Functional near-infrared spectroscopy in toddlers: Neural differentiation of communicative cues and relation to future language abilities

Do Children's Brains Function Differently During Book Reading and Screen Time? A fNIRS Study

Previous research suggests that book reading and screen time have contrasting effects on language and brain development. However, few studies have explicitly investigated whether children's brains function differently during these two activities. The present study used functional near-infrared spectroscopy (fNIRS) to measure brain response in 28 typically developing preschool-aged children (36-72 months old) during two conditions-a book reading condition, in which children listened to a story read by a live experimenter while viewing words and pictures in a book, and a screen time condition, in which children listened to a story that was played via an audio recording while viewing words and pictures on a screen. Analyses revealed significant activation in the right temporal parietal junction (TPJ) during the book reading condition only. Across regions of interest (ROIs), including the inferior and middle frontal gyrus (IMFG), the superior and middle temporal gyrus (SMTG), and the TPJ, brain response during the book reading condition was greater in right-lateralized ROIs than left-lateralized ROIs, while brain response during the screen time condition was similar across left and right ROIs. Findings suggest that the lateralization of preschool-aged children's brain function within these ROIs differs during book reading and screen time, which provides a possible neurobiological explanation for why book reading and screen time impact language development in such different ways. Findings provide important insights into how children's brains function during different types of activities (dyadic vs. solitary) and when using different types of media (print vs. digital).

Speech-Processing Network Formation of Cochlear-Implanted Toddlers With Early Hearing Experiences

To reveal the formation process of speech processing with early hearing experiences, we tracked the development of functional connectivity in the auditory and language-related cortical areas of 84 (36 female) congenitally deafened toddlers using repeated functional near-infrared spectroscopy for up to 36 months post cochlear implantation (CI). Upon hearing restoration, the CI children lacked the modular organization of the mature speech-processing network and demonstrated a higher degree of immaturity in temporo-parietal than temporo-frontal connections. The speech-processing network appeared to form rapidly with early CI experiences, with two-thirds of the developing connections following nonlinear trajectories reflecting possibly more than one synaptogenesis-pruning cycle. A few key features of the mature speech-processing network emerged within the first year of CI hearing, including left-hemispheric advantage, differentiation of the dorsal and ventral processing streams, and functional state (speech listening vs. resting) specific patterns of connectivity development. The developmental changes were predictable of future auditory and verbal communication skills of the CI children, with prominent contribution from temporo-parietal connections in the dorsal stream, suggesting a mediating role of speech-processing network formation with early hearing experiences in speech acquisition.

Individualized post-operative prediction of cochlear implantation outcomes in children with prelingual deafness using functional near-infrared spectroscopy

Objective

The goal of this study was to develop an objective measure and predictor of cochlear implantation (CI) outcomes using functional near-infrared spectroscopy (fNIRS) for young children with prelingual deafness.

Methods

Sound-evoked hemodynamic responses were recorded from auditory and language-related cortical regions of 47 child CI recipients (35.47 ± 17.24 months of age) using fNIRS shortly after CI activation (0.26 ± 0.30 months). There were four sound conditions (natural speech, instrumental music, multi-speaker babble noise, and speech-in-noise). Post-CI auditory and verbal communication performance was evaluated using clinical questionnaires with caretakers. Both classification and individualized regression models were constructed to predict post-CI behavioral improvement from fNIRS data using support vector machine (SVM) learning algorithms.

Results

Auditory cortical responses shortly after CI hearing onset yielded highly accurate prediction of behavioral development in young CI children. For classification models, optimal prediction was achieved using cortical responses to two or more sound conditions, with the highest accuracy of 98.20% (precision = 98.17%, sensitivity = 98.96%, area under the curve of the receiver operating characteristic curve = 99.61%) obtained with the combination of speech, noise, and music stimuli. Similarly, for regression models, best prediction of individual development was achieved using three (highest r = 0.919) or four (r = 0.966) sound conditions. The predictability of cortical responses far outperformed (Cohen's d: 18.56) that of the collection of audiological and demographic parameters (classification accuracy: 0.62) under the same SVM algorithms and could not benefit from the inclusion of the latter.

Conclusion

Machine learning models using auditory cortical hemodynamic responses shortly after CI activation were able to predict individualized post-CI behavioral improvement in children with prelingual deafness.

Level of Evidence

Level 5.

