Metamemory and executive function mediate the age-related decline in memory.

OBJECTIVE: Although the effect of aging on episodic memory is relatively well studied, little is known about how aging influences metamemory. In addition, while executive function (EF) is known to mediate the age-related decline in episodic memory, the role of metamemory in aging-related memory differences beyond EF remains unknown. This study aimed to elucidate the effect of aging on metamemory and to clarify the role of metamemory in the age-related decline in memory. METHOD: One hundred and four adults aged 18-79 years (50 M, 54 F) performed several EF tasks, as well as a face-scene paired-associate learning task that required them to make judgments of learning, feeling-of-knowing judgments, and retrospective confidence judgments. RESULTS: Aging was significantly associated with poor metamemory accuracy and increased confidence across metamemory judgment types, even after controlling for EF and memory performance. A parallel mediation analysis indicated that both confidence of learning and EF performance had significant partial mediation effects on the relationship between aging and memory, albeit in different ways. Specifically, poor EF explained the age-related decline in memory, whereas increased confidence of learning served to compensate for this memory decline. CONCLUSIONS: Aging is associated with general changes (i.e., poor inferences from cues) rather than specific changes (i.e., declined activation or utilization of certain cues) in metamemory monitoring. Also, changes in confidence of learning and in EF ability contribute to the preservation and decline of memory during aging, respectively. Therefore, boosting confidence during encoding and enhancing EF skills might be complementary memory intervention strategies for older adults.

Effects of age on the interactions of attentional and emotional processes: a prefrontal fNIRS study.

The aging of attentional and emotional functions has been extensively studied but relatively independently. Therefore, the relationships between aging and the interactions of attentional and emotional processes remain elusive. This study aimed to determine how age affected the interactions between attentional and emotional processes during adulthood. One-hundred forty adults aged 18-79 performed the emotional variant of the Attention Network Test, which probed alerting, orienting, and executive control in the presence and absence of threatening faces. During this task, contexts with varying levels of task preparatory processes were created to modulate the effect of threatening faces on attention, and functional near-infrared spectroscopy (fNIRS) was used to examine the neural underpinnings of the behavioural effects. The behavioural results showed that aging was associated with a significant decline in alerting efficiency, and there was a statistical trend for age-related deficits in executive control. Despite these age differences, age did not significantly moderate the interactions among attentional networks or between attention and emotion. Additionally, the fNIRS results showed that decreased frontal cortex functioning might underlie the age-related decline in executive control. Therefore, while aging has varying effects on different attentional networks, the interactions of attentional and emotional processes remain relatively unaffected by age.

Causal Prefrontal Contributions to Stop-Signal Task Performance in Humans.

The frontal lobes have long been implicated in inhibitory control, but a full understanding of the underlying mechanisms remains elusive. The stop-signal task has been widely used to probe instructed response inhibition in cognitive neuroscience. The processes involved have been modeled and related to putative brain substrates. However, there has been surprisingly little human lesion research using this task, with the few existing studies implicating different prefrontal regions. Here, we tested the effects of focal prefrontal damage on stop-signal task performance in a large sample of people with chronic focal damage affecting the frontal lobes (n = 42) and demographically matched healthy individuals (n = 60). Patients with damage to the left lateral, right lateral, dorsomedial, or ventromedial frontal lobe had slower stop-signal RT compared to healthy controls. There were systematic differences in the patterns of impairment across frontal subgroups: Those with damage to the left or right lateral and dorsomedial frontal lobes, but not those with ventromedial frontal damage, were slower than controls to "go" as well as to stop. These findings suggest that multiple prefrontal regions make necessary but distinct contributions to stop-signal task performance. As a consequence, stop-signal RT slowing is not strongly localizing within the frontal lobes.

An optical window into brain function in children and adolescents: A systematic review of functional near-infrared spectroscopy studies.

