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This study evaluates a low-cost, single-channel fNIRS device in cognitive neuroscience, aiming to overcome the financial barriers of commercial systems by testing its efficacy in tasks of varying complexity. Twenty-six participants engaged in motor control (finger-tapping), working memory (n-back), and creativity (AUT) tasks while their prefrontal cortex activity was monitored using the device, with behavioral and cerebral blood flow changes recorded. Results showed the device’s capability to detect significant blood flow variations across different tasks, thereby supporting its use in cognitive research. The study confirms the potential of single-channel fNIRS as a cost-effective tool for diverse cognitive assessments, from simple motor actions to complex creative thinking.

Deaf and hard-of-hearing infants' hemodynamic response function (HRF) has not yet been characterized. However, without an appropriate estimate of their HRF, neuroimaging modalities relying on hemodynamic responses, e.g., functional magnetic resonance imaging (fMRI) or functional near-infrared spectroscopy (fNIRS), cannot be used reliably in this population, e.g., prior to and following cochlear implantation. We contribute to better theoretical models of and more suitable therapeutic interventions for the neural changes induced by auditory and language deprivation in deaf infants. We aim to characterize the parameters of the HRF of deaf and hard-of-hearing infants in response to Italian. We measured 2- to 20-month-old Italian-exposed infants' HRF to Italian using fNIRS in the bilateral temporal, i.e., auditory, cortices. We characterized the HRF for all infants and for three clinically relevant subsets: (i) monolingual Italian infants, (ii) genetically deaf infants, and (iii) infants aged 5 to 12 months. We computed the following parameters: peak amplitude, time-to-peak, full width at half maximum, and where present, the amplitude and latency of the initial dip and/or the final undershoot, using a model-based parameter fitting approach. We statistically compared these HRF parameters to those of typically hearing infants. Deaf and typically hearing infants showed largely similar HRFs, with both groups reaching comparable main peak amplitudes. Minor differences have been found in the latencies of some response components. Our results provide the first detailed characterization of the hemodynamic response to native-language speech in deaf and hard-of-hearing infants, improving clinical and therapeutic approaches through more accurate analysis of fMRI and fNIRS data.

Interhemispheric imbalance after stroke impedes motor recovery. Although repetitive transcranial magnetic stimulation (rTMS) shows therapeutic potential, the neural mechanisms underlying its effects-particularly on cortical excitability and interhemispheric interaction-remain unclear. Understanding these mechanisms is essential for optimizing personalized neuromodulation strategies in stroke rehabilitation. To explore how low-frequency rTMS facilitates motor recovery post-stroke, especially in regulating interhemispheric inhibition (IHI), functional connectivity, and cortical excitability, we used a multimodal approach that included paired-pulse TMS, functional near-infrared spectroscopy (fNIRS), and motor outcomes. A total of 27 patients with stroke were randomized to receive 2 weeks of either real ( ) or sham ( ) 1 Hz rTMS over the contralesional primary motor cortex (M1). Paired-pulse TMS was used to measure IHI and laterality quotient (LQ), whereas fNIRS was used to measure resting-state functional connectivity (RSFC). Clinical scales were also used to assess behavioral-level motor functioning. Compared with the sham group, rTMS significantly modulated IHI, as evidenced by a reduction in inhibitory drive from the stimulated contralesional M1 to ipsilesional M1 (mean difference = 15.57%, ). In parallel, RSFC analysis revealed decreased connectivity from contralesional M1 to ipsilesional premotor and supplementary motor areas [ , , false discovery rate-corrected]. Between-group comparisons further showed greater LQ improvements in the rTMS group than in the sham group. Changes in selected neurophysiological measures were significantly correlated with improvements in upper limb motor function. We showed that low-frequency rTMS promotes motor recovery after stroke by rebalancing cortical excitability and reducing maladaptive connectivity patterns. The integration of TMS and fNIRS provides converging evidence for rTMS-induced cortical plasticity and highlights the potential of these tools for guiding personalized neuromodulation strategies in stroke rehabilitation.

