Makii Muthalib - Profile on Academia.edu (original) (raw)

Papers by Makii Muthalib

Introduction: Transcranial alternating current stimulation (tACS) is an established means to modu... more Introduction: Transcranial alternating current stimulation (tACS) is an established means to modulate neural oscillations. Ongoing oscillations can hugely impact the effects of tACS. Retinofugal alternating current stimulation (rtACS) is a novel and promising application of ACS. It has already shown effects on neural oscillations outlasting the stimulation duration and a therapeutic effect on vision restoration. To optimise its efficacy, we assessed the influence of ongoing oscillations in form of alpha suppression on rtACS. Methods: To address this question, we stimulated 8 healthy subjects with rtACS at a frequency of 10 Hz while recording EEG. Prior to stimulation, we assessed electrode impedances and phosphene thresholds and recorded a resting state EEG. We then applied rtACS in 6 blocks of 30s stimulation. In a randomized order, the subjects either opened or closed their eyes for the duration of these blocks.

Faculty of Health Institute of Health and Biomedical Innovation School of Exercise Nutrition Sciences, Jun 2, 2013

A time domain 32-channel fNIRS instrument was employed to map bilateral sensorimotor (SMC) 26 and... more A time domain 32-channel fNIRS instrument was employed to map bilateral sensorimotor (SMC) 26 and prefrontal (PFC) cortical activities during voluntary (VOL) and neuromuscular electrical 27 stimulation (NMES)-evoked wrist extension movements in nine healthy volunteers. The NMES-28 evoked wrist extension paradigm significantly increased activation of the contralateral SMC, 29 which was comparable to VOL. However, a greater bilateral SMC and PFC activation was found 30 during the higher NMES current intensities, which could be due in part to a nociceptive response 31 to NMES. 32 33

The use of near-infrared spectroscopy in understanding skeletal muscle physiology: recent developments

Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, 2011

This article provides a snapshot of muscle near-infrared spectroscopy (NIRS) at the end of 2010 s... more This article provides a snapshot of muscle near-infrared spectroscopy (NIRS) at the end of 2010 summarizing the recent literature, offering the present status and perspectives of the NIRS instrumentation and methods, describing the main NIRS studies on skeletal muscle physiology, posing open questions and outlining future directions. So far, different NIRS techniques (e.g. continuous-wave (CW) and spatially, time- and frequency-resolved spectroscopy) have been used for measuring muscle oxygenation during exercise. In the last four years, approximately 160 muscle NIRS articles have been published on different physiological aspects (primarily muscle oxygenation and haemodynamics) of several upper- and lower-limb muscle groups investigated by using mainly two-channel CW and spatially resolved spectroscopy commercial instruments. Unfortunately, in only 15 of these studies were the advantages of using multi-channel instruments exploited. There are still several open questions in the application of NIRS in muscle studies: (i) whether NIRS can be used in subjects with a large fat layer; (ii) the contribution of myoglobin desaturation to the NIRS signal during exercise; (iii) the effect of scattering changes during exercise; and (iv) the effect of changes in skin perfusion, particularly during prolonged exercise. Recommendations for instrumentation advancements and future muscle NIRS studies are provided.

Annals of Physical and Rehabilitation Medicine, 2015

Anodal transcranial direct current stimulation (a-tDCS) of the primary motor cortex (M1) elicits ... more Anodal transcranial direct current stimulation (a-tDCS) of the primary motor cortex (M1) elicits an increase in cortical excitability that outlasts the period of stimulation. However, little is known about effects of a-tDCS on the contralateral M1 during and after ipsilateral M1 stimulation. Therefore, we investigated the changes in corticospinal excitability and inhibition of the left M1 during and after 20mins of a-tDCS to the right M1. Material and methods Eight healthy participants received real (2mA) and sham a-tDCS to the right M1 randomised across 2 testing sessions. Single-and paired-pulse transcranial magnetic stimulation (TMS) was applied to the left M1 to measure changes motor-evoked potential (MEP) amplitude from the right extensor carpi radialis (ECR) at 130% of resting and active motor threshold, cortical silent period (CSP) and short-interval cortical inhibition (SICI). Active motor threshold was measured during a wrist extension contraction that was less than 5% of maximal electromyography of the ECR. All measures were recorded at baseline, every 5mins for 20mins during and 10mins after a-tDCS.

