existing research constrain the interpretations of research findings. In our longitudinal study, we related three different indices of frontocentral theta activity (absolute and relative power, and an index of theta modulation by novel content) at 6 and 12 months to cognitive development level, language skills, and visual attention at 24 months. We found an increase in theta power over the course of novel information encoding at 6 and 12 months, replicating prior studies. Both absolute and relative theta power, but not theta modulation index, showed a large degree of stability in individual differences from 6 to 12 months. Finally, absolute theta power at 6 and 12 months was a positive predictor of the general cognitive level, but not of specific skills (selective attention, language) at 24 months. Of note, we observed similar effects for absolute power in the alpha frequency band, suggesting that the effects are not specific to the theta frequency band. Our results support the involvement of the theta rhythm in cognitive development in infancy and point to absolute power as the potentially most sensitive index of individual differences in theta activity.