fNIRS and Neurodevelopment: How Preterm Infants Process Faces With and Without Masks

A BrainLatam2026 reading on NIRS/fNIRS, face perception, early social cognition, Damasian Mind, APUS and Jiwasa

Before talking about the brain, we need to return to the face.

The face is one of the first human landscapes. Before words, before explanations, before school, the infant meets eyes, mouth, expression, warmth, breathing and presence. In this sensitive field, an important part of belonging begins: the infant does not simply “see” another person; the infant begins to organize the body in front of another body.

That is why the publication “Face perception and impact of face masks at 6 months post-term age in preterm and term infants (The BabyFace Study)”, by Celina Brunsch, Eri Nanizawa, Srikar Vallabhapurapu and colleagues, published in Scientific Reports in 2026, is so important.

The study investigated, using fNIRS — functional near-infrared spectroscopy, how preterm and term infants process full happy faces and happy faces partially covered by masks.

The article asks a simple, delicate and powerful question:

Do preterm infants, at 6 months post-term age, process full faces and masked faces in the same way as term-born infants?

This question deserves attention because it emerges from a real clinical and social situation. The COVID-19 pandemic changed face-to-face interaction. Masks covered important facial zones, especially the mouth and nose, precisely the regions that help infants integrate emotion, intention and social communication.

The strength of this article is that it transforms a social and clinical concern into a measurable experimental question. The researchers did not remain only in behavioral observation. They used multichannel fNIRS, a non-invasive NIRS technology well tolerated in infants, to measure changes in oxygenated and deoxygenated hemoglobin while infants looked at faces.

This is science with materiality: a human question, a compatible experimental design and a physiological measure capable of observing the developing brain.

The study assessed 24 preterm infants, born between 23 and 30 weeks of gestation, and 24 term-born infants, all at 6 months post-term age. During the task, infants viewed short 5-second trials with images of full happy faces or masked happy faces, interspersed with 9-to-15-second baseline trials. The fNIRS montage covered inferior-frontal, temporo-parietal and lateral occipital regions, areas related to face perception, emotion and social processing.

The findings are highly relevant. Term infants showed a higher oxygenated hemoglobin response than preterm infants to full faces in the right inferior-frontal region. Term infants also showed higher activation for full faces than masked faces in the right temporo-parietal region. Preterm infants, however, did not show this same differentiation between full and masked faces.

The authors’ interpretation is careful: the findings suggest lower brain activation in preterm infants in the inferior-frontal region, which is important for face and emotion processing. They also suggest that preterm infants may show altered face perception at 6 months post-term age, since they did not present a clear differential brain response between full and masked faces.

From the BrainLatam2026 perspective, this article allows us to say something deeper, without going beyond the evidence:

belonging begins before language.

In the Damasian Mind, consciousness emerges through the integration of body, interoception and proprioception. An infant does not interpret a face as an adult interprets an image. The infant feels patterns: eyes, mouth, expression, approach, safety, rhythm and presence. The face of the other participates in the early formation of the self because it helps the infant’s body predict the world.

Here, Iam becomes an important avatar-lens: the infant begins to form an “I” because there is another body that responds. Jiwasa also appears, because the face is one of the first forms of “we”: I look, you respond; I regulate, you smile; my body learns that there is a shared world. And APUS enters because the caregiver’s face is not only an image; it is an affective territory.

This study also speaks directly to Decolonial Neuroscience: what kind of sensory world are we offering to infants?

This is not about blaming masks, hospitals or health professionals. Masks were necessary protection in many moments. The scientific and political question is different: when a child is born preterm and spends weeks or months in a neonatal intensive care unit, what ecology of face, voice, touch, smell, light, sound and presence supports that child’s development?

The authors were responsible in recognizing limitations. The sample is small, as often happens in infant fNIRS studies. Infant movement and attention create data loss. The results are preliminary and require replication in larger studies. The study also cannot fully separate the effects of prematurity, prolonged exposure to masked faces in the NICU, and developmental maturation.

That careful tone increases the value of the publication. The article does not promise more than it can deliver. It opens a path.

From the article’s question to a BrainLatam2026 experimental design

The article asked:

How do preterm and term infants process full and masked faces at 6 months post-term age?

To answer this, the authors measured:

hemodynamic responses using fNIRS in inferior-frontal, temporo-parietal and lateral occipital regions while infants viewed full happy faces and masked happy faces.

