Biomedical subjects

Naofumi Tanaka

Publications and source records attributed to Naofumi Tanaka.

4 recordsLinked to original sources

PubMed2005

Motor strategies responsible for maintaining standing posture after deafferentation of the unilateral leg.

OBJECTIVE: To identify the motor strategies responsible for maintaining standing posture after deafferentation of the unilateral leg. DESIGN: Pretest-posttest, repeated-measures design. SETTING: A Japanese university hospital rehabilitation facility. PARTICIPANTS: Nine healthy subjects aged 25 to 32 years. INTERVENTION: Two separate sessions that consisted of prolonged standing (control task) and standing until the H-reflex disappeared through the application of an inflated pneumatic cuff above the right knee. MAIN OUTCOME MEASURES: Center of pressure (COP), hip and ankle joint positions, and electromyographic activities. RESULTS: In the control task, no time-related change during prolonged standing was found in any of the measured parameters. After deafferentation, the right soleus activity decreased significantly (P<.01), so the mean velocities of the COP in the anteroposterior and mediolateral directions were greater and the average COP position under the right foot shifted backward compared with those in the previous periods (P<.01). Also, the left tibialis anterior and soleus were activated, as was the bilateral gluteus medius. CONCLUSIONS: The unilateral loss of leg and foot sensory information necessitated additional regulatory activities to stabilize the standing posture. The newly organized posture appeared to partly simulate the standing posture in patients with sensory disturbance of a unilateral leg.

Adult↗

PubMed2005

Identification of a simple screening tool for dysphagia in patients with stroke using factor analysis of multiple dysphagia variables.

OBJECTIVE: To identify a most useful and simple clinical screening tool to predict videofluoroscopic aspiration in patients with stroke. DESIGN: Factor analysis of multiple dysphagia variables and sensitivity and specificity testing with chi-square test. PATIENTS: Sixty-one consecutive stroke patients with symptoms suggestive of dysphagia admitted to a university hospital and its 4 affiliated hospitals in Japan. METHODS: Factors were extracted from 6 oromotor examinations (lip closure, tongue movement, palatal elevation, gag reflex, voice quality and motor speech function), 2 swallow screen tests (saliva swallowing test and our modified water swallowing test using 30 ml of water) and 4 parameters evaluated with a videofluoroscopic swallow study. Sensitivity and specificity of each dysphagia-related variable was determined against aspiration in a videofluoroscopic swallow study. RESULTS: Factor analysis revealed that cough/voice change in the water swallowing test and aspiration on videofluoroscopic swallow study belonged to the same factor. Chi-square analysis showed that cough/voice change in the water swallowing test was the only variable that was significantly associated with aspiration on videofluoroscopic swallow study, with a sensitivity of 72% (95% CI: 61-83%) and a specificity of 67% (CI: 55-79%) as a predictor of aspiration (p<0.05). CONCLUSION: We recommend our modified 30 ml water-swallowing test as a useful single task-screening tool to detect aspiration.

Adult↗

PubMed2004

Spinal excitation and inhibition decrease as humans age.

Although changes in the soleus H-reflex (an electrical analog of the tendon jerk) with age have been examined in a number of studies, some controversy remains. Also, the effect of age on inhibitory reflexes has received little attention. The purpose of this paper was to examine some excitatory and inhibitory reflexes systematically in healthy human subjects having a wide range of ages. We confirmed that both the maximum H-reflex (Hmax) and the maximum M-wave (Mmax) (from direct stimulation of motor axons) decrease gradually with age. The decrease in Hmax was larger so the Hmax/Mmax ratio decreased dramatically with age. Interestingly, the modulation of the H-reflex during walking was essentially the same at all ages, suggesting that the pathways that modulate the H-reflex amplitude during walking are relatively well preserved during the aging process. We showed for the first time that the short-latency, reciprocal inhibitory pathways from the common peroneal nerve to soleus muscle and from the tibial nerve to the tibialis anterior muscle also decreased with age, when measured as a depression of ongoing voluntary activity. These results suggest that there may be a general decrease in excitability of spinal pathways with age. Thus, the use of age-matched controls is particularly important in assessing abnormalities resulting from disorders that occur primarily in the elderly.

Adult↗

PubMed2003

Spinal reciprocal inhibition in human locomotion.

The purpose of this paper was to study spinal inhibition during several different motor tasks in healthy human subjects. The short-latency, reciprocal inhibitory pathways from the common peroneal (CP) nerve to the soleus muscle and from the tibial nerve to the tibialis anterior muscle were studied as a depression of ongoing voluntary electromyograph (EMG) activity. First, the effect of stimulus intensity on the amount of inhibition was examined to decide an appropriate stimulation to study the task-dependent modulation of inhibition. Then, the inhibition at one level of stimulation (1.5 x motor threshold) was investigated during standing, walking, and running. The change in slope of inhibition vs. EMG level, which approximates the fraction of ongoing activity that is inhibited, decreased with CP stimulation from 0.52 during standing to 0.30 during fast walking (6 km/h) to 0.17 during running at 9 km/h. Similarly, the slope decreased with tibial nerve stimulation from 0.68 (standing) to 0.42 (fast walking) to 0.35 (running at 9 km/h). All differences, except the last one, were highly significant (P < 0.01, Student's t-test). However, the difference between walking (0.42) and running (0.36) at the same speed (6 km/h) was not significant with tibial nerve stimulation and only significant at P < 0.05 with CP nerve stimulation (0.30, 0.20). Also, the difference between standing (0.52) and slow walking (3 km/h; 0.41) with CP stimulation was not significant, but it was significant (P < 0.01) with tibial nerve stimulation (0.68, 0.49). In conclusion, our findings indicate that spinal reciprocal inhibition decreases substantially with increasing speed and only changes to a lesser extent with task.

Adult↗