Biomedical subjects

Tetsuo Kida

Publications and source records attributed to Tetsuo Kida.

At least 19 recordsLinked to original sources

PubMed2006

Objective examination for two-point stimulation using a somatosensory oddball paradigm: an MEG study.

OBJECTIVE: To establish an objective two-point discrimination test using magnetoencephalography (MEG). METHODS: First, we determined the discrimination threshold (DT) of the two-points. In the first experiment, we applied 0.9DT as standard stimuli, and 0.8DT, 1.1DT and 2DT as deviant stimuli in Conditions 1, 2 and 3, respectively. In the second experiment, we used 2DT and 0.9DT as the standard and deviant stimuli, respectively, in Condition 1. We applied two-stimuli that subjects felt as definitely one point or two-points in Condition 2 and 3, respectively. RESULTS: In the first experiment, the components peaking around 30-70 and 150-250ms following deviant stimuli were significantly larger than those following standard stimuli. Considering the peak latency, these components seem consistent with the magnetic mismatch field (MMF). In the second experiment, the MMF was recorded only in Condition 1. Therefore, it is considered that the MMF was recorded only when subjects automatically discriminate one point from two-points stimuli. CONCLUSIONS: This novel method can be used in neurophysiological two-point discrimination tests without the need to rely on the examiners' skills and subjects' reactions. SIGNIFICANCE: We confirmed that our new method could be used for the objective examination of two-point spatial discrimination.

Adult↗

PubMed2006

Pre-movement modulation of tibial nerve SEPs caused by a self-initiated dorsiflexion.

OBJECTIVE: To investigate the centrifugal effect on somatosensory evoked potentials (SEPs), we recorded the pre-movement modulation of SEPs following stimulation of the tibial nerve caused by a self-initiated dorsiflexion. METHODS: SEPs following stimulation of the right tibial nerve at the popliteal fossa were recorded during self-initiated dorsiflexion of the right ankle every 5-7s. Based on the onset of Bereitschaftspotential and negative slope, the preparatory period before dorsiflexion was divided into four sub-periods (pre-BP, BP1a, BP1b and BP2 sub-period), and SEPs in each sub-period were averaged. SEPs were also recorded in a stationary condition. RESULTS: P30, N40, P50 and N70 were identified at Cz in all subjects. The amplitude of P30 was significantly smaller in the BP2 sub-period than in the pre-BP sub-period. The N40 amplitude was significantly attenuated in the BP2 sub-period compared with the stationary condition, the pre-BP sub-period, the BP1a sub-period and the BP1b sub-period. CONCLUSIONS: These results suggested that the motor-related areas involved in generating negative slope modulated the tibial nerve SEPs preceding a self-initiated contraction of the agonist muscle. SIGNIFICANCE: The centrifugal gating effect on SEPs extends to the somatosensory information from the antagonistic body part.

Adult↗

PubMed2006

Active attention modulates passive attention-related neural responses to sudden somatosensory input against a silent background.

To reveal whether active attention modulates neuronal responses related to passive attention to somatosensory stimuli presented suddenly against a silent background, we examined the passive attention-related change in amplitude of the event-related brain potentials (ERPs), caused by temporal infrequency of stimuli. Eighteen healthy subjects performed passive and active attention tasks in two stimulus conditions. In the oddball condition, frequent (80%, standard) and infrequent (20%, deviant) electrical stimuli were randomly delivered to the second and third digits of the left hand. In the deviant-alone condition, the deviant stimulus (deviant-alone stimulus) was delivered with the same timing and sequence as in the oddball condition without standard stimuli. The P100, N140, and P200 elicited by the deviant-alone stimulus were enhanced in amplitude compared to those evoked by the oddball deviant stimulus in both the active and passive tasks. Moreover, active attention increased the enhancement of P100 and N140. The difference waveform (deviant-alone minus oddball deviant) provided similar findings. In conclusion, active attention enhances neural responses related to passive shifts of attention to somatosensory signals suddenly presented against a silent background. The results indicate that top-down signals for detecting target stimuli interact with passive shifts of attention caused by bottom-up signals.

Action Potentials↗

PubMed2006

Centrifugal regulation of human cortical responses to a task-relevant somatosensory signal triggering voluntary movement.