The study showed:

differences between preterm and term infants in inferior-frontal activation, and a difference between full and masked faces in term infants that was not observed in preterm infants.

From this contribution, BrainLatam2026 can ask:

How does the quality of face-to-face interaction — face, voice, breathing, touch and presence — participate in the early formation of belonging, bodily regulation and social perception in preterm infants?

That new question would require a compatible experimental design combining:

fNIRS/NIRS + EEG/ERP + eye-tracking + respiration + HRV/RMSSD + possible caregiver-infant hyperscanning.

fNIRS remains essential because it allows non-invasive measurement of cortical responses in infants. EEG/ERP could capture the fast temporal dynamics of face perception, including early visual and social processing. Eye-tracking would show whether infants look more at the eyes, mouth or masked regions. Respiration and HRV/RMSSD could indicate whether the infant enters greater regulation or alertness. And fNIRS hyperscanning between caregiver and infant, when possible, could investigate whether adult-infant synchrony changes depending on full face exposure, masked face exposure, affective voice or bodily contact.

This is the difference between choosing technology because it is fashionable and choosing technology because the question requires it.

We do not use NIRS, fNIRS, EEG, ERP or Hyperscanning because the equipment looks sophisticated. We use them because each scientific question requires a specific way of listening to the body, the brain and the territory.

Why this article matters for researchers working with NIRS, fNIRS, EEG and neurodevelopment

This publication shows that fNIRS can be a powerful tool for studying early social development.

In adults, many questions about face perception can be investigated with fMRI, EEG or ERP. But with infants, especially preterm infants, the experimental design must be more delicate, portable, tolerable and compatible with natural movement. This is where NIRS/fNIRS becomes extremely relevant for academic research in neonatology, developmental psychology, cognitive neuroscience and public health.

For Latin American laboratories, this kind of study opens many possibilities:

How do infants in public neonatal intensive care units process face, voice and touch?
How does skin-to-skin contact modify fNIRS responses?
How does the presence of the mother, father or another caregiver change inferior-frontal and temporo-parietal activity?
How do prematurity, social inequality, hospital environment and early bonding intersect in neurodevelopment?
How can we design fNIRS and EEG/ERP protocols that respect infants, families and territories?

From the BrainLatam2026 perspective, this publication opens a door to thinking about neurodevelopment as embodied belonging.

The preterm infant is not merely an organism at risk. It is a life in formation, trying to synchronize body, brain, face, voice, smell, touch and world. The NICU is not only a technical space; it is a sensory territory. And if sensory territory matters, then public policy, hospital architecture, family presence, parental leave, humanized care and technologies such as fNIRS also belong to the same conversation.

DREX Cidadão, public policy and the metabolism of care

DREX Cidadão enters here as a concept of social metabolism. If society wants to protect early neurodevelopment, it must guarantee that families have the material conditions to remain close, to care, to accompany and to sustain presence.

There is no healthy neurodevelopment without available bodies.
There is no bonding without time.
There is no belonging without minimum social conditions.

This study shows, through fNIRS, that the infant brain responds in measurable ways to how the human face appears. BrainLatam2026 expands this question into the social field: what kind of State, hospital, city and economy allow infants to encounter enough faces, voices and bodies to develop Jiwasa?

Closing

This article matters because it shows that face perception in preterm infants can be investigated with rigor, delicacy and appropriate technology. It values an essential question: how does the social brain begin to recognize the other?

From BrainLatam2026, the answer begins in the body.
It begins in the face.
It begins in the gaze.
It begins before language.

And perhaps one of the great tasks of Decolonial Neuroscience is this: to remember that every developing brain needs territory, presence and belonging in order to become fully human.

Suggested hashtags

#fNIRS #NIRS #EEG #ERP #Neurodevelopment #PretermInfants #FacePerception #Neonatology #DevelopmentalNeuroscience #BrainLatam2026 #BrainSupport #DamasianMind #Jiwasa #APUS #DecolonialNeuroscience #Hyperscanning #Neurotechnology #AcademicResearch

Reference

Brunsch, C., Nanizawa, E., Vallabhapurapu, S., Keurentjes, N., Van Lint, K., Sijbring, A., Walker, D., Laycock, R., & Wong, F. (2026). Face perception and impact of face masks at 6 months post-term age in preterm and term infants (The BabyFace Study). Scientific Reports. https://doi.org/10.1038/s41598-026-48027-y