Convergent and divergent fMRI responses in children and adults to increasing language production demands

In adults, patterns of neural activation associated with perhaps the most basic language skill—overt object naming—are extensively modulated by the psycholinguistic and visual complexity of the stimuli. Do children's brains react similarly when confronted with increasing processing demands, or they solve this problem in a different way? Here we scanned 37 children aged 7–13 and 19 young adults who performed a well-normed picture-naming task with 3 levels of difficulty. While neural organization for naming was largely similar in childhood and adulthood, adults had greater activation in all naming conditions over inferior temporal gyri and superior temporal gyri/supramarginal gyri. Manipulating naming complexity affected adults and children quite differently: neural activation, especially over the dorsolateral prefrontal cortex, showed complexity-dependent increases in adults, but complexity-dependent decreases in children. These represent fundamentally different responses to the linguistic and conceptual challenges of a simple naming task that makes no demands on literacy or metalinguistics. We discuss how these neural differences might result from different cognitive strategies used by adults and children during lexical retrieval/production as well as developmental changes in brain structure and functional connectivity

Reduced neural sensitivity to social stimuli in infants at risk for autism

In the hope of discovering early markers of autism, attention has recently turned to the study of infants at risk owing to being the younger siblings of children with autism. Because the condition is highly heritable, later-born siblings of diagnosed children are at substantially higher risk for developing autism or the broader autism phenotype than the general population. Currently, there are no strong predictors of autism in early infancy and diagnosis is not reliable until around 3 years of age. Because indicators of brain functioning may be sensitive predictors, and atypical social interactions are characteristic of the syndrome, we examined whether temporal lobe specialization for processing visual and auditory social stimuli during infancy differs in infants at risk. In a functional near-infrared spectroscopy study, infants aged 4–6 months at risk for autism showed less selective neural responses to social stimuli (auditory and visual) than low-risk controls. These group differences could not be attributed to overall levels of attention, developmental stage or chronological age. Our results provide the first demonstration of specific differences in localizable brain function within the first 6 months of life in a group of infants at risk for autism. Further, these differences closely resemble known patterns of neural atypicality in children and adults with autism. Future work will determine whether these differences in infant neural responses to social stimuli predict either later autism or the broader autism phenotype frequently seen in unaffected family members

Using functional near-infrared spectroscopy to study the early developing brain: future directions and new challenges

Significance: Functional near-infrared spectroscopy (fNIRS) is a frequently used neuroimaging tool to explore the developing brain, particularly in infancy, with studies spanning from birth to toddlerhood (0 to 2 years). We provide an overview of the challenges and opportunities that the developmental fNIRS field faces, after almost 25 years of research.Aim: We discuss the most recent advances in fNIRS brain imaging with infants and outlines the trends and perspectives that will likely influence progress in the field in the near future.Approach: We discuss recent progress and future challenges in various areas and applications of developmental fNIRS from methodological and technological innovations to data processing and statistical approaches.Results and Conclusions: The major trends identified include uses of fNIRS "in the wild," such as global health contexts, home and community testing, and hyperscanning; advances in hardware, such as wearable technology; assessment of individual variation and developmental trajectories particularly while embedded in studies examining other environmental, health, and context specific factors and longitudinal designs; statistical advances including resting-state network and connectivity, machine learning and reproducibility, and collaborative studies. Standardization and larger studies have been, and will likely continue to be, a major goal in the field, and new data analysis techniques, statistical methods, and collaborative cross-site projects are emerging. (c) The Authors. Published by SPIE under a Creative Commons Attribution 4.0 International License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI

Are you talking to me? Neural activations in 6-month-old infants in response to being addressed during natural interactions

Human interactions are guided by continuous communication among the parties involved, in which verbal communication plays a primary role. However, speech does not necessarily reveal to whom it is addressed, especially for young infants who are unable to decode its semantic content. To overcome such difficulty, adults often explicitly mark their communication as infant-directed. In the present study we investigated whether ostensive signals, which would disambiguate the infant as the addressee of a communicative act, would modulate the brain responses of 6-month-old infants to speech and gestures in an ecologically valid setting. In Experiment 1, we tested whether the gaze direction of the speaker modulates cortical responses to infant-direct speech. To provide a naturalistic environment, two infants and their parents participated at the same time. In Experiment 2, we tested whether a similar modulation of the cortical response would be obtained by varying the intonation (infant versus adult directed speech) of the speech during face-to-face communication, one on one. The results of both experiments indicated that only the combination of ostensive signals (infant directed speech and direct gaze) led to enhanced brain activation. This effect was indicated by responses localized in regions known to be involved in processing auditory and visual aspects of social communication. This study also demonstrated the potential of fNIRS as a tool for studying neural responses in naturalistic scenarios, and for simultaneous measurement of brain function in multiple participants

Test–retest reliability of functional near infrared spectroscopy in infants

Abstract. There has been a rapid rise in the number of publications using functional near infrared spectroscopy (fNIRS) for human developmental research over the past decade. However test–retest reliability of this measure of brain activation in infants remains unknown. To assess this, we utilized data from a longitudinal cohort who participated in an fNIRS study on social perception at two age points. Thirteen infants had valid data from two sessions held 8.5 months apart (4 to 8 months and 12 to 16 months). Inter- and intrasession fNIRS test–retest reliability was assessed at the individual and group levels using the oxyhemoglobin (HbO2) signal. Infant compliance with the study was similar in both sessions (assessed by the proportion of time infants looked to the stimuli), and there was minimal discrepancy in sensor placement over the targeted area between sessions. At the group level, good spatial overlap of significant responses and signal reliability was seen (spatial overlap was 0.941 and average signal change within an region of interest was r=0.896). At participant level, spatial overlap was acceptable (>0.5 on average across infants) although signal reliability varied between participants. This first study of test–retest reliability of fNIRS in infants shows encouraging results, particularly for group-based analysis

