Relationship between working memory performance and neural activation measured using near-infrared spectroscopy

Assessing Frontal Lobe Function on Verbal Fluency and Emotion Recall in Autism Spectrum Disorder by fNIRS

This study applied the functional near-infrared spectroscopy (fNIRS) to investigate frontal activity in autism when performing verbal fluency test and emotion recall task. We recruited 32 autistic adults without intellectual disability and 30 typically-developing controls (TDC). Prefrontal hemodynamic changes were evaluated by fNIRS when the participants performed the verbal fluency test and emotion recall task. fNIRS signals in the prefrontal cortex were compared between autism and TDC. Compared to TDC, autistic adults showed comparable performance on the verbal fluency test but exhibited lower frontal activity on the vegetable category. In the verbal fluency test, left frontal activity in TDC significantly increased in the vegetable category (vs. fruit category). In the emotion recall task, left frontal activity increased significantly in TDC when recalling emotional (vs. neutral) events. This increase of left frontal activity on the more difficult works was not found in autism. Similarly, brain activities were related to test performance only in TDC but not in autism. In addition, more severe social deficits were associated with lower frontal activity when recalling emotional events, independent of autism diagnosis. Findings suggested reduced frontal activity in autism, as compared to TDC, when performing verbal fluency tests. The reduction of left frontal activation in verbal fluency test and emotion recall tasks might reflect on the social deficits of the individual. The fNIRS may potentially be applied in assessing frontal lobe function in autism and social deficits in general population. Trial registration number: NCT04010409.

Basic Examination of Haemoglobin Phase of Oxygenation and Deoxygenation in Resting State and Task Periods in Adults Using fNIRS

Functional near-infrared spectroscopy (fNIRS) is a neuroimaging technique used to measure the relative changes in concentrations of oxygenated haemoglobin (oxy-Hb) and deoxygenated haemoglobin (deoxy-Hb) in the cerebral cortex. While most previous studies using fNIRS have relied only on a single oxy-Hb or deoxy-Hb parameter to infer about neural activation, the phase difference between the oxy- and deoxy-Hb signals (haemoglobin phase of oxygenation and deoxygenation: hPod) has been reported to be an important biomarker for analysing haemodynamic characteristics of the brain in infants. In this study, we examined the basic characteristics of adult hPod to develop a new analysis method to detect more sensitive signals that reflect neural activation in adults using fNIRS. We measured the hPod of 12 healthy adults in the frontal and occipital cortex during rest and upon exposure to visual stimuli and the verbal working memory (WM) task. We found that the average hPod values during the entire measurement period ranged between π and 1.5π rad in all conditions. This result indicates that the phase differences in adults were generally close to a stable antiphase pattern (hPod values around π), regardless of the presence or absence of tasks and stimuli. However, when dynamic changes in hPod values were analysed, significant differences between the resting state and WM tasks were observed during activation period in the frontal and occipital regions. These results suggest that the analysis of dynamic hPod change is useful for detecting a subtle activation for cognitive tasks.

Muscle and cerebral oxygenation during cycling in chronic obstructive pulmonary disease: A scoping review

To synthesize evidence for prefrontal cortex (PFC), quadriceps, and respiratory muscle oxygenation using near-infrared spectroscopy (NIRS) during cycling in individuals with chronic obstructive pulmonary disease (COPD). A scoping review was performed searching databases (inception-August 2020): Ovid MEDLINE, EMBASE, Cochrane Systematic Reviews, Cochrane Central Register of Controlled Clinical Trials, CINAHL, SPORTDiscus and Pedro. The search focused on COPD, cycling, and NIRS outcomes. 29 studies (541 COPD participants) were included. Compared to healthy individuals (8 studies), COPD patients at lower cycling workloads had more rapid increases in vastus lateralis (VL) deoxygenated hemoglobin (HHb); lower increases in VL total hemoglobin (tHb) and blood flow; and lower muscle tissue saturation (StO₂). Heliox and bronchodilators were associated with smaller and slower increases in VL HHb. Heliox increased VL and intercostal blood flow compared to room air and supplemental oxygen in COPD patients (1 study). PFC oxygenated hemoglobin (O₂Hb) increased in COPD individuals during cycling in 5 of 8 studies. Individuals with COPD and heart failure demonstrated worse VL and PFC NIRS outcomes compared to patients with only COPD-higher or more rapid increase in VL HHb and no change or decrease in PFC O₂Hb. Individuals with COPD present with a mismatch between muscle oxygen delivery and utilization, characterized by more rapid increase in VL HHb, lower muscle O₂Hb and lower muscle StO₂. PFC O₂Hb increases or tends to increase in individuals with COPD during exercise, but this relationship warrants further investigation. NIRS can be used to identify key deoxygenation thresholds during exercise to inform PFC and muscle oxygenation.

