Biology subjects

Naito, E.

Publications and source records attributed to Naito, E..

12 recordsLinked to original sources

bioRxiv2026

Causal contribution of motor-parietal network to conscious kinesthetic perception

Bodily awareness, including the conscious experience of limb movement (kinesthesia), is a fundamental form of human consciousness. Tendon vibration-induced kinesthetic illusions provide a tractable model for probing its neural basis. Although previous studies have reported coactivation of the primary motor cortex (M1), the right inferior parietal lobule (IPL), and the right inferior frontal gyrus (IFG) during illusory movement, their causal contributions to conscious kinesthetic experience remain unclear. Here, we combined functional MRI and regional facilitative dual-site transcranial direct current stimulation (tDCS) to establish a causal link between these cortices and illusory foot movement. fMRI revealed that the M1-IPL network supports kinesthetic illusion elicited by bottom-up sensory processing, whereas the IFG plays a role in top-down monitoring of the kinesthetic experience. Critically, concurrent facilitative dual-site tDCS applied to the M1 and IPL significantly enhanced the subjective strength of the illusion, compared with the sham and concurrent tDCS to the M1 and IFG. This effect was replicated without increasing muscle activity in another tDCS study and exceeded those observed with single-site (M1 or IPL) or concurrent higher-order IPL-IFG tDCS. Our findings provide the first compelling causal evidence that conscious kinesthetic perception can be augmented through coordinated interactions between the modality-specific kinesthetic-motor cortex (M1) and the higher-order right inferior parietal cortex (IPL). This coordinated interaction between modality-specific and higher-order cortical regions underlying conscious kinesthetic perception is consistent with the Global Neuronal Workspace hypothesis. Our findings have therefore extended the applicability of this framework from exteroceptive perception to bodily awareness.

neuroscience↗

bioRxiv2024

Gray matter volume increase in the retrosplenial/posterior cingulate cortices of blind soccer players

Spatial navigation is a crucial brain function that occurs when an individual moves from one location to another. This function normally relies on vision, and the retrosplenial/posterior cingulate cortices (RSC/PCC) and parahippocampal cortex (PHC) play crucial roles. However, an extraordinary adaptation can be observed in blind soccer players, where the human brain can perform spatial navigation without vision. Therefore, this study tested the possible increase in gray matter (GM) volume in the RSC/PCC and PHC in the brains of a worlds top blind soccer player and other blind soccer players. We collected structural magnetic resonance imaging (MRI) scans from six blind soccer players (including the worlds top player) and eight blind non-soccer players. Using voxel-based morphometry (VBM) analysis (single-case VBM approach), we examined GM volume increase in each participant compared to 250 sighted participants (all of whom had never played blind soccer). Compared with the sighted participants, the worlds top blind soccer player had a significant increase in GM volume in the bilateral RSC/PCC. Two of the other five blind soccer players also showed an increase in the left RSC/PCC. However, such an increase in GM volume was not observed in the blind non-soccer players. Eventually, the probability of a significant increase in the RSC/PCC was significantly higher in the blind soccer group than in the blind non-soccer group. In contrast, only one blind soccer player (not the top player) showed a significant increase in the PHC, and no between-group difference was observed in the probability of a significant increase in the PHC. This study, unveiling the characteristics of the brains of the worlds top blind soccer player and of other blind soccer players, for the first time demonstrates that blind soccer training, which requires spatial navigation based on non-visual cues, may enlarge the human RSC/PCC and provide findings that promote understanding the brains of challenged persons playing blind soccer.

neuroscience↗

bioRxiv2024

Theoretical proposal for restoration of hand motor function utilizing plasticity of motor-cortical interhemispheric interaction