Many studies have reported a movement-related modulation of response in the primary and secondary somatosensory cortices (SI and SII) to a task-irrelevant stimulation in primates. In the present study, magnetoencephalography (MEG) was used to examine the top-down centrifugal regulation of neural responses in the human SI and SII to a task-relevant somatosensory signal triggering a voluntary movement. Nine healthy adults participated in the study. A visual warning signal was followed 2 s later by a somatosensory imperative signal delivered to the right median nerve at the wrist. Three kinds of warning signal informed the participants of the reaction which should be executed on presentation of the imperative signal (rest or extension of the right index finger, extension of the left index finger). The somatosensory stimulation was used to both generate neural responses and trigger voluntary movement and therefore was regarded as a task-relevant signal. The responses were recorded using a whole-head MEG system. The P35m response around the SI was reduced in magnitude without alteration of the primary SI response, N20m, when the signal triggered a voluntary movement compared to the control condition, whereas bilateral SII responses peaking at 70-100 ms were enhanced and the peak latency was shortened. The peak latency of the responses in the SI and SII preceded the onset of the earliest voluntary muscle activation in each subject. Later bilateral perisylvian responses were also enhanced with movement. In conclusion, neural activities in the SI and SII evoked by task-relevant somatosensory signals are regulated differently by motor-related neural activities before the afferent inputs. The present findings indicate a difference in function between the SI and SII in somatosensory-motor regulation.

Adult↗

PubMed2006

Higher anticipated force required a stronger inhibitory process in go/nogo tasks.

OBJECTIVE: We investigated the effect of the inhibitory process with increasing muscle force on event-related potentials (ERPs) and motor evoked potentials (MEPs). METHODS: The subjects performed a S1-S2 paradigm with go/nogo tasks. S1 was an auditory tone burst, and S2 was an electrical stimulation applied to the second (go stimuli) or fifth digit (nogo stimuli) of the left hand. The recordings were conducted at 3 force levels; 10, 30 and 50% maximal voluntary contraction (MVC). After the presentation of S2, the subjects were instructed to adjust their force level to match the target line with a force trajectory line in only the go trials. RESULTS: Nogo-N140 was significantly more negative in amplitude than go-N140 in all conditions, and became larger with increasing muscle force. The MEP, which was recorded at 150 ms after S2, became significantly smaller with increasing muscle force in nogo trials, whereas it became larger in go trials. CONCLUSIONS: Our results indicated that stronger inhibitory cerebral activity was needed for a nogo stimulus, in the case where a stronger response was needed for a go stimulus. SIGNIFICANCE: The present study showed a significant relationship between cortical inhibitory process and muscle force.

Acoustic Stimulation↗

PubMed2006

[Examination of attenuation correction using low-dose computed tomography].

Attenuation correction is necessary for the reconstruction of SPECT images. One report has mentioned that attenuation correction by X-ray computed tomography (CT) is effective for a non-uniform attenuation body. We examined the effect of attenuation correction on SPECT images by changing the scanning conditions of CT, and evaluated the possibility of attenuation correction by low-dose CT. The phantom was scanned under several X-ray tube conditions varying from 80 kV to 135 kV and from 7.5 mAs to 200 mAs. We obtained equations of attenuation correction based on the Hounsfield Unit (HU) units of each pixel and compared the effects of attenuation correction. The results showed that the equation for attenuation correction under each condition did not vary significantly, and the effects of attenuation correction by the equations did not vary significantly between CT of low dose and that of clinical dose. This result suggest that the attenuation correction obtained by low-dose CT was equal to that obtained by the clinical dose. In conclusion, it seemed that the equation and map of attenuation correction matched with each radionuclide yielded more adequate attenuation correction than conventional methods.

Image Processing, Computer-Assisted↗

PubMed2006

Centrifugal regulation of a task-relevant somatosensory signal triggering voluntary movement without a preceding warning signal.