Pitch Processing Can Indicate Cognitive Alterations in Chronic Liver Disease: An fNIRS Study

Early detection and evaluation of cognitive alteration in chronic liver disease is important for predicting the subsequent development of hepatic encephalopathy. While visuomotor tasks have been rigorously employed for cognitive evaluation in chronic liver disease, there is a paucity of auditory processing task. Here we focused on auditory perception and examined behavioral and haemodynamic responses to a melodic contour identification task (CIT) to compare cognitive abilities in patients with chronic liver disease (CLD, N = 30) and healthy controls (N = 25). Further, we used support vector machines to examine the optimal combination of channels of functional near-infrared spectroscopy that can classify cognitive alterations in CLD. Behavioral findings showed that CIT performance was significantly worse in the patient group and CIT significantly correlated with neurocognitive evaluation (i.e., number connection test, digit span test). The findings indicated that CIT can measure auditory cognitive capacity and its difference existing between patient group and healthy controls. Additionally, optimal subsets classified the 16-dimensional haemodynamic data with 78.35% classification accuracy, yielding markers of cognitive alterations in the prefrontal regions (CH6, CH7, CH10, CH13, CH14, and CH16). The results confirmed the potential use of behavioral as well as haemodynamic responses to music perception as an alternative or supplementary method for evaluating cognitive alterations in chronic liver disease.

Differences in prefrontal cortex activity based on difficulty in a working memory task using near-infrared spectroscopy

The Prefrontal cortex (PFC) has been highly related to executive functions such as working memory (WM). This study assesses the activity of the PFC in performing the Sternberg WM task (ST) with three levels of difficulty (easy, medium and hard) using the near-infrared spectroscopy (fNIRS) technique. Participants were 43 young and healthy right-handed women. Nine WM task blocks were pseudo randomly presented, three for each difficulty task. The results showed that the participant's performance was better in the easy trials than in the medium and hard trials. Performance in the medium trials was also better than in the hard ones. Bonferroni-corrected paired post-hoc t-tests indicated higher oxygenation in medium and hard tasks than in the easy ones for times between 13 and 42 s in the left lateral PFC and in both, medial and lateral, right PFC. Significant differences in Oxygenated hemoglobin (HbO), Total hemoglobin (HbT) and oxygenation (Oxy) changes depending on the Sternberg WM task were found. Unlike previous studies with fNIRS and WM, the current study uses a highly controlled WM task that differentiates between encoding, retention and retrieval phases, comparing different levels of task load.

Multiple-Time-Scale Analysis of Attention as Revealed by EEG, NIRS, and Pupil Diameter Signals During a Free Recall Task: A Multimodal Measurement Approach

Attention plays a fundamental role in acquiring and understanding information. Therefore, it is useful to evaluate attention objectively in such fields as education and mental health. Aimed at extracting objective indicators of attention from physiological signals, this study examined the characteristics of electroencephalography (EEG), near-infrared spectroscopy (NIRS), and pupil diameter signals during a free recall task. The objective was to clarify the temporal characteristics of these signals in relation to attention. We used a free recall task as a cognitive task with an attentional load. The participants attempted to memorize and then recall 13 serially presented words. Our hypothesis was that the significant physiological responses should differ depending on the time scale of the attention evaluation. The physiological responses were compared on the basis of differences between success and failure to recall a word on a short time scale, in terms of the attentional state among five serial position groups on a middle time scale, and on the basis of differences between trials with many and few words recalled on a long time scale. We found that the response of each physiological signal depended on the attention in the different time-scale comparisons. (1) The P300 amplitudes of the EEG signals for the words that were recalled were significantly higher than those for the words that were not recalled. (2) Pupillary dilation differed significantly depending on the serial position group. (3) Functional connectivity in the right hemisphere revealed by NIRS was significantly stronger in trials with many words recalled than in those with few words recalled. Different temporal characteristics of physiological signals with respect to attention were suggested by multimodal measurement and multiple-time-scale analysis. Consideration of these characteristics should help in the development of applications requiring objective attention evaluation.