After stroke, the poorer recovery of motor function of upper extremities compared to other body parts is a longstanding problem. Based on our recent functional MRI evidence on healthy volunteers, this perspective paper proposes systematic hand motor rehabilitation utilizing the plasticity of interhemispheric interaction between motor cortices and following its developmental rule. We first discuss the effectiveness of proprioceptive intervention on the paralyzed (immobile) hand synchronized with voluntary movement of the intact hand to induce muscle activity in the paretic hand. In healthy participants, we show that this bilateral proprioceptive-motor coupling intervention activates the bilateral motor cortices (= bilaterally active mode), facilitates interhemispheric motor-cortical functional connectivity, and augments muscle activity of the passively-moved hand. Next, we propose training both hands to perform different movements, which would be effective for stroke patients who become able to manage to move the paretic hand. This bilaterally different movement training may guide the motor cortices into left-right independent mode to improve interhemispheric inhibition and hand dexterity, because we have shown in healthy older adults that this training reactivates motor-cortical interhemispheric inhibition (= left-right independent mode) declined with age, and can improve hand dexterity. Transition of both motor cortices from the bilaterally active mode to the left-right independent mode is a developmental rule of hand motor function and a common feature of motor function recovery after stroke. Hence, incorporating the brains inherent capacity for spontaneous recovery and adhering to developmental principles may be crucial considerations in designing effective rehabilitation strategies.

neuroscience↗

bioRxiv2024

Younger adult brain utilizes interhemispheric strategy of recruiting ipsilateral dorsal premotor cortex for complex finger movement, but not aging brain

The ipsilateral sensorimotor cortices (dorsal premotor cortex [PMd], primary motor cortex [M1], primary somatosensory cortex [S1], and superior parietal cortex of Area 2) are often activated when the healthy younger and older adult brains perform complex finger movements. Prompted by clinical evidence that the ipsilateral PMd plays particularly important roles to complement the movements after stroke, we tested whether the ipsilateral PMd also plays particularly important (complementary) roles among the ipsilateral sensorimotor cortices when healthy younger adults perform a complex motor task by augmenting interhemispheric functional connectivity with the contralateral sensorimotor cortices. We also examined possible strategic difference when older adults with degraded interhemispheric inhibition perform the complex task when compared to younger adults with mature one. We addressed these questions by measuring brain activity with functional magnetic resonance imaging while healthy right-handed younger and older adults performed simple (button pressing with the right index finger) and complex (stick rotation requiring coordination between the right fingers) motor tasks. In younger group, the ipsilateral PMd, S1, Area 2 activated during the complex task, while the ipsilateral M1 remained deactivated as in the simple task, suggesting an existence of interregional difference. The ipsilateral PMd and S1/Area 2 more activated in the individuals with less dexterous performance. The anterior ipsilateral PMd enhanced interhemispheric functional coupling consistently with all of the contralateral sensorimotor cortices during the complex task. In contrast, in older group, all of the ipsilateral cortices including the M1 activated during the complex task, however, none of the cortices showed performance-related activity change. Increase in functional connectivity within the contralateral sensorimotor cortices rather than interhemispheric connectivity was observed during the complex task. The results suggest the importance and complementary role of the ipsilateral PMd for complex finger movement in the younger brains, and the strategic difference (interhemispheric vs. intrahemispheric) when the younger and aging brains perform the movement.

neuroscience↗

bioRxiv2024

Role of the right middle occipital gyrus in egocentric spatial orientation in reference to gravitational information: Evidence from a pre-registered rTMS study

Accurate perception of the orientation of external objects relative to the body, known as egocentric spatial orientation, is fundamental to action. Previously, we found via behavioral and magnetic resonance imaging voxel-based morphometry studies that egocentric spatial orientation is distorted when the whole body is tilted with respect to gravity, and that the magnitude of this perceptual distortion is correlated with grey matter volume in the right middle occipital gyrus (rMOG). In the present pre-registered study, we demonstrated that neural processing in the rMOG is indeed a cause of the perceptual distortion. We transiently suppressed neural activity in the rMOG by applying low-frequency repetitive transcranial magnetic stimulation (rTMS) and evaluated the consequent effect on perceptual distortion. Our results showed that while rTMS over the rMOG significantly reduced perceptual distortion when the body was tilted with respect to gravity, it did not affect egocentric spatial orientation when in the upright position. No changes in perceptual distortion were observed when rTMS was applied to a control site (right temporoparietal junction) or to air (sham TMS). These results indicate that neural processing in the rMOG during body tilt is an essential cause of perceptual distortion, suggesting that the rMOG is engaged in egocentric spatial orientation concerning gravitational information. Significance statementThe findings of this pre-registered study support a causal role of neural activity in the right middle occipital gyrus (rMOG) in the perceptual distortion of egocentric spatial orientation induced by whole-body tilt relative to gravity. We suppressed neural activity in the rMOG using low-frequency repetitive transcranial magnetic stimulation (rTMS) and measured perceptual distortion. We observed a significant reduction in perceptual distortion after rTMS over the rMOG, but not after control or sham rTMS. These results provide, for the first time, direct evidence of the engagement of the rMOG in egocentric spatial orientation in reference to gravitational information.

