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Shoemaker JK, Gros R. A century of exercise physiology: key concepts in neural control of the circulation. Eur J Appl Physiol 2024; 124:1323-1336. [PMID: 38441688 PMCID: PMC11055701 DOI: 10.1007/s00421-024-05451-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2023] [Accepted: 02/26/2024] [Indexed: 04/28/2024]
Abstract
Early in the twentieth century, Walter B. Cannon (1871-1945) introduced his overarching hypothesis of "homeostasis" (Cannon 1932)-the ability to sustain physiological values within a narrow range necessary for life during periods of stress. Physical exercise represents a stress in which motor, respiratory and cardiovascular systems must be integrated across a range of metabolic stress to match oxygen delivery to oxygen need at the cellular level, together with appropriate thermoregulatory control, blood pressure adjustments and energy provision. Of these, blood pressure regulation is a complex but controlled variable, being the function of cardiac output and vascular resistance (or conductance). Key in understanding blood pressure control during exercise is the coordinating role of the autonomic nervous system. A long history outlines the development of these concepts and how they are integrated within the exercise context. This review focuses on the renaissance observations and thinking generated in the first three decades of the twentieth century that opened the doorway to new concepts of inquiry in cardiovascular regulation during exercise. The concepts addressed here include the following: (1) exercise and blood pressure, (2) central command, (3) neurovascular transduction with emphasis on the sympathetic nerve activity and the vascular end organ response, and (4) tonic neurovascular integration.
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Affiliation(s)
- J Kevin Shoemaker
- School of Kinesiology, The University of Western Ontario, London, ON, N6A 3K7, Canada.
- Department of Physiology and Pharmacology, The University of Western Ontario, London, ON, N6A 3K7, Canada.
| | - Robert Gros
- Department of Physiology and Pharmacology, The University of Western Ontario, London, ON, N6A 3K7, Canada
- Department of Medicine, The University of Western Ontario, London, ON, N6A 3K7, Canada
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Groenland EH, van Kleef MEAM, Hendrikse J, Spiering W, Siero JCW. The effect of endovascular baroreflex amplification on central sympathetic nerve circuits and cerebral blood flow in patients with resistant hypertension: A functional MRI study. FRONTIERS IN NEUROIMAGING 2022; 1:924724. [PMID: 37555165 PMCID: PMC10406262 DOI: 10.3389/fnimg.2022.924724] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/20/2022] [Accepted: 06/28/2022] [Indexed: 08/10/2023]
Abstract
BACKGROUND Endovascular baroreflex amplification (EVBA) by implantation of the MobiusHD is hypothesized to lower blood pressure by decreasing sympathetic activity through the mechanism of the baroreflex. In the present exploratory study we investigated the impact of MobiusHD implantation on central sympathetic nerve circuits and cerebral blood flow (CBF) in patients with resistant hypertension. MATERIALS AND METHODS In thirteen patients, we performed blood oxygenation level-dependent functional magnetic resonance imaging (BOLD fMRI) at rest and during Valsalva maneuvers, before and 3 months after EVBA. Data were analyzed using a whole-brain approach and a brainstem-specific analysis. CBF was assessed using arterial spin labeling MRI. RESULTS Resting-state fMRI analysis did not reveal significant differences in functional connectivity at 3 months after EVBA. For the Valsalva maneuver data, the whole-brain fMRI analysis revealed significantly increased activation in the posterior and anterior cingulate, the insular cortex, the precuneus, the left thalamus and the anterior cerebellum. The brainstem-specific fMRI analysis showed a significant increase in BOLD activity in the right midbrain 3 months after EVBA. Mean gray matter CBF (partial volume corrected) decreased significantly from 48.9 (9.9) ml/100 gr/min at baseline to 43.4 (13.0) ml/100 gr/min (p = 0.02) at 3 months. CONCLUSIONS This first fMRI pilot study in patients with resistant hypertension treated with EVBA showed a significant increase in BOLD activity during the Valsalva maneuver in brain regions related to sympathetic activity. No notable signal intensity changes were observed in brain areas involved in the baroreflex circuit. Future randomized controlled studies are needed to investigate whether the observed changes are directly caused by EVBA. CLINICAL TRIAL REGISTRATION www.clinicaltrials.gov, identifier: NCT02827032.
