[show abstract][hide abstract] ABSTRACT: When confronted with complex visual scenes in daily life, how do we know which visual information represents our own hand? We investigated the cues used to assign visual information to one's own hand. Wrist tendon vibration elicits an illusory sensation of wrist movement. The intensity of this illusion attenuates when the actual motionless hand is visually presented. Testing what kind of visual stimuli attenuate this illusion will elucidate factors contributing to visual detection of one's own hand. The illusion was reduced when a stationary object was shown, but only when participants knew it was controllable with their hands. In contrast, the visual image of their own hand attenuated the illusion even when participants knew that it was not controllable. We suggest that long-term knowledge about the appearance of the body and short-term knowledge about controllability of a visual object are combined to robustly extract our own body from a visual scene.
Proceedings of the Royal Society B: Biological Sciences 05/2012; 279(1742):3476-81. · 5.68 Impact Factor
[show abstract][hide abstract] ABSTRACT: Considerable progress has been made in developing models of cerebellar function in sensorimotor control, as well as in identifying key problems that are the focus of current investigation. In this consensus paper, we discuss the literature on the role of the cerebellar circuitry in motor control, bringing together a range of different viewpoints. The following topics are covered: oculomotor control, classical conditioning (evidence in animals and in humans), cerebellar control of motor speech, control of grip forces, control of voluntary limb movements, timing, sensorimotor synchronization, control of corticomotor excitability, control of movement-related sensory data acquisition, cerebro-cerebellar interaction in visuokinesthetic perception of hand movement, functional neuroimaging studies, and magnetoencephalographic mapping of cortico-cerebellar dynamics. While the field has yet to reach a consensus on the precise role played by the cerebellum in movement control, the literature has witnessed the emergence of broad proposals that address cerebellar function at multiple levels of analysis. This paper highlights the diversity of current opinion, providing a framework for debate and discussion on the role of this quintessential vertebrate structure.
The Cerebellum 12/2011; 11(2):457-87. · 2.60 Impact Factor
[show abstract][hide abstract] ABSTRACT: Prompted by our neuroimaging findings in 60 normal people, we examined whether focal damage to the hand section of precentral motor regions impairs hand kinesthesia in a patient, and investigated brain regions related to recovery of kinesthetic function. The damage impaired contralateral kinesthesia. The peri-lesional cerebral motor region, together with the ipsilateral intermediate cerebellum, participated in the recovered kinesthetic processing. The study confirmed the importance of precentral motor regions in human kinesthesia, and indicated a contribution of the peri-lesional cerebral region in recovered kinesthesia after precentral damage, which conceptually fits with cases of recovery of motor function.
[show abstract][hide abstract] ABSTRACT: Procedural motor learning includes a period when no substantial gain in performance improvement is obtained even with repeated, daily practice. Prompted by the potential benefit of high-frequency transcutaneous electrical stimulation, we examined if the stimulation to the hand reduces redundant motor activity that likely exists in an acquired hand motor skill, so as to further upgrade stable motor performance. Healthy participants were trained until their motor performance of continuously rotating two balls in the palm of their right hand became stable. In the series of experiments, they repeated a trial performing this cyclic rotation as many times as possible in 15 s. In trials where we applied the stimulation to the relaxed thumb before they initiated the task, most reported that their movements became smoother and they could perform the movements at a higher cycle compared to the control trials. This was not possible when the dorsal side of the wrist was stimulated. The performance improvement was associated with reduction of amplitude of finger displacement, which was consistently observed irrespective of the task demands. Importantly, this kinematic change occurred without being noticed by the participants, and their intentional changes of motor strategies (reducing amplitude of finger displacement) never improved the performance. Moreover, the performance never spontaneously improved during one-week training without stimulation, whereas the improvement in association with stimulation was consistently observed across days during training on another week combined with the stimulation. The improved effect obtained in stimulation trials on one day partially carried over to the next day, thereby promoting daily improvement of plateaued performance, which could not be unlocked by the first-week intensive training. This study demonstrated the possibility of effectively improving a plateaued motor skill, and pre-movement somatic stimulation driving this behavioral change.
PLoS ONE 01/2011; 6(10):e25670. · 3.73 Impact Factor
[show abstract][hide abstract] ABSTRACT: Our results demonstrate that neuronal activity in the human parietal cortex, which is involved in the spatial processing of self-referential physical distance, seems to be associated with the evaluation of social distance between self and others. Thus, our neuroimaging finding raises a possibility that the human parietal cortex may have social-cognitive function
[show abstract][hide abstract] ABSTRACT: Humans can judge whether an object is graspable or not by merely glancing at it. This judgment is possible because of the brain's pragmatic function that links action with perception, i.e., the spatial property of the object is immediately associated with the motor capability of hands. In this study, we investigated the neural correlates of this cognitive-motor process by conducting an event-related functional magnetic resonance imaging experiment. Healthy right-handed participants were made to judge whether they could grasp visually presented objects with their right hand without generating any actual movements [motor evaluation (ME) task]. Objects of various sizes were presented to the participants in front of their hands; they judged the graspability of the object as soon as possible. For the control, the participants simply compared the size of the presented object and the static size of their fists [size comparison (SC) task]. Thus, only in the former task, the participants had to evaluate their motor capability by briefly simulating their range of hand motion. Rostral parts of the dorsal premotor cortices (prePMd) were activated bilaterally only during the ME task, and the activities were positively correlated with the duration of the evaluation. The prePMd participates in the judgment of graspability for external objects by evaluating hand motor capability. This function may assure a basic premise for the selection of an appropriate motor option when our hands interact with a variety of external objects.