neuroscience↗

bioRxiv2023

Structural and functional features characterizing the brains of individuals with higher controllability of motor imagery

Motor imagery is a higher-order cognitive brain function that mentally simulates movements without performing the actual physical one. Although many studies have dealt with motor imagery, neural bases that determine individual differences in motor imagery ability are not well understood. Using magnetic resonance imaging and controllability of motor imagery (CMI) test that can objectively evaluate individual ability to manipulate ones imaginary postures, we show that the bilateral superior frontoparietal white matter region expands in higher CMI test scorers. In addition, CMI test activates the bilateral dorsal premotor cortex (PMD) and superior parietal lobule (SPL); specifically, the left PMD and/or the right SPL enhance functional coupling with the visual body, somatosensory, and motor/kinesthetic areas in the higher scorers. This study elucidated the structural and functional features that characterize the brains of individuals with higher controllability of motor imagery, and advanced understanding of individual differences in motor imagery ability.

neuroscience↗

bioRxiv2023

CD4+ T-cell immunity of SARS-CoV-2 patients determine pneumonia development

Most humans infected with SARS-CoV-2 will recover without developing pneumonia. A few SARS-CoV-2 infected patients, however, develop pneumonia, and occasionally develop cytokine storms. In such cases, it is assumed that there is an inadequate immune response to eliminate viral infected cells and an excessive inappropriate immune response causing organ damage, but little is known about this mechanism. In this study, we used single cell RNA sequencing and mass cytometry to analyze peripheral blood T cells from patients hospitalized with proven COVID-19 infection in order to clarify the differences in host immune status among COVID-19 pneumonia cases, non-pneumonia cases, and healthy controls. The results showed that a specific CD4+ T cell cluster with chemokine receptor expression patterns, CXCR3+CCR4-CCR6+ (Th1/17), was less abundant in COVID-19 pneumonia patients. Interestingly, these CD4+ T-cell clusters were identical to those we have reported to correlate with antitumor immunity and predict programmed cell death (PD)-1 blockade treatment response in lung cancer. The Th1/17 cell percentages had biomarker performance in diagnosing pneumonia cases. In addition, CTLA-4 expression of type17 helper T cells (Th17) and regulatory T cells (Treg) was found to be significantly lower. This indicates that functional suppression of Th17 was less effective and Treg function was impaired in pneumonia cases. These results suggest that imbalance of CD4+ T-cell immunity generates excessive immunity that does not lead to viral eradication. This might be a potential therapeutic target mechanism to prevent severe viral infections. ImportanceIn this observational study, 49 consecutive patients with SARS-CoV-2 infection confirmed by PCR testing and admitted to Saitama Medical University Hospital and Saitama Medical University International Medical Centre between December 4, 2020 and January 17, 2022 were included. Of these 49 patients, 29 were diagnosed with COVID-19 pneumonia by computed tomography (CT) scan (Table 1). The unique CD4+ T-cell immunity with less abundant Th1/17 CD4+ T-cell cluster and low expression of CTLA-4 in Th17 and Treg was consistently found in SARS-CoV-2 pneumonia patients on admission and 1-week of admission. The imbalance of CD4+ T-cell immunity may contribute to develop pneumonia in SARS-CoV-2 virus infected patients by delaying viral clearance and resulting in an excessive immune response. O_TBL View this table: org.highwire.dtl.DTLVardef@1aac015org.highwire.dtl.DTLVardef@128c14dorg.highwire.dtl.DTLVardef@aacabaorg.highwire.dtl.DTLVardef@e39c8eorg.highwire.dtl.DTLVardef@13b439a_HPS_FORMAT_FIGEXP M_TBL O_FLOATNOTable 1C_FLOATNO O_TABLECAPTIONPatient demographics C_TABLECAPTION C_TBL

immunology↗

bioRxiv2022

Hyper-adaptation in the Human Brain: Functional and structural changes in the foot section of the primary motor cortex in a top wheelchair racing Paralympian