Optical imaging during toddlerhood: brain responses during naturalistic social interactions

Despite the importance of our ability to interact and communicate with others, the early development of the social brain network remains poorly understood. We examined brain activity in 12- to 14-month-old infants while they were interacting live with an adult in two different naturalistic social scenarios (i.e., reading a picture book versus singing nursery rhymes with gestures), as compared to baseline (i.e., showing infants a toy without eye contact or speech). We used functional near-infrared spectroscopy (fNIRS) recorded over the right temporal lobe of infants to assess the role of the superior temporal sulcus - temporoparietal junction (STS-TPJ) region during naturalistic social interactions. We observed increased cortical activation in the STS-TPJ region to live social stimuli in both socially engaging conditions compared to baseline during real life interaction, with greater activation evident for the joint attention (reading book) condition relative to the social nursery rhymes. These results supported the view that the STS-TPJ region, engaged in the cortical social brain network, is already specialized in infants for processing social signals and is sensitive to communicative situations. This study also highlighted the potential of fNIRS for studying brain function in infants entering toddlerhood during live social interaction

Non-invasive measurement of a metabolic marker of infant brain function

While near-infrared spectroscopy (NIRS) haemodynamic measures have proven to be vastly useful in investigating human brain development, the haemodynamic response function (HRF) in infants is not yet fully understood. NIRS measurements of the oxidation state of mitochondrial enzyme cytochrome-c-oxidase (oxCCO) have the potential to yield key information about cellular oxygen utilisation and therefore energy metabolism. We used a broadband NIRS system to measure changes in oxCCO, in addition to haemodynamic changes, during functional activation in a group of 33 typically developing infants aged between 4 and 6 months. The responses were recorded over the right temporal lobe while the infants were presented with engaging videos containing social content. A significant increase in oxCCO was found in response to the social stimuli, with maximum increase of 0.238 ± 0.13 μM. These results are the first reported significant change in oxCCO in response to stimulus-evoked activation in human infants and open new vistas for investigating human infant brain function and its energy metabolism

Coregistering functional near-infrared spectroscopy with underlying cortical areas in infants

Functional near-infrared spectroscopy (fNIRS) is becoming a popular tool in developmental neuroscience for mapping functional localized brain responses. However, as it cannot provide information about underlying anatomy, researchers have begun to conduct spatial registration of fNIRS channels to cortical anatomy in adults. The current work investigated this issue with infants by coregistering fNIRS and magnetic resonance imaging (MRI) data from 55 individuals. Our findings suggest that fNIRS channels can be reliably registered with regions in the frontal and temporal cortex of infants from 4 to 7 months of age. Although some macro-anatomical regions are difficult to consistently define, others are more stable and fNIRS channels on an age-appropriate MRI template are often consistent with individual infant MRIs. We have generated a standardized scalp surface map of fNIRS channel locators to reliably locate cortical regions for fNIRS developmental researchers. This new map can be used to identify the inferior frontal gyrus, superior temporal sulcus (STS) region [which includes the superior and middle temporal gyri (MTG) nearest to the STS], and MTG and temporal-parietal regions in 4- to 7-month-old infants. Future work will model data for the whole head, taking into account the properties of light transport in tissue, and expanding to different ages across development

fNIRS for tracking brain development in the context of global health projects

Over the past 25 years, functional near-infrared spectroscopy (fNIRS) has emerged as a valuable tool to study brain function, and it is in younger participants where it has found, arguably, its most successful application. Thanks to its infant-friendly features, the technology has helped shape research in the neurocognitive development field by contributing to our understanding of the neural underpinnings of sensory perception and socio-cognitive skills. Furthermore, it has provided avenues of exploration for markers of compromised brain development. Advances in fNIRS instrumentation and methods have enabled the next step in the evolution of its applications including the investigation of the effects of complex and interacting socio-economic and environmental adversities on brain development. To do this, it is necessary to take fNIRS out of well-resourced research labs (the majority located in high-income countries) to study at-risk populations in resource-poor settings in low- and middle-income countries (LMICs). Here we review the use of this technology in global health studies, we discuss the implementation of fNIRS studies in LMICs with a particular emphasis on the Brain Imaging for Global Health (BRIGHT) project, and we consider its potential in this emerging field

Cortical activation to action perception is associated with action production abilities in young infants

The extent to which perception and action share common neural processes is much debated in cognitive neuroscience. Taking a developmental approach to this issue allows us to assess whether perceptual processing develops in close association with the emergence of related action skills within the same individual. The current study used functional near-infrared spectroscopy (fNIRS) to investigate the perception of human action in 4- to 6-month-old human infants. In addition, the infants' manual dexterity was assessed using the fine motor component of The Mullen Scales of Early Learning and an in-house developed Manual Dexterity task. Results show that the degree of cortical activation, within the posterior superior temporal sulcus—temporoparietal junction (pSTS-TPJ) region, to the perception of manual actions in individual infants correlates with their own level of fine motor skills. This association was not fully explained by either measures of global attention (i.e., looking time) or general developmental stage. This striking concordance between the emergence of motor skills and related perceptual processing within individuals is consistent with experience-related cortical specialization in the developing brain