Despite decades of research, our understanding of functional brain development throughout childhood and adolescence remains limited due to the challenges posed by certain neuroimaging modalities. Recently, there has been a growing interest in using functional near-infrared spectroscopy (fNIRS) to elucidate the neural basis of cognitive and socioemotional development and identify the factors shaping these types of development. This article, focusing on the fNIRS methods, presents an up-to-date systematic review of fNIRS studies addressing the effects of age and other factors on brain functions in children and adolescents. Literature searches were conducted using PubMed and PsycINFO. A total of 79 fNIRS studies involving healthy individuals aged 3-17 years that were published in peer-reviewed journals in English before July 2020 were included. Six methodological aspects of these studies were evaluated, including the research design, experimental paradigm, fNIRS measurement, data preprocessing, statistical analysis, and result presentation. The risk of bias, such as selective outcome reporting, was assessed throughout the review. A qualitative synthesis of study findings in terms of the factor effects on changes in oxyhemoglobin concentration was also performed. This unregistered review highlights the strengths and limitations of the existing literature and suggests directions for future research to facilitate the improved use of fNIRS in developmental cognitive neuroscience research.

A Systematic Review of the Application of Functional Near-Infrared Spectroscopy to the Study of Cerebral Hemodynamics in Healthy Aging.

Positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) studies have shown that healthy aging is associated with functional brain deterioration that preferentially affects the prefrontal cortex. This article reviews the application of an alternative method, functional near-infrared spectroscopy (fNIRS), to the study of age-related changes in cerebral hemodynamics and factors that influence cerebral hemodynamics in the elderly population. We conducted literature searches in PudMed and PsycINFO, and selected only English original research articles that used fNIRS to study healthy individuals with a mean age of ≥ 55 years. All articles were published in peer-reviewed journals between 1977 and May 2019. We synthesized 114 fNIRS studies examining hemodynamic changes that occurred in the resting state and during the tasks of sensation and perception, motor control, semantic processing, word retrieval, attentional shifting, inhibitory control, memory, and emotion and motivation in healthy older adults. This review, which was not registered in a registry, reveals an age-related reduction in resting-state cerebral oxygenation and connectivity in the prefrontal cortex. It also shows that aging is associated with a reduction in functional hemispheric asymmetry and increased compensatory activity in the frontal lobe across multiple task domains. In addition, this article describes the beneficial effects of healthy lifestyles and the detrimental effects of cardiovascular disease risk factors on brain functioning among nondemented older adults. Limitations of this review include exclusion of gray and non-English literature and lack of meta-analysis. Altogether, the fNIRS literature provides some support for various neurocognitive aging theories derived from task-based PET and fMRI studies. Because fNIRS is relatively motion-tolerant and environmentally unconstrained, it is a promising tool for fostering the development of aging biomarkers and antiaging interventions.

Neurocognitive development of flanker and Stroop interference control: A near-infrared spectroscopy study.

The abilities to resolve flanker and Stroop interference, which are primarily mediated by the prefrontal cortex (PFC), have been shown to be dissociable at the individual difference level. However, the relationship between the neurocognitive development of these two aspects of interference control remains unclear. This study examined developmental changes in inhibition performance and PFC activation during flanker and Stroop interference control using functional near-infrared spectroscopy (fNIRS). Twenty-eight healthy children and adolescents aged 7-16 years (16 males) underwent the arrow flanker and color-word matching Stroop paradigms while changes in oxyhemoglobin concentration in the PFC were monitored by fNIRS. We found developmental improvements in inhibition performance in terms of the interference scores on both the flanker and Stroop tasks. There were also developmental increases in PFC activation, particularly in the medial region, while resolving flanker and Stroop interference. Despite developmental changes in inhibition performance and medial PFC activation during both tasks, the developmental changes that we observed for these two aspects of interference control were found to be relatively independent of each other. Our findings support the heterogeneous view of interference control and suggest that the neurocognitive development of flanker and Stroop interference control is only weakly associated, if not dissociable.

Photobiomodulation improves the frontal cognitive function of older adults.