The human brain has the capacity to drastically alter its somatotopic representations in response to congenital or acquired limb deficiencies and dysfunctions. The main purpose of the present study was to elucidate such extreme adaptability in the brain of an active top wheelchair racing Paralympian (participant P1) who has congenital paraplegia (dysfunction of bilateral lower limbs). Participant P1 has undergone long-term wheelchair racing training using bilateral upper limbs and has won a total of 19 medals in six consecutive summer Paralympic games as of 2021. We examined the functional and structural changes in the foot section of the primary motor cortex (M1) in participant P1 as compared to able-bodied control participants. We also examined the functional and structural changes in three other individuals (participants P2, P3, and P4) with acquired paraplegia, who also had long-term non-use period of the lower limbs and had undergone long-term training for wheelchair sports (but not top athletes at the level of participant P1). We measured brain activity in all the participants using functional magnetic resonance imaging (MRI) when bimanual wrist extension-flexion movement was performed, and the structural MRI images were collected. Compared to 37 control participants, participant P1 showed significantly greater activity in the M1 foot section during the bimanual task, and significant local GM expansion in this section. Significantly greater activity in the M1 foot section was also observed in participant P4, but not in P2 and P3, and the significant local GM expansion was observed in participant P2, but not in P3 and P4. Thus, functional or structural change was observed in an acquired paraplegic participant, but was not observed in all the paraplegic participants. The functional and structural changes typically observed in participant P1 may represent extreme adaptability of the human brain. We discuss the results in terms of a new idea of hyper-adaptation.

neuroscience↗

bioRxiv2021

Transcranial magnetic stimulation of the occipital cortex interferes with foot movements in blind individuals

Research has shown that the occipital cortex can be reorganized and repurposed for nonvisual perception and cognitive functions following visual loss in blind individuals. However, no studies have directly examined the involvement of the visual cortex in motor function. Here, we show that a rhythmic foot movement performed by acquired blind individuals can be disrupted by transcranial magnetic stimulation (TMS) to their primary and secondary visual cortex (V1/V2). This disruptive effect was absent for congenitally blind or sighted individuals. As a control, TMS to the neck muscles of acquired blind individuals confirms that this disruptive effect was not caused solely by the sensory (tactile/auditory) sensations accompanying the stimulation. Our results provide the direct evidence that functional repurposing of the human visual cortex is not restricted to perception and cognitive functions but also extends to motor function. Moreover, our findings suggest the nessecity of the visual experience before visual loss for the functional reorganization of the visual cortex for motor function. Significance statementThe brain can adapt remarkably after sensory loss. One striking example is that after visual loss, the visual cortex--deprived of visual input--is often reused for nonvisual perception and higher cognition. Here, we show that it can also support motor control. Using transcranial magnetic stimulation, we transiently disrupted processing in the visual cortex while participants performed rhythmic foot movements. This disruption impaired performance in people who became blind after birth, but not in sighted individuals or those blind from birth. These findings demonstrate that the visual cortex can take on a motor function after vision is lost, but only with prior visual experience.

