Takehito Hayami

The effect of CyberDome, a novel 3-dimensional dome-shaped display system, on laparoscopic procedures

BackgroundLaparoscopic surgeons require extended experience of cases to overcome the lack of depth perception on a two-dimensional (2D) display. Although a three-dimensional (3D) display was reported to be useful over two decades ago, 3D systems have not been widely used. Recently, we developed a novel 3D dome-shaped display (3DD) system, CyberDome.Study designIn the present study, a total of 23 students volunteered. We evaluated the effects of the 3DD system on depth perception and laparoscopic procedures in comparison with the 2D, a conventional 3D (3DP) or the 2D high definition (HD) systems using seven tasks.ResultsThe 3DD system significantly improved depth perception and laparoscopic performance compared with the 2D system in six new tasks. We further found that the 3DD system shortened the execution time and reduced the number of errors during suturing and knot tying. The 3DD system also provided more depth perception than the 3DP and 2D HD systems.ConclusionsThe novel 3DD system is a promising tool for providing depth perception with high resolution to laparoscopic surgeons.

Effectiveness of automotive warning system presented with multiple sensory modalities

It goes without saying that it is very important to drive safely by drivers themselves. However, it is impossible to find drivers who do not make mistakes during driving. Therefore, vehicles should be equipped with a system that automatically detect hazardous state and warn if of drivers so that such a preventive safety can contribute to the reduction of traffic accidents due to the oversight of important information necessary for safety driving. This study paid attention to the preventive safety technology, and discussed how the warning should be presented to drivers. It was explored whether simultaneously presenting warning to multiple sensory organs such as visual and auditory systems can promote (quicken) the perception of warning even under the situation, where interference between information of the same sensory modality occurs. The auditory-tactile warning was found to lead to quicker and more accurate reaction to a hazardous scene during a simulated driving.

Short circuit in deep brain stimulation

OBJECT The authors undertook this study to investigate the incidence, cause, and clinical influence of short circuits in patients treated with deep brain stimulation (DBS). METHODS After the incidental identification of a short circuit during routine follow-up, the authors initiated a policy at their institution of routinely evaluating both therapeutic impedance and system impendence at every outpatient DBS follow-up visit, irrespective of the presence of symptoms suggesting possible system malfunction. This study represents a report of their findings after 1 year of this policy. RESULTS Implanted DBS leads exhibiting short circuits were identified in 7 patients (8.9% of the patients seen for outpatient follow-up examinations during the 12-month study period). The mean duration from DBS lead implantation to the discovery of the short circuit was 64.7 months. The symptoms revealing short circuits included the wearing off of therapeutic effect, apraxia of eyelid opening, or dysarthria in 6 patients with Parkinson disease (PD), and dystonia deterioration in 1 patient with generalized dystonia. All DBS leads with short circuits had been anchored to the cranium using titanium miniplates. Altering electrode settings resulted in clinical improvement in the 2 PD cases in which patients had specific symptoms of short circuits (2.5%) but not in the other 4 cases. The patient with dystonia underwent repositioning and replacement of a lead because the previous lead was located too anteriorly, but did not experience symptom improvement. CONCLUSIONS In contrast to the sudden loss of clinical efficacy of DBS caused by an open circuit, short circuits may arise due to a gradual decrease in impedance, causing the insidious development of neurological symptoms via limited or extended potential fields as well as shortened battery longevity. The incidence of short circuits in DBS may be higher than previously thought, especially in cases in which DBS leads are anchored with miniplates. The circuit impedance of DBS should be routinely checked, even after a long history of DBS therapy, especially in cases of miniplate anchoring.

Proposal of automotive 8-directional warning system that makes use of tactile apparent movement

We proposed a tactile 8-directional warning system which informs drivers of hazardous traffic situations hidden in 8 directions via tactile apparent movement. The effectiveness of the proposed warning system was compared with that of a warning system by simultaneous two-point stimulation and a system without warning. As a result, the apparent lead to quick reaction and higher hit rate (higher accuracy of hazard perception and recognition) as compared with the simultaneous two-point stimulation. However, this was limited to the front and the rear hazard, and was not true for all directions. The vibrotactile warning system that can recognize hazards from all of eight directions should be developed in future research.

Effects of Coil Parameters on the Stimulated Area by Transcranial Magnetic Stimulation

In this study, we investigate the relationships between the eddy current density and the coil configuration of transcranial magnetic stimulation (TMS). The aim of this study is to determine the coil parameters such as the radius of the coil and the bending angle of the coil to stimulate specified area such as the dorsolateral prefrontal cortex (DLPFC). We used a realistic 3-D human head model with inhomogeneous conductivity to obtain accurate eddy current distributions. In the TMS model, eddy current distributions were obtained for figure-eight coils with radius of 30, 40 and 50 mm, and a bending angle of the coil changed from 0 to 30 degrees. Computer simulations show that the maximum value of the eddy current increases linearly with the increase of the radius and the bending-angle of the coil. The maximum eddy current density was 87.6 A/m2 under the case where the bending-angle was 30 degrees and the radius was 50 mm. The stimulated area increased with the increase of the radius and bending-angle of the coil. It is possible to determine coil parameters to stimulate target area appropriately.