Functional neuroimaging of prefrontal cortex in Parkinson's disease using near infra-red spectroscopy: effects of cognitive task during seated and standing postures

Frontiers in Human Neuroscience, 2015

Journal of Science and Medicine in Sport, 2000

2000). The effects of a repeated bout of eccentric exercise on indices of muscle damage and delay... more 2000). The effects of a repeated bout of eccentric exercise on indices of muscle damage and delayed onset muscle soreness. Journal of Science and Medicine in Sport 3 (1): 35-43.

Exergaming as a Viable Therapeutic Tool to Improve Static and Dynamic Balance among Older Adults and People with Idiopathic Parkinson’s Disease: A Systematic Review and Meta-Analysis

Frontiers in Aging Neuroscience, 2015

The use of virtual reality games (known as "exer... more The use of virtual reality games (known as "exergaming") as a neurorehabilitation tool is gaining interest. Therefore, we aim to collate evidence for the effects of exergaming on the balance and postural control of older adults and people with idiopathic Parkinson's disease (IPD). Six electronic databases were searched, from inception to April 2015, to identify relevant studies. Standardized mean differences (SMDs) and 95% confidence intervals (CI) were used to calculate effect sizes between experimental and control groups. I (2) statistics were used to determine levels of heterogeneity. 325 older adults and 56 people with IPD who were assessed across 11 -studies. The results showed that exergaming improved static balance (SMD 1.069, 95% CI 0.563-1.576), postural control (SMD 0.826, 95% CI 0.481-1.170), and dynamic balance (SMD -0.808, 95% CI -1.192 to -0.424) in healthy older adults. Two IPD studies showed an improvement in static balance (SMD 0.124, 95% CI -0.581 to 0.828) and postural control (SMD 2.576, 95% CI 1.534-3.599). Our findings suggest that exergaming might be an appropriate therapeutic tool for improving balance and postural control in older adults, but more -large-scale trials are needed to determine if the same is true for people with IPD.

Changes in the number of circulating CD34+ cells after eccentric exercise of the elbow flexors in relation to muscle damage

Journal of Sport and Health Science, 2014

Journal of Biomedical Optics, 2010

We examine the test-retest reliability of biceps brachii tissue oxygenation index ͑TOI͒ parameter... more We examine the test-retest reliability of biceps brachii tissue oxygenation index ͑TOI͒ parameters measured by near-infrared spectroscopy during a 10-s sustained and a 30-repeated ͑1-s contraction, 1-s relaxation͒ isometric contraction task at 30% of maximal voluntary contraction ͑30% MVC͒ and maximal ͑100% MVC͒ intensities. Eight healthy men ͑23 to 33 yr͒ were tested on three sessions separated by 3 h and 24 h, and the within-subject reliability of torque and each TOI parameter were determined by Bland-Altman± 2 SD limits of agreement plots and coefficient of variation ͑CV͒. No significant ͑P Ͼ 0.05͒ differences between the three sessions were found for mean values of torque and TOI parameters during the sustained and repeated tasks at both contraction intensities. All TOI parameters were within± 2 SD limits of agreement. The CVs for torque integral were similar between the sustained and repeated task at both intensities ͑4 to 7%͒; however, the CVs for TOI parameters during the sustained and repeated task were lower for 100% MVC ͑7 to 11%͒ than for 30% MVC ͑22 to 36%͒. It is concluded that the reliability of the biceps brachii NIRS parameters during both sustained and repeated isometric contraction tasks is acceptable.

Frontal Cortex Activation During Electrical Muscle Stimulation as Revealed by Functional Near-Infrared Spectroscopy

Advances in Experimental Medicine and Biology, 2011

nodal transcranial direct current stimulation (a-tDCS) is a noninvasive electrical brain stimulat... more nodal transcranial direct current stimulation (a-tDCS) is a noninvasive electrical brain stimulation technique that has been shown to increase cortical neuronal excitability and activity [1]. An indirect marker of increases in cortical neuronal activity is the subsequent increase in the regional cerebral blood flow (rCBF). Functional near-infrared spectroscopy (fNIRS) is a noninvasive neuroimaging method, which measures changes in regional cortical hemodynamics (rCHD) via oxyhemoglobin (HbO2) and deoxyhemoglobin (HHb) concentrations, such that an increase in HbO2 and decrease in HHb are considered a good index of increases in rCBF [2]. A previous fNIRS study [3] showed that 10 min of a-tDCS on the left prefrontal cortex (PFC) with the cathode on the right PFC induced an increase in rCHD in the cortical regions under the anode and cathode after a-tDCS (offline effects). However, the time course of changes in rCHD during a-tDCS (online effects) revealing an index of neuronal modulatio...

Effects of Increasing Neuromuscular Electrical Stimulation Current Intensity on Cortical Sensorimotor Network Activation: A Time Domain fNIRS Study

PLOS ONE, 2015

Neuroimaging studies have shown neuromuscular electrical stimulation (NMES)-evoked movements acti... more Neuroimaging studies have shown neuromuscular electrical stimulation (NMES)-evoked movements activate regions of the cortical sensorimotor network, including the primary sensorimotor cortex (SMC), premotor cortex (PMC), supplementary motor area (SMA), and secondary somatosensory area (S2), as well as regions of the prefrontal cortex (PFC) known to be involved in pain processing. The aim of this study, on nine healthy subjects, was to compare the cortical network activation profile and pain ratings during NMES of the right forearm wrist extensor muscles at increasing current intensities up to and slightly over the individual maximal tolerated intensity (MTI), and with reference to voluntary (VOL) wrist extension movements. By exploiting the capability of the multi-channel time domain functional near-infrared spectroscopy technique to relate depth information to the photon time-of-flight, the cortical and superficial oxygenated (O2Hb) and deoxygenated (HHb) hemoglobin concentrations were estimated. The O2Hb and HHb maps obtained using the General Linear Model (NIRS-SPM) analysis method, showed that the VOL and NMES-evoked movements significantly increased activation (i.e., increase in O2Hb and corresponding decrease in HHb) in the cortical layer of the contralateral sensorimotor network (SMC, PMC/SMA, and S2). However, the level and area of contralateral sensorimotor network (including PFC) activation was significantly greater for NMES than VOL. Furthermore, there was greater bilateral sensorimotor network activation with the high NMES current intensities which corresponded with increased pain ratings. In conclusion, our findings suggest that greater bilateral sensorimotor network activation profile with high NMES current intensities could be in part attributable to increased attentional/pain processing and to increased bilateral sensorimotor integration in these cortical regions.

Frontiers in Aging Neuroscience, 2015

The use of progressive resistance training (PRT) to improve gait and balance in people with Parki... more The use of progressive resistance training (PRT) to improve gait and balance in people with Parkinson's disease (PD) is an emerging area of interest. However, the main effects of PRT on lower limb functions such as gait, balance, and leg strength in people with PD remain unclear. Therefore, the aim of the meta-analysis is to evaluate the evidence surrounding the use of PRT to improve gait and balance in people with PD. Five electronic databases, from inception to December 2014, were searched to identify the relevant studies. Data extraction was performed by two independent reviewers and methodological quality was assessed using the PEDro scale. Standardized mean differences (SMD) and 95% confidence intervals (CIs) of fixed and random effects models were used to calculate the effect sizes between experimental and control groups and I 2 statistics were used to determine levels of heterogeneity. In total, seven studies were identified consisting of 172 participants (experimental n = 84; control n = 88). The pooled results showed a moderate but significant effect of PRT on leg strength (SMD 1.42, 95% CI 0.464-2.376); however, no significant effects were observed for gait speed (SMD 0.418, 95% CI −0.219 to 1.055). No significant effects were observed for balance measures included in this review. In conclusion, our results showed no discernable effect of PRT on gait and balance measures, although this is likely due to the lack of studies available. It may be suggested that PRT be performed in conjunction with balance or task-specific functional training to elicit greater lower limb functional benefits in people with PD.

Exercise immunology review, 2006

We compared changes in markers of muscle damage and systemic inflammation after submaximal and ma... more We compared changes in markers of muscle damage and systemic inflammation after submaximal and maximal lengthening muscle contractions of the elbow flexors. Using a cross-over design, 10 healthy young men not involved in resistance training completed a submaximal trial (10 sets of 60 lengthening contractions at 10% maximum isometric strength, 1 min rest between sets), followed by a maximal trial (10 sets of three lengthening contractions at 100% maximum isometric strength, 3 min rest between sets). Lengthening contractions were performed on an isokinetic dynamometer. Opposite arms were used for the submaximal and maximal trials, and the trials were separated by a minimum of two weeks. Blood was sampled before, immediately after, 1 h, 3 h, and 1-4 d after each trial. Total leukocyte and neutrophil numbers, and the serum concentration of soluble tumor necrosis factor-alpha receptor 1 were elevated after both trials (P < 0.01), but there were no differences between the trials. Serum...

High-definition transcranial direct current stimulation (HD-tDCS) targeting the primary sensorimo... more High-definition transcranial direct current stimulation (HD-tDCS) targeting the primary sensorimotor cortex (SMC) can produce comparable "Offline" excitability changes to conventional tDCS in a polarity specific manner (1). However, it is not clear how HD-tDCS modifies "Online" neuronal activity and haemodynamics within the modulated cortical sensorimotor network at rest and during a motor task. In this proof-of-principle case study, we first setup a HD-tDCS-neuroimaging (electrophysiological-EEG and haemodynamic-fNIRS) platform to target the SMC and simultaneously measure bilateral cortical sensorimotor network activation. Then we tested the system on one healthy subject to compare the "Online" and "Offline" effects of anodal HD-tDCS on fNIRS and EEG components.

2012 Annual International Conference of the IEEE Engineering in Medicine and Biology Society, 2012

Directionality analysis of signals originating from different parts of brain during motor tasks h... more Directionality analysis of signals originating from different parts of brain during motor tasks has gained a lot of interest. Since brain activity can be recorded over time, methods of time series analysis can be applied to medical time series as well. Granger Causality is a method to find a causal relationship between time series. Such causality can be referred to as a directional connection and is not necessarily bidirectional. The aim of this study is to differentiate between different motor tasks on the basis of activation maps and also to understand the nature of connections present between different parts of the brain. In this paper, three different motor tasks (finger tapping, simple finger sequencing, and complex finger sequencing) are analyzed. Time series for each task were extracted from functional magnetic resonance imaging (fMRI) data, which have a very good spatial resolution and can look into the sub-cortical regions of the brain. Activation maps based on fMRI images show that, in case of complex finger sequencing, most parts of the brain are active, unlike finger tapping during which only limited regions show activity. Directionality analysis on time series extracted from contralateral motor cortex (CMC), supplementary motor area (SMA), and cerebellum (CER) show bidirectional connections between these parts of the brain. In case of simple finger sequencing and complex finger sequencing, the strongest connections originate from SMA and CMC, while connections originating from CER in either direction are the weakest ones in magnitude during all paradigms.

Frontiers in Human Neuroscience, 2014

Several neuroimaging studies of cognitive aging revealed deficits in episodic memory abilities as... more Several neuroimaging studies of cognitive aging revealed deficits in episodic memory abilities as a result of prefrontal cortex (PFC) limitations. Improving episodic memory performance despite PFC deficits is thus a critical issue in aging research. Listening to music stimulates cognitive performance in several non-purely musical activities (e.g., language and memory). Thus, music could represent a rich and helpful source during verbal encoding and therefore help subsequent retrieval. Furthermore, such benefit could be reflected in less demand of PFC, which is known to be crucial for encoding processes. This study aimed to investigate whether music may improve episodic memory in older adults while decreasing the PFC activity. Sixteen healthy older adults (µ = 64.5 years) encoded lists of words presented with or without a musical background while their dorsolateral prefrontal cortex (DLPFC) activity was monitored using a eight-channel continuous-wave near-infrared spectroscopy (NIRS) system (Oxymon Mk III, Artinis, The Netherlands). Behavioral results indicated a better source-memory performance for words encoded with music compared to words encoded with silence (p < 0.05). Functional NIRS data revealed bilateral decrease of oxyhemoglobin values in the music encoding condition compared to the silence condition (p < 0.05), suggesting that music modulates the activity of the DLPFC during encoding in a less-demanding direction.Taken together, our results indicate that music can help older adults in memory performances by decreasing their PFC activity. These findings open new perspectives about music as tool for episodic memory rehabilitation on special populations with memory deficits due to frontal lobe damage such as Alzheimer's patients.

Frontiers in Microbiology, 2013

Listening to music engages the whole brain, thus stimulating cognitive performance in a range of ... more Listening to music engages the whole brain, thus stimulating cognitive performance in a range of non-purely musical activities such as language and memory tasks. This article addresses an ongoing debate on the link between music and memory for words. While evidence on healthy and clinical populations suggests that music listening can improve verbal memory in a variety of situations, it is still unclear what specific memory process is affected and how. This study was designed to explore the hypothesis that music specifically benefits the encoding part of verbal memory tasks, by providing a richer context for encoding and therefore less demand on the dorsolateral prefrontal cortex (DLPFC).Twentytwo healthy young adults were subjected to functional near-infrared spectroscopy (fNIRS) imaging of their bilateral DLPFC while encoding words in the presence of either a music or a silent background. Behavioral data confirmed the facilitating effect of music background during encoding on subsequent item recognition. fNIRS results revealed significantly greater activation of the left hemisphere during encoding (in line with the HERA model of memory lateralization) and a sustained, bilateral decrease of activity in the DLPFC in the music condition compared to silence. These findings suggest that music modulates the role played by the DLPFC during verbal encoding, and open perspectives for applications to clinical populations with prefrontal impairments, such as elderly adults or Alzheimer's patients.

Introduction: Transcranial alternating current stimulation (tACS) is an established means to modu... more Introduction: Transcranial alternating current stimulation (tACS) is an established means to modulate neural oscillations. Ongoing oscillations can hugely impact the effects of tACS. Retinofugal alternating current stimulation (rtACS) is a novel and promising application of ACS. It has already shown effects on neural oscillations outlasting the stimulation duration and a therapeutic effect on vision restoration. To optimise its efficacy, we assessed the influence of ongoing oscillations in form of alpha suppression on rtACS. Methods: To address this question, we stimulated 8 healthy subjects with rtACS at a frequency of 10 Hz while recording EEG. Prior to stimulation, we assessed electrode impedances and phosphene thresholds and recorded a resting state EEG. We then applied rtACS in 6 blocks of 30s stimulation. In a randomized order, the subjects either opened or closed their eyes for the duration of these blocks.

Faculty of Health Institute of Health and Biomedical Innovation School of Exercise Nutrition Sciences, Jun 2, 2013

A time domain 32-channel fNIRS instrument was employed to map bilateral sensorimotor (SMC) 26 and... more A time domain 32-channel fNIRS instrument was employed to map bilateral sensorimotor (SMC) 26 and prefrontal (PFC) cortical activities during voluntary (VOL) and neuromuscular electrical 27 stimulation (NMES)-evoked wrist extension movements in nine healthy volunteers. The NMES-28 evoked wrist extension paradigm significantly increased activation of the contralateral SMC, 29 which was comparable to VOL. However, a greater bilateral SMC and PFC activation was found 30 during the higher NMES current intensities, which could be due in part to a nociceptive response 31 to NMES. 32 33

The use of near-infrared spectroscopy in understanding skeletal muscle physiology: recent developments

Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, 2011

This article provides a snapshot of muscle near-infrared spectroscopy (NIRS) at the end of 2010 s... more This article provides a snapshot of muscle near-infrared spectroscopy (NIRS) at the end of 2010 summarizing the recent literature, offering the present status and perspectives of the NIRS instrumentation and methods, describing the main NIRS studies on skeletal muscle physiology, posing open questions and outlining future directions. So far, different NIRS techniques (e.g. continuous-wave (CW) and spatially, time- and frequency-resolved spectroscopy) have been used for measuring muscle oxygenation during exercise. In the last four years, approximately 160 muscle NIRS articles have been published on different physiological aspects (primarily muscle oxygenation and haemodynamics) of several upper- and lower-limb muscle groups investigated by using mainly two-channel CW and spatially resolved spectroscopy commercial instruments. Unfortunately, in only 15 of these studies were the advantages of using multi-channel instruments exploited. There are still several open questions in the application of NIRS in muscle studies: (i) whether NIRS can be used in subjects with a large fat layer; (ii) the contribution of myoglobin desaturation to the NIRS signal during exercise; (iii) the effect of scattering changes during exercise; and (iv) the effect of changes in skin perfusion, particularly during prolonged exercise. Recommendations for instrumentation advancements and future muscle NIRS studies are provided.

Annals of Physical and Rehabilitation Medicine, 2015

Anodal transcranial direct current stimulation (a-tDCS) of the primary motor cortex (M1) elicits ... more Anodal transcranial direct current stimulation (a-tDCS) of the primary motor cortex (M1) elicits an increase in cortical excitability that outlasts the period of stimulation. However, little is known about effects of a-tDCS on the contralateral M1 during and after ipsilateral M1 stimulation. Therefore, we investigated the changes in corticospinal excitability and inhibition of the left M1 during and after 20mins of a-tDCS to the right M1. Material and methods Eight healthy participants received real (2mA) and sham a-tDCS to the right M1 randomised across 2 testing sessions. Single-and paired-pulse transcranial magnetic stimulation (TMS) was applied to the left M1 to measure changes motor-evoked potential (MEP) amplitude from the right extensor carpi radialis (ECR) at 130% of resting and active motor threshold, cortical silent period (CSP) and short-interval cortical inhibition (SICI). Active motor threshold was measured during a wrist extension contraction that was less than 5% of maximal electromyography of the ECR. All measures were recorded at baseline, every 5mins for 20mins during and 10mins after a-tDCS.

Functional neuroimaging of prefrontal cortex in Parkinson's disease using near infra-red spectroscopy: effects of cognitive task during seated and standing postures

Frontiers in Human Neuroscience, 2015

Journal of Science and Medicine in Sport, 2000

2000). The effects of a repeated bout of eccentric exercise on indices of muscle damage and delay... more 2000). The effects of a repeated bout of eccentric exercise on indices of muscle damage and delayed onset muscle soreness. Journal of Science and Medicine in Sport 3 (1): 35-43.