Functional near-infrared spectroscopy and language development: An integrative review

Functional near-infrared spectroscopy (fNIRS) stands poised to revolutionize our understanding of auditory detection, speech perception, and language development in infants. In this study, we conducted a meticulous integrative review across Medline, Scopus, and LILACS databases, targeting investigations utilizing fNIRS to explore language-related features and cortical activation during auditory stimuli in typical infants. We included studies that used the NIRS technique to study language and cortical activation in response to auditory stimuli in typical infants between 0 and 3 years old. We used the ROBINS-I tool to assess the quality and the risk of bias in the studies. Our analysis, encompassing 66 manuscripts, is presented in standardized tables for streamlined data extraction. We meticulously correlated findings with children's developmental stages, delineating crucial insights into brain development and its intricate interplay with language outcomes. Although most studies have a high risk for overall bias, especially due to the high loss of data in NIRS studies, the low risk in the other domains is predominant and homogeneous among the studies. Highlighted are the unique advantages of fNIRS for pediatric studies, underscored by its innate suitability for use in children. This review accentuates fNIRS' capacity to elucidate the neural correlates of language processing and the sequential steps of language acquisition. From birth, infants exhibit abilities that lay the foundation for language development. The progression from diffuse to specific neural activation patterns is extremely influenced by exposure to languages, social interaction, and prosodic features and, reflects the maturation of brain networks involved in language processing. In conclusion, fNIRS emerges as an indispensable functional imaging modality, providing insights into the temporal dynamics of language acquisition and associated developmental milestones. This synthesis presents the pivotal role of fNIRS in advancing our comprehension of early language development and paves the way for future research endeavors in this domain.

Anti-phasic oscillatory development for speech and noise processing in cochlear implanted toddlers

Human brain demonstrates amazing readiness for speech and language learning at birth, but the auditory development preceding such readiness remains unknown. Cochlear implanted (CI) children (n = 67; mean age 2.77 year ± 1.31 SD; 28 females) with prelingual deafness provide a unique opportunity to study this stage. Using functional near-infrared spectroscopy, it was revealed that the brain of CI children was irresponsive to sounds at CI hearing onset. With increasing CI experiences up to 32 months, the brain demonstrated function, region and hemisphere specific development. Most strikingly, the left anterior temporal lobe showed an oscillatory trajectory, changing in opposite phases for speech and noise. The study provides the first longitudinal brain imaging evidence for early auditory development preceding speech acquisition.

The Neural Bases of Language Processing During Social and Non-Social Contexts: A fNIRS Study of Autistic and Neurotypical Preschool-Aged Children

Background

Little is known about how the brains of autistic children process language during real-world "social contexts," despite the fact that challenges with language, communication, and social interaction are core features of Autism Spectrum Disorder (ASD).

Methods

We investigated the neural bases of language processing during social and non-social contexts in a sample of N=20 autistic and N=20 neurotypical (NT) preschool-aged children, 3 to 6 years old. Functional near-infrared spectroscopy (fNIRS) was used to measure children's brain response to "live language" spoken by a live experimenter during an in-person social context (i.e., book reading), and "recorded language" played via an audio recording during a non-social context (i.e., screen time). We examined within-group and between-group differences in the strength and localization of brain response to live language and recorded language, as well as correlations between children's brain response and language skills measured by the Preschool Language Scales.

Results

In the NT group, brain response to live language was greater than brain response to recorded language in the right temporal parietal junction (TPJ). In the ASD group, the strength of brain response did not differ between conditions. The ASD group showed greater brain response to recorded language than the NT group in the right inferior and middle frontal gyrus (IMFG). Across groups, children's language skills were negatively associated with brain response to recorded language in the right IMFG, suggesting that processing recorded language required more cognitive effort for children with lower language skills. Children's language skills were also positively associated with the difference in brain response between conditions in the right TPJ, demonstrating that children who showed a greater difference in brain response to live language versus recorded language had higher language skills.

Limitations

Findings should be considered preliminary until they are replicated in a larger sample.

Conclusions

Findings suggest that the brains of NT children, but not autistic children, process language differently during social and non-social contexts. Individual differences in how the brain processes language during social and non-social contexts may help to explain why language skills are so variable across children with and without autism.

