Spatial correspondence of cortical activity measured with whole head fNIRS and fMRI: Toward clinical use within subject.

Functional near infrared spectroscopy (fNIRS) and functional magnetic resonance imaging (fMRI) both measure the hemodynamic response, and so both imaging modalities are expected to have a strong correspondence in regions of cortex adjacent to the scalp. To assess whether fNIRS can be used clinically in a manner similar to fMRI, 22 healthy adult participants underwent same-day fMRI and whole-head fNIRS testing while they performed separate motor (finger tapping) and visual (flashing checkerboard) tasks. Analyses were conducted within and across subjects for each imaging approach, and regions of significant task-related activity were compared on the cortical surface. The spatial correspondence between fNIRS and fMRI detection of task-related activity was good in terms of true positive rate, with fNIRS overlap of up to 68 % of the fMRI for analyses across subjects (group analysis) and an average overlap of up to 47.25 % for individual analyses within subject. At the group level, the positive predictive value of fNIRS was 51 % relative to fMRI. The positive predictive value for within subject analyses was lower (41.5 %), reflecting the presence of significant fNIRS activity in regions without significant fMRI activity. This could reflect task-correlated sources of physiologic noise and/or differences in the sensitivity of fNIRS and fMRI measures to changes in separate (vs. combined) measures of oxy and de-oxyhemoglobin. The results suggest whole-head fNIRS as a noninvasive imaging modality with promising clinical utility for the functional assessment of brain activity in superficial regions of cortex physically adjacent to the skull.

Neural circuits underpinning face tuning in male depression.

Reading bodies and faces is essential for efficient social interactions, though it may be thought-provoking for individuals with depression. Yet aberrations in the face sensitivity and underwriting neural circuits are not well understood, in particular, in male depression. Here, we use cutting-edge analyses of time course and dynamic topography of gamma oscillatory neuromagnetic cortical activity during administration of a task with Arcimboldo-like images. No difference in face tuning was found between individuals with depression and their neurotypical peers. Furthermore, this behavioral outcome nicely dovetails with magnetoencephalographic data: at early processing stages, the gamma oscillatory response to images resembling a face was rather similar in patients and controls. These bursts originated primarily from the right medioventral occipital cortex and lateral occipital cortex. At later processing stages, however, its topography altered remarkably in depression with profound engagement of the frontal circuits. Yet the primary difference in depressive individuals as compared with their neurotypical peers occurred over the left middle temporal cortices, a part of the social brain, engaged in feature integration and meaning retrieval. The outcome suggests compensatory recruitment of neural resources in male depression.

The Effect of Various Spinal Neurostimulation Paradigms on the Supraspinal Somatosensory Evoked Response: A Systematic Review.

INTRODUCTION: Spinal neurostimulation is a therapy for otherwise intractable chronic pain. Spinal neurostimulation includes stimulation of the spinal cord (SCS), dorsal root ganglion (DRGS), and dorsal root entry zone (DREZS). New paresthesia-free neurostimulation paradigms may rely on different mechanisms of action from those of conventional tonic neurostimulation. The aim of this systematic review is to assess the existing knowledge on the effect of spinal neurostimulation on somatosensory processing in patients with chronic pain. We therefore reviewed the existing literature on the effect of various spinal neurostimulation paradigms on the supraspinal somatosensory evoked response (SER). MATERIALS AND METHODS: Multiple scientific data bases were searched for studies that assessed the effect of spinal neurostimulation on the supraspinal SER, evoked by painful or nonpainful peripheral stimuli in patients with chronic pain. We found 205 studies, of which 24 were included. Demographic data, study design, and study outcome were extracted. RESULTS: Of the 24 included studies, 23 used electroencephalography to assess the SER; one study used magnetoencephalography. Fifteen studies evaluated tonic SCS; six studies (also) evaluated paresthesia-free paradigms; three studies evaluated the effect of tonic DRGS or DREZS. Sixteen studies used nonpainful stimuli to elicit the SER, 14 observed a decreased SER amplitude. Ten studies used painful stimuli to elicit the SER, yielding mixed results. DISCUSSION: The included studies suggest that both paresthesia-based and paresthesia-free spinal neurostimulation paradigms can decrease (part of) the SER elicited by a nonpainful peripheral stimulus. The observed SER amplitude reduction likely is the effect of various spinal and supraspinal mechanisms of spinal neurostimulation that also contribute to pain relief. CONCLUSIONS: Spinal neurostimulation modulates the processing of a peripherally applied nonpainful stimulus. For painful stimuli, the results are not conclusive. It is not yet clear whether paresthesia-free neurostimulation affects the SER differently from paresthesia-based neurostimulation.