A warning signal followed by an imperative signal generates anticipatory and preparatory activities, which regulate sensory evoked neuronal activities through a top-down centrifugal mechanism. The present study investigated the centrifugal regulation of neuronal responses evoked by a task-relevant somatosensory signal, which triggers a voluntary movement without a warning signal. Eleven healthy adults participated in this study. Electrical stimulation was delivered to the right median nerve at a random interstimulus interval (1.75-2.25 s). The participants were instructed to extend the second digit of the right hand as fast as possible when the electrical stimulus was presented (ipsilateral reaction condition), or extend that of the left hand (contralateral reaction condition). They also executed repetitively extension of the right second digit at a rate of about 0.5 Hz, irrespective of electrical stimulation (movement condition), to count silently the number of stimuli (counting condition). In the control condition, they had no task to perform. The amplitude of short-latency somatosensory evoked potentials, the central P25, frontal N30, and parietal P30, was significantly reduced in both movement and ipsilateral reaction conditions compared to the control condition. The amplitude of long-latency P80 was significantly enhanced only in the ipsilateral reaction condition compared to the control, movement, contralateral reaction, and counting conditions. The long-latency N140 was significantly enhanced in both movement and ipsilateral reaction conditions compared to the control condition. In conclusion, short- and long-latency neuronal activities evoked by task-relevant somatosensory signals were regulated differently through a centrifugal mechanism even when the signal triggered a voluntary movement without a warning signal. The facilitation of activities at a latency of around 80 ms is associated with gain enhancement of the task-relevant signals from the body part involved in the action, whereas that at a latency of around 140 ms is associated with unspecific gain regulation generally induced by voluntary movement. These may be dissociated from the simple effect of directing attention to the stimulation.

Adolescent↗

PubMed2006

The characteristics of the nogo-N140 component in somatosensory go/nogo tasks.

Nogo-related brain potentials may not be dependent on sensory modalities but reflect common neural activities specific to the inhibitory process. Recent studies reported that nogo potentials were elicited by not only visual and auditory but also somatosensory stimulation. However, the characteristics of this nogo potential evoked by somatosensory stimulation have been unclear because of the small number of reports. In the present study, therefore, to determine the characteristics of this potential, the effects of stimulus site and response hand were investigated. Electrical stimulation was delivered to the second and fifth digit of one hand, and the subjects had to respond to a go stimulus by pushing a button with the thumb contralateral to the stimulated side as quickly as possible. The amplitudes of the nogo-N140 component (N140 evoked by the nogo stimuli), which is very similar to the nogo-N2 components following visual and auditory stimulation, were unrelated to the stimulated digits, the second and fifth digit of the left and right hand. However, differences between go and nogo ERPs were significantly larger in the hemisphere contralateral to the response hand than the ipsilateral hemisphere. This result was inconsistent with visual and auditory go/nogo studies showing a right-hemisphere dominance or bilateral activities in nogo trials. Therefore, nogo-N140 should be considered to reflect the inhibitory process especially in the hemisphere contralateral to the response hand and the sensory modality dependency of nogo potentials.

Acoustic Stimulation↗

PubMed2005

Centrifugal regulation of task-relevant somatosensory signals to trigger a voluntary movement.

Many previous papers have reported the modulation of somatosensory evoked potentials (SEPs) during voluntary movement, but the locus and mechanism underlying the movement-induced centrifugal modulation of the SEPs elicited by a task-relevant somatosensory stimulus still remain unclear. We investigated the centrifugal modulation of the SEPs elicited by a task-relevant somatosensory stimulus which triggers a voluntary movement in a forewarned reaction time task. A pair of warning (S1: auditory) and imperative stimuli (S2: somatosensory) was presented with a 1 s interstimulus interval. Subjects were instructed to respond by moving the hand ipsilateral or contralateral to the somatosensory stimulation which elicits the SEPs. In four experiments, the locus and selectivity of the SEPs' modulation, the contribution of cutaneous afferents and the effect of contraction magnitude were examined, respectively. A control condition where subjects had no task to perform was compared to several task conditions. The amplitude of the frontal N30, parietal P30, and central P25 was decreased and that of the long latency P80 and N140 was increased when the somatosensory stimuli triggered a voluntary movement of the stimulated finger compared to the control condition. The N60 decreased with the movement of any finger. These results were considered to be caused by the centrifugal influence of neuronal activity which occurs before a somatosensory imperative stimulus. The present findings did not support the hypothesis that the inhibition of afferent inputs by descending motor commands can occur at subcortical levels. A higher contraction magnitude produced a further attenuation of the amplitude of the frontal N30, while it decreased the enhancement of the P80. Moreover, the modulation of neuronal responses seems to result mainly from the modulation of cutaneous afferents, especially from the moved body parts. In conclusion, the short- and long-latency somatosensory neuronal activities evoked by task-relevant ascending afferents from the moved body parts are regulated differently by motor-related neuronal activities before those afferent inputs. The latter activities may be associated with sensory gain regulation related to directing attention to body parts involved in the action.