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bioRxiv2021

Bimanual digit training improves right-hand dexterity in older adults by reactivating declined ipsilateral motor-cortical inhibition

Improving deteriorated sensorimotor functions in older individuals is a social necessity in a super-aging society. Previous studies suggested that the declined interhemispheric sensorimotor inhibition observed in older adults is associated with their deteriorated hand/finger dexterity. Here, we examined whether bimanual digit exercises, which can train the interhemispheric inhibitory system, improve deteriorated hand/finger dexterity in older adults. Forty-eight healthy, right-handed, older adults (65-78 years old) were divided into two groups, i.e., the bimanual (BM) digit training and right-hand (RH) training groups, and intensive daily training was performed for 2 months. Before and after the training, we evaluated individual right hand/finger dexterity using a peg task, and the individual state of interhemispheric sensorimotor inhibition by analyzing ipsilateral sensorimotor deactivation via functional magnetic resonance imaging when participants experienced a kinesthetic illusory movement of the right-hand without performing any motor tasks. Before training, the degree of reduction/loss of ipsilateral motor-cortical deactivation was associated with dexterity deterioration. After training, the dexterity improved only in the BM group, and the dexterity improvement was correlated with reduction in ipsilateral motor-cortical activity. The capability of the brain to inhibit ipsilateral motor-cortical activity during a simple right-hand sensory-motor task is tightly related to right-hand dexterity in older adults.

neuroscience↗

bioRxiv2021

Age dependency and lateralization in the three branches of the human superior longitudinal fasciculus

The superior longitudinal fascicle/fasciculus (SLF) is a major white matter tract connecting the frontal and parietal cortices in humans. Although the SLF has often been analyzed as a single entity, several studies have reported that the SLF is segregated into three distinct branches (SLF I, II, and III). They have also reported the right lateralization of the SLF III volume and discussed its relationship with lateralized cortical functions in the fronto-parietal network. However, to date, the homogeneity or heterogeneity of the age dependency and lateralization properties of SLF branches have not been fully clarified. Through this study, we aimed to clarify the age dependency and lateralization of SLF I-III by analyzing diffusion-weighted MRI (dMRI) and quantitative R1 (qR1) map datasets collected from a wide range of age groups, mostly comprising right-handed children, adolescents, adults, and seniors (6 to 81 years old). The age dependency in dMRI measurement (fractional anisotropy, FA) was heterogeneous among the three SLF branches, suggesting that these branches are regulated by distinct developmental and aging processes. Lateralization analysis on SLF branches revealed that the right SLF III was larger than the left SLF III in adults, replicating previous reports. FA measurement also suggested that, in addition to SLF III, SLF II was lateralized to the right hemisphere in adolescents and adults. We further found a left lateralization of SLF I in qR1 data, a microstructural measurement sensitive to myelin levels, in adults. These findings suggest that the SLF sub-bundles are distinct entities in terms of age dependency and lateralization.

neuroscience↗

bioRxiv2018

Cortical activation associated with motor preparation can be used to predict the freely chosen effector of an upcoming movement and reflects response time: An fMRI decoding study

Motor action is prepared in the human brain for rapid initiation at the appropriate time. Recent non-invasive decoding techniques have shown that brain activity for action preparation represents various parameters of an upcoming action. In the present study, we demonstrated that a freely chosen effector can be predicted from brain activity measured using functional magnetic resonance imaging (fMRI) before initiation of the action. Furthermore, the activity was related to response time (RT). We measured brain activity with fMRI while 12 participants performed a finger-tapping task using either the left or right hand, which was freely chosen by them. Using fMRI decoding, we identified brain regions in which activity during the preparatory period could predict the hand used for the upcoming action. We subsequently evaluated the relationship between brain activity and the RT of the upcoming action to determine whether correct decoding was associated with short RT. We observed that activity in the supplementary motor area, dorsal premotor cortex, and primary motor cortex measured before action execution predicted the hand used to perform the action with significantly above-chance accuracy (approximately 70%). Furthermore, in most participants, the RT was shorter in trials for which the used hand was correctly predicted. The present study showed that preparatory activity in cortical motor areas represents information about the effector used for an upcoming action, and that well-formed motor representations in these regions are associated with reduced response times.\n\nHighlightsO_LIBrain activity measured by fMRI was used to predict freely chosen effectors.\nC_LIO_LIM1/PMd and SMA activity predicted the effector hand prior to action initiation.\nC_LIO_LIResponse time was shorter in trials in which effector hand was correctly predicted.\nC_LIO_LIFreely chosen action is represented in the M1/PMd and SMA.\nC_LIO_LIWell-formed preparatory motor representations lead to reduced response time.\nC_LI

neuroscience↗