Exergaming as a Viable Therapeutic Tool to Improve Static and Dynamic Balance among Older Adults and People with Idiopathic Parkinson’s Disease: A Systematic Review and Meta-Analysis

Frontiers in Aging Neuroscience, 2015

The use of virtual reality games (known as &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;exer... more The use of virtual reality games (known as &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;exergaming&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;) as a neurorehabilitation tool is gaining interest. Therefore, we aim to collate evidence for the effects of exergaming on the balance and postural control of older adults and people with idiopathic Parkinson&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s disease (IPD). Six electronic databases were searched, from inception to April 2015, to identify relevant studies. Standardized mean differences (SMDs) and 95% confidence intervals (CI) were used to calculate effect sizes between experimental and control groups. I (2) statistics were used to determine levels of heterogeneity. 325 older adults and 56 people with IPD who were assessed across 11 -studies. The results showed that exergaming improved static balance (SMD 1.069, 95% CI 0.563-1.576), postural control (SMD 0.826, 95% CI 0.481-1.170), and dynamic balance (SMD -0.808, 95% CI -1.192 to -0.424) in healthy older adults. Two IPD studies showed an improvement in static balance (SMD 0.124, 95% CI -0.581 to 0.828) and postural control (SMD 2.576, 95% CI 1.534-3.599). Our findings suggest that exergaming might be an appropriate therapeutic tool for improving balance and postural control in older adults, but more -large-scale trials are needed to determine if the same is true for people with IPD.

Changes in the number of circulating CD34+ cells after eccentric exercise of the elbow flexors in relation to muscle damage

Journal of Sport and Health Science, 2014

Journal of Biomedical Optics, 2010

We examine the test-retest reliability of biceps brachii tissue oxygenation index ͑TOI͒ parameter... more We examine the test-retest reliability of biceps brachii tissue oxygenation index ͑TOI͒ parameters measured by near-infrared spectroscopy during a 10-s sustained and a 30-repeated ͑1-s contraction, 1-s relaxation͒ isometric contraction task at 30% of maximal voluntary contraction ͑30% MVC͒ and maximal ͑100% MVC͒ intensities. Eight healthy men ͑23 to 33 yr͒ were tested on three sessions separated by 3 h and 24 h, and the within-subject reliability of torque and each TOI parameter were determined by Bland-Altman± 2 SD limits of agreement plots and coefficient of variation ͑CV͒. No significant ͑P Ͼ 0.05͒ differences between the three sessions were found for mean values of torque and TOI parameters during the sustained and repeated tasks at both contraction intensities. All TOI parameters were within± 2 SD limits of agreement. The CVs for torque integral were similar between the sustained and repeated task at both intensities ͑4 to 7%͒; however, the CVs for TOI parameters during the sustained and repeated task were lower for 100% MVC ͑7 to 11%͒ than for 30% MVC ͑22 to 36%͒. It is concluded that the reliability of the biceps brachii NIRS parameters during both sustained and repeated isometric contraction tasks is acceptable.

Frontal Cortex Activation During Electrical Muscle Stimulation as Revealed by Functional Near-Infrared Spectroscopy

Advances in Experimental Medicine and Biology, 2011

nodal transcranial direct current stimulation (a-tDCS) is a noninvasive electrical brain stimulat... more nodal transcranial direct current stimulation (a-tDCS) is a noninvasive electrical brain stimulation technique that has been shown to increase cortical neuronal excitability and activity [1]. An indirect marker of increases in cortical neuronal activity is the subsequent increase in the regional cerebral blood flow (rCBF). Functional near-infrared spectroscopy (fNIRS) is a noninvasive neuroimaging method, which measures changes in regional cortical hemodynamics (rCHD) via oxyhemoglobin (HbO2) and deoxyhemoglobin (HHb) concentrations, such that an increase in HbO2 and decrease in HHb are considered a good index of increases in rCBF [2]. A previous fNIRS study [3] showed that 10 min of a-tDCS on the left prefrontal cortex (PFC) with the cathode on the right PFC induced an increase in rCHD in the cortical regions under the anode and cathode after a-tDCS (offline effects). However, the time course of changes in rCHD during a-tDCS (online effects) revealing an index of neuronal modulatio...

