Naotaka Sakai

An fMRI study of musicians with focal dystonia during tapping tasks.

Musician’s dystonia is a type of task specific dystonia for which the pathophysiology is not clear. In this study, we performed functional magnetic resonance imaging to investigate the motor-related brain activity associated with musician’s dystonia. We compared brain activities measured from subjects with focal hand dystonia and normal (control) musicians during right-hand, left-hand, and both-hands tapping tasks. We found activations in the thalamus and the basal ganglia during the tapping tasks in the control group but not in the dystonia group. For both groups, we detected significant activations in the contralateral sensorimotor areas, including the premotor area and cerebellum, during each tapping task. Moreover, direct comparison between the dystonia and control groups showed that the dystonia group had greater activity in the ipsilateral premotor area during the right-hand tapping task and less activity in the left cerebellum during the both-hands tapping task. Thus, the dystonic musicians showed irregular activation patterns in the motor-association system. We suggest that irregular neural activity patterns in dystonic subjects reflect dystonic neural malfunction and consequent compensatory activity to maintain appropriate voluntary movements.

Measurement of a number of indices of hand and movement angles in pianists with overuse disorders.

Abduction angles of the thumb and little finger, hand span, length of thumb, middle finger and little finger were measured using radiographs of the right hand with the thumb and the little finger abducted, in a comparative study of 220 pianists with overuse disorder and 62 unaffected pianists. Overuse disorders included tenosynovitis, lateral and medial epicondylitis, forearm flexor muscle pain, distal tendinitis of the wrist extensors and flexors and intrinsic muscle pain. Hand span or other hand size parameters showed significant differences, while abduction angles showed no difference. The patients’ group had smaller hand size than the controls when analyzed for tenosynovitis, epicondylitis and muscle pain. From these results we hypothesize that pianists with small hands tend to hyper-abduct and hyper-extend the thumb to attain greater hand span. Their little finger is also stiffer and the hypothenar muscle and the wrist flexors need greater strength to resist the reaction force in each piano key.

Strain in the nail at fingertip compression.

Purpose: Distribution of nail strain due to compressive force in the finger pulp was investigated.

The effect of measurement position on brachial-ankle pulse wave velocity.

Arterial stiffness measurements are primarily used for the early detection of arteriosclerosis. Methods and devices that can easily measure arterial stiffness at home are in demand. We propose a simple method for measuring brachial-ankle pulse wave velocity (baPWV) at home using a reclining chair and investigate the effects of positioning on baPWV measurement. We measured baPWV in 50 healthy men (21-70 years) in seven different measurement positions, including the supine position, sitting, sitting with the knees flexed at 45°, sitting with the knees flexed at 0°, reclining at 37°, reclining at 50°, and standing. BaPWV was significantly lower in the supine position (P < 0.01) than in the other positions. It was significantly higher in the sitting position (P < 0.01) than in the reclining position (37°). No changes in baPWV were seen changing the knee flexion angle alone while sitting. Strong correlations were also ob- served between baPWV in the supine position and that in other positions. We showed that baPWV in the supine position can be calcu- lated by making corrections to baPWV measured in the sitting position at a reclining angle. Utilizing this corrected value would allow easy measurement at home using a reclining chair.

Non-invasive Serum Cholesterol Detection Using Near-infrared Light Transmission

This paper investigated whether a simple, non-invasive blood vessel visualization technique using near-infrared light is suitable for determining serum cholesterol levels. Six-week-old male Wistar rats were divided into 6 groups (n = 10/group) and were fed either control diet alone or control diet with 0.5%, 1.0%, 1.25%, 1.5%, or 2.0% cholesterol for 8 weeks. A cuff was subsequently placed on the proximal part of the tail (cuff pressure, 80 mmHg), the tail distal to the compression site was exposed to near-infrared light (wavelength, 850 nm), and transmitted light was photographed. Near-infrared transmission images were acquired before and after cuff inflation, and hemoglobin and haematocrit levels in veins distal to the compression site were determined. Increased dietary cholesterol levels resulted in increased total serum cholesterol levels. Before cuff inflation, rats that were fed the 2.0% cholesterol diet had significantly lower hemoglobin levels than those that fed the control diet (P 150 mg/dL (r = 0.449, P 150 mg/dL, increased cholesterol levels affected erythrocyte membranes and probably reduced their deformability, resulting in decreased hemoglobin levels (anemia) with erythrocyte destruction in the spleen as the rate-determining factor. This decrease was detected as changes in near-infrared light transmission.

A Study on the Friction Characteristics of Human Finger Pulp

We developed an experimental device to measure the coefficient of friction of human finger pulp and investigated the influence of three factors (angle of contact with the friction surface, moisture condition of the fingertip, and roughness of the friction surface) on the coefficient of friction. Ten male subjects who had no hand injuries (average age : 23.8 years) were selected. Each subject was instructed to touch the friction plate (acryl plate) using the right index fingertip while applying a vertical force of approximately 20 N and then to slide the right index fingertip at a speed of approximately 5 mm/s. The angle of contact with the friction surface was defined as the angle between the central axis of the finger and the friction plate, and was set to 30, 45, and 60 degrees. In order to investigate the influence of the moisture condition, artificial sweat was applied to the fingertip to simulate three conditions (dry, appropriate moisture, and excess moisture conditions). In order to investigate the influence of the roughness of the friction surface, four aluminum plates processed by straight knurling under different conditions were used as friction plates to produce different surface roughnesses. The maximum coefficient of friction at the start of finger sliding was taken as the maximum coefficient of static friction μs, while the average coefficient of friction during sliding was taken as the coefficient of dynamic friction μk of the subject. As the angle of contact increased, μs and, μs tended to decrease, and μs at an angle of contact of 30 degrees was significantly greater than that at 60 degrees. No significant difference was observed for μk. With respect to the influence of the moisture condition, μk for the appropriate moisture condition was significantly greater than that for the dry condition. In addition, μk for the excess moisture condition did not differ from that for the dry condition. In the case of μs, there was no significant difference between the three conditions. With respect to the influence of the roughness of the friction surface, as the surface roughness increased, μs increased, and when the surface roughness exceeded a certain fixed level, it did not affect μs or μk.

Effect of Knee Flexion Angle and Tensile Direction on the Strength of Ligament Insertion to Bone

This study investigated how knee flexion angle and tensile direction affect the strength of anterior cruciate ligament (ACL) insertion to tibia using swine femur-ACL-tibia complexs. Four tensile tests at displacement rate of 10 mm/min were performed at flexion angles of 0°, 45°, and 90°on the condition that the tensile direction was along the tibial axias, and at flexion angle of 90° on the condition that the tensile direction was along the femoral axis. The modes of failure and load-displacement curves were measured and compared among all tensile tests. As for the mode of failure, there was a difference between the tensile direction along the tibial axis and along the femoral axis. At flexion angles of 0°, 45°, and 90°on tensile direction along the tibial axis, the ACL failure occurred initially by failure of posterior lateral bundle followed by failure of anterior medial bundle until the complete separation of ACL to tibia, whereas at flexion angle of 90 on tensile direction along the femoral axis, the avulsion fractures suddenly occurred. As for the load-displacement curve, the maximum load at flexion angle of 0° on tensile direction along the tibial axis was significantly larger than that at flexion angle of 90°. The maximum load at flexion angle of 90°on tensile direction along the femoral axis was larger than those at flexion angles of 45° and 90° on tensile direction along the tibial axis. Therefore, the strength of ACL insertion to tibia was affected by both knee flexion angle and tensile direction.