OBJECTIVES: The frontal lobe hypothesis of age-related cognitive decline suggests that the deterioration of the prefrontal cortical regions that occurs with aging leads to executive function deficits. Photobiomodulation (PBM) is a newly developed, noninvasive technique for enhancing brain function, which has shown promising effects on cognitive function in both animals and humans. This randomized, sham-controlled study sought to examine the effects of PBM on the frontal brain function of older adults. METHODS/DESIGNS: Thirty older adults without a neuropsychiatric history performed cognitive tests of frontal function (ie, the Eriksen flanker and category fluency tests) before and after a single 7.5-minute session of real or sham PBM. The PBM device consisted of three separate light-emitting diode cluster heads (633 and 870 nm), which were applied to both sides of the forehead and posterior midline, and delivered a total energy of 1349 J. RESULTS: Significant group (experimental, control) × time (pre-PBM, post-PBM) interactions were found for the flanker and category fluency test scores. Specifically, only the older adults who received real PBM exhibited significant improvements in their action selection, inhibition ability, and mental flexibility after vs before PBM. CONCLUSIONS: Our findings support that PBM may enhance the frontal brain functions of older adults in a safe and cost-effective manner.

Reduced Frontal Activations at High Working Memory Load in Mild Cognitive Impairment: Near-Infrared Spectroscopy.

BACKGROUND: Some functional magnetic resonance imaging studies have reported altered activations in the frontal cortex during working memory (WM) performance in individuals with mild cognitive impairment (MCI), but the findings have been mixed. The objective of the present study was to utilize near-infrared spectroscopy (NIRS), an alternative imaging technique, to examine neural processing during WM performance in individuals with MCI. METHODS: Twenty-six older adults with MCI (7 males; mean age 69.15 years) were compared with 26 age-, gender-, handedness-, and education-matched older adults with normal cognition (NC; 7 males; mean age 68.87 years). All of the participants undertook an n-back task with a low (i.e., 0-back) and a high (i.e., 2-back) WM load condition while their prefrontal dynamics were recorded by a 16-channel NIRS system. RESULTS: Although behavioral results showed that the two groups had comparable task performance, neuroimaging results showed that the MCI group, unlike the NC group, did not exhibit significantly increased frontal activations bilaterally when WM load increased. Compared to the NC group, the MCI group had similar frontal activations at low load (p > 0.05 on all channels) but reduced activations at high load (p < 0.05 on 4 channels), thus failing to demonstrate WM-related frontal activations (p < 0.05 on 9 channels). In addition, we found a positive correlation between the left WM-related frontal activations and WM ability primarily in the NC group (rs = 0.42, p = 0.035), suggesting a relationship between frontal hypoactivation and WM difficulties. CONCLUSION: The present findings suggest the presence of frontal dysfunction that is dependent on WM load in individuals with MCI.

Longitudinal changes in executive function in autism spectrum disorder: A systematic review and meta-analyses.

Individuals with an autism spectrum disorder (ASD) diagnosis show impairment in executive function (EF). However, findings are mixed regarding differences in the age effect on EF between autistic individuals and persons with typical development (TD). Questions remain regarding whether the age-related trajectories of EF in ASD are the same as or different from those in TD. To bridge this knowledge gap, we conducted a systematic review and meta-analyses of longitudinal studies that compared age-related changes in EF between ASD and TD groups (preregistration: osf.io/j5764). A literature search was conducted using PubMed, PsycINFO, and Web of Science on January 29, 2024. After screening by two independent reviewers, 14 longitudinal studies were included. Random-effects meta-analyses of studies involving a maximum total of 518 autistic and 3558 TD children and adolescents (mean baseline ages: 5.7-12.0 years) showed that ASD had significantly poorer EF than TD at both baseline and follow-up. However, there was no significant group difference in the age-related change in EF across domains, including working memory, inhibition, shifting, and planning. Robust Bayesian meta-analyses also provided substantial evidence in favor of the null hypothesis that ASD and TD groups showed similar changes over time for most EF processes. Limitations of the literature included the limited number of longitudinal studies and a narrow range of developmental stages and EF constructs analyzed across studies. Altogether, these findings suggest that autistic children and adolescents generally can improve in EF over time similarly to their neurotypical peers. This has important implications for parents and educators, encouraging appropriate EF training and intervention for autistic children and adolescents at an early stage.

