| 1. |
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| 2. |
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| 3. |
- Kenet, T., et al.
(författare)
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Disconnectivity of the cortical ocular motor control network in autism spectrum disorders
- 2012
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Ingår i: Neuroimage. - : Elsevier BV. - 1053-8119. ; 61:4, s. 1226-1234
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Tidskriftsartikel (refereegranskat)abstract
- Response inhibition, or the suppression of prepotent but contextually inappropriate behaviors, is essential to adaptive, flexible responding. Individuals with autism spectrum disorders (ASD) consistently show deficient response inhibition during antisaccades. In our prior functional MRI study, impaired antisaccade performance was accompanied by reduced functional connectivity between the frontal eye field (FEF) and dorsal anterior cingulate cortex (dACC), regions critical to volitional ocular motor control. Here we employed magnetoencephalography (MEG) to examine the spectral characteristics of this reduced connectivity. We focused on coherence between FEF and dACC during the preparatory period of antisaccade and prosaccade trials, which occurs after the presentation of the task cue and before the imperative stimulus. We found significant group differences in alpha band mediated coherence. Specifically, neurotypical participants showed significant alpha band coherence between the right inferior FEF and right dACC and between the left superior FEF and bilateral dACC across antisaccade, prosaccade, and fixation conditions. Relative to the neurotypical group, ASD participants showed reduced coherence between these regions in all three conditions. Moreover, while neurotypical participants showed increased coherence between the right inferior FEF and the right dACC in preparation for an antisaccade compared to a prosaccade or fixation, ASD participants failed to show a similar increase in preparation for the more demanding antisaccade. These findings demonstrate reduced long-range functional connectivity in ASD, specifically in the alpha band. The failure in the ASD group to increase alpha band coherence with increasing task demand may reflect deficient top-down recruitment of additional neural resources in preparation to perform a difficult task. (C) 2012 Elsevier Inc. All rights reserved.
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| 4. |
- Krämer, Heidrun H, et al.
(författare)
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Central correlation of muscle sympathetic nerve activation during baroreflex unloading - a microneurography-positron emission tomography study
- 2014
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Ingår i: European Journal of Neuroscience. - : Wiley. - 0953-816X .- 1460-9568. ; 39:4, s. 623-629
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Tidskriftsartikel (refereegranskat)abstract
- The baroreceptor reflex controls spontaneous fluctuations in blood pressure. One major control variable of the baroreflex is the sympathetic vasoconstrictor activity to muscles [MSNA; burst frequency (BF) and burst incidence (BI)], which can be quantitatively assessed by microneurography. We aimed to investigate the central regions involved in baroreflex regulation of MSNA. Healthy men (mean age 25 years) participated in three experimental sessions. (i) Microneurography recordings of MSNA from the left peroneal nerve during rest and baroreflex unloading, induced by lower body negative pressure (LBNP; -40 mmHg). If MSNA could be reliably recorded throughout this procedure (n = 15), the subjects entered the positron emission tomography (PET) experiments. The two PET sessions took place in a randomised order. Cerebral glucose metabolism (18-fluorodeoxyglucose) was analysed after: (ii) baroreflex unloading (LBNP); and (iii) control condition (lying in the LBNP chamber without suction). The PET data were analysed employing SPM8. LBNP elicited a significant increase in MSNA in all successfully recorded subjects (BI: P = 0.001; F = 5.54; BF: P < 0.001; F = 36.59). As compared with the control condition, LBNP was associated with increased PET regional glucose metabolism bilaterally in the orbitofrontal cortex (OFC; BA 11, 47). Related to the rise of BF, there was increased activation of the left OFC (BA 11); related to the rise of BI there was increased activation of the brainstem corresponding to the rostral ventrolateral medulla. Our data support a role for the ventrolateral medulla and the OFC in baroreflex-mediated control of MSNA in humans. © 2013 Federation of European Neuroscience Societies and John Wiley & Sons Ltd.
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| 5. |
- Orekhova, Elena V, 1967, et al.