Effects of Increasing Neuromuscular Electrical Stimulation Current Intensity on Cortical Sensorimotor Network Activation: A Time Domain fNIRS Study

PLOS ONE, 2015

Neuroimaging studies have shown neuromuscular electrical stimulation (NMES)-evoked movements acti... more Neuroimaging studies have shown neuromuscular electrical stimulation (NMES)-evoked movements activate regions of the cortical sensorimotor network, including the primary sensorimotor cortex (SMC), premotor cortex (PMC), supplementary motor area (SMA), and secondary somatosensory area (S2), as well as regions of the prefrontal cortex (PFC) known to be involved in pain processing. The aim of this study, on nine healthy subjects, was to compare the cortical network activation profile and pain ratings during NMES of the right forearm wrist extensor muscles at increasing current intensities up to and slightly over the individual maximal tolerated intensity (MTI), and with reference to voluntary (VOL) wrist extension movements. By exploiting the capability of the multi-channel time domain functional near-infrared spectroscopy technique to relate depth information to the photon time-of-flight, the cortical and superficial oxygenated (O2Hb) and deoxygenated (HHb) hemoglobin concentrations were estimated. The O2Hb and HHb maps obtained using the General Linear Model (NIRS-SPM) analysis method, showed that the VOL and NMES-evoked movements significantly increased activation (i.e., increase in O2Hb and corresponding decrease in HHb) in the cortical layer of the contralateral sensorimotor network (SMC, PMC/SMA, and S2). However, the level and area of contralateral sensorimotor network (including PFC) activation was significantly greater for NMES than VOL. Furthermore, there was greater bilateral sensorimotor network activation with the high NMES current intensities which corresponded with increased pain ratings. In conclusion, our findings suggest that greater bilateral sensorimotor network activation profile with high NMES current intensities could be in part attributable to increased attentional/pain processing and to increased bilateral sensorimotor integration in these cortical regions.

Frontiers in Aging Neuroscience, 2015

The use of progressive resistance training (PRT) to improve gait and balance in people with Parki... more The use of progressive resistance training (PRT) to improve gait and balance in people with Parkinson's disease (PD) is an emerging area of interest. However, the main effects of PRT on lower limb functions such as gait, balance, and leg strength in people with PD remain unclear. Therefore, the aim of the meta-analysis is to evaluate the evidence surrounding the use of PRT to improve gait and balance in people with PD. Five electronic databases, from inception to December 2014, were searched to identify the relevant studies. Data extraction was performed by two independent reviewers and methodological quality was assessed using the PEDro scale. Standardized mean differences (SMD) and 95% confidence intervals (CIs) of fixed and random effects models were used to calculate the effect sizes between experimental and control groups and I 2 statistics were used to determine levels of heterogeneity. In total, seven studies were identified consisting of 172 participants (experimental n = 84; control n = 88). The pooled results showed a moderate but significant effect of PRT on leg strength (SMD 1.42, 95% CI 0.464-2.376); however, no significant effects were observed for gait speed (SMD 0.418, 95% CI −0.219 to 1.055). No significant effects were observed for balance measures included in this review. In conclusion, our results showed no discernable effect of PRT on gait and balance measures, although this is likely due to the lack of studies available. It may be suggested that PRT be performed in conjunction with balance or task-specific functional training to elicit greater lower limb functional benefits in people with PD.

Exercise immunology review, 2006

We compared changes in markers of muscle damage and systemic inflammation after submaximal and ma... more We compared changes in markers of muscle damage and systemic inflammation after submaximal and maximal lengthening muscle contractions of the elbow flexors. Using a cross-over design, 10 healthy young men not involved in resistance training completed a submaximal trial (10 sets of 60 lengthening contractions at 10% maximum isometric strength, 1 min rest between sets), followed by a maximal trial (10 sets of three lengthening contractions at 100% maximum isometric strength, 3 min rest between sets). Lengthening contractions were performed on an isokinetic dynamometer. Opposite arms were used for the submaximal and maximal trials, and the trials were separated by a minimum of two weeks. Blood was sampled before, immediately after, 1 h, 3 h, and 1-4 d after each trial. Total leukocyte and neutrophil numbers, and the serum concentration of soluble tumor necrosis factor-alpha receptor 1 were elevated after both trials (P < 0.01), but there were no differences between the trials. Serum...

High-definition transcranial direct current stimulation (HD-tDCS) targeting the primary sensorimo... more High-definition transcranial direct current stimulation (HD-tDCS) targeting the primary sensorimotor cortex (SMC) can produce comparable "Offline" excitability changes to conventional tDCS in a polarity specific manner (1). However, it is not clear how HD-tDCS modifies "Online" neuronal activity and haemodynamics within the modulated cortical sensorimotor network at rest and during a motor task. In this proof-of-principle case study, we first setup a HD-tDCS-neuroimaging (electrophysiological-EEG and haemodynamic-fNIRS) platform to target the SMC and simultaneously measure bilateral cortical sensorimotor network activation. Then we tested the system on one healthy subject to compare the "Online" and "Offline" effects of anodal HD-tDCS on fNIRS and EEG components.

