Rika Soma

Improvement of motor functions by noisy vestibular stimulation in central neurodegenerative disorders

Through the cerebellar vermis, the vestibular nerves are known to influence the basal ganglia and the limbic system. By means of noisy galvanic vestibular stimulation (GVS), it may be possible to ameliorate movement disorders, particularly akinesic symptoms, in patients with central neurodegenerative disorders. We evaluated the effect of 24-hour noisy GVS on a power-law temporal autocorrelation exponent of daytime wrist activity, separately for higher (local maxima) and lower (local minima) levels of activity, in 14 hospitalized patients. The power-law exponent for the local maxima was significantly (p < 0.002) lower with the noisy GVS than with sham stimulation, suggestive of more frequent switching behavior from low to high levels of activity or less severe akinesia. The noisy GVS may thus potentially improve certain motor dysfunctions in patients with distinct central neurodegenerative diseases.

Noise-induced compensation for postural hypotension in primary autonomic failure.

Noise can have a beneficial effect on sensory neurological systems, enhancing detection of small afferent signals and thereby improve efferent neural responses. We hypothesized whether a similar mechanism would facilitate impaired neural transmission associated with neurological disease, and tested whether addition of external noise to baroreceptor signaling could improve blunted autonomic efferent responses to a postural challenge in patients with primary autonomic failure (PAF). Five PAF patients were tested, one in duplicate and another triplicate, for their transient responses of heart rate (measured from electrocardiographic RR intervals; RRIs) and systolic (SBP) and diastolic (DBP) blood pressures to either 30 degrees or 60 degrees head-up tilt, with and without continuous application of beat-to-beat Gaussian white noise to the carotid sinus baroreceptors. Also, the effects of noise were compared with those by a continuous positive pressure applied to the carotid sinus baroreceptors. The data were fit to a first order model to evaluate the speed (by the time constant; tau) and the magnitudes (by the steady state gains; Gs) of RRI and blood pressure responses. The PAF patients exhibited marked drops in SBP and DBP and a blunted increase in heart rate upon transition from a supine to a head-up position. Addition of noise, not the continuous positive pressure, to the arterial baroreceptors significantly (P<0.05) increased the G in RRI and diminished the Gs in SBP and DBP, though the time courses (taus) of both the RRI and blood pressure responses were unaffected. The addition of external noise to baroreceptor signaling ameliorated the marked postural hypotension seen in patients with PAF.

Effect of endurance training on oxidation of lactate in mice after supramaximal exercise

Abstract The effect of endurance training on lactate metabolism after supramaximal exercise was investigated in male ddY mice. The blood lactate concentration 20 min after supramaximal exercise in the trained mice was significantly lower than that in the control mice. No significant effect of endurance training on the amount of 14CO2 expired from [14C]lactate injected was found during the recovery period from supramaximal exercise. The muscle [14C]glycogen concentration after 20 min of recovery in the trained mice was significantly higher than that in the control mice. These results suggest that endurance training does not enhance oxidative removal of lactate, which is the most important pathway of lactate metabolism, and activates muscle glycogen resynthesis from lactate in mice after supramaximal exercise.

Effect of dichloroacetate on oxidative removal of lactate in mice after supramaximal exercise

1. The effect of dichloroacetate (DCA), which activates substrate oxidation on oxidative removal of lactate in mice after supramaximal exercise was investigated. 2. DCA significantly decreased the blood lactate concentration and increased the oxidative removal of lactate during prolonged exercise. 3. No significant differences were found in the removal of the blood lactate concentration, in oxidative removal of lactate after supramaximal exercise. 4. It is concluded that DCA administration which activates lactate oxidation during exercise does not activate lactate oxidation in mice after supramaximal exercise.

Noise-induced sensitization of human brain

In the past decade, it has been recognized that noise can enhance the response of nonlinear systems to weak signals, via a mechanism known as stochastic resonance (SR). Particularly, the concept of SR has generated considerable interest in sensory biology, because it has been shown in several experimental studies that noise can assist neural systems in detecting weak signals which could not be detected in its absence. Recently, we have shown a similar type of noise-induced sensitization of human brain; externally added noise to the brain stem baroreflex centers sensitized their responses in maintaining adequate blood perfusion to the brain itself. Furthermore, the addition of noise has also shown to be useful in compensating for dysfunctions of the baroreflex centers in certain neurological diseases. It is concluded that the statistical physics concept of SR could be useful in sensitizing human brain in health and disease.

Functional stochastic resonance in human baroreflex induced by 1/f-type noisy galvanic vestibular stimulation

We hypothesized that 1/f noise is more beneficial than the conventional white noise in optimizing the brains response to a weak input signal, and showed that externally added 1/f noise outperforms white noise in sensitizing human baroreflex centers in the brain. We examined the compensatory heart rate response to weak periodic signal introduced at the venous blood pressure receptor, while adding either 1/f or white noise with the same variance to the brain stem by electrically stimulating the bilateral vestibular afferents cutaneously. This stochastic galvanic vestibular stimulation, activating the vestibulo-sympathetic pathway in the brain stem, optimized covariance between weak input signals and the heart rate responses both with 1/f and white noise. Further, the optimal noise level with 1/f noise was significantly lower than that with white noise, suggesting the functional benefit of 1/f noise for the neuronal information transfer in the brain.

Can Electrical Vestibular Noise Be Used for the Treatment of Brain Diseases

The therapy currently available for the treatment of degenerative neurological diseases is far from satisfactory, and a novel therapeutic strategy, especially for pharmacologically unresponsive patients, would be welcomed. The vestibular nerves are known to influence neuronal circuits in the medullary cardiovascular areas and, through the cerebellar vermis, the basal ganglia and the limbic system. By means of noisy galvanic vestibular stimulation (GVS), it may now be possible to ameliorate blunted responsiveness of degenerated neuronal circuits in the brains of multiple system atrophy (MSA) and/or Parkinson’s disease (PD) patients, through a mechanism known as stochastic resonance. We evaluate the effect of 24‐hour noisy GVS on long‐term heart rate dynamics in seven MSA patients, and on daytime locomotor activity dynamics in twelve patients with either PD or levodopa unresponsive parkinsonism. Short‐range heart rate variability and long‐range anti‐correlation of trunk activity are significantly increased ...

Functional Roles of Noise and Fluctuations in the Human Brain

In the past decade, it has been recognized that noise can enhance the response of nonlinear systems to weak signals, via a mechanism known as stochastic resonance (SR). In this short review, we introduce our experimental demonstration of SR‐type behavior in the human brain, and medical (neurological) applications and a possible mechanism of such phenomenon.

Noise‐Induced Sensitization of Human Brain: Toward the Neurological Application of Stochastic Resonance

In the past decade, it has been recognized that noise can enhance the response of nonlinear systems to weak signals, via a mechanism known as stochastic resonance (SR). Particularly, the concept of SR has generated considerable interest in sensory biology, because it has been shown in several experimental studies that noise can assist neural systems in detecting weak signals which could not be detected in its absence. Recently, we have shown a similar type of noise‐induced sensitization of human brain; externally added noise to the brain stem baroreflex centers sensitized their responses in maintaining adequate blood perfusion to the brain itself. Furthermore, the addition of noise has also shown to be useful in compensating for dysfunctions of the baroreflex centers in certain neurological diseases. It is concluded that the statistical physics concept of SR could be useful in sensitizing human brain in health and disease.