Papers by Hakuei Fujiyama
older adults preparation and execution of left hand movements in Functional role of left PMd and ... more older adults preparation and execution of left hand movements in Functional role of left PMd and left M1 during You might find this additional info useful...
Frontiers in Aging Neuroscience, Jun 6, 2014
Despite the abundance of research reporting the neurophysiological and behavioral effects of tran... more Despite the abundance of research reporting the neurophysiological and behavioral effects of transcranial direct current stimulation (tDCS) in healthy young adults and clinical populations, the extent of potential neuroplastic changes induced by tDCS in healthy older adults is not well understood. The present study compared the extent and time course of anodal tDCS-induced plastic changes in primary motor cortex (M1) in young and older adults. Furthermore, as it has been suggested that neuroplasticity and associated learning depends on the brain-derived neurotrophic factor (BDNF) gene polymorphisms, we also assessed the impact of BDNF polymorphism on these effects. Corticospinal excitability was examined using transcranial magnetic stimulation before and following (0, 10, 20, 30 min) anodal tDCS (30 min, 1 mA) or sham in young and older adults. While the overall extent of increases in corticospinal excitability induced by anodal tDCS did not vary reliably between young and older adults, older adults exhibited a delayed response; the largest increase in corticospinal excitability occurred 30 min following stimulation for older adults, but immediately post-stimulation for the young group. BDNF genotype did not result in significant differences in the observed excitability increases for either age group. The present study suggests that tDCS-induced plastic changes are delayed as a result of healthy aging, but that the overall efficacy of the plasticity mechanism remains unaffected.
European Journal of Applied Physiology
Purpose Acute intermittent hypoxia (AIH) is a safe and non-invasive treatment approach that uses ... more Purpose Acute intermittent hypoxia (AIH) is a safe and non-invasive treatment approach that uses brief, repetitive periods of breathing reduced oxygen air alternated with normoxia. While AIH is known to affect spinal circuit excitability, the effects of AIH on cortical excitability remain largely unknown. We investigated the effects of AIH on cortical excitability within the primary motor cortex. Methods Eleven healthy, right-handed participants completed two testing sessions: (1) AIH (comprising 3 min in hypoxia [fraction of inspired oxygen ~ 10%] and 2 min in normoxia repeated over five cycles) and (2) normoxia (NOR) (equivalent duration to AIH). Single- and paired-pulse transcranial magnetic stimulations were delivered to the primary motor cortex, before and 0, 25, and 50 min after AIH and normoxia. Results The mean nadir in arterial oxygen saturation was lower (p < 0.001) during the cycles of AIH (82.5 ± 4.9%) than NOR (97.8 ± 0.6%). There was no significant difference in cor...
1 mechanisms underlying motor learning and retention: implications for rehabilitation 2 3 Abbrevi... more 1 mechanisms underlying motor learning and retention: implications for rehabilitation 2 3 Abbreviated Title: Mechanisms of motor learning and retention 4 5 Authors: Mark R. Hinder, Paola Reissig, Hakuei Fujiyama 6 7 1. Human Motor Control Laboratory, School of Psychology, University of Tasmania, 8 Australia. 9 2. Faculty of Health Science Graduate Research Program, University of Tasmania, Australia. 10 3. Movement Control and Neuroplasticity Research Group, Department of Kinesiology, K.U. 11 Leuven, 3001, Belgium 12 13 : Mark R. Hinder [email protected] 14 Private Bag 30, School of Psychology, University of Tasmania 15 Tasmania 7001, Australia 16 Tel: +61 (0) 3 6226 2243. Fax: +61 (0) 3 6226 2883 17 18
learning and retention: implications for rehabilitation interact with the mechanisms underlying m... more learning and retention: implications for rehabilitation interact with the mechanisms underlying motor Noninvasive brain stimulation can elucidate and You might find this additional info useful...