(författare)
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Auditory Cortex Responses to Clicks and Sensory Modulation Difficulties in Children with Autism Spectrum Disorders (ASD)
- 2012
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Ingår i: Plos One. - : Public Library of Science (PLoS). - 1932-6203. ; 7:6
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Tidskriftsartikel (refereegranskat)abstract
- Auditory sensory modulation difficulties are common in autism spectrum disorders (ASD) and may stem from a faulty arousal system that compromises the ability to regulate an optimal response. To study neurophysiological correlates of the sensory modulation difficulties, we recorded magnetic field responses to clicks in 14 ASD and 15 typically developing (TD) children. We further analyzed the P100m, which is the most prominent component of the auditory magnetic field response in children and may reflect preattentive arousal processes. The P100m was rightward lateralized in the TD, but not in the ASD children, who showed a tendency toward P100m reduction in the right hemisphere (RH). The atypical P100m lateralization in the ASD subjects was associated with greater severity of sensory abnormalities assessed by Short Sensory Profile, as well as with auditory hypersensitivity during the first two years of life. The absence of right-hemispheric predominance of the P100m and a tendency for its right-hemispheric reduction in the ASD children suggests disturbance of the RH ascending reticular brainstem pathways and/or their thalamic and cortical projections, which in turn may contribute to abnormal arousal and attention. The correlation of sensory abnormalities with atypical, more leftward, P100m lateralization suggests that reduced preattentive processing in the right hemisphere and/or its shift to the left hemisphere may contribute to abnormal sensory behavior in ASD.
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| 6. |
- Orekhova, Elena V, 1967, et al.
(författare)
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Auditory Magnetic Response to Clicks in Children and Adults: Its Components, Hemispheric Lateralization and Repetition Suppression Effect
- 2013
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Ingår i: Brain Topography. - : Springer Science and Business Media LLC. - 0896-0267 .- 1573-6792. ; 26:3, s. 410-427
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Tidskriftsartikel (refereegranskat)abstract
- The auditory magnetic event-related fields (ERF) qualitatively change through the child development, reflecting maturation of auditory cortical areas. Clicks presented with long inter-stimulus interval produce distinct ERF components, and may appear useful to characterize immature EFR morphology in children. The present study is aimed to investigate morphology of the auditory ERFs in school-age children, as well as lateralization and repetition suppression of ERF components evoked by the clicks. School-age children and adults passively listened to pairs of click presented to the right ear, left ear or binaurally, with 8-11 s intervals between the pairs and a 1 s interval within a pair. Adults demonstrated a typical P50m/N100m response. Unlike adults, children had two distinct components preceding the N100m-P50m (at similar to 65 ms) and P100m (at similar to 100 ms). The P100m dominated the child ERF, and was most prominent in response to binaural stimulation. The N100m in children was less developed than in adults and partly overlapped in time with the P100m, especially in response to monaural clicks. Strong repetition suppression was observed for P50m both in children and adults, P100m in children and N100m in adults. Both children and adults demonstrated ERF amplitude and/or latency right hemispheric advantage effects that may reflect right hemisphere dominance for preattentive arousal processes. Our results contribute to the knowledge concerning development of auditory processing and its lateralization in children and have implications for investigation of the auditory evoked fields in developmental disorders.
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| 7. |
- Ackerley, Rochelle, 1980, et al.