Motivation and emotional distraction interact and affect executive functions.

Previous research on cool-hot executive function (EF) interactions has examined the effects of motivation and emotional distraction on cool EF separately, focusing on one EF component at a time. Although both incentives and emotional distractors have been shown to modulate attention, how they interact and affect cool EF processes is still unclear. Here, we used an experimental paradigm that manipulated updating, inhibition, and shifting demands to determine the interactions of motivation and emotional distraction in the context of cool EF. Forty-five young adults (16 males, 29 females) completed the go/no-go (inhibition), two-back (updating), and task-switching (shifting) tasks. Monetary incentives were implemented to manipulate motivation, and task-irrelevant threatening or neutral faces were presented before the target stimulus to manipulate emotional distraction. We found that incentives significantly improved no-go accuracy, two-back accuracy, and reaction time (RT) switch cost. While emotional distractors had no significant effects on overall task performance, they abolished the incentive effects on no-go accuracy and RT switch cost. Altogether, these findings suggest that motivation and emotional distraction interact in the context of cool EF. Specifically, transient emotional distraction disrupts the upregulation of control activated by incentives. The present investigation has advanced knowledge about the relationship between cool and hot EF and highlights the importance of considering motivation-emotion interactions for a fuller understanding of control.

Modifiable risk factors for mild cognitive impairment among cognitively normal community-dwelling older adults: A systematic review and meta-analysis.

Although numerous studies have investigated modifiable risk factors for mild cognitive impairment (MCI) among community-dwelling seniors, no meta-analysis has summarized these findings. Five databases were searched from January 1, 2000, to December 30, 2023. The protocol was registered with PROSPERO. Data were extracted and reported following Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Relevant meta-analyses of modifiable risk factors were performed. The evidence of each factor was assessed by the GRADE for cohort studies. Of 16,651 citations, 87 studies involving 225,584 community-dwelling seniors were included. Fourteen meta-analyses involving 20 studies with 44,199 participants were performed. The analyses revealed low-to-moderate-quality evidence supporting that diabetes, 2 or more comorbidities, anxiety, apathy, depressive symptoms, and physical frailty were risk factors for incident MCI in older adults. Conversely, hypertension, agitation, and irritability might not be risk factors. Additionally, moderate-quality evidence supports the protective effect of engaging in cognitive-demanding activities on the onset of MCI. Collectively, this study constitutes the first extensive compilation of evidence regarding the various risk factors for the development of MCI in older adults. Our findings hold significant potential to guide the formulation of prevention and management strategies to either prevent or potentially reverse the onset of MCI.

The prefrontal cortex is differentially involved in implicit and explicit facial emotion processing: An fNIRS study.

Despite extensive research, the differential roles of the prefrontal cortex (PFC) in implicit and explicit facial emotion processing remain elusive. Functional near-infrared spectroscopy (fNIRS) is a neuroimaging technique that can measure changes in both oxyhemoglobin (HbO) and deoxyhemoglobin (HbR) concentrations. Currently, how HbO and HbR change during facial emotion processing remains unclear. Here, fNIRS was used to examine and compare PFC activation during implicit and explicit facial emotion processing. Forty young adults performed a facial-matching task that required either emotion discrimination (explicit task) or age discrimination (implicit task), and the activation of their PFCs was measured by fNIRS. Participants attempted the task on two occasions to determine whether their activation patterns were maintained over time. The PFC displayed increases in HbO and/or decreases in HbR during the implicit and explicit facial emotion tasks. Importantly, there were significantly greater changes in PFC HbO during the explicit task, whereas no significant difference in HbR changes between conditions was found. Between sessions, HbO changes were reduced across tasks, but the difference in HbO changes between the implicit and explicit tasks remained unchanged. The test-retest reliability of the behavioral measures was excellent, whereas that of fNIRS measures was mostly poor to fair. Thus, the PFC plays a specific role in recognizing facial expressions, and its differential involvement in implicit and explicit facial emotion processing can be consistently captured at the group level by changes in HbO. This study demonstrates the potential of fNIRS for elucidating the neural mechanisms underlying facial emotion recognition.