Frontiers in Aging Neuroscience, 2020
Recent transcranial magnetic stimulation (TMS) research indicated that the ability of the dorsola... more Recent transcranial magnetic stimulation (TMS) research indicated that the ability of the dorsolateral prefrontal cortex (DLPFC) to disinhibit the contralateral primary motor cortex (M1) during motor preparation is an important predictor for bimanual motor performance in both young and older healthy adults. However, this DLPFC-M1 disinhibition is reduced in older adults. Here, we transiently suppressed left DLPFC using repetitive TMS (rTMS) during a cyclical bimanual task and investigated the effect of left DLPFC suppression: (1) on the projection from left DLPFC to the contralateral M1; and (2) on motor performance in 21 young (mean age ± SD = 21.57 ± 1.83) and 20 older (mean age ± SD = 69.05 ± 4.48) healthy adults. As predicted, without rTMS, older adults showed compromised DLPFC-M1 disinhibition as compared to younger adults and less preparatory DLPFC-M1 disinhibition was related to less accurate performance, irrespective of age. Notably, rTMS-induced DLPFC suppression restored DLPFC-M1 disinhibition in older adults and improved performance accuracy right after the local suppression in both age groups. However, the rTMS-induced gain in disinhibition was not correlated with the gain in performance. In sum, this novel rTMS approach advanced our mechanistic understanding of how left DLPFC regulates right M1 and allowed us to establish the causal role of left DLPFC in bimanual coordination.
PLOS ONE, 2019
A lack of diversity limits progression of science. Thus, there is an urgent demand in science and... more A lack of diversity limits progression of science. Thus, there is an urgent demand in science and the wider community for approaches that increase diversity, including gender diversity. We developed a novel, data-driven approach to conference speaker selection that identifies potential speakers based on scientific impact metrics that are frequently used by researchers, hiring committees, and funding bodies, to convincingly demonstrate parity in the quality of peer-reviewed science between men and women. The approach enables high quality conference programs without gender disparity, as well as generating a positive spiral for increased diversity more broadly in STEM.
NeuroImage, 2019
Response inhibition, the ability to withhold a dominant and prepotent response following a change... more Response inhibition, the ability to withhold a dominant and prepotent response following a change in circumstance or sensory stimuli, declines with advancing age. While non-invasive brain stimulation (NiBS) has shown promise in alleviating some cognitive and motor functions in healthy older individuals, NiBS research focusing on response inhibition has mostly been conducted on younger adults. These extant studies have primarily focused on modulating the activity of distinct neural regions known to be critical for response inhibition, including the right inferior frontal gyrus (rIFG) and the pre-supplementary motor area (pre-SMA). However, given that changes in structural and functional connectivity have been associated with healthy aging, this review proposes that NiBS protocols aimed at modulating the functional connectivity between the rIFG and pre-SMA may be the most efficacious approach to investigate-and perhaps even alleviate-age-related deficits in inhibitory control.
The Journal of Physiology, 2017
Neurobiology of aging, Mar 1, 2016
Functional motor declines that often occur with advancing age-including reduced efficacy to learn... more Functional motor declines that often occur with advancing age-including reduced efficacy to learn new skills-can have a substantial impact on the quality of life. Recent studies using noninvasive brain stimulation indicate that priming the corticospinal system by lowering the threshold for the induction of long-term potentiation-like plasticity before skill training may facilitate subsequent skill learning. Here, we used "priming" protocol, in which we used transcranial direct current stimulation (tDCS) applying the cathode over the primary motor cortex (M1) before the anode placed over M1 during unimanual isometric force control training (FORCEtraining). Older individuals who received tDCS with the cathode placed over M1 before tDCS with the anode placed over M1 concurrent with FORCEtraining showed greater skill improvement and corticospinal excitability increases following the tDCS/FORCEtraining protocol compared with both young and older individuals who did not receive ...