(författare)
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Cutaneous warmth, but not touch, increases muscle sympathetic nerve activity during a muscle fatigue hand-grip task
- 2020
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Ingår i: Experimental Brain Research. - : Springer Science and Business Media LLC. - 0014-4819 .- 1432-1106. ; 238, s. 1035-1042
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Tidskriftsartikel (refereegranskat)abstract
- In homeostasis, somatosensory C fibre afferents are hypothesised to mediate input to the brain about interactions with external stimuli and sympathetic efference provides the output that regulates bodily functions. We aimed to test this hypothesis and whether different types of innocuous somatosensory input have differential effects. Healthy volunteers performed a muscle fatigue (hand-grip) task to exhaustion, which produces increased muscle sympathetic nerve activity (MSNA), as measured through microneurography. Participants completed the muscle fatigue task without concurrent cutaneous sensory stimulation (control) or we applied skin warming (heat pack) as a C fibre stimulation, slow brush stroking as C and A beta fibre stimulation, or vibration as A beta fibre stimulation, to the participant's forearm. We also measured heart rate, the duration of the hand-grip task, and ratings of pain at the end of the task. Concurrent skin warming showed increased MSNA compared to the other conditions. Tactile stimuli (brushing, vibration) were not significantly different to the control (no intervention) condition. Warming increased the pain from the muscle contraction, whereas the tactile stimuli did not. We interpret the effect of warming on MSNA as providing relevant afferent information during muscle contraction, which needed to be counteracted via vasoconstriction to maintain homeostasis. Brushing and vibration were less homeostatically relevant stimuli for the muscle contraction and hence had no significant effect. The findings add sensory specificity to our current understanding of homeostatic regulation through somatosensory afferent and sympathetic efferent pathways.
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| 8. |
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| 9. |
- Donadio, V., et al.
(författare)
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Muscle sympathetic response to arousal predicts neurovascular reactivity during mental stress
- 2012
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Ingår i: Journal of Physiology-London. - : Wiley. - 0022-3751. ; 590:12, s. 2885-2896
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Tidskriftsartikel (refereegranskat)abstract
- Key points Mental stress (MS) is often initiated by a sensory or cognitive stimulus, which induces a brief arousal reaction followed by a longer stress phase. Both phases induce blood pressure (BP) increases whereas effects on muscle sympathetic nerve activity (MSNA) vary: in approximately 50% of healthy subjects (responders) arousal induces a brief MSNA reduction, which is absent in the remaining 50% (non-responders). We now report a link between the arousal response and neurovascular effects of MS in healthy males. Our data show that during MS, responders to arousal exhibited a significant decrease of MSNA and a lesser BP increase compared to non-responders. The whole material displayed a positive correlation between MSNA responses induced by arousal and MS. In addition, arousal induced MSNA changes correlated positively with BP changes during MS. We conclude that the MSNA response to arousal predicts MSNA and BP responses to MS.
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| 10. |
- Fhager, A., et al.
(författare)
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Microwave Diagnostics Ahead
- 2018
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Ingår i: Ieee Microwave Magazine. - : Institute of Electrical and Electronics Engineers (IEEE). - 1527-3342. ; 19:3, s. 78-90
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Tidskriftsartikel (refereegranskat)abstract
- Microwave technology has the potential to revolutionize how, when, and what care can be delivered to patients with acute, life-threatening medical conditions. The prospects are that microwave systems can both improve diagnostic ability and accuracy and enable earlier diagnosis. Early diagnosis is a key factor in acute situations, especially when breathing and circulation are affected. Conventional imaging modalities used for diagnostics, such as magnetic resonance imaging (MRI) and X-ray computed tomography (CT), are powerful but normally available only at hospitals.
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| 11. |
- Gustafsson, Karin M, 1983-
(författare)
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The importance of trust. : a study of knowledge production of biodiversity.
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The loss of biological diversity is one of today’s greatest environmental problems. Scientific knowledge is typically presented as the premise to solve this problem. However, science alone is not sufficient to produce knowledge of biodiversity. Other actors are also involved in knowledge production. The aim of this thesis is to analyse how different actors create knowledge of the environmental problem of biodiversity loss and to further investigate the importance of trust in the relationships between these knowledge producers.This thesis uses a discourse analytical perspective and conducts interviews and document studies to explore how actors use different narratives to legitimate their knowledge production. Through four papers addressing different aspects of knowledge production, this thesis discusses conditions for knowledge production, particularly the importance of trust.The results show that actors other than scientific experts also have the ability to act in knowledgeable ways and to be involved in knowledge production of biodiversity. Knowledge is produced by making use of many different dimensions and aspects, such as global, regional, local, and science, politics, and everyday life. The result also shows how trust, distrust, and as-if trust are key activities in knowledge production of environmental problems, such as the loss of biodiversity.This thesis argues that the actors involved need to realise and acknowledge that knowledge production is a mutual process in which actors must engage in trust and distrust activities. In so doing, it will be possible to understand the complexity of the loss of biodiversity and thus to better manage this problem.