Functional and/or structural brain changes in response to resistance exercises and resistance training lead to cognitive improvements - a systematic review

BACKGROUND

During the aging process, physical capabilities (e.g., muscular strength) and cognitive functions (e.g., memory) gradually decrease. Regarding cognitive functions, substantial functional (e.g., compensatory brain activity) and structural changes (e.g., shrinking of the hippocampus) in the brain cause this decline. Notably, growing evidence points towards a relationship between cognition and measures of muscular strength and muscle mass. Based on this emerging evidence, resistance exercises and/or resistance training, which contributes to the preservation and augmentation of muscular strength and muscle mass, may trigger beneficial neurobiological processes and could be crucial for healthy aging that includes preservation of the brain and cognition. Compared with the multitude of studies that have investigated the influence of endurance exercises and/or endurance training on cognitive performance and brain structure, considerably less work has focused on the effects of resistance exercises and/or resistance training. While the available evidence regarding resistance exercise-induced changes in cognitive functions is pooled, the underlying neurobiological processes, such as functional and structural brain changes, have yet to be summarized. Hence, the purpose of this systematic review is to provide an overview of resistance exercise-induced functional and/or structural brain changes that are related to cognitive functions.

METHODS AND RESULTS

A systematic literature search was conducted by two independent researchers across six electronic databases; 5957 records were returned, of which 18 were considered relevant and were analyzed.

SHORT CONCLUSION

Based on our analyses, resistance exercises and resistance training evoked substantial functional brain changes, especially in the frontal lobe, which were accompanied by improvements in executive functions. Furthermore, resistance training led to lower white matter atrophy and smaller white matter lesion volumes. However, based on the relatively small number of studies available, the findings should be interpreted cautiously. Hence, future studies are required to investigate the underlying neurobiological mechanisms and to verify whether the positive findings can be confirmed and transferred to other needy cohorts, such as older adults with dementia, sarcopenia and/or dynapenia.

Prefrontal Activity Measured by Functional Near Infrared Spectroscopy During Divergent and Convergent Thinking in Bipolar Disorder

Introduction

Biographical research as well as some controlled studies point out to a relationship between bipolar disorder (BD) and creativity. Neurobiological underpinnings of this relationship are unclear. Although there is no consensus on the definition of creativity, Alternative uses Test (AuT) and Remote Association Test (RAT) are frequently used to measure convergent and divergent creativity. We aimed to examine prefrontal cortex (PFC) activity with functional near-infrared spectroscopy (fNIRS) during the RAT and AuT tests in subjects with BD.

Methods

We measured PFC activity in subjects with remitted BD (N=31) and healthy control subjects (N=27) with fNIRS during divergent and convergent thinking tasks (AuT and RAT respectively). We were particularly interested in the antero-posterior dissociation of the activity within the PFC according to the two task domains.

Results

We found that the index subjects displayed lower performance than healthy controls during the AuT and the RAT. AuT and RAT were associated with different activities in the two groups. Anterior PFC (aPFC) activity was higher than posterior PFC (pPFC) activity during the RAT in the index group, and during the AuT in the control group. aPFC activity was negatively correlated with the RAT performance in the index group.

Conclusion

Higher activity in the aPFC may be the functional neuro-anatomical correlate of low convergent creativity performance in BD.

Effects of movement music therapy with a percussion instrument on physical and frontal lobe function in older adults with mild cognitive impairment: a randomized controlled trial

OBJECTIVES

We tested the hypothesis that performing a rhythmic physical task accompanied by a cognitive task, such as multitask movement music therapy (MMT) involving repetitive rhythmic movement with a musical instrument (the Naruko clapper), may improve pre-frontal cortex (PFC) function and cognitive performance.

METHOD

Forty-five older adult participants with MCI (74.62 ± 5.05 years) participated in this randomized, controlled, single-blind intervention trial. 35 were assigned to the MMT group and 10 to the control STT group. Before and after the 12-week exercise program, we administered six physical function tests, the Frontal Assessment Battery (FAB), and measured relative oxyhemoglobin concentrations using 45-multichannel functional near-infrared spectroscopy as a reflection of hemodynamic responses in the PFC.

RESULTS

We observed significant improvements in FAB scores only in the MMT group. Cerebral blood flow (CBF) in the PFC during the exercise was significantly increased in the MMT group compared with the STT group. The CBF increase was significantly correlated among various channels in the MMT group.

CONCLUSIONS

The MMT program appeared to stimulate the PFC and improve cognitive performance in our older adult participants with MCI, suggesting that the repetitive, rhythmic movements of MMT can activate the prefrontal area in older adults.

TRIAL REGISTRATION

Clinical Trial Registry Numbers: R000026130, UMIN000022671 (2016/06/08) [(University Hospital Medical Information Network (UMIN) Center] retrospectively registered.

High Oxygen Exchange to Music Indicates Auditory Distractibility in Acquired Brain Injury: An fNIRS Study with a Vector-Based Phase Analysis

Attention deficits due to auditory distractibility are pervasive among patients with acquired brain injury (ABI). It remains unclear, however, whether attention deficits following ABI specific to auditory modality are associated with altered haemodynamic responses. Here, we examined cerebral haemodynamic changes using functional near-infrared spectroscopy combined with a topological vector-based analysis method. A total of thirty-seven participants (22 healthy adults, 15 patients with ABI) performed a melodic contour identification task (CIT) that simulates auditory distractibility. Findings demonstrated that the melodic CIT was able to detect auditory distractibility in patients with ABI. The rate-corrected score showed that the ABI group performed significantly worse than the non-ABI group in both CIT1 (target contour identification against environmental sounds) and CIT2 (target contour identification against target-like distraction). Phase-associated response intensity during the CITs was greater in the ABI group than in the non-ABI group. Moreover, there existed a significant interaction effect in the left dorsolateral prefrontal cortex (DLPFC) during CIT1 and CIT2. These findings indicated that stronger hemodynamic responses involving oxygen exchange in the left DLPFC can serve as a biomarker for evaluating and monitoring auditory distractibility, which could potentially lead to the discovery of the underlying mechanism that causes auditory attention deficits in patients with ABI.

Cognitive Load Changes during Music Listening and its Implication in Earcon Design in Public Environments: An fNIRS Study

A key for earcon design in public environments is to incorporate an individual’s perceived level of cognitive load for better communication. This study aimed to examine the cognitive load changes required to perform a melodic contour identification task (CIT). While healthy college students (N = 16) were presented with five CITs, behavioral (reaction time and accuracy) and cerebral hemodynamic responses were measured using functional near-infrared spectroscopy. Our behavioral findings showed a gradual increase in cognitive load from CIT1 to CIT3 followed by an abrupt increase between CIT4 (i.e., listening to two concurrent melodic contours in an alternating manner and identifying the direction of the target contour, p < 0.001) and CIT5 (i.e., listening to two concurrent melodic contours in a divided manner and identifying the directions of both contours, p < 0.001). Cerebral hemodynamic responses showed a congruent trend with behavioral findings. Specific to the frontopolar area (Brodmann’s area 10), oxygenated hemoglobin increased significantly between CIT4 and CIT5 (p < 0.05) while the level of deoxygenated hemoglobin decreased. Altogether, the findings indicate that the cognitive threshold for young adults (CIT5) and appropriate tuning of the relationship between timbre and pitch contour can lower the perceived cognitive load and, thus, can be an effective design strategy for earcon in a public environment.

A Functional Near-Infrared Spectroscopy Study of State Anxiety and Auditory Working Memory Load