Scientific reports, Jan 25, 2016
Previously, transcranial direct current stimulation (tDCS) over the primary motor cortex (M1) has... more Previously, transcranial direct current stimulation (tDCS) over the primary motor cortex (M1) has resulted in improved performance in simple motor tasks. For a complex bimanual movement, studies using functional magnetic resonance imaging and transcranial magnetic stimulation indicated the involvement of the left dorsolateral prefrontal cortex (DLPFC) as well as left M1. Here we investigated the relative effect of up-regulating the cortical function in left DLPFC and left M1 with tDCS. Participants practised a complex bimanual task over four days while receiving either of five stimulation protocols: anodal tDCS applied over M1, anodal tDCS over DLPFC, sham tDCS over M1, sham tDCS over DLPFC, or no stimulation. Performance was measured at the start and end of each training day to make a distinction between acquisition and consolidation. Although task performance improved over days, no significant difference between stimulation protocols was observed, suggesting that anodal tDCS had l...
Cortex, 2016
Even though it has been suggested that the dorsolateral prefrontal cortex (DLPFC) and dorsal prem... more Even though it has been suggested that the dorsolateral prefrontal cortex (DLPFC) and dorsal premotor cortex (PMd) are highly involved in the planning of bimanual movements, the exact nature (facilitatory or inhibitory) of their role is not well understood. Using a dual-site transcranial magnetic stimulation (TMS) paradigm, we examined the functional influence from DLPFC and PMd to the contralateral primary cortex (M1) during the preparation of a complex bimanual coordination task in which inter-hand movement frequency was manipulated. Only the left PMd showed inter-hand frequency-specific modulations in the interaction with the contralateral M1. Left PMd-right M1 interaction became facilitatory during the preparation phase when the left hand had to move faster than the right hand, while inhibitory modulation was observed when the movement frequency arrangement was reversed. Interestingly, bilateral DLPFC showed a facilitatory interaction with the contralateral M1s during the preparation period only in difficult conditions, irrespective of the inter-hand frequency ratio, suggesting a less task-specific role in the organization of complex bimanual actions. Observed task-related modulations in DLPFC-M1 and left PMd-right M1 interactions during preparation were significantly correlated with up-coming performance, predicting successful bimanual movements. These observations highlight the distinct roles of DLPFC and left PMd in the preparation of bimanual movements that require a differential contribution of each limb.
The Journal of neuroscience : the official journal of the Society for Neuroscience, Jan 10, 2016
Changes in both brain structure and neurophysiological function regulating homotopic as well as h... more Changes in both brain structure and neurophysiological function regulating homotopic as well as heterotopic interhemispheric interactions (IHIs) are assumed to be responsible for the bimanual performance deficits in older adults. However, how the structural and functional networks regulating bimanual performance decline in older adults, as well as the interplay between brain structure and function remain largely unclear. Using a dual-site transcranial magnetic stimulation paradigm, we examined the age-related changes in the interhemispheric effects from the dorsolateral prefrontal cortex and dorsal premotor cortex onto the contralateral primary motor cortex (M1) during the preparation of a complex bimanual coordination task in human. Structural properties of these interactions were assessed with diffusion-based fiber tractography. Compared with young adults, older adults showed performance declines in the more difficult bimanual conditions, less optimal brain white matter (WM) micro...
Frontiers in aging neuroscience, 2015
The brain derived neurotrophic factor (BDNF) Val66Met polymorphism and stimulation duration are t... more The brain derived neurotrophic factor (BDNF) Val66Met polymorphism and stimulation duration are thought to play an important role in modulating motor cortex plasticity induced by non-invasive brain stimulation (NBS). In the present study we sought to determine whether these factors interact or exert independent effects in older adults. Fifty-four healthy older adults (mean age = 66.85 years) underwent two counterbalanced sessions of 1.5 mA anodal transcranial direct current stimulation (atDCS), applied over left M1 for either 10 or 20 min. Single pulse transcranial magnetic stimulation (TMS) was used to assess corticospinal excitability (CSE) before and every 5 min for 30 min following atDCS. On a group level, there was an interaction between stimulation duration and BDNF genotype, with Met carriers (n = 13) showing greater post-intervention potentiation of CSE compared to Val66Val homozygotes homozygotes (n = 37) following 20 min (p = 0.002) but not 10 min (p = 0.219) of stimulatio...