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| 12. |
- Lambert, Elisabeth A, et al.
(författare)
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Single-unit muscle sympathetic nervous activity and its relation to cardiac noradrenaline spillover.
- 2011
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Ingår i: The Journal of physiology. - : Wiley. - 1469-7793 .- 0022-3751. ; 589:Pt 10, s. 2597-605
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Tidskriftsartikel (refereegranskat)abstract
- Recent work using single-unit sympathetic nerve recording techniques has demonstrated aberrations in the firing pattern of sympathetic nerves in a variety of patient groups. We sought to examine whether nerve firing pattern is associated with increased noradrenaline release. Using single-unit muscle sympathetic nerve recording techniques coupled with direct cardiac catheterisation and noradrenaline isotope dilution methodology we examined the relationship between single-unit firing patterns and cardiac and whole body noradrenaline spillover to plasma. Participants comprised patients with hypertension (n=6), depression (n=7) and panic disorder (n =9) who were drawn from our ongoing studies. The patient groups examined did not differ in their single-unit muscle sympathetic nerve firing characteristics nor in the rate of spillover of noradrenaline to plasma from the heart. The median incidence of multiple spikes per beat was 9%. Patients were stratified according to the firing pattern: low level of incidence (less than 9% incidence of multiple spikes per beat) and high level of incidence (greater than 9% incidence of multiple spikes per beat). High incidence of multiple spikes within a cardiac cycle was associated with higher firing rates (P <0.0001) and increased probability of firing (P <0.0001). Whole body noradrenaline spillover to plasma and (multi-unit) muscle sympathetic nerve activity in subjects with low incidence of multiple spikes was not different to that of those with high incidence of multiple spikes. In those with high incidence of multiple spikes there occurred a parallel activation of the sympathetic outflow to the heart, with cardiac noradrenaline spillover to plasma being two times that of subjects with low nerve firing rates (11.0 ± 1.5 vs. 22.0 ± 4.5 ng min⁻¹, P <0.05). This study indicates that multiple within-burst firing and increased single-unit firing rates of the sympathetic outflow to the skeletal muscle vasculature is associated with high cardiac noradrenaline spillover.
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| 13. |
- Lautenschlager, G., et al.
(författare)
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The impact of baroreflex function on endogenous pain control: a microneurography study
- 2015
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Ingår i: European Journal of Neuroscience. - : Wiley. - 0953-816X. ; 42:11, s. 2996-3003
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Tidskriftsartikel (refereegranskat)abstract
- The interaction between sympathetic vasoconstrictor activity to muscles [muscle sympathetic nerve activity (MSNA), burst frequency (BF) and burst incidence (BI)] and different stress and somatosensory stimuli is still unclear. Eighteen healthy men (median age 28 years) underwent microneurography recordings from the peroneal nerve. MSNA was recorded during heat pain (HP) and cold pain (CP) alone as well as combined with different stress tasks (mental arithmetic, singing, giving a speech). An additional nine healthy men (median age 26 years) underwent the stimulation protocol with an additional control task (thermal pain combined with listening to music) to evaluate possible attentional confounders. MSNA was significantly increased by CP and HP. CP-evoked responses were smaller. The diastolic blood pressure followed the time course of MSNA while heart rate remained unchanged. The mental stress tasks further increased MSNA and were sufficient to reduce pain while the control task had no effect. MSNA activity correlated negatively with pain intensity and positively with analgesia. High blood pressure values were associated with lower pain intensity. Our study indicates an impact of central sympathetic drive on pain and pain control.
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| 14. |
- Olausson, Håkan, 1965, et al.
(författare)
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Functional role of unmyelinated tactile afferents in human hairy skin: sympathetic response and perceptual localization.
- 2008
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Ingår i: Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale. - : Springer Science and Business Media LLC. - 1432-1106. ; 184:1, s. 135-40
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Tidskriftsartikel (refereegranskat)abstract
- In addition to A-beta fibres the human hairy skin has unmyelinated (C) fibres responsive to light touch. Previous functional magnetic resonance imaging (fMRI) studies in a subject with a neuronopathy who specifically lacks A-beta afferents indicated that tactile C afferents (CT) activate insular cortex, whereas no response was seen in somatosensory areas 1 and 2. Psychophysical tests suggested that CT afferents give rise to an inconsistent perception of weak and pleasant touch. By examining two neuronopathy subjects as well as control subjects we have now demonstrated that CT stimulation can elicit a sympathetic skin response. Further, the neuronopathy subjects' ability to localize stimuli which activate CT afferents was very poor but above chance level. The findings support the interpretation that the CT system is well suited to underpin affective rather than discriminative functions of tactile sensations.
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| 15. |
- Olausson, Håkan, 1965, et al.
(författare)
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Unmyelinated tactile afferents have opposite effects on insular and somatosensory cortical processing.
- 2008
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Ingår i: Neuroscience letters. - : Elsevier BV. - 0304-3940. ; 436:2, s. 128-32
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Tidskriftsartikel (refereegranskat)abstract
- A previous functional magnetic resonance imaging (fMRI) study of an A-beta deafferented subject (GL) showed that stimulation of tactile C afferents (CT) activates insular cortex whereas no activation was seen in somatosensory cortices. Psychophysical studies suggested that CT afferents contribute to affective but not to discriminative aspects of tactile stimulation. We have now examined cortical processing following CT stimulation in a second similarly deafferented subject (IW), as well as revisited the data from GL. The results in IW showed similar activation of posterior insular cortex following CT stimulation as in GL and so strengthen the view that CT afferents underpin emotional aspects of touch. In addition, CT stimulation evoked significant fMRI deactivation in somatosensory cortex in both subjects supporting the notion that CT is not a system for discriminative touch.
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| 16. |
- O'Reilly, L., et al.
(författare)
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Examining protective factors for substance use problems and self-harm behavior during adolescence: A longitudinal co-twin control study
- 2022
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Ingår i: Development and Psychopathology. - : Cambridge University Press (CUP). - 0954-5794 .- 1469-2198. ; 34:5, s. 1781-1802
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Tidskriftsartikel (refereegranskat)abstract
- Sports participation, physical activity, and friendship quality are theorized to have protective effects on the developmental emergence of substance use and self-harm behavior in adolescence, but existing research has been mixed. This ambiguity could reflect, in part, the potential for confounding of observed associations by genetic and environmental factors, which previous research has been unable to rigorously rule out. We used data from the prospective, population-based Child and Adolescent Twin Study in Sweden (n = 18,234 born 1994-2001) and applied a co-twin control design to account for potential genetic and environmental confounding of sports participation, physical activity, and friendship quality (assessed at age 15) as presumed protective factors for adolescent substance use and self-harm behavior (assessed at age 18). While confidence intervals widened to include the null in numerous co-twin control analyses adjusting for childhood psychopathology, parent-reported sports participation and twin-reported positive friendship quality were associated with increased odds of alcohol problems and nicotine use. However, parent-reported sports participation, twin-reported physical activity, and twin-reported friendship quality were associated with decreased odds of self-harm behavior. The findings provide a more nuanced understanding of the risks and benefits of putative protective factors for risky behaviors that emerge during adolescence.
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| 17. |
- Orekhova, Elena V, 1967, et al.
(författare)
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Excess of high frequency electroencephalogram oscillations in boys with autism.
- 2007
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Ingår i: Biological Psychiatry. - : Elsevier BV. - 0006-3223. ; 62:9, s. 1022-1099
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: An elevated excitation/inhibition ratio has been suggested as one mechanism underpinning autism. An imbalance between cortical excitation and inhibition may manifest itself in electroencephalogram (EEG) abnormalities in the high frequency range. The aim of this study was to investigate whether beta and gamma range EEG abnormalities are characteristic for young boys with autism (BWA). METHODS: EEG was recorded during sustained visual attention in two independent samples of BWA from Moscow and Gothenburg, aged 3 to 8 years, and in age matched typically developing boys (TDB). High frequency EEG spectral power was analyzed. RESULTS: In both samples, BWA demonstrated a pathological increase of gamma (24.4-44.0 Hz) activity at the electrode locations distant from the sources of myogenic artefacts. In both samples, the amount of gamma activity correlated positively with degree of developmental delay in BWA. CONCLUSIONS: The excess of high frequency oscillations may reflect imbalance in the excitation-inhibition homeostasis in the cortex. Given the important role of high frequency EEG rhythms for perceptual and cognitive processes, early and probably genetically determined abnormalities in the neuronal mechanisms generating high frequency EEG rhythms may contribute to development of the disorder. Further studies are needed to investigate the specificity of the findings for autism.
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| 18. |
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| 19. |
- Stroganova, Tatiana A, et al.
(författare)
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Abnormal EEG lateralization in boys with autism.
- 2007
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Ingår i: Clinical Neurophysiology. - : Elsevier BV. - 1388-2457. ; 118:8, s. 1842-1854
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: Functional brain abnormalities associated with autism in 3-8-year-old boys were studied with EEG recorded under controlled experimental condition of sustained visual attention and behavioral stillness. METHODS: EEG was recorded in two independent samples of boys with autism (BWA) from Moscow (N=21) and Gothenburg (N=23) and a corresponding number of age-matched typically developing boys (TDB). EEG spectral power (SP) and SP interhemispheric asymmetry within delta, theta and alpha bands were analyzed. RESULTS: BWA comprised a non-homogeneous group in relation to theta and alpha SP. When four outliers were excluded the only between-group difference in absolute SP was a higher amount of prefrontal delta in BWA. BWA of both samples demonstrated atypical leftward broadband EEG asymmetry with a maximum effect over the mid-temporal regions. Concurrently, the normal leftward asymmetry of mu rhythm was absent in BWA. CONCLUSIONS: The abnormal broadband EEG asymmetry in autism may point to a diminished capacity of right temporal cortex to generate EEG rhythms. The concurrent lack of normal leftward asymmetry of mu rhythm suggests that abnormalities in EEG lateralization in autism may be regionally/functionally specific. SIGNIFICANCE: The data provide evidence for abnormal functional brain lateralization in autism.
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| 20. |
- Sverrisdóttir, Y B, et al.
(författare)
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Is the somatotropic axis related to sympathetic nerve activity in healthy ageing men?
- 2001
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Ingår i: Journal of hypertension. - 0263-6352. ; 19:11, s. 2019-24
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Tidskriftsartikel (refereegranskat)abstract
- The mechanisms underlying the age-related increase in blood pressure and sympathetic nerve activity remain largely unknown. The decline in growth hormone (GH) secretion and insulin-like growth factor-I (IGF-I) with age has been related to several cardiovascular risk factors. Low serum IGF-I levels in severe adult GH deficiency is associated with markedly increased sympathetic nerve activity. This study evaluates whether a relationship between serum IGF-I and sympathetic nerve traffic exists in healthy aging men.Sympathetic nerve activity to the muscle vascular bed (MSA) was recorded in 56 healthy normotensive males, and related to age (range 21-71 years), body mass index (BMI, range 18.4-32.2), serum IGF-I and plasma nitrate levels. Blood pressure, BMI and MSA increased with age, whereas IGF-I and plasma nitrate decreased. In a forward stepwise multiple regression analysis, age explained 40% of the variability in MSA and excluded other variables. Omitting age, IGF-I became the strongest independent predictor, explaining 23% of the variability in MSA. MSA was an independent predictor of diastolic blood pressure, but its influence (10%) was less than that of BMI (28%). BMI was not related to MSA or IGF-I.Decreased serum IGF-I levels are coupled to increased MSA during ageing, an effect independent from the impact of increased body weight. Although MSA is a weak predictor of rising blood pressure with age, it constitutes one possible pathway for the somatotropic axis to affect cardiovascular function in ageing.
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| 21. |
- Sverrisdóttir, Y B, et al.
(författare)
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Sympathetic neural burst amplitude distribution: A more specific indicator of sympathoexcitation in human heart failure.
- 2000
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Ingår i: Circulation. - 1524-4539. ; 102:17, s. 2076-81
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Tidskriftsartikel (refereegranskat)abstract
- Human muscle sympathetic nerve activity (MSNA) is usually measured as the number of pulse-synchronous bursts in multiunit mean voltage recordings. We recently suggested burst amplitude distribution as a more sensitive indicator of altered MSNA in congestive heart failure (CHF). Here, we test whether this distribution can discriminate between different conditions with increased MSNA burst frequency and whether it reflects single vasoconstrictor fiber firing intensity.We analyzed resting multiunit MSNA in 36 CHF patients (24 with mild to moderate CHF, 12 with severe CHF investigated before and after heart transplantation), 14 patients with pituitary deficiency, 25 matched healthy control subjects, and an additional 56 healthy men with a wider age range (21 to 71 years). Pituitary deficiency was associated with increased MSNA burst frequency (60 versus 37 bursts/min in control subjects), equivalent to that in mild to moderate CHF (61 bursts/min). However, burst amplitude distribution in hypopituitary patients (median burst amplitude, 37%) did not deviate from matched control subjects (36%), whereas amplitudes increased with disease severity in CHF (43% in mild to moderate, 52% in severe) and normalized after transplantation (36%). In the larger healthy group, MSNA burst frequency increased with age, and burst amplitude distribution remained unaffected. In 8 CHF patients, single-unit firing frequency showed a close positive relationship to multiunit burst amplitude distribution (r=0.82, P:<0.01) but none to burst frequency (r=0.39, P:=0.3).Muscle vasoconstrictor fiber activity is better reflected by multiunit MSNA burst amplitude distribution than by burst frequency, at least in CHF. This distribution can discriminate between conditions with increased burst frequency.
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| 22. |
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| 23. |
- Wallin, Gunnar B, 1936, et al.
(författare)
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Two neural mechanisms for respiration-induced cutaneous vasodilatation in humans?
- 1998
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Ingår i: The Journal of physiology. - : Wiley. - 0022-3751. ; 513 ( Pt 2), s. 559-69
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Tidskriftsartikel (refereegranskat)abstract
- 1. In humans, a deep breath is known to induce cutaneous vasoconstriction in the warm state, and vasodilatation in the cold state. To investigate whether vasodilatation in the cold state is related to reduction of sympathetic vasoconstrictor nerve traffic, we studied the effect of a deep breath on vascular resistance in a skin area on the dorsum of the hand, in which release of noradrenaline from sympathetic nerves was blocked by iontophoretic pretreatment with bretylium tosylate. Simultaneous measurements were made in two control areas. In eight healthy subjects, data were obtained from deep breaths taken before bretylium in the warm state, after general cooling to a finger skin temperature below 25 C and after rewarming to above 32 C. 2. In the warm state before bretylium pretreatment, the deep breath evoked short-lasting vasoconstrictions at all sites. In the cold state there was no change of vascular resistance in the bretylium-pretreated area, whereas in the control areas an initial tendency towards vasoconstriction was followed by a significant transient vasodilatation. After rewarming, transient vasoconstrictions reappeared at the control sites, whereas only a transient vasodilatation occurred at the bretylium-pretreated site. 3. In six healthy subjects we also monitored the effects of a deep breath on skin sympathetic nerve activity (recorded by microneurography in the peroneal nerve), and skin vascular resistance within the innervation zone of the impaled nerve fascicle in the foot. Data from thirty deep breaths per subject were averaged. 4. In the cold state, the deep breath induced a strong increase in neural discharge, followed by a transient reduction of nerve traffic lasting approximately 15 s and associated with a subsequent reduction of vascular resistance. 5. We conclude that the deep breath-induced vasodilatation in the cold state is due to reduction of sympathetic vasoconstrictor nerve traffic. The vasodilatation after bretylium treatment in the warm state raises the possibility that a deep breath induces two simultaneous neural reactions, a vasoconstrictor and an active vasodilator component, the latter being weaker and normally masked by the strong vasoconstrictor component.
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