Cognitive studies have suggested that anxiety is correlated with cognitive performance. Previous research has focused on the relationship between anxiety level and the perceptual load within the frontal region, such as the dorsolateral prefrontal and anterior cingulate cortices. High-anxious individuals are predicted to have worse performance on cognitively-demanding tasks requiring efficient cognitive processing. A few functional magnetic resonance imaging studies have specifically discussed the performance and brain activity involving working memory for high-anxious individuals. This topic has been further explored with electroencephalography, although these studies have mostly provided results involving visual face-related stimuli. In this study, we used auditory stimulation to manipulate the working memory load and attempted to interpret the deficiency of cognitive function in high-anxious participants or patients using functional near infrared spectroscopy (fNIRS). The fNIRS signals of 30 participants were measured while they were performing an auditory working memory task. For the auditory n-back task, there were three experimental conditions, including two n-back task conditions of stimuli memorization with different memory load and a condition of passive listening to the stimuli. Hemodynamic responses from frontal brain regions were recorded using a wireless fNIRS device. Brain activation from the ventrolateral and orbital prefrontal cortex were measured with signals filtered and artifacts removed. The fNIRS signals were then standardized with statistical testing and group analysis was performed. The results revealed that there were significantly stronger hemodynamic responses in the right ventrolateral and orbital prefrontal cortex when subjects were attending to the auditory working memory task with higher load. Furthermore, the right lateralization of the prefrontal cortex was negatively correlated with the level of state anxiety. This study revealed the possibility of incorporating fNIRS signals as an index to evaluate cognitive performance and mood states given its flexibility regarding portable applications compared to other neuroimaging techniques.

Exploring the role of task performance and learning style on prefrontal hemodynamics during a working memory task

Existing literature outlines the quality and location of activation in the prefrontal cortex (PFC) during working memory (WM) tasks. However, the effects of individual differences on the underlying neural process of WM tasks are still unclear. In this functional near infrared spectroscopy study, we administered a visual and auditory n-back task to examine activation in the PFC while considering the influences of task performance, and preferred learning strategy (VARK score). While controlling for age, results indicated that high performance (HP) subjects (accuracy > 90%) showed task dependent lower activation compared to normal performance subjects in PFC region Specifically HP groups showed lower activation in left dorsolateral PFC (DLPFC) region during performance of auditory task whereas during visual task they showed lower activation in the right DLPFC. After accounting for learning style, we found a correlation between visual and aural VARK score and level of activation in the PFC. Subjects with higher visual VARK scores displayed lower activation during auditory task in left DLPFC, while those with higher visual scores exhibited higher activation during visual task in bilateral DLPFC. During performance of auditory task, HP subjects had higher visual VARK scores compared to NP subjects indicating an effect of learning style on the task performance and activation. The results of this study show that learning style and task performance can influence PFC activation, with applications toward neurological implications of learning style and populations with deficits in auditory or visual processing.

Differential effects of physical activity and sleep duration on cognitive function in young adults

PURPOSE

Although exercise and sleep duration habits are associated with cognitive function, their beneficial effects on cognitive function remain unclear. We aimed to examine the effect of sleep duration and daily physical activity on cognitive function, elucidating the neural mechanisms using near-infrared spectroscopy (NIRS).

METHODS

A total of 23 healthy young adults (age 22.0 ± 2.2 years) participated in this study. Exercise amount was assessed using a uniaxial accelerometer. We evaluated total sleep time (TST) and sleep efficiency by actigraphy. Cognitive function was tested using the N-back task, the Wisconsin Card Sorting Test (WCST), and the Continuous Performance Test-Identical Pairs (CPT-IP), and the cortical oxygenated hemoglobin levels during a word fluency task were measured with NIRS.

RESULTS

Exercise amount was significantly correlated with reaction time on 0- and 1-back tasks (r = -0.602, p = 0.002; r = -0.446, p = 0.033, respectively), whereas TST was significantly correlated with % corrects on the 2-back task (r = 0.486, p = 0.019). Multiple regression analysis, including exercise amount, TST, and sleep efficiency, revealed that exercise amount was the most significant factor for reaction time on 0- and 1-back tasks (β = -0.634, p = 0.002; β = -0.454, p = 0.031, respectively), and TST was the most significant factor for % corrects on the 2-back task (β = 0.542, p = 0.014). The parameter measured by WCST and CPT-IP was not significantly correlated with TST or exercise amount. Exercise amount, but not TST, was significantly correlated with the mean area under the NIRS curve in the prefrontal area (r = 0.492, p = 0.017).

CONCLUSION

Exercise amount and TST had differential effects on working memory and cortical activation in the prefrontal area. Daily physical activity and appropriate sleep duration may play an important role in working memory.