Brain research 12/2009; 1313:134-42. · 2.46 Impact Factor
[show abstract][hide abstract] ABSTRACT: We examined whether visual information on the dynamic aspect of the actions performed by an individual can influence an observer's action. Sixteen participants cyclically generated an isometric precision grip force with their right thumb and index finger in synchronization with the contraction (in-phase) or relaxation phase of an experimenter's hand, foot, and mouth movements presented in videos. Visual information of the hand action significantly enhanced the observer's grip force, and this enhancement exclusively occurred during the in-phase condition. These results suggest that the effector matching between the observed and the performed actions and the temporal coincidence in the movement phase are the key factors when visual information on the dynamics of the action of an individual influences the observer's action.
[show abstract][hide abstract] ABSTRACT: Near-infrared spectroscopy (NIRS) has recently been used to measure human motor-cortical activation, enabling the classification of the content of a sensory-motor event such as whether the left or right hand was used. Here, we advance this NIRS application by demonstrating quantitative estimates of multiple sensory-motor events from single-trial NIRS signals. It is known that different degrees of sensory-motor activation are required to generate various hand/finger force levels. Thus, using a sparse linear regression method, we examined whether the temporal changes in different force levels could be reconstructed from NIRS signals. We measured the relative changes in oxyhemoglobin concentrations in the bilateral sensory-motor cortices while participants performed an isometric finger-pinch force production with their thumb and index finger by repeatedly exerting one of three target forces (25, 50, or 75% of the maximum voluntary contraction) for 12 s. To reconstruct the generated forces, we determined the regression parameters from the training datasets and applied these parameters to new test datasets to validate the parameters in the single-trial reconstruction. The temporal changes in the three different levels of generated forces, as well as the baseline resting state, could be reconstructed, even for the test datasets. The best reconstruction was achieved when using only the selected NIRS channels dominantly located in the contralateral sensory-motor cortex, and with a four second hemodynamic delay. These data demonstrate the potential for reconstructing different levels of external loads (forces) from those of the internal loads (activation) in the human brain using NIRS.
[show abstract][hide abstract] ABSTRACT: Across cultures, social relationships are often thought of, described, and acted out in terms of physical space (e.g. "close friends" "high lord"). Does this cognitive mapping of social concepts arise from shared brain resources for processing social and physical relationships? Using fMRI, we found that the tasks of evaluating social compatibility and of evaluating physical distances engage a common brain substrate in the parietal cortex. The present study shows the possibility of an analytic brain mechanism to process and represent complex networks of social relationships. Given parietal cortex's known role in constructing egocentric maps of physical space, our present findings may help to explain the linguistic, psychological and behavioural links between social and physical space.
PLoS ONE 02/2009; 4(2):e4360. · 3.73 Impact Factor
[show abstract][hide abstract] ABSTRACT: We used functional magnetic resonance imaging (fMRI) to identify brain areas involved in auditory rhythm perception. Participants listened to three rhythm sequences that varied in temporal predictability. The most predictable sequence was an isochronous rhythm sequence of a single interval (ISO). The other two sequences had nine intervals with unequal durations. One of these had interval durations of integer ratios relative to the shortest interval (METRIC). The other had interval durations of non-integer ratios relative to the shortest interval (NON-METRIC), and was thus perceptually more complex than the other two. In addition, we presented unpredictable sequences with randomly distributed intervals (RAN). We tested two hypotheses. Firstly, that areas involved in motor timing control would also process the temporal predictability of sensory cues. Therefore, there was no active task included in the experiment that could influence the participant perception or induce motor preparation. We found that dorsal premotor cortex (PMD), SMA, preSMA, and lateral cerebellum were more active when participants listen to rhythm sequences compared to random sequences. The activity pattern in supplementary motor area (SMA) and preSMA suggested a modulation dependent on sequence predictability, strongly suggesting a role in temporal sensory prediction. Secondly, we hypothesized that the more complex the rhythm sequence, the more it would engage short-term memory processes of the prefrontal cortex. We found that the superior prefrontal cortex was more active when listening to METRIC and NON-METRIC compared to ISO. We argue that the complexity of rhythm sequences is an important factor in modulating activity in many of the rhythm areas. However, the difference in complexity of our stimuli should be regarded as continuous.