Acoustic Stimulation↗

PubMed2005

Gating of SEPs by contraction of the contralateral homologous muscle during the preparatory period of self-initiated plantar flexion.

To investigate the centrifugal change in somatosensory information processing caused by contraction of the contralateral homologous muscle, we recorded the somatosensory-evoked potentials (SEPs) during the preparatory period of a self-initiated plantar flexion. The SEPs following stimulation of the right tibial nerve at the popliteal fossa were recorded in nine healthy subjects. Self-initiated plantar flexion of the left ankle was performed once every 5 to 7 s. The electrical stimulation was delivered continuously, and the subjects were instructed to concentrate on the movement and not to pay attention to the electrical stimulation. Based on the components of movement-related cortical potential, Bereitschaftspotential (BP) and Negative slope (NS), the preparatory period was divided into four sub-periods (NS, BP-1, BP-2, and Pre-BP). To obtain pre-movement SEPs, the signals following stimulation in each sub-period were averaged. SEPs were attenuated in the preparatory period, especially in the NS sub-period. The amplitude of N40 component was significantly attenuated compared with that in the stationary state and other sub-periods. The amplitude of P53 and N70 was smaller in the NS sub-period than other pre-movement sub-periods. Since there was no centripetal effect on SEPs in the preparatory period, these findings suggested that the activity of motor-related areas modulated the somatosensory information from the contralateral non-movement limb (centrifugal gating). It was assumed that an inhibition on the somatosensory inputs from contralateral limb was caused by the projection via either the corpus callosum or ipsilateral cortico-cortical projections.

Adult↗

PubMed2005

Differential modulation in human primary and secondary somatosensory cortices during the preparatory period of self-initiated finger movement.

To elucidate the mechanisms underlying sensorimotor integration, we investigated modulation in the primary (SI) and secondary (SII) somatosensory cortices during the preparatory period of a self-initiated finger extension. Electrical stimulation of the right median nerve was applied continuously, while the subjects performed a self-initiated finger extension and were instructed not to pay attention to the stimulation. The preparatory period was divided into five sub-periods from the onset of the electromyogram to 3000 ms before movement and the magnetoencephalogram signals following stimulation in each sub-period were averaged. Multiple source analysis indicated that the equivalent current dipoles (ECDs) were located in SI and bilateral SII. Although the ECD moment for N 20 m (the upward deflection peaking at around 20 ms) was not significantly changed, that for P 30 m (the downward deflection peaking at around 30 m) was significantly smaller in the 0- to -500-ms sub-period than the -2000- to -3000-ms sub-period. As for SII, the ECD moment for the SII ipsilateral to movement showed no significant change, while that for the contralateral SII was significantly larger in the 0- to -500-ms sub-period than the -1500- to -2000-ms or -2000- to -3000-ms sub-period. The opposite effects of movement on SI and SII cortices indicated that these cortical areas play a different role in the function of the sensorimotor integration and are affected differently by the centrifugal process.

Adult↗

PubMed2005

Effects of habitual moderate exercise on response processing and cognitive processing in older adults.

We examined the effects of habitual moderate exercise on central information processing in older individuals using the reaction time (RT) and P3 component of event-related brain potentials (ERP). The present study was designed to assess cognitive function by comparing groups of 20 older individuals (69.20 +/- 1.3 years active group) who regularly engage in moderate physical activity with 20 subjects (66.90 +/- 1.1 years inactive group) who do comparatively little exercise. Subjects performed a somatosensory oddball task composed of pressing a button with their right foot as fast as possible following an electrical stimulus applied to the right index finger, and not responding to an electrical stimulus applied to the left index finger. Electroencephalogram (EEG) was recorded at the frontal (Fz), central (Cz), and parietal (Pz) sites according to the International 10-20 system referenced to linked earlobes. The RT was faster for the active group than for the inactive group, and the P3 amplitude of the active group was significantly larger than that of the inactive group. Moreover, the P3 amplitude for the active group was maximum at Pz and significantly larger than at Fz and Cz, but for the inactive group it was identical between Fz and Pz. The results suggest that habitual moderate exercise exerts positive influences in older adults not only on response processing, but also on cognitive processing.

Aged↗

PubMed2004

Load- and cadence-dependent modulation of somatosensory evoked potentials and Soleus H-reflexes during active leg pedaling in humans.

Modulation of transmission in group I muscle afferent pathways to the somatosensory cortex and those to the alpha-motoneuron were investigated during active leg pedaling. Cerebral somatosensory evoked potentials (SEPs) and Soleus (Sol) H-reflexes following posterior tibial nerve stimulation were recorded at four different pedaling phases. The subjects were asked to perform pedaling at three different cadences (30, 45 and 60 rpm with 0.5 kp, cadence task; C-task) and with three different workloads (at 45 rpm with 0.0, 0.5 and 1.0 kp, load task; L-task). In both C- and L-tasks, Sol H-reflexes were modulated in a phase-dependent manner, showing an increase in the power phase and a decrease in the recovery phase. In contrast, the early SEP (P30-N40) components were modulated in a phase-dependent manner when the cadence and load were low. When focusing on the power phases, significant cadence- and load-dependent modulations of the P30-N40 were found, and inversely graded with the cadence and load. The H-reflex was found to be significantly decreased at the highest cadence, i.e., cadence-dependent modulation. In contrast, the H-reflex during the L-task was found to be proportional to the load. The correlation analysis between the size of H-reflex and the amount of background (BG) electromyographic (EMG) activity demonstrated that the H-reflex in the power phase did not depend on the BG EMG in either C- or L-task. These findings suggested that transmission of muscle afferents along the ascending pathways to the cerebral cortex and the spinal cord is independently controlled in accordance with the biomechanical constraints of active pedaling.

Adult↗

PubMed2004

Effects of ISI and stimulus probability on event-related go/nogo potentials after somatosensory stimulation.

The present study investigated the characteristics of the middle-latency negative potential of event-related potentials (ERPs) using somatosensory go/nogo tasks. We manipulated interstimulus interval (ISI) in Experiment 1 and stimulus probability in Experiment 2 and analyzed the subtracted difference waveform resulting from subtraction of the ERP evoked by the go stimulation from that evoked by the nogo stimulation. In Experiment 1, the peak latency of negativity became significantly longer as the ISI increased, but the peak amplitude was unchanged. The reaction time (RT) was longer with increasing ISI. In Experiment 2, manipulation of the stimulus probability yielded an increase in peak amplitude with decreasing probability of the nogo stimulus, but did not affect the latency. The RT increased as the probability of a nogo stimulus rose. Because manipulation of the ISI and stimulus probability elicited different brain activities, we hypothesized that manipulation of the ISI elicited a delay of the stimulus evaluation process including response inhibition, and that stimulus probability significantly affected the strength of the response inhibition process.

Adult↗

PubMed2004

Differential influences of exercise intensity on information processing in the central nervous system.

The influence of exercise intensity on information processing in the central nervous system was investigated using P300 and no-go P300 event-related potentials. Twelve subjects (22-33 years) performed a go/no-go reaction time task in a control condition, and again after high-, medium-, and low-intensity pedaling exercises. Compared to the control condition, P300 amplitude decreased after high-intensity pedaling exercise and increased after medium-intensity pedaling exercise. There was no change after low-intensity pedaling exercise. These results suggested that the amount of attentional resources devoted to a given task decreased after high-intensity exercise and increased after medium-intensity exercise. The findings also suggest that changes in P300 amplitude are an inverted U-shaped behavior of differences in exercise intensity. In addition, no-go P300 amplitude showed the same changes as P300 amplitude at different exercise intensities. This indicates that differences in exercise intensity influenced not only the intensity of processing the requirement for a go response, but also processing of the need for a no-go response. It is concluded that differences in exercise intensity influenced information processing in the CNS.

Adult↗

PubMed2004

Effects of a go/nogo task on event-related potentials following somatosensory stimulation.