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Affiliation(s)
- Eline H. Groenland
- Department of Vascular Medicine, University Medical Center Utrecht, Utrecht University, Utrecht, Netherlands
| | - Monique E. A. M. van Kleef
- Department of Vascular Medicine, University Medical Center Utrecht, Utrecht University, Utrecht, Netherlands
| | - Jeroen Hendrikse
- Department of Radiology, University Medical Center Utrecht, Utrecht University, Utrecht, Netherlands
| | - Wilko Spiering
- Department of Vascular Medicine, University Medical Center Utrecht, Utrecht University, Utrecht, Netherlands
| | - Jeroen C. W. Siero
- Department of Radiology, University Medical Center Utrecht, Utrecht University, Utrecht, Netherlands
- Spinoza Centre for Neuroimaging Amsterdam, Amsterdam, Netherlands
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Forstenpointner J, Maallo AMS, Elman I, Holmes S, Freeman R, Baron R, Borsook D. The Solitary Nucleus Connectivity to Key Autonomic Regions in Humans MRI and Literature based Considerations. Eur J Neurosci 2022; 56:3938-3966. [PMID: 35545280 DOI: 10.1111/ejn.15691] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2021] [Revised: 05/04/2022] [Accepted: 05/05/2022] [Indexed: 11/03/2022]
Abstract
The nucleus tractus solitarius (NTS), is a key brainstem structure relaying interoceptive peripheral information to the interrelated brain centers for eliciting rapid autonomic responses and for shaping longer-term neuroendocrine and motor patterns. Structural and functional NTS' connectivity has been extensively investigated in laboratory animals. But there is limited information about NTS' connectome in humans. Using MRI, we examined diffusion and resting state data from 20 healthy participants in the Human Connectome Project. The regions within the brainstem (n=8), subcortical (n=6), cerebellar (n=2) and cortical (n=5) parts of the brain were selected via a systematic review of the literature and their white matter NTS connections were evaluated via probabilistic tractography along with functional and directional (i.e., Granger-causality) analyses. The underlying study confirms previous results from animal models and provides novel aspects on NTS integration in humans. Two key findings can be summarized: (i) the NTS predominantly processes afferent input and (ii) a lateralization towards a predominantly left-sided NTS processing. Our results lay the foundations for future investigations into the NTS' tripartite role comprised of interoreceptors' input integration, the resultant neurochemical outflow and cognitive/affective processing. The implications of these data add to the understanding of NTS' role in specific aspects of autonomic functions.
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Affiliation(s)
- Julia Forstenpointner
- Center for Pain and the Brain, Boston Children's Hospital, Department of Anesthesia, Critical Care and Pain Medicine, Harvard Medical School, Boston, MA, USA.,Division of Neurological Pain Research and Therapy, Department of Neurology, University Hospital Schleswig-Holstein, Kiel, Germany
| | - Anne Margarette S Maallo
- Center for Pain and the Brain, Boston Children's Hospital, Department of Anesthesia, Critical Care and Pain Medicine, Harvard Medical School, Boston, MA, USA
| | - Igor Elman
- Center for Pain and the Brain, Boston Children's Hospital, Department of Anesthesia, Critical Care and Pain Medicine, Harvard Medical School, Boston, MA, USA.,Cambridge Health Alliance, Harvard Medical School, Cambridge, MA, USA
| | - Scott Holmes
- Center for Pain and the Brain, Boston Children's Hospital, Department of Anesthesia, Critical Care and Pain Medicine, Harvard Medical School, Boston, MA, USA
| | - Roy Freeman
- Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA
| | - Ralf Baron
- Division of Neurological Pain Research and Therapy, Department of Neurology, University Hospital Schleswig-Holstein, Kiel, Germany
| | - David Borsook
- Center for Pain and the Brain, Boston Children's Hospital, Department of Anesthesia, Critical Care and Pain Medicine, Harvard Medical School, Boston, MA, USA.,Department of Radiology and Psychiatry, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA
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Pal A, Ogren JA, Aguila AP, Aysola R, Kumar R, Henderson LA, Harper RM, Macey PM. Functional organization of the insula in men and women with obstructive sleep apnea during Valsalva. Sleep 2021; 44:5864015. [PMID: 32592491 DOI: 10.1093/sleep/zsaa124] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2020] [Revised: 05/11/2020] [Indexed: 12/26/2022] Open
Abstract
STUDY OBJECTIVES Obstructive sleep apnea (OSA) patients show impaired autonomic regulation, perhaps related to functional reorganization of the insula, which in healthy individuals shows sex-specific anterior and right dominance during sympathetic activation. We examined insular organization of responses to a Valsalva maneuver in OSA with functional magnetic resonance imaging (fMRI). METHODS We studied 43 newly diagnosed OSA (age mean ± SD: 46.8 ± 8.7 years; apnea-hypopnea index (AHI) ± SD: 32.1 ± 20.1 events/hour; 34 males) and 63 healthy (47.2 ± 8.8 years; 40 males) participants. Participants performed four 18-second Valsalva maneuvers (1-minute intervals, pressure ≥ 30 mmHg) during scanning. fMRI time trends from five insular gyri-anterior short (ASG); mid short (MSG); posterior short (PSG); anterior long (ALG); and posterior long (PLG)-were assessed for within-group responses and between-group differences with repeated measures ANOVA (p < 0.05); age and resting heart rate (HR) influences were also assessed. RESULTS Right and anterior fMRI signal dominance appeared in OSA and controls, with no between-group differences. Separation by sex revealed group differences. Left ASG anterior signal dominance was lower in OSA versus control males. Left ASG and ALG anterior dominance was higher in OSA versus control females. In all right gyri, only OSA females showed greater anterior dominance than controls. Right dominance was apparent in PSG and ALG in all groups; females showed right dominance in MSG and PLG. OSA males did not show PLG right dominance. Responses were influenced substantially by HR but modestly by age. CONCLUSIONS Anterior and right insular fMRI dominance appears similar in OSA versus control participants during the sympathetic phase of the Valsalva maneuver. OSA and control similarities were present in just males, but not necessarily females, which may reflect sex-specific neural injury.
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Affiliation(s)
- Amrita Pal
- UCLA School of Nursing, University of California, Los Angeles, CA
| | - Jennifer A Ogren
- Department of Neurobiology, David Geffen School of Medicine at UCLA, University of California, Los Angeles, CA
| | - Andrea P Aguila
- UCLA School of Nursing, University of California, Los Angeles, CA
| | - Ravi Aysola
- Division of Pulmonary and Critical Care, David Geffen School of Medicine at UCLA, University of California, Los Angeles, CA
| | - Rajesh Kumar
- Department of Anesthesiology, David Geffen School of Medicine at UCLA, University of California, Los Angeles, CA.,Department of Radiological Sciences, David Geffen School of Medicine at UCLA, University of California, Los Angeles, CA
| | - Luke A Henderson
- Department of Anatomy and Histology, Sydney Medical School, University of Sydney, Sydney, Australia
| | - Ronald M Harper
- Department of Neurobiology, David Geffen School of Medicine at UCLA, University of California, Los Angeles, CA
| | - Paul M Macey
- UCLA School of Nursing, University of California, Los Angeles, CA
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Pal A, Ogren JA, Aysola RS, Kumar R, Henderson LA, Harper RM, Macey PM. Insular functional organization during handgrip in females and males with obstructive sleep apnea. PLoS One 2021; 16:e0246368. [PMID: 33600443 PMCID: PMC7891756 DOI: 10.1371/journal.pone.0246368] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2020] [Accepted: 01/18/2021] [Indexed: 11/18/2022] Open
Abstract
STUDY OBJECTIVES Brain regulation of autonomic function in obstructive sleep apnea (OSA) is disrupted in a sex-specific manner, including in the insula, which may contribute to several comorbidities. The insular gyri have anatomically distinct functions with respect to autonomic nervous system regulation; yet, OