Yuko Kuwahara

Arousal electrical stimuli evoke sudomotor activity related to P300, and skin vasoconstrictor activity related to N140 in humans.

OBJECTIVE Arousal stimuli evoke bursts of skin sympathetic nerve activity (SSNA). SSNA usually contains sudomotor and vasoconstrictor neural spikes. The aim of this study was to elucidate which components of event-related potentials (ERPs) are related to sudomotor and vasoconstrictor responses comprising arousal SSNA bursts. METHODS We recorded SSNA from the tibial nerve by microneurography, with corresponding sympathetic skin response (SSR), sympathetic flow response (SFR), and ERPs in 10 healthy subjects. Electrical stimulation of the median nerve was used to induce arousal responses. ERPs were classified by the occurrence of SSR and SFR. RESULTS SSNA bursts followed by SSR were associated with larger P300 than SSNA bursts followed by no SSR. For N140, no difference in the amplitude was found between SSNA bursts with and without SSR. SSNA bursts followed by SFR were associated with larger N140 than SSNA bursts followed by no SFR. However, there were no differences in the amplitude of P300 between SSNA bursts with and without SFR. CONCLUSIONS Sudomotor and skin vasoconstrictor responses to arousal stimuli were differently associated with distinct ERP components. SIGNIFICANCE The possibility that sudomotor and skin vasoconstrictor activities comprising arousal SSNA reflect different stages of the cognitive process is suggested.

Effects of Defecation Strain at Various Bed Reclining Angles on Intrarectal Pressure and Cardiovascular Responses.

BackgroundThere is no clear information about the optimal bed reclining angle for promoting efficient and safe defecation in bedfast patients. ObjectiveThe aim of this study was to examine the optimal bed reclining angle for facilitating increases in intrarectal pressure without causing marked cardiovascular changes in order to develop an efficient and safe defecation position for bedfast patients. MethodsTwelve healthy men participated in this study. The subjects were required to strain for 15 seconds at the end stage of inspiration while their bed was reclined at 0° (supine), 15°, 30°, or 60°. During straining, the subjects were asked to maintain (a) an intrarectal pressure of 20 mm Hg or (b) the maximal intrarectal pressure. Intrarectal pressure, blood pressure, heart rate, and abdominal muscle activity (electromyographic activity) were recorded continuously throughout the study period. ResultsDuring straining, intrarectal pressure increased with the reclining angle, and a significant linear correlation was detected between the sine of the reclining angle of the bed and intrarectal pressure (&eegr;2 = .57, p < .01). When subjects were straining with the aim of maintaining maximal intrarectal pressure, the extent of the observed changes (delta) in blood pressure and heart rate did not differ significantly across the reclining angles. When subjects were straining with the aim of maintaining an intrarectal pressure of 20 mm Hg, the delta blood pressure decreased as the reclining angle increased 0°: M = 23.7, SD = 15.3 mm Hg, 95% CI [11.9, 35.4]; 15°: M = 25.9, SD = 10.8 mm Hg, 95% CI [17.6, 34.2]; 30°: M = 17.7, SD = 9.4 mm Hg, 95% CI [10.4, 24.9]; 60°: M = 15.5, SD = 9.5 mm Hg, 95% CI [8.1, 22.8]; 15° versus 30°: p < .05; 15° versus 60°: p < .05. The amount of muscle activity observed during straining decreased as the reclining angle increased. DiscussionIn bedfast patients, it is suggested that higher reclining angles may enable safer and more efficient defecation, because it decreases the amount of muscle activity required to increase the intrarectal pressure and reduces the potentially deleterious effects of straining on the cardiovascular system to develop an efficient and safe defecation position for bedfast patients.

Skin Sympathetic Nerve Activity and Thermoregulatory Control in Humans

Skin sympathetic nerve activity (SSNA) is microneurographically recorded from the skin nerve fascicle in the peripheral nerves with properties of an irregular, pulse asynchronous burst with respiratory variation, followed by sweating and/or vasoconstriction, elicited by mental stress and arousal stimuli. It comprises sudomotor and vasoconstrictor nerve activities as well as vasodilator ones. SSNA function in thermoregulation in humans, however, is also elicited by mental stress or cognition. SSNA is lowest at thermoneutral temperature and enhanced in the presence of ambient warm and cool air. Burst amplitude is well correlated to sweat rate change or skin blood flow reduction rate. The clinical application of SSNA comprises the following: (1) clarification of sweating events, (2) clarification and diagnosis of anhidrosis or hyperhidrosis, (3) clarification of thermoregulatory function and diagnosis of thermoregulatory disorder, (4) clarification of pathophysiology and diagnosis of vascular disorders, (5) clarification of the relationship between cognitive function and SSNA, and (6) determination of pharmacological effects attributable to change in neuroeffector responses. Lastly, SSNA’s significance as a feedforward thermoregulatory tool is discussed since SSNA contributes more to rapid thermoregulatory response than thermoregulation using convectional thermotransmission. Especially feedforward thermoregulatory sweating response is estimated to be highly phylogenetic than vasoconstrictive response.

11. Relationships between skin sympathetic nerve activities and evoked potentials induced by voluntary or involuntary muscle contractions: Comparison between sudomotor and vasoconstrictor components

Human brain mapping with near infrared spectroscopy (NIRS) measurements poses two major problems that limit its effectiveness for localizing cortical activation. One is lower spatial resolution and the other is artifacts due to physiological noises most exemplified by non-cortical skin blood flow changes. In this study, we propose a novel solution for these problems by simultaneously implementing a high-density probe arrangement and independent component analysis (ICA)-based signal processing. To achieve high spatial information density, oxygenated hemoglobin signals during a fast-finger-tapping (4 Hz) task were measured with double-density optical topography (DDOT), which consists of data from two alternately embedded single-density optical topographies (SDOT). Then, the measured signals were subjected to ICA to extract the signal components representing cortical activation. DDOT data can be decomposed into two different sets of SDOT data. Comparisons between SDOT and DDOT data revealed that DDOT portrayed both the spatially focused activation and the temporal structure relevant to hemodynamic response, whereas the SDOT data could only portray one or the other. The spatial resolution of DDOT might appear excessive, but it does indeed enable more efficient source separation than SDOT, leading to more robust spatial and temporal analyzes.

Valsalva maneuver effects on heart rate, blood pressure, and intrarectal pressure — Supine vs. sitting

To clarify the trajectory of the hypothalamo-spinal pathway involved with thermal sweating (TS), I made a qualitative study of 38 patients with lateral medullary syndrome, 37 infarctions and one probable inflammation. Five patients showed “normal” thermal sweating and 33 an “abnormal” thermal sweating; ipsilateral hypohidrosis was present chiefly in the upper body. Relative hypohidrosis in the side of the body opposite to the side of the brain lesionwas seen in 4 cases. Contralateral facial sweating before heating was seen in 4 cases. Quantitative data (mg/cm/min) from 13 subjects in the “abnormal” thermal sweating group were compared to those in age-matched control subjects with “normal” thermal sweating. Sweat volume (SV) at the forehead on the side contralateral to the lesion in the patient group was significantly larger than on the ipsilateral side (p=0.0007) and also larger than in the control group (p=0.0442). In contrast, sweat volume at the ipsilateral forearm in the patient group was significantly lesser than on the contralateral side (p=0.0012), and also lesser than in the control group. Sweat volume at the ipsilateral side of the forehead, at the contralateral forearm, and at both legs showed no significant difference between patients and control subjects. The results indicated that the hypothalamo-spinal pathway does not evenly innervate the entire body, but has some regional predominance. The hypohidrosis at the ipsilateral forearm suggests that the hypothalamo-spinal pathway may exert a facilitatory influence on sweating of the upper body. The absence of any apparent reduction of thermal sweating at the legs suggests that there might be crossing fibers in the hypothalamo-spinal pathway involved in the thermal sweating of the lower body; another possibility is that there are cross-communicating fibers in more peripheral parts of the pathway, as suggested on morphological grounds by Cowley & Yeager (1964) and Webber (1956). Furthermore, excessive sweating at the forehead on the side contralateral to the lesion may be due mainly to a damage to the inhibitory pathway, and the pathway may be related predominantly to sweating of the upper body, particularly of the face and neck. (The Autonomic Nervous System, 47: 479–484, 2010)

P2-23 Time relationship between motor and sympathetic activation in a voluntary handgrip

intervals of heart rate and brain waves were analyzed for the evaluation of ANS and CNS function, respectively. This study was approved by the Ethics Committee of Shizuoka University. Results: Inhalation of the odor from YBGE in most subjects, but not all, tended to produce an increase in both parasympathetic nervous activity and in brain wave alpha/beta ratio. Conclusions: The odor of YBGE tended to stimulate ANS and CNS activity in within human subjects, but the extent of these changes varied individually, suggesting that an association between ANS and CNS is involved in odor-induced anti-stress in nervous system function. Further studies are required to further elucidate the effects of odor of green plants on the nervous system.

S6-4 Conduction velocity of C-fibers in humans

Patients with cortical myoclonus have motor cortex hyperexcitability, expressed neurophysiologically in the form of high-amplitude waves in the cortical components of the somatosensory-evoked potentials (giant SSEPs). We recently studied the HFOs in a group of 20 patients with cortical myoclonus of different origins, comparing the results obtained with the amplitude and latency of the classical SSEPs waves. Nine patients had no HFOs, and another nine patients had low-amplitude and/or delayed HFOs. The remaining two patients, the only without ataxia, had very high-amplitude HFOs with a long latency. These results suggest a heterogeneity in the pathophysiology of cortical myoclonus, and point toward a possible contribution of the cerebellum in the build-up of cortical high-frequency oscillations. On the other hand, the use of deep brain stimulation has allowed the direct recording of oscillatory activity from subcortical structures in human patients. During the last years, we have recorded high-frequency activity in the SSEPs in deep structures, like the VIM nucleus of the thalamus and the subthalamic nucleus, in several patients with deep brain stimulators implanted, including two subjects with cortical myoclonus.

P36-22 Relationship between cognitive function and sympathetic skin response evoked by muscle contraction

Conclusion: The symmetrically distributed PCA component during BP and NS could reflect activity of the premotor areas with radially oriented cortical generators. A second component started to appear during BP but was maximal and prevalent during MP. It probably represents bilateral activity of the motor cortex with generators oriented tangentially. Using PCA, it is possible to distinguish different components of the SRCP, probably corresponding to premotor and motor cortical activity.