OBJECTIVE: We investigated the effects of a go/nogo task on event-related potentials (ERPs) evoked by somatosensory stimuli. METHODS: ERPs following electrical stimulation of the second (go stimulus) or fifth (nogo stimulus) left-handed digit were recorded from 9 subjects. The recordings were conducted in 3 conditions: Control, Count and Movement. The subjects were instructed to count the go stimuli silently in Count, and respond to the go stimuli by grasping right hands in Movement. Go and nogo stimuli were presented at an even probability. RESULTS: N140 was recorded in all conditions and P300 in Count and Movement. The mean amplitudes of the nogo stimuli in the interval 140-200 msec and nogo-N140 amplitude were significantly more negative than those of the go stimuli in Count or Movement. Nogo-P300 was larger in amplitude than go-P300 in Movement but not Count. The effect of P300 was applied to Fz and Cz, but not at Pz. CONCLUSIONS: In the present study, effects of a somatosensory go/nogo task on ERPs were investigated, and our findings were very similar to those of previous studies using visual and auditory go/nogo tasks. Therefore, we suggest that cortical activities relating to go/nogo tasks are not dependent on sensory modalities. SIGNIFICANCE: The present study showed for the first time the go/nogo effects on somatosensory-evoked ERPs. These effects were similar to those in visual and auditory ERP studies.

Acoustic Stimulation↗

PubMed2004

Passive enhancement of the somatosensory P100 and N140 in an active attention task using deviant alone condition.

OBJECTIVE: We investigated the changes in the somatosensory P100 and N140 during passive (reading) versus active tasks (counting, button pressing) and oddball (target=20%, standard=80%) versus deviant alone conditions (standards were omitted). METHODS: Nine healthy subjects performed the 3 tasks (reading, counting and button pressing) under two conditions. Standard and target electrical stimuli were presented in a random order to the index or middle fingers of the left hand at a constant 800 ms interstimulus interval in the oddball conditions. In the deviant alone conditions, only target stimuli were presented with the same timing as in the oddball conditions. RESULTS: The N140 amplitude increased for the deviant alone stimuli compared with the oddball standard and target stimuli regardless of whether the task was passive or active, indicating passive shifts of attention related to temporal infrequency. The P100 amplitude also increased for the deviant alone stimuli compared with the oddball standard and target stimuli in both passive and active tasks, but the enhancement seemed to be even smaller than that of the N140 amplitude. CONCLUSIONS: The somatosensory N140 passively increased even if subjects tried to attend actively to the stimulus source when the deviant alone condition was used. This change in N140 amplitude may be related to a strong orienting effect against a 'silent' background. SIGNIFICANCE: The present study provided evidence that the N140 is an indicator of passive attention against a silent background when the deviant alone condition or long interstimulus interval was used.

Adult↗

PubMed2004

Differential modulation of the short- and long-latency somatosensory evoked potentials in a forewarned reaction time task.

OBJECTIVE: We investigated modulation of the short- and long-latency somatosensory evoked potentials (SEPs) in a forewarned reaction time task. METHODS: A pair of warning (auditory) and imperative stimuli (somatosensory) was presented with a 2 s interstimulus interval. In movement condition, subjects responded by grip movement with the ipsilateral hand to the somatosensory stimulation when the imperative stimulus was presented. In counting condition, they silently counted the number of imperative stimuli. The SEPs in response to the imperative stimuli were recorded. RESULTS: Frontal N30 and central N60 amplitudes were significantly smaller in the movement than in the counting or rest conditions. None of the short-latency components differed between the counting and rest conditions. In contrast to the short-latency components, P80 was significantly larger in the counting than in the rest condition, and showed a further increase from the counting to the movement condition. The N140 amplitude was significantly larger in the movement than the rest condition, but was not changed between the counting and the rest conditions. CONCLUSIONS: The attenuation of the frontal N30 and central N60, and the enhancement of the P80 and possibly the N140 resulted from the centrifugal mechanism. The present findings may show the different effects of voluntary movement on the early and subsequent cortical processing of the relevant somatosensory information requiring a behavioral response. SIGNIFICANCE: The present study demonstrated the differential modulation of short- and long-latency components of SEPs in a forewarned reaction time task.

Acoustic Stimulation↗