PLoS ONE, 2012
Neural interactions between contralateral motor regions are thought to be instrumental in the suc... more Neural interactions between contralateral motor regions are thought to be instrumental in the successful preparation, and execution, of volitional movements. Here we investigated whether healthy ageing is associated with a change in functional connectivity, as indicated by the ability to modulate interhemispheric interactions during movement preparation in a manner that assists rapid movement responses. Thirteen young (mean age 22.2 years) and thirteen older (68.5 years) adults rapidly abducted their left index finger as soon as possible in response to a visual imperative signal, presented 500 ms after a visual warning signal. Interactions between left dorsal premotor cortex (LPMd) and right primary motor cortex (RM1) and between left primary motor cortex (LM1) and RM1 were investigated at six time points between the warning signal and the volitional response using paired-pulse transcranial magnetic stimulation. Relative to the inhibitory interactions measured at rest, both young and older adults released LM1-RM1 inhibition beginning 250 ms after the warning signal, with no significant differences between groups. LPMd-RM1 interactions became facilitatory (from the onset of the imperative signal onwards) in the older, but not the young, group. Regression analyses revealed that for the older adults, modulation of LPMd-RM1 interactions early in the preparation period was associated with faster responses, suggesting that specifically timed modulation of these pathways may be a compensatory mechanism to offset, at least in part, slowing of motor responses. The results suggest a greater reliance on premotor regions during the preparation of simple motor actions with advancing age.
PLoS ONE, 2014
The default mode of the motor system is a coupling between limbs. However, in some movements, a d... more The default mode of the motor system is a coupling between limbs. However, in some movements, a decoupling is required and thus calls for selection and facilitation/inhibition processes. Here, we investigate the relative contribution of recruitment versus selection processes to the overall processing complexity. To this aim we proposed a new multilimb reaction-time task (MUL-RT). Simple, choice and normalized (choice minus simple) RT were analysed together with error rates in thirty-six young adults for 15 coordination modes including all possible configuration of limb recruitment. Simple and normalized RTs were respectively assumed to be indicative of the recruitment and selection processes. Results supported a model of coupling/decoupling interactions respectively reporting weak, intermediate and strong interaction for selecting diagonal, ipsilateral and homologous limbs. Movement laterality (left vs. right) had no effect on selection complexity, whereas selecting upper limbs was less challenging than selecting lower limbs. Results in the different coordination modes suggested that recruitment complexity decreased as follows: 3 limbs = 4 limbs.2 limbs (homologous, ipsilateral and diagonal).1 limb, and selection complexity as follows: 2 diagonal limbs.3 limbs.2 ipsilateral limbs.1 limb = 2 homologous limbs.4 limbs. Based on these ordinal scales of recruitment and selection complexity, we extrapolated the overall processing complexity of the simple and choice MUL-RT. This method was efficient in reproducing the absolute results we obtained on a ratio scale (ms) and demonstrated that processing complexity in simple RT was mainly governed by the 'recruitment principle' (the more limbs recruited the lower the performance), whereas contributions of recruitment and 'selection principle' (nature of the coordination determines performance) to overall processing complexity were similar in choice RT.
Journal of Neurophysiology, 2013
Seminal work in animals indicates that learning a motor task results in long-term potentiation (L... more Seminal work in animals indicates that learning a motor task results in long-term potentiation (LTP) in primary motor cortex (M1) and a subsequent occlusion of LTP induction (Rioult-Pedotti et al. J Neurophysiol 98: 3688–3695, 2007). Using various forms of noninvasive brain stimulation in conjunction with a motor learning paradigm, Cantarero et al. ( J Neurosci 33: 12862–12869, 2013) recently provided novel evidence to support the hypothesis that retention of motor skill is contingent upon this postlearning occlusion.
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Papers by Hakuei Fujiyama