Context-specific effects of threatening faces on alerting, orienting, and executive control: A fNIRS study.

Real-world threatening faces possess both useful and irrelevant attributes with respect to the current goal. How these attributes interact and affect attention, which comprises at least three processes hypothesized to engage the frontal lobes (alerting, orienting, and executive control), remains poorly understood. Here, the neurocognitive effects of threatening facial expressions on the three processes of attention were examined through the emotional Attention Network Test (ANT) and functional near-infrared spectroscopy (fNIRS). Forty-seven (20M, 27F) young adults performed a blocked version of the arrow flanker task with neutral and angry facial cues applied in three cue conditions (no, center, and spatial). Hemodynamic changes occurring in participants' frontal cortices during task performance were recorded by multichannel fNIRS. Behavioral results indicated that alerting, orienting, and executive control processes existed in both the neutral and angry conditions. However, depending on the context, angry facial cues affected these processes differently compared with neutral facial cues. Specifically, the angry face disrupted the classical decrease in reaction time from the no-cue to center-cue condition specifically during the congruent condition. Additionally, fNIRS results revealed significant frontal cortical activation during the incongruent vs. congruent task; neither cue nor emotion significantly affected frontal activation. Thus, the findings suggest that the angry face affects all three attentional processes while exerting context-specific effects on attention. They also imply that during the ANT, the frontal cortex is most involved in executive control. The present study offers essential insights into how various attributes of threatening faces interact and alter attention.

Effects of age, gender, and education on task performance and prefrontal cortex processing during emotional and non-emotional verbal fluency tests.

The emotional semantic fluency test (SFT) is an emerging verbal fluency test that requires controlled access to emotional lexical information. Currently, how demographic variables influence neurocognitive processing during this test remains elusive. The present study compared the effects of age, gender, and education on task performance and prefrontal cortex (PFC) processing during the non-emotional and emotional SFTs. One-hundred and thirty-three Cantonese-speaking adults aged 18-79 performed the non-emotional and emotional SFTs while their PFC activation was measured using functional near-infrared spectroscopy. Results showed that more education predicted better non-emotional SFT performance, whereas younger age, being female, and more education predicted better emotional SFT performance. Only age significantly affected PFC activation during the SFTs, and the effect was comparable between the two SFTs. Thus, compared with its non-emotional analog, the emotional SFT is influenced by overlapping yet distinct demographic variables. There is a similar age-related reorganization of PFC function across SFT performances.

Changes in task performance and frontal cortex activation within and over sessions during the n-back task.

The n-back task is a popular paradigm for studying neurocognitive processing at varying working memory loads. Although much is known about the effects of load on behavior and neural activation during n-back performance, the temporal dynamics of such effects remain unclear. Here, we investigated the within- and between-session stability and consistency of task performance and frontal cortical activation during the n-back task using functional near-infrared spectroscopy (fNIRS). Forty healthy young adults performed the 1-back and 3-back conditions three times per condition. They then undertook identical retest sessions 3 weeks later (M = 21.2 days, SD = 0.9). Over the course of the task, activation in the participants' frontopolar, dorsomedial, dorsolateral, ventrolateral, and posterolateral frontal cortices was measured with fNIRS. We found significantly improved working memory performance (difference between 1-back and 3-back accuracies) over time both within and between sessions. All accuracy and reaction time measures exhibited good to excellent consistency within and across sessions. Additionally, changes in frontal oxyhemoglobin (HbO) and deoxyhemoglobin (HbR) concentration were maintained over time across timescales, except that load-dependent (3-back > 1-back) HbO changes, particularly in the ventrolateral PFC, diminished over separate sessions. The consistency of fNIRS measures varied greatly, with changes in 3-back dorsolateral and ventrolateral HbO demonstrating fair-to-good consistency both within and between sessions. Overall, this study clarified the temporal dynamics of task performance and frontal activation during the n-back task. The findings revealed the neural mechanisms underlying the change in n-back task performance over time and have practical implications for future n-back research.

Frontal cortical activation during emotional and non-emotional verbal fluency tests.

There has been growing recognition of the utility of combining the verbal fluency test and functional near-infrared spectroscopy (fNIRS) to assess brain functioning and to screen for psychiatric disorders. Recently, an emotional analogue of the semantic fluency test (SFT) has been developed that taps partly different processes from conventional verbal fluency tests. Nevertheless, neural processing during the emotional SFT remains elusive. Here, fNIRS was used to compare frontal cortical activation during emotional and non-emotional SFTs. The goal was to determine whether the emotional SFT activated overlapping yet distinct frontal cortical regions compared with the conventional, non-emotional SFT. Forty-three healthy young adults performed the emotional and non-emotional SFTs while hemodynamic changes in the bilateral frontopolar, dorsomedial, dorsolateral, ventrolateral, and posterolateral frontal cortices were measured by fNIRS. There were significant increases in oxyhemoglobin concentration and significant decreases in deoxyhemoglobin concentration (i.e., activation) in frontopolar, dorsolateral, and ventrolateral frontal regions during both the non-emotional and emotional SFTs. Also, complementary analyses conducted on changes in the two chromophores using classical and Bayesian hypothesis testing suggested that comparable frontal cortical regions were activated while performing the two tests. This similarity in activation occurred in a context where non-emotional and emotional SFT performances exhibited differential relationships with the overall level of negative mood symptoms. In conclusion, frontal cortical activation during the emotional SFT is similar to that during the conventional, non-emotional SFT. Given that there is evidence for discriminant validity for the emotional SFT, the neural mechanisms underlying the uniqueness of this test warrant further investigation.

A systematic review and meta-analysis of facial emotion recognition in autism spectrum disorder: The specificity of deficits and the role of task characteristics.

This review assessed the specificity of facial emotion recognition impairment and the role of task characteristics in facial emotion recognition in autism spectrum disorder (ASD). Based on subsets of 148 studies identified in PubMed and PsycINFO, random-effects meta-analyses showed significant impairment in recognizing all basic facial emotions in ASD. Additionally, ASD involves poorer facial emotion recognition than other clinical conditions and has similar impairment in recognizing emotional and nonemotional facial attributes, as well as in recognizing emotion in faces and other modalities. Furthermore, there are significant moderating effects for emotion complexity and holistic processing, a statistical trend for task type, and no significant effect for motion, social relevance, or stimulus salience on facial emotion recognition in ASD. Altogether, this review suggests nonselective facial emotion recognition impairment in ASD. Such impairment is relatively specific to ASD but is not specific to the recognition of emotional facial attributes or emotion recognition in the face modality. Identifying the role of task characteristics improves our understanding of the mechanisms underlying facial emotion recognition in ASD.

Stability and consistency of metamemory judgments within a session.