Neuroimaging research on child development in low- and middle-income countries (LMICs) remains limited, in part due to substantial implementation challenges. Although functional near-infrared spectroscopy (fNIRS) is a promising tool in these contexts, its use is constrained by barriers that are not yet systematically characterized. We systematically evaluate the challenges encountered during a 3-year longitudinal fNIRS project with children in Dhaka, Bangladesh. We aim to identify the major challenges affecting data quality and collection, compare our findings with similar studies in other LMICs, and gather practical guidance for fNIRS implementation in LMICs. We applied failure mode and effects analysis to systematically identify the major challenges in the project. We also polled researchers with experience in similar fNIRS studies in other LMICs and compiled mitigation strategies. High-risk challenges were primarily related to fNIRS headcap fit, onsite staff procedures, and environmentally related fNIRS equipment functionality. Most of these challenges were also reported by other polled sites. Effective mitigation strategies have been compiled based on experience in Dhaka and insights from multiple LMICs. We provide valuable insights into the challenges of implementing fNIRS in LMICs by identifying high-priority challenges and effective mitigation strategies, ultimately informing more equitable and reliable fNIRS research in global child health.

Tone processing is essential in tonal languages such as Mandarin. Understanding how post-stroke aphasia (PSA) affects tone perception can guide targeted rehabilitation, especially in linguistically unique populations. We aimed to explore the neural mechanisms of tone perception in Mandarin-speaking PSA patients and examine how brain network reorganization supports or hinders phonological processing. Using functional near-infrared spectroscopy (fNIRS) and a tone-based auditory oddball paradigm, we compared cortical activation and functional connectivity (FC) patterns between PSA patients and healthy controls. Patients with PSA showed reduced/reversed hemodynamic responses in the left Broca's area but increased FC with the right motor cortex. Despite this local hyperconnectivity, overall FC was lower in patients than in controls, especially among highly connected links ( ), suggesting either compensatory or maladaptive reorganization. Moreover, deoxygenated hemoglobin changes in the left Broca's area were positively associated with language function, as measured by aphasia quotient scores. The findings highlight altered auditory-motor network dynamics in PSA, with Broca's area playing a central role in tone-based phonological processing. These results support the potential of fNIRS for clinical assessment and underscore the importance of accounting for network-level changes in aphasia rehabilitation strategies for tonal languages.

Very preterm infants are prone to large fluctuations in their blood glucose concentration (BGC), i.e., they can experience episodes of hyper- and hypoglycemia, due to impaired glucose control. To date, the relationship among how specific regions of the brain respond to glycemic events has not been fully explored, and characterizing how glucose fluctuations affect region-specific functional connectivity at birth may provide insight into neurodevelopment and could help identify early biomarkers of brain vulnerability in very preterm infants. The aim is to evaluate whether the differences in task-free functional connectivity (tfFC) patterns before and after experiencing several days of BGC fluctuations were correlated with changes in the glucose profile during this time interval. We continuously monitored both glucose concentration with a continuous glucose monitoring device and brain hemodynamics with diffuse optical tomography in a group of very preterm newborns to conduct tfFC analysis ( ). Changes in tfFC patterns between the left frontal and left parietal regions were found to be correlated with the standard deviation of the glucose profile, whereas changes between the central prefrontal cortex and the right prefrontal region were found to be correlated with the maximum value of glucose concentration. We suggest that changes in the coupling of these brain areas during rest are dependent on and occur during exposures to glycemic changes in the preterm brain.

Neonates undergo rapid development, yet the examination of emerging brain markers across paradigms, cognitive domains, and diverse global populations remains limited. We investigated whether brain responses at 1 month of age could be interrogated across paradigms to offer deeper context-specific insights into neurodevelopment. Functional near-infrared spectroscopy was used to assess frontal and temporal brain responses during natural sleep in 181 infants from a low-income setting (rural Gambia) and 58 infants from a higher-income setting (Cambridge, United Kingdom) during three auditory paradigms: social selectivity, habituation and novelty detection, and functional connectivity. Paradigm-level brain responses were analyzed using threshold-free cluster enhancement and cross-paradigm comparisons of individual responses. Both Gambian and UK infants showed habituation but not novelty responses, higher inter- versus intra-hemispheric connectivity, stronger inter-hemispheric connectivity in temporal relative to frontal regions, stronger inter-regional connectivity between right temporal and left frontal regions, and nonvocal > vocal selectivity (UK infants only). Cross-cohort differences in the cross-paradigm analyses suggest that context-specific developmental markers are evident within the first month of life and show high individual variability. Cross-paradigm analyses revealed that greater vocal selectivity (UK) is associated with higher inter-hemispheric connectivity, potentially allowing us to identify biomarkers of more mature neurodevelopment within the first weeks of postnatal life.