Multi-Sensory Integration Impairment in Patients with Minimal Hepatic Encephalopathy

Paper-and-pencil-based psychometric tests are the gold standard for diagnosis of cognitive dysfunction in liver disease. However, they take time, can be affected by demographic factors, and lack ecological validity. This study explored multi-sensory integration ability to discriminate cognitive dysfunction in cirrhosis. Thirty-two healthy controls and 30 cirrhotic patients were recruited. The sensory integration test presents stimuli from two different modalities (e.g., image/sound) with a short time lag, and subjects judge which stimuli appeared first. Repetitive tests reveal the sensory integration capability. Performance in the sensory integration test, psychometric tests, and functional near-infrared spectroscopy for patients was compared to controls. Sensory integration capability, the perceptual threshold to discriminate the time gap between an image and sound stimulus, was significantly impaired in cirrhotic patients with minimal hepatic encephalopathy (MHE) compared to controls (p < 0.01) and non-MHE patients (p < 0.01). Sensory integration test showed good correlation with psychometric tests (NCT-A, r = 0.383, p = 0.002; NCT-B, r = 0.450, p < 0.01; DST-F, r = -0.322, p = 0.011; DST- B, r = -0.384, p = 0.002; ACPT, r = -0.467, p < 0.01). Psychometric tests were dependent on age and education level, while the sensory integration test was not affected. The sensory integration test, where a cut-off value for the perceptual threshold was 133.3ms, recognized MHE patients at 90% sensitivity and 86.5% specificity.

Prefrontal Activation During Executive Tasks Emerges Over Early Childhood: Evidence From Functional Near Infrared Spectroscopy

Functional Near Infrared Spectroscopy (fNIRS) is a brain imaging technique that is well-suited for use in young children, making it particularly useful for investigating the neural bases of the development of executive functions. In the present study, children (ages 4-10) underwent fNIRS while completing response inhibition and working memory tasks. While both tasks were associated with increases in oxyhemoglobin and decreases in deoxyhemoglobin, we found that strength of activation increased with age and with improvements in task performance. These findings support the relation between emerging executive functions and maturation of the prefrontal cortex.

Left Lateral Prefrontal Activity Reflects a Change of Behavioral Tactics to Cope with a Given Rule: An fNIRS Study

Rules prescribe human behavior and our attempts to choose appropriate behavior under a given rule. Cognitive control, a mechanism to choose and evaluate actions under a rule, is required to determine the appropriate behavior within the limitations of that rule. Consequently, such cognitive control increases mental workload. However, the workload caused by a cognitive task might be different when an additional rule must be considered in choosing the action. The present study was a functional near-infrared spectroscopy (fNIRS) investigation of an experimental task, in which the difficulty of an operation and existence of an additional rule were manipulated to dissociate the influence of that additional rule on cognitive processing. Twenty healthy Japanese volunteers participated. The participants performed an experimental task, in which the player caught one of five colored balls from the upper part of a computer screen by operating a mouse. Four task conditions were prepared to manipulate the task difficulty, which was defined in terms of operational difficulty. In turn, operational difficulty was determined by the width of the playable space and the existence of an additional rule, which reduced the score when a red ball was not caught. The 52-channel fNIRS data were collected from the forehead. Two regions of interest (ROIs) associated with the bilateral lateral prefrontal cortices (LPFCs) were determined, and a three-way repeated-measures analysis of variance (ANOVA) was performed using the task-related signal changes from each ROI. The fNIRS results revealed that bilateral LPFCs showed large signal changes with the increase in mental workload. The ANOVA showed a significant interaction between the existence of an additional rule and the location of the ROIs; that is, the left lateral prefrontal area showed a significant increase in signal intensity when the additional rule existed, and the participant occasionally decided to avoid catching a ball to successfully catch the red-colored ball. Thus, activation of the left LPFC corresponded more closely to the increase in cognitive control underlying the behavioral change made to cope with the additional rule.

A Brief Review of Research Using Near-Infrared Spectroscopy to Measure Activation of the Prefrontal Cortex during Emotional Processing: The Importance of Experimental Design

During the past two decades there has been a pronounced increase in the number of published research studies that have employed near-infrared spectroscopy (NIRS) to measure neural activation. The technique is now an accepted neuroimaging tool adopted by cognitive neuroscientists to investigate a number of fields, one of which is the study of emotional processing. Crucially, one brain region that is important to the processing of emotional information is the prefrontal cortex (PFC) and NIRS is ideally suited to measuring activity in this region. Compared to other methods used to record neural activation, NIRS reduces the discomfort to participants, makes data collection from larger sample sizes more achievable, and allows measurement of activation during tasks involving physical movement. However, the use of NIRS to investigate the links between emotion and cognition has revealed mixed findings. For instance, whilst some studies report increased PFC activity associated with the processing of negative information, others show increased activity in relation to positive information. Research shows differences in PFC activity between different cognitive tasks, yet findings also vary within similar tasks. This work reviews a selection of recent studies that have adopted NIRS to study PFC activity during emotional processing in both healthy individuals and patient populations. It highlights the key differences between research findings and argues that variations in experimental design could be a contributing factor to the mixed results. Guidance is provided for future work in this area in order to improve consistency within this growing field.