2012 Annual International Conference of the IEEE Engineering in Medicine and Biology Society, 2012

Directionality analysis of signals originating from different parts of brain during motor tasks h... more Directionality analysis of signals originating from different parts of brain during motor tasks has gained a lot of interest. Since brain activity can be recorded over time, methods of time series analysis can be applied to medical time series as well. Granger Causality is a method to find a causal relationship between time series. Such causality can be referred to as a directional connection and is not necessarily bidirectional. The aim of this study is to differentiate between different motor tasks on the basis of activation maps and also to understand the nature of connections present between different parts of the brain. In this paper, three different motor tasks (finger tapping, simple finger sequencing, and complex finger sequencing) are analyzed. Time series for each task were extracted from functional magnetic resonance imaging (fMRI) data, which have a very good spatial resolution and can look into the sub-cortical regions of the brain. Activation maps based on fMRI images show that, in case of complex finger sequencing, most parts of the brain are active, unlike finger tapping during which only limited regions show activity. Directionality analysis on time series extracted from contralateral motor cortex (CMC), supplementary motor area (SMA), and cerebellum (CER) show bidirectional connections between these parts of the brain. In case of simple finger sequencing and complex finger sequencing, the strongest connections originate from SMA and CMC, while connections originating from CER in either direction are the weakest ones in magnitude during all paradigms.

Frontiers in Human Neuroscience, 2014

Several neuroimaging studies of cognitive aging revealed deficits in episodic memory abilities as... more Several neuroimaging studies of cognitive aging revealed deficits in episodic memory abilities as a result of prefrontal cortex (PFC) limitations. Improving episodic memory performance despite PFC deficits is thus a critical issue in aging research. Listening to music stimulates cognitive performance in several non-purely musical activities (e.g., language and memory). Thus, music could represent a rich and helpful source during verbal encoding and therefore help subsequent retrieval. Furthermore, such benefit could be reflected in less demand of PFC, which is known to be crucial for encoding processes. This study aimed to investigate whether music may improve episodic memory in older adults while decreasing the PFC activity. Sixteen healthy older adults (µ = 64.5 years) encoded lists of words presented with or without a musical background while their dorsolateral prefrontal cortex (DLPFC) activity was monitored using a eight-channel continuous-wave near-infrared spectroscopy (NIRS) system (Oxymon Mk III, Artinis, The Netherlands). Behavioral results indicated a better source-memory performance for words encoded with music compared to words encoded with silence (p < 0.05). Functional NIRS data revealed bilateral decrease of oxyhemoglobin values in the music encoding condition compared to the silence condition (p < 0.05), suggesting that music modulates the activity of the DLPFC during encoding in a less-demanding direction.Taken together, our results indicate that music can help older adults in memory performances by decreasing their PFC activity. These findings open new perspectives about music as tool for episodic memory rehabilitation on special populations with memory deficits due to frontal lobe damage such as Alzheimer's patients.

Frontiers in Microbiology, 2013

Listening to music engages the whole brain, thus stimulating cognitive performance in a range of ... more Listening to music engages the whole brain, thus stimulating cognitive performance in a range of non-purely musical activities such as language and memory tasks. This article addresses an ongoing debate on the link between music and memory for words. While evidence on healthy and clinical populations suggests that music listening can improve verbal memory in a variety of situations, it is still unclear what specific memory process is affected and how. This study was designed to explore the hypothesis that music specifically benefits the encoding part of verbal memory tasks, by providing a richer context for encoding and therefore less demand on the dorsolateral prefrontal cortex (DLPFC).Twentytwo healthy young adults were subjected to functional near-infrared spectroscopy (fNIRS) imaging of their bilateral DLPFC while encoding words in the presence of either a music or a silent background. Behavioral data confirmed the facilitating effect of music background during encoding on subsequent item recognition. fNIRS results revealed significantly greater activation of the left hemisphere during encoding (in line with the HERA model of memory lateralization) and a sustained, bilateral decrease of activity in the DLPFC in the music condition compared to silence. These findings suggest that music modulates the role played by the DLPFC during verbal encoding, and open perspectives for applications to clinical populations with prefrontal impairments, such as elderly adults or Alzheimer's patients.