The developmental functional near-infrared spectroscopy (fNIRS) literature relies heavily on measurements acquired during natural sleep, yet it remains unclear whether and how different sleep stages modulate infant hemodynamic responses and potentially confound interpretations of early brain activation. This study investigates the effect of quiet sleep (QS) and active sleep (AS) on fNIRS-measured hemodynamic responses to two auditory paradigms-social selectivity and habituation and novelty detection (HaND)-in 1-month-old infants from the United Kingdom ( ) and the Gambia ( ). The infants were tested during natural sleep with an 18-channel bilateral frontal-temporal fNIRS array. Sleep stages were coded from video using a micro-coding scheme. For the social selectivity paradigm, infants in both cohorts showed robust responses to vocal and non-vocal stimuli and non-vocal selectivity. In the HaND paradigm, UK infants in AS exhibited a higher initial response and stronger habituation in both chromophores than QS infants. In the Gambian cohort, infants in QS showed a more widespread initial response and evidence of habituation, whereas infants in AS did not. Sleep stage can modulate infant hemodynamic responses, with patterns differing across paradigms and cohorts, underscoring the importance of modeling sleep stages in neuroimaging studies with sleeping infants.

Adolescents with attention-deficit/hyperactivity disorder (ADHD) have reduced dorsolateral prefrontal cortex (DLPFC) activation during cognitive control tasks and weaker attention performance, with higher DLPFC activity linked to better complex attention, showing a connection between neural function and behavior. These findings support prefrontal dysfunction and hemispheric asymmetry in ADHD adolescents. We aimed to compare brain activation during cognitive control tasks between adolescents with ADHD and typically developing (TD) individuals using functional near-infrared spectroscopy (fNIRS). Sixty-eight adolescents participated: 30 ADHD and 38 TD, and were assessed using the Korean ADHD Rating Scale, Comprehensive Attention Test, Korean Beck Depression Inventory-II, and Korean Beck Anxiety Inventory. Brain activation during the Stroop Color and Word Test (ST) was measured with fNIRS. Psychological scales, cognition-related tests, and brain activation data were analyzed. The ADHD group recorded decreased scores for congruence and incongruence of ST compared with the TD group. TD adolescents showed significantly greater increases in oxygenated hemoglobin concentration ( ) in the prefrontal cortex (DLPFC) than adolescents with ADHD. DLPFC activation was negatively correlated with ADHD symptom severity (all participants). Correlations were observed between DLPFC and cognitive function, particularly complex attention. We found distinct brain activation patterns in the DLPFC for ADHD adolescents during cognitive control tasks. fNIRS measured these differences, helping to understand the developmental trajectory of ADHD in adolescents and providing evidence of functional impairment in complex executive function tasks.

To learn mathematics, young children require accurate interpretations of mathematics vocabulary. When school language differs from children's home language, mathematics performance often decreases. Little is known about cortical activation during mathematics vocabulary processing in different languages. Although behavioral data highlight a difference in L1 and L2 mathematics learning, neuroimaging insights will help us to better understand how and why there is a difference in children's mathematical learning in multilingual societies. We investigated behavioral and brain responses (fNIRS) of 42 isiZulu and Sesotho (L1) first graders (6.75 to 7.83 years, 22 girls) who learn mathematics in English (L2) at school when they encounter mathematics vocabulary in L2 compared with L1 and mathematics vocabulary compared with object recognition in L1. The results show that higher accuracy in the L1 mathematics vocabulary, as compared with the L2 mathematics vocabulary, comes with the costs of higher cognitive demands in the right superior and middle frontal gyri for first graders. Mathematics vocabulary required longer response time than object recognition and a higher activation in the right superior frontal gyrus. No parietal difference was observed between conditions. Neuroimaging revealed that children engaged additional frontoparietal regions when processing L1 mathematics vocabulary-patterns not detectable through behavioral measures alone. Increased frontal activation suggests that the interpretation of mathematics vocabulary in L2 is not yet automatized. This study demonstrates how educational neuroimaging refines interpretations of behavioral outcomes within multilingual contexts.