Melodic Contour Identification Reflects the Cognitive Threshold of Aging

Cognitive decline is a natural phenomenon of aging. Although there exists a consensus that sensitivity to acoustic features of music is associated with such decline, no solid evidence has yet shown that structural elements and contexts of music explain this loss of cognitive performance. This study examined the extent and the type of cognitive decline that is related to the contour identification task (CIT) using tones with different pitches (i.e., melodic contours). Both younger and older adult groups participated in the CIT given in three listening conditions (i.e., focused, selective, and alternating). Behavioral data (accuracy and response times) and hemodynamic reactions were measured using functional near-infrared spectroscopy (fNIRS). Our findings showed cognitive declines in the older adult group but with a subtle difference from the younger adult group. The accuracy of the melodic CITs given in the target-like distraction task (CIT2) was significantly lower than that in the environmental noise (CIT1) condition in the older adult group, indicating that CIT2 may be a benchmark test for age-specific cognitive decline. The fNIRS findings also agreed with this interpretation, revealing significant increases in oxygenated hemoglobin (oxyHb) concentration in the younger (p < 0.05 for Δpre - on task; p < 0.01 for Δon – post task) rather than the older adult group (n.s for Δpre - on task; n.s for Δon – post task). We further concluded that the oxyHb difference was present in the brain regions near the right dorsolateral prefrontal cortex. Taken together, these findings suggest that CIT2 (i.e., the melodic contour task in the target-like distraction) is an optimized task that could indicate the degree and type of age-related cognitive decline.

Nonverbal auditory working memory: Can music indicate the capacity?

Different working memory (WM) mechanisms that underlie words, tones, and timbres have been proposed in previous studies. In this regard, the present study developed a WM test with nonverbal sounds and compared it to the conventional verbal WM test. A total of twenty-five, non-music major, right-handed college students were presented with four different types of sounds (words, syllables, pitches, timbres) that varied from two to eight digits in length. Both accuracy and oxygenated hemoglobin (oxyHb) were measured. The results showed significant effects of number of targets on accuracy and sound type on oxyHb. A further analysis showed prefrontal asymmetry with pitch being processed by the right hemisphere (RH) and timbre by the left hemisphere (LH). These findings suggest a potential for employing musical sounds (i.e., pitch and timbre) as a complementary stimuli for conventional nonverbal WM tests, which can additionally examine its asymmetrical roles in the prefrontal regions.

Executive n-back tasks for the neuropsychological assessment of working memory

Working memory (WM) has been defined as a cerebral function which allows us to maintain and manipulate information "online". One of the most widely used paradigms to assess WM is the n-back test. Despite its extensive application, some authors have questioned its capacity to assess the manipulation of WM load. The present study introduces a new version of the n-back test to carry out this assessment. We use functional near-infrared spectroscopy (fNIRS) to evaluate prefrontal cortex (PFC) activation. The modified n-back requires monitoring of sequentially presented stimuli (in this case the days of the week). The target response relates to a stimulus which appears previously, from 0 to 2 items back, on the computer screen. Our data reveals that while modified and unmodified n-back activate the same regions of the left PFC, our modified 2-back version shows significantly higher activation in the left dorsolateral PFC (DLPFC) and the left frontal opercula. These results suggest that increased complexity in verbal WM tasks entail greater executive control, which would lead to an increase in cerebral blood flow to the areas associated with verbal WM. Therefore, an increase in the manipulation of WM load in verbal tasks reflects greater physiological activity in the left DLPFC and the left frontal opercula. The modified n-back test may also be incorporated into the armamentarium of valid instruments for the neuropsychological assessment of the maintenance and manipulation of verbal information in tasks requiring working memory.