Encouraging pointing with the right hand, but not the left hand, gives right-handed 3-year-olds a linguistic advantage

Previous research has shown a strong positive association between right-handed gesturing and vocabulary development. However, the causal nature of this relationship remains unclear. In the current study, we tested whether gesturing with the right hand enhances linguistic processing in the left hemisphere, which is contralateral to the right hand. We manipulated the gesture hand children used in pointing tasks to test whether it would affect their performance. In either a linguistic task (verb learning) or a non-linguistic control task (memory), 131 typically developing right-handed 3-year-olds were encouraged to use either their right hand or left hand to respond. While encouraging children to use a specific hand to indicate their responses had no effect on memory performance, encouraging children to use the right hand to respond, compared to the left hand, significantly improved their verb learning performance. This study is the first to show that manipulating the hand with which children are encouraged to gesture gives them a linguistic advantage. Language lateralization in healthy right-handed children typically involves a dominant left hemisphere. Producing right-handed gestures may therefore lead to increased activation in the left hemisphere which may, in turn, facilitate forming and accessing lexical representations. It is important to note that this study manipulated gesture handedness among right-handers and does therefore not support the practice of encouraging children to become right-handed in manual activities. RESEARCH HIGHLIGHTS: Right-handed 3-year-olds were instructed to point to indicate their answers exclusively with their right or left hand in either a memory or verb learning task. Right-handed pointing was associated with improved verb generalization performance, but not improved memory performance. Thus, gesturing with the right hand, compared to the left hand, gives right-handed 3-year-olds an advantage in a linguistic but not a non-linguistic task. Right-handed pointing might lead to increased activation in the left hemisphere and facilitate forming and accessing lexical representations.

Shedding light on neuroscience: Two decades of functional near-infrared spectroscopy applications and advances from a bibliometric perspective

Functional near-infrared spectroscopy (fNIRS) is a noninvasive optical brain-imaging technique that detects changes in hemoglobin concentration in the cerebral cortex. fNIRS devices are safe, silent, portable, robust against motion artifacts, and have good temporal resolution. fNIRS is reliable and trustworthy, as well as an alternative and a complement to other brain-imaging modalities, such as electroencephalography or functional magnetic resonance imaging. Given these advantages, fNIRS has become a well-established tool for neuroscience research, used not only for healthy cortical activity but also as a biomarker during clinical assessment in individuals with schizophrenia, major depressive disorder, bipolar disease, epilepsy, Alzheimer's disease, vascular dementia, and cancer screening. Owing to its wide applicability, studies on fNIRS have increased exponentially over the last two decades. In this study, scientific publications indexed in the Web of Science databases were collected and a bibliometric-type methodology was developed. For this purpose, a comprehensive science mapping analysis, including top-ranked authors, journals, institutions, countries, and co-occurring keywords network, was conducted. From a total of 2310 eligible documents, 6028 authors and 531 journals published fNIRS-related papers, Fallgatter published the highest number of articles and was the most cited author. University of Tübingen in Germany has produced the most trending papers since 2000. USA was the most prolific country with the most active institutions, followed by China, Japan, Germany, and South Korea. The results also revealed global trends in emerging areas of research, such as neurodevelopment, aging, and cognitive and emotional assessment.

Functional near-infrared spectroscopy in toddlers: Neural differentiation of communicative cues and relation to future language abilities

The toddler and preschool years are a time of significant development in both expressive and receptive communication abilities. However, little is known about the neurobiological underpinnings of language development during this period, likely due to difficulties acquiring functional neuroimaging data. Functional near‐infrared spectroscopy (fNIRS) is a motion‐tolerant neuroimaging technique that assesses cortical brain activity and can be used in very young children. Here, we use fNIRS during perception of communicative and noncommunicative speech and gestures in typically developing 2‐ and 3‐year‐olds (Study 1, n = 15, n = 12 respectively) and in a sample of 2‐year‐olds with both fNIRS data collected at age 2 and language outcome data at age 3 (Study 2, n = 18). In Study 1, 2‐ and 3‐year‐olds differentiated between communicative and noncommunicative stimuli as well as between speech and gestures in the left lateral frontal region. However, 2‐year‐olds showed different patterns of activation from 3‐year‐olds in right medial frontal regions. In Study 2, which included two toddlers identified with early language delays along with 16 typically developing toddlers, neural differentiation of communicative stimuli in the right medial frontal region at age 2 predicted receptive language at age 3. Specifically, after accounting for variance related to verbal ability at age 2, increased neural activation for communicative gestures (vs. both communicative speech and noncommunicative gestures) at age 2 predicted higher receptive language scores at age 3. These results are discussed in the context of the underlying mechanisms of toddler language development and use of fNIRS in prediction of language outcomes.