[show abstract][hide abstract] ABSTRACT: Combination of visual and kinesthetic information is essential to perceive bodily movements. We conducted behavioral and functional magnetic resonance imaging experiments to investigate the neuronal correlates of visuokinesthetic combination in perception of hand movement. Participants experienced illusory flexion movement of their hand elicited by tendon vibration while they viewed video-recorded flexion (congruent: CONG) or extension (incongruent: INCONG) motions of their hand. The amount of illusory experience was graded by the visual velocities only when visual information regarding hand motion was concordant with kinesthetic information (CONG). The left posterolateral cerebellum was specifically recruited under the CONG, and this left cerebellar activation was consistent for both left and right hands. The left cerebellar activity reflected the participants' intensity of illusory hand movement under the CONG, and we further showed that coupling of activity between the left cerebellum and the "right" parietal cortex emerges during this visuokinesthetic combination/perception. The "left" cerebellum, working with the anatomically connected high-order bodily region of the "right" parietal cortex, participates in online combination of exteroceptive (vision) and interoceptive (kinesthesia) information to perceive hand movement. The cerebro-cerebellar interaction may underlie updating of one's "body image," when perceiving bodily movement from visual and kinesthetic information.
[show abstract][hide abstract] ABSTRACT: The question of how the brain represents the spatial relationship between the own body and external objects is fundamental. Here we investigate the neural correlates of the somatic perception of bimanual interaction with an external object. A novel bodily illusion was used in conjunction with functional magnetic resonance imaging (fMRI). During fMRI scanning, seven blindfolded right-handed participants held a cylinder between the palms of the two hands while the tendon of the right wrist extensor muscle was vibrated. This elicited a kinesthetic illusion that the right hand was flexing and that the hand-held cylinder was shrinking from the right side. As controls, we vibrated the skin surface over the nearby bone beside the tendon or vibrated the tendon when the hands were not holding the object. Neither control condition elicited this illusion. The significance of the illusion was also confirmed in supplementary experiments outside the scanner on another 16 participants. The "bimanual shrinking-object illusion" activated anterior parts of the superior parietal lobule (SPL) bilaterally. This region has never been activated in previous studies on unimanual hand or hand-object illusion. The illusion also activated left-hemispheric brain structures including area 2 and inferior parietal lobule, an area related to illusory unimanual hand-object interaction between a vibrated hand and a touched object in our previous study. The anterior SPL seems to be involved in the somatic perception of bimanual interaction with an external object probably by computing the spatial relationship between the two hands and a hand-held object.
Journal of Neurophysiology 03/2008; 99(2):695-703. · 3.30 Impact Factor
[show abstract][hide abstract] ABSTRACT: When both visual and kinesthetic information of a limb are available, vision is usually the dominant source of information used to perceive the spatial location. In this study, we conducted behavioral and functional magnetic resonance imaging (fMRI) experiments to examine the brain mechanisms underlying the visual dominance over kinesthesia in perceiving the position of a hand. We used tendon vibration to induce an illusory percept of flexion movement of an immobile hand, while the participants viewed a live image of either the vibrated or nonvibrated static hand through an on-line video camera. The intensity of illusory movement was significantly attenuated (for both the left and right hands) only when the participants viewed the static image of the vibrated hand. The fMRI study showed that the posterior parietal cortex (PPC) is specifically involved in the attenuation of illusory movement and that the activity of the PPC was associated with the degree of attenuation. This indicates that PPC is involved in the multisensory processing that occurs when vision overrules simultaneously available kinesthetic information for estimating the spatial location of a limb. It is thus suggested that the human parietal cortex may play a critical role in the maintenance of a coherent body image when the brain receives potentially conflicting multisensory information from the body.
Journal of Neuroscience 07/2007; 27(26):7047-53. · 6.91 Impact Factor
[show abstract][hide abstract] ABSTRACT: Sensing movements of the upper and lower extremities is important in controlling whole-body movements. We have shown that kinesthetic illusory hand movements activate motor areas and right-sided fronto-parietal cortices. We investigated whether illusions for the upper and lower extremities, i.e. right or left hand or foot, activate the somatotopical sections of motor areas, and if an illusion for each limb engages the right-sided cortices. We scanned the brain activity of 19 blindfolded right-handed participants using functional magnetic resonance imaging (fMRI) while they experienced an illusion for each limb elicited by vibrating its tendon at 110 Hz (ILLUSION). As a control, we applied identical stimuli to the skin over a nearby bone, which does not elicit illusions (VIBRATION). The illusory movement (ILLUSION vs. VIBRATION) of each immobile limb activated limb-specific sections of the contralateral motor cortex (along with somatosensory area 3a), dorsal premotor cortex (PMD), supplementary motor area (SMA), cingulate motor area (CMA), and the ipsilateral cerebellum, which normally participate in execution of movements of the corresponding limb. We found complex non-limb-specific representations in rostral parts of the bilateral SMA and CMA, and illusions for all limbs consistently engaged concentrated regions in right-sided fronto-parietal cortices and basal ganglia. This study demonstrated complete sets of brain representations related to kinesthetic processing of single-joint movements of the four human extremities. The kinesthetic function of motor areas suggests their importance in somatic perception of limb movement, and the non-limb-specific representations indicate high-order kinesthetic processing related to human somatic perception of one's own body.
European Journal of Neuroscience 07/2007; 25(11):3476-87. · 3.75 Impact Factor