Study on cursor shape suitable for eye-gaze input system

The aim of this study was to identify the cursor shape suitable for eye-gaze interfaces. The conventional arrow shape was, irrespective of the number of targets in the display, not suitable for an eye-gaze input system from the perspective of task completion time, number of errors, and subjective rating on usability. It is recommended that the cursor shape of an eye-gaze input system should be cross or ellipse. When the distance between targets is wider, the ellipse type is proper.

Measurements of evoked electroencephalograph by transcranial magnetic stimulation applied to motor cortex and posterior parietal cortex

To investigate the functional connectivity, the evoked potentials by stimulating at the motor cortex, the posterior parietal cortex, and the cerebellum by transcranial magnetic stimulation (TMS) were measured. It is difficult to measure the evoked electroencephalograph (EEG) by the magnetic stimulation because of the large artifact induced by the magnetic pulse. We used an EEG measurement system with sample-and-hold circuit and an independent component analysis to eliminate the electromagnetic interaction emitted from TMS. It was possible to measure EEG signals from all electrodes over the head within 10 ms after applying the TMS. When the motor area was stimulated by TMS, the spread of evoked electrical activity to the contralateral hemisphere was observed at 20 ms after stimulation. However, when the posterior parietal cortex was stimulated, the evoked electrical activity to the contralateral hemisphere was not observed. When the cerebellum was stimulated, the cortical activity propagated from the stimu...

NIRS Measurement of Hemodynamic Evoked Responses in the Primary Sensorimotor Cortex

To investigate the relationship between neuronal activity and hemodynamics, we carried out a near-infrared spectroscopy (NIRS) study to measure the regional changes of hemoglobin concentration associated with cortical activation in the human sensorimotor cortex (SMI) to both voluntary and nonvoluntary tasks. We measured the hemodynamic evoked responses to voluntary finger movement and nonvoluntary electrical stimulation applied on the fingers (thumb and ring finger, respectively). Measurements were performed on 6 healthy right-handed volunteers using block paradigms and we analyzed both the spatial/temporal features and the magnitude of the optical signal induced by cerebral activation during these protocols. We constantly observed an increase in the cerebral concentration of oxygenated hemoglobin at the cortical side contralateral to the stimulated side. Our findings are in agreement with results in positron emission tomography (PET), functional magnetic resonance imaging (fMRI) and EEG (Electroencephalogram).

NIRS Measurement of Hemodynamic Evoked Responses in the Primary Somatosensory Cortex by Finger Stimulation

To investigate the relationship between neuronal activity and hemodynamics, we carried out an NIRS study (near-infrared spectroscopy) to measure the regional changes of hemoglobin concentration associated with cortical activation in the primary somatosensory cortex (SI) to electrical stimuli. We examined the hemodynamic evoked responses to the electrical stimuli applied on the fingers (right thumb and ring finger, respectively). NIRS measurements were performed on 6 healthy right-handed volunteers using block paradigms and we analyzed both the spatial/temporal features and the magnitude of the optical signal induced by cerebral activation during these paradigms. Based on the experiment data, we consistently found an increase/decrease in the cerebral concentration of oxygenated hemoglobin [oxy-Hb]/deoxygenated hemoglobin [deoxy-Hb] at the cortical side contralateral to the stimulated side. Firstly, we found that, using NIRS, we can distinguish the local distribution of fingers on SI, whose result is in good accordance with the anatomical arrangement of hand area in SI. Secondly, we investigated the effects of electrical stimuli intensity on the hemodynamic evoked responses in SI. We found that, after raising the electrical stimuli intensity, an obvious increment of [oxy-Hb] in SI can be observed. Our findings based on NIRS optical imaging are in agreement with results in positron emission tomography (PET), functional magnetic resonance imaging (fMRI) and EEG (Electroencephalogram).

Measurements of the mu/beta ERD and gamma ERS during the imagination of body parts movement

In recent years, many studies shows that the ERS (event-related synchronization) in the gamma band is associated with cortical activation during the imagination of body parts movement. It is also known that the ERD (event-related desynchronization) in the mu and beta band are caused by the imagination of body parts movement. In this study, we investigated the relationship between the gamma ERS and mu/beta ERDs. We recorded 64-channel EEG in order to obtain the power map of the gamma component. Furthermore, we compared the characteristics of the gamma waveform and mu/beta waveforms at the locations where the gamma ERS appeared clearly. As a result, we obtained three conclusions. Firstly, gamma ERS caused by the imagination of body parts movement appears at near somatosensory area and motor area. Gamma ERS caused by the imagination of right arm movement appears at the left side of the somatosenrosy area, that of left arm movement appears at the right side of the somatosensory area, and that of the foot movement appears at the center of the motor area. Secondly, mu/beta ERDs appear simultaneously with the preparation of the imagination, and they continue during the imagination. However, gamma ERS appeared simultaneously with the imagination of body parts movement. Finally, the power of the mu/beta component decrease gradually, but that of the gamma component increases significantly.