Effect of dual-task interaction combining postural and visual perturbations on cortical activity and postural control ability.

Previous studies have suggested cortical involvement in postural control in humans by measuring cortical activities and conducting dual-task paradigms. In dual-task paradigms, task performance deteriorates and can be facilitated in specific dual-task settings. Theoretical frameworks explaining these dual-task interactions have been proposed and debated for decades. Therefore, we investigated postural control performance under different visual conditions using a virtual reality system, simultaneously measuring cortical activities with a functional near-infrared spectroscopy system. Twenty-four healthy participants were included in this study. Postural stability and cortical activities after perturbations were measured under several conditions consisting of postural and visual perturbations. The results showed that concurrent visual and postural perturbations could facilitate cortical activities in the supplementary motor area and superior parietal lobe. Additionally, visual distractors deteriorated postural control ability and cortical activation of the supplementary motor area. These findings supported the theoretical framework of the "Cross talk model", in which concurrent tasks using similar neural domains can facilitate these task performances. Furthermore, it indicated that the cortical resource capacity and domains activated for information processing should be considered in experiments involving dual-task paradigms and training.

Relative and absolute reliability of somatosensory evoked potentials in response to non-noxious electrical stimulation of the paraspinal muscles in healthy participants at an interval of 3-months.

BACKGROUND: Somatosensory evoked potentials (SEPs) are used extensively to quantify cortical activity in response to noxious and/or non-noxious sensory stimuli. However, data demonstrating the reliability of SEP measures in response to non-noxious stimulation over time are scarce. AIM: We investigated the relative and absolute reliability, and the smallest detectable change at 95% confidence (SDC95) for SEPs evoked by non-noxious electrical stimulation of the paraspinal muscles in thirty-nine healthy participants at a 3-month interval. METHODS: SEPs were evoked at an intensity three-times that of each participant's perceptual threshold and recorded from a single electrode placed over the primary somatosensory cortex (S1). RESULTS: Our analyses reveal that i) latency, as a measure of activity onset, has poor relative reliability but good absolute reliability; ii) area, as a measure of cortical activity, has good relative and absolute reliability (except for the N150 component) and iii) perceptual threshold and stimulation intensity was not reliable over time. CONCLUSION: These findings suggest that the area of the N80 and P260 SEP components, and the area of the N80-N150-P260 SEP complex, can be utilised in future studies as reliable markers of cortical activity.

A Review of Effects of Spinal Cord Stimulation on Spectral Features in Resting-State Electroencephalography.

BACKGROUND: Spinal cord stimulation (SCS) is an effective therapy for patients with refractory chronic pain syndromes. Although studies have shown that SCS has both spinal and supraspinal effects, the current understanding of cortical effects is still limited. Neuroimaging techniques, such as magnetoencephalography (MEG) and electroencephalography (EEG), combined here as M/EEG, can reveal modulations in ongoing resting-state cortical activity. We aim to provide an overview of available literature on resting-state M/EEG in patients with chronic pain who have been treated with SCS. MATERIALS AND METHODS: We searched multiple online data bases for studies on SCS, chronic pain, and resting-state M/EEG. Primary outcome measures were changes in spectral features, combined with brain regions in which these changes occurred. RESULTS: We included eight studies reporting various SCS paradigms (tonic, burst, high-dose, and high-frequency stimulation) and revealing heterogeneity in outcome parameters. We summarized changes in cortical activity in various frequency bands: theta (4-7 Hz), alpha (7-12 Hz), beta (13-30 Hz), and gamma (30-44 Hz). In multiple studies, the somatosensory cortex showed modulation of cortical activity under tonic, burst, and high-frequency stimulation. Changes in connectivity were found in the dorsal anterior cingulate cortex, dorsolateral prefrontal cortex, and parahippocampus. CONCLUSIONS: The large heterogeneity observed in outcome measures is probably caused by the large variety in study designs, stimulation paradigms, and spectral features studied. Paresthesia-free paradigms have been compared with tonic stimulation in multiple studies. These studies suggest modulation of medial, lateral, and descending pathways for paresthesia-free stimulation, whereas tonic stimulation predominantly modulates lateral and descending pathways. Moreover, multiple studies have reported an increased alpha peak frequency, increased alpha power, and/or decreased theta power when SCS was compared with baseline, indicating modulation of thalamocortical pathways. Further studies with well-defined groups of responders and nonresponders to SCS are recommended to independently study the cortical effects of pain relief and SCS.

Heterogeneous Cortical Effects of Spinal Cord Stimulation.

OBJECTIVES: The understanding of the cortical effects of spinal cord stimulation (SCS) remains limited. Multiple studies have investigated the effects of SCS in resting-state electroencephalography. However, owing to the large variation in reported outcomes, we aimed to describe the differential cortical responses between two types of SCS and between responders and nonresponders using magnetoencephalography (MEG). MATERIALS AND METHODS: We conducted 5-minute resting-state MEG recordings in 25 patients with chronic pain with active SCS in three sessions, each after a one-week exposure to tonic, burst, or sham SCS. We extracted six spectral features from the measured neurophysiological signals: the alpha peak frequency; alpha power ratio (power 7-9 Hz/power 9-11 Hz); and average power in the theta (4-7.5 Hz), alpha (8-12.5 Hz), beta (13-30 Hz), and low-gamma (30.5-60 Hz) frequency bands. We compared these features (using nonparametric permutation t-tests) for MEG sensor and cortical map effects across stimulation paradigms, between participants who reported low (< 5, responders) vs high (≥ 5, nonresponders) pain scores, and in three representative participants. RESULTS: We found statistically significant (p < 0.05, false discovery rate corrected) increased MEG sensor signal power below 3 Hz in response to burst SCS compared with tonic and sham SCS. We did not find statistically significant differences (all p > 0.05) between the power spectra of responders and nonresponders. Our data did not show statistically significant differences in the spectral features of interest among the three stimulation paradigms or between responders and nonresponders. These results were confirmed by the MEG cortical maps. However, we did identify certain trends in the MEG source maps for all comparisons and several features, with substantial variation across participants. CONCLUSIONS: The considerable variation in cortical responses to the various SCS treatment options necessitates studies with sample sizes larger than commonly reported in the field and more personalized treatment plans. Studies with a finer stratification between responders and nonresponders are required to advance the knowledge on SCS treatment effects.

Regional difference in prefrontal oxygenation before and during overground walking in humans: a wearable multichannel NIRS study.

Using wireless multichannel near-infrared spectroscopy, regional difference in cortical activity over the prefrontal cortex (PFC) was examined before and during overground walking and in response to changes in speed and cognitive demand. Oxygenated-hemoglobin concentration (Oxy-Hb) as index of cortical activity in ventrolateral PFC (VLPFC), dorsolateral PFC (DLPFC), and frontopolar cortex (FPC) was measured in 14 subjects, whereas heart rate was measured as estimation of exercise intensity in six subjects. The impact of mental imagery on prefrontal Oxy-Hb was also explored. On both sides, Oxy-Hb in VLPFC, DLPFC, and lateral FPC was increased before the onset of normal-speed walking, whereas Oxy-Hb in medial FPC did not respond before walking onset. During the walking, Oxy-Hb further increased in bilateral VLPFC, whereas Oxy-Hb was decreased in DLPFC and lateral and medial FPC. Increasing walking speed did not alter the increase in Oxy-Hb in VLPFC but counteracted the decrease in Oxy-Hb in DLPFC (but not in lateral and medial FPC). Treadmill running evoked a greater Oxy-Hb increase in DLPFC (n = 5 subjects). Furthermore, increasing cognitive demand during walking, by deprivation of visual feedback, counteracted the decrease in Oxy-Hb in DLPFC and lateral and medial FPC, but it did not affect the increase in Oxy-Hb in VLPFC. Taken together, the profound and localized Oxy-Hb increase is a unique response for the VLPFC. The regional heterogeneity of the prefrontal Oxy-Hb responses to natural overground walking was accentuated by increasing walking speed or cognitive demand, suggesting functional distinction within the PFC.

Comparing different montages of transcranial direct current stimulation on dual-task walking and cortical activity in chronic stroke: double-blinded randomized controlled trial.

BACKGROUND: Transcranial direct current stimulation (tDCS) is a noninvasive brain stimulation to modulate cortical activity for improving motor function. However, the different tDCS applications for modulating cortical activity and dual task gait performance in chronic stroke have not yet been investigated. This study investigated the effects of different tDCS applications on dual task gait performance and contralesional M1 activation in chronic stroke. METHODS: Forty-eight participants were randomized to anodal, bilateral, cathodal, and sham tDCS groups. Each group received 20 min of tDCS stimulation, except the sham group. Gait performance was measured by GaitRite system during cognitive dual task (CDT) walking, motor dual task (MDT) walking, and single walking (SW). Contralesional M1 activity of unaffected tibialis anterior (TA) was measured using transcranial magnetic stimulation (TMS). Intragroup difference was analyzed by Wilconxon sign ranks test with Bonferroni correction, and Kruskal-Wallis one-way analysis of variance by ranks was used for intergroup comparisons, followed by post-hoc Mann-Whitney U tests with Bonferroni correction. RESULTS: The bilateral tDCS (p = 0.017) and cathodal tDCS (p = 0.010) improved the CDT walking speed more than sham group. The bilateral tDCS (p = 0.048) and cathodal tDCS (p = 0.048) also improved the MDT walking speed more than sham group. Furthermore, bilateral tDCS (p = 0.012) and cathodal tDCS (p = 0.040) increased the silent period (SP) more than the anodal and sham group. Thus, one-session of bilateral and cathodal tDCS improved dual task walking performance paralleled with increasing contralesional corticomotor inhibition in chronic stroke. CONCLUSIONS: Our results indicate that one-session of bilateral and cathodal tDCS increased contralesional corticomotor inhibition and improved dual task gait performance in chronic stroke. TRIAL REGISTRATION: Thai Clinical Trials Registry (TCTR20180116001). Registered prospectively on 16th Jan, 2018 at http://www.thaiclinicaltrials.org .

Brain oxygenation during multiple sets of isometric and dynamic resistance exercise of equivalent workloads: Association with systemic haemodynamics.

Brain function relies on sufficient blood flow and oxygen supply. Changes in cerebral oxygenation during exercise have been linked to brain activity and central command. Isometric- and dynamic-resistance exercise-(RE) may elicit differential responses in systemic circulation, neural function and metabolism; all important regulators of cerebral circulation. We examined whether (i) cerebral oxygenation differs between isometric- and dynamic-RE of similar exercise characteristics and (ii) cerebral oxygenation changes relate to cardiovascular adjustments occurring during RE. Fourteen men performed, randomly, an isometric-RE and a dynamic-RE of similar characteristics (bilateral-leg-press, 2-min×4-sets, 30% of maximal-voluntary-contraction, equivalent tension-time-index/workload). Cerebral-oxygenation (oxyhaemoglobin-O2Hb; total haemoglobin-tHb/blood-volume-index; deoxyhemoglobin-HHb) was assessed by NIRS and beat-by-beat haemodynamics via photoplethysmography. Cerebral-O2Hb and tHb progressively increased from the 1st to 4th set in both RE-protocols (p < 0.05); HHb slightly decreased (p < 0.05). Changes in NIRS-parameters were similar between RE-protocols within each exercise-set (p = 0.91-1.00) and during the entire protocol (including resting-phases) (p = 0.48-0.63). O2Hb and tHb changes were not correlated with changes in systemic haemodynamics. In conclusion, cerebral oxygenation/blood-volume steadily increased during multiple-set RE-protocols. Isometric- and dynamic-RE of matched exercise characteristics resulted in similar prefrontal oxygenation/blood volume changes, suggesting similar cerebral haemodynamic and possibly neuronal responses to maintain a predetermined force.

Combining Cortical Voltage Imaging and Hippocampal Electrophysiology for Investigating Global, Multi-Timescale Activity Interactions in the Brain.

A new generation of optogenetic tools for analyzing neural activity has been contributing to the elucidation of classical open questions in neuroscience. Specifically, voltage imaging technologies using enhanced genetically encoded voltage indicators have been increasingly used to observe the dynamics of large circuits at the mesoscale. Here, we describe how to combine cortical wide-field voltage imaging with hippocampal electrophysiology in awake, behaving mice. Furthermore, we highlight how this method can be useful for different possible investigations, using the characterization of hippocampal-neocortical interactions as a case study.

Sensorimotor Cortical Activity during Respiratory Arousals in Obstructive Sleep Apnea.

Intensity of respiratory cortical arousals (RCA) is a pathophysiologic trait in obstructive sleep apnea (OSA) patients. We investigated the brain oscillatory features related to respiratory arousals in moderate and severe OSA. Raw electroencephalography (EEG) data recorded during polysomnography (PSG) of 102 OSA patients (32 females, mean age 51.6 ± 12 years) were retrospectively analyzed. Among all patients, 47 had moderate (respiratory distress index, RDI = 15−30/h) and 55 had severe (RDI > 30/h) OSA. Twenty RCA per sleep stage in each patient were randomly selected and a total of 10131 RCAs were analyzed. EEG signals obtained during, five seconds before and after the occurrence of each arousal were analyzed. The entropy (approximate (ApEn) and spectral (SpEn)) during each sleep stage (N1, N2 and REM) and area under the curve (AUC) of the EEG signal during the RCA was computed. Severe OSA compared to moderate OSA patients showed a significant decrease (p < 0.0001) in the AUC of the EEG signal during the RCA. Similarly, a significant decrease in spectral entropy, both before and after the RCA was observed, was observed in severe OSA patients when compared to moderate OSA patients. Contrarily, the approximate entropy showed an inverse pattern. The highest increase in approximate entropy was found in sleep stage N1. In conclusion, the dynamic range of sensorimotor cortical activity during respiratory arousals is sleep-stage specific, dependent on the frequency of respiratory events and uncoupled from autonomic activation. These findings could be useful for differential diagnosis of severe OSA from moderate OSA.

Monitoring the Cortical Activity of Children and Adults during Cognitive Task Completion.

In this paper, we used an EEG system to monitor and analyze the cortical activity of children and adults at a sensor level during cognitive tasks in the form of a Schulte table. This complex cognitive task simultaneously involves several cognitive processes and systems: visual search, working memory, and mental arithmetic. We revealed that adults found numbers on average two times faster than children in the beginning. However, this difference diminished at the end of table completion to 1.8 times. In children, the EEG analysis revealed high parietal alpha-band power at the end of the task. This indicates the shift from procedural strategy to less demanding fact-retrieval. In adults, the frontal beta-band power increased at the end of the task. It reflects enhanced reliance on the top-down mechanisms, cognitive control, or attentional modulation rather than a change in arithmetic strategy. Finally, the alpha-band power of adults exceeded one of the children in the left hemisphere, providing potential evidence for the fact-retrieval strategy. Since the completion of the Schulte table involves a whole set of elementary cognitive functions, the obtained results were essential for developing passive brain-computer interfaces for monitoring and adjusting a human state in the process of learning and solving cognitive tasks of various types.

Modifications in Prefrontal Cortex Oxygenation in Linear and Curvilinear Dual Task Walking: A Combined fNIRS and IMUs Study.

Increased oxygenated hemoglobin concentration of the prefrontal cortex (PFC) has been observed during linear walking, particularly when there is a high attention demand on the task, like in dual-task (DT) paradigms. Despite the knowledge that cognitive and motor demands depend on the complexity of the motor task, most studies have only focused on usual walking, while little is known for more challenging tasks, such as curved paths. To explore the relationship between cortical activation and gait biomechanics, 20 healthy young adults were asked to perform linear and curvilinear walking trajectories in single-task and DT conditions. PFC activation was assessed using functional near-infrared spectroscopy, while gait quality with four inertial measurement units. The Figure-of-8-Walk-Test was adopted as the curvilinear trajectory, with the "Serial 7s" test as concurrent cognitive task. Results show that walking along curvilinear trajectories in DT led to increased PFC activation and decreased motor performance. Under DT walking, the neural correlates of executive function and gait control tend to be modified in response to the cognitive resources imposed by the motor task. Being more representative of real-life situations, this approach to curved walking has the potential to reveal crucial information and to improve people' s balance, safety, and life's quality.

Neurofeedback of scalp bi-hemispheric EEG sensorimotor rhythm guides hemispheric activation of sensorimotor cortex in the targeted hemisphere.

Oscillatory electroencephalographic (EEG) activity is associated with the excitability of cortical regions. Visual feedback of EEG-oscillations may promote sensorimotor cortical activation, but its spatial specificity is not truly guaranteed due to signal interaction among interhemispheric brain regions. Guiding spatially specific activation is important for facilitating neural rehabilitation processes. Here, we tested whether users could explicitly guide sensorimotor cortical activity to the contralateral or ipsilateral hemisphere using a spatially bivariate EEG-based neurofeedback that monitors bi-hemispheric sensorimotor cortical activities for healthy participants. Two different motor imageries (shoulder and hand MIs) were selected to see how differences in intrinsic corticomuscular projection patterns might influence activity lateralization. We showed sensorimotor cortical activities during shoulder, but not hand MI, can be brought under ipsilateral control with guided EEG-based neurofeedback. These results are compatible with neuroanatomy; shoulder muscles are innervated bihemispherically, whereas hand muscles are mostly innervated contralaterally. We demonstrate the neuroanatomically-inspired approach enables us to investigate potent neural remodeling functions that underlie EEG-based neurofeedback via a BCI.

Roles of motor and cortical activity in sleep rebound in rat.

Sleep pressure that builds up gradually during the extended wakefulness results in sleep rebound. Several lines of evidence, however, suggest that wake per se may not be sufficient to drive sleep rebound and that rapid eye movement (REM) and non-rapid eye movement (NREM) sleep rebound may be differentially regulated. In this study, we investigated the relative contribution of brain versus physical activities in REM and NREM sleep rebound by four sets of experiments. First, we forced locomotion in rats in a rotating wheel for 4 hr and examined subsequent sleep rebound. Second, we exposed the rats lacking homeostatic sleep response after prolonged quiet wakefulness and arousal brain activity induced by chemoactivation of parabrachial nucleus to the same rotating wheel paradigm and tested if physical activity could rescue the sleep homeostasis. Third, we varied motor activity levels while concurrently inhibiting the cortical activity by administering ketamine or xylazine (motor inhibitor), or ketamine + xylazine mixture and investigated if motor activity in the absence of activated cortex can cause NREM sleep rebound. Fourth and finally, we manipulated cortical activity by administering ketamine (that induced active wakefulness and waking brain) alone or in combination with atropine (that selectively inhibits the cortex) and studied if cortical inhibition irrespective of motor activity levels can block REM sleep rebound. Our results demonstrate that motor activity but not cortical activity determines NREM sleep rebound whereas cortical activity but not motor activity determines REM sleep rebound.

Neuroinflammation, cortical activity, and fatiguing behaviour during self-paced exercise.

The present study aimed to identify whether or not the release of interleukin (IL)-6 and soluble (s) IL-6 receptor (R) is associated with fatiguing behaviour and changes in cortical activity during self-paced exercise. Relationships between the IL-6 and its soluble receptors, total work, reductions in power output, and changes in slow, alpha (α) and fast, beta (ß) brain waves during self-paced exercise were evaluated. Different intensities and environments were used to manipulate the release of IL-6, whereby seven active males cycled for 60 min in heat stress (HS) or thermoneutral (TN) environments at a clamped rating of perceived exertion (RPE) equating to low intensity (RPE = 12) or high intensity (RPE = 16). IL-6 and sIL-6R were positively associated with total work, but not with reductions in power output. There was greater α activity in high-intensity conditions, which was associated with the reduction in power output. Both high-intensity conditions appeared to have greater ß activity, and there was a positive correlation between ß activity and total work and ß activity and sIL-6R. We conclude that IL-6 and sIL-6R may contribute to perturbations in cortical activity and are associated with total work output, but reductions in power output are likely influenced greater by other internal and external factors.

Effect of moderate exercise intensities on the cortical activity in young adults.

[Purpose] To examine the influence of different exercise intensities on cortical activity. [Participants and Methods] Twenty-six healthy adults aged 20-30 years performed exercise at three intensities on a bicycle ergometer as follows: (a) 15-minute exercise at 40% peak oxygen uptake, (b) same as (a) but at 60% peak oxygen uptake, and (c) 15 minutes of rest. The cognitive function of the participants was measured before and after exercise by the Paced Auditory Serial Addition Test (PASAT) under these three conditions. The cerebral blood flow in the left prefrontal and temporal cortices was measured using near-infrared spectroscopy during the PASAT. [Results] The PASAT score was significantly higher after exercise under condition (b) than before exercise (41.4 ± 9.1 vs. 47.7 ± 8.3). The cerebral blood flow in the prefrontal cortex under condition (b) was significantly increased compared to that under condition (c), as determined by the Tukey method (0.019 ± 0.030 vs. -0.008 ± 0.044). Significant differences were not observed in the cerebral blood flow in the temporal cortex under these three conditions. [Conclusion] Cortical activation of the frontal lobe increased after high-intensity aerobic exercise with no change in the cortical activity of the temporal lobe.

Effects of physical activity on the P300 component in elderly people: a systematic review.

The effects of physical activity on brain function can be assessed through event-related potentials (P300) that reflect cortical activities related to cognitive functions. P300 latency represents the information processing time; longer latencies represent slower processing. P300 amplitude is associated with the attentional system and working memory, with higher amplitudes representing more preserved functions. This systematic review summarizes the literature concerning the effects of physical activity and exercise on P300 in the elderly. Databases, including Web of Science, Scopus, PsycINFO, MEDLINE/PubMed, and Biological Abstracts, were searched for articles up to November 2015. Articles were considered for inclusion if they were studies of the elderly, assessed P300, and evaluated the influence of physical activity on P300 or the effect of physical exercise training on P300. Of the 1227 articles found, 14 investigations matched the inclusion criteria. Nine analyzed the influence of physical activity on P300 in the elderly, and five examined the effects of physical exercise on P300 in the elderly. The obtained results showed that physically active elderly people have shortened P300 latency and higher amplitude. Physical exercise, especially those involving aerobic or resistance training, seems to have marked beneficial effects on P300 in the elderly. Evidence shows that physical activity and physical exercise positively influence cortical activities related to cognitive functions, as indicated by P300, in elderly people.

Assessing cortical synchronization during transcranial direct current stimulation: A graph-theoretical analysis.

Transcranial direct current stimulation (tDCS) is a neuromodulation technique that can alter cortical excitability and modulate behaviour in a polarity-dependent way. Despite the widespread use of this method in the neuroscience field, its effects on ongoing local or global (network level) neuronal activity are still not foreseeable. A way to shed light on the neuronal mechanisms underlying the cortical connectivity changes induced by tDCS is provided by the combination of tDCS with electroencephalography (EEG). In this study, twelve healthy subjects underwent online tDCS-EEG recording (i.e., simultaneous), during resting-state, using 19 EEG channels. The protocol involved anodal, cathodal and sham stimulation conditions, with the active and the reference electrodes in the left frontocentral area (FC3) and on the forehead over the right eyebrow, respectively. The data were processed using a network model, based on graph theory and the synchronization likelihood. The resulting graphs were analysed for four frequency bands (theta, alpha, beta and gamma) to evaluate the presence of tDCS-induced differences in synchronization patterns and graph theory measures. The resting state network connectivity resulted altered during tDCS, in a polarity-specific manner for theta and alpha bands. Anodal tDCS weakened synchronization with respect to the baseline over the fronto-central areas in the left hemisphere, for theta band (p<0.05). In contrast, during cathodal tDCS a significant increase in inter-hemispheric synchronization connectivity was observed over the centro-parietal, centro-occipital and parieto-occipital areas for the alpha band (p<0.05). Local graph measures showed a tDCS-induced polarity-specific differences that regarded modifications of network activities rather than specific region properties. Our results show that applying tDCS during the resting state modulates local synchronization as well as network properties in slow frequency bands, in a polarity-specific manner.