There has been much interest in assessing individual and group differences in metamemory skills. These endeavors require or would benefit from enhanced knowledge about the stability and consistency of metamemory judgments over successive trials. However, few studies have examined these aspects. Thus, the present study investigated and compared the within-session stability and consistency of three major types of metamemory judgment: judgment of learning (JOL), feeling-of-knowing judgment (FOK), and retrospective confidence judgment (RCJ), using a single-task paradigm. A total of 38 healthy young adults (17 males, 21 females) completed three trials of a face-scene associative learning task designed to assess metamemory. In each trial, participants rated their JOLs while studying a new set of face-scene pairs, and then rated their FOKs and RCJs while their memory was being tested. The stability and consistency of the mean confidence ratings and the relationships between confidence rating and memory performance, indexed by two gamma estimates, were analyzed and compared across types of metamemory judgments. Over trials, there was a significant decrease in the mean rating for JOL but not for FOK or RCJ. Also, the gamma scores of JOL, but not that of FOK or RCJ, significantly improved with practice. Furthermore, for each type of metamemory judgment, the mean confidence rating showed excellent consistency across trials. Depending on the judgment type and gamma estimation method, the consistency of gamma scores ranged from poor to excellent. Thus, the present study clarified the temporal dynamics of various types of metamemory judgments and the consistency of metamemory measures.

Prefrontal Activation During Effortful Processing Differentiates Memory Abilities in Adults with Memory Complaints.

BACKGROUND: Identifying individuals at increased risks for developing Alzheimer's disease (AD) is crucial for early intervention. Memory complaints are associated with brain abnormalities characteristic of AD in cognitively normal older people. However, the utility of memory complaints for predicting mild cognitive impairment (MCI) or AD onset remains controversial, likely due to the heterogeneous nature of this construct. OBJECTIVE: We investigated whether prefrontal oxygenation changes measured by functional near-infrared spectroscopy (fNIRS) during an arduous cognitive task, previously shown to be associated with the AD syndrome, could differentiate memory abilities among individuals with memory complaints. Episodic memory performance was adopted as a proxy for MCI/AD risks since it has been shown to predict AD progression across stages. METHODS: Thirty-six adults self-reporting memory complaints in the absence of memory impairment completed a verbal list learning test and underwent a digit n-back paradigm with an easy (0-back) and a difficult (2-back) condition. K-means clustering was applied to empirically derive memory complaint subgroups based on fNIRS-based prefrontal oxygenation changes during the effortful 2-back task. RESULTS: Cluster analysis revealed two subgroups characterized by high (n = 12) and low (n = 24) bilateral prefrontal activation during the 2-back but not a 0-back task. The low activation group was significantly less accurate across the n-back task and recalled significantly fewer words on the verbal memory test compared to the high activation group. CONCLUSION: fNIRS may have the potential to differentiate verbal memory abilities in individuals with self-reported memory complaints.

Viewing neurovascular coupling through the lens of combined EEG-fNIRS: A systematic review of current methods.

Neurovascular coupling is a key physiological mechanism that occurs in the healthy human brain, and understanding this process has implications for understanding the aging and neuropsychiatric populations. Combined electroencephalography (EEG) and functional near-infrared spectroscopy (fNIRS) has emerged as a promising, noninvasive tool for probing neurovascular interactions in humans. However, the utility of this approach critically depends on the methodological quality used for multimodal integration. Despite a growing number of combined EEG-fNIRS applications reported in recent years, the methodological rigor of past studies remains unclear, limiting the accurate interpretation of reported findings and hindering the translational application of this multimodal approach. To fill this knowledge gap, we critically evaluated various methodological aspects of previous combined EEG-fNIRS studies performed in healthy individuals. A literature search was conducted using PubMed and PsycINFO on June 28, 2021. Studies involving concurrent EEG and fNIRS measurements in awake and healthy individuals were selected. After screening and eligibility assessment, 96 studies were included in the methodological evaluation. Specifically, we critically reviewed various aspects of participant sampling, experimental design, signal acquisition, data preprocessing, outcome selection, data analysis, and results presentation reported in these studies. Altogether, we identified several notable strengths and limitations of the existing EEG-fNIRS literature. In light of these limitations and the features of combined EEG-fNIRS, recommendations are made to improve and standardize research practices to facilitate the use of combined EEG-fNIRS when studying healthy neurovascular coupling processes and alterations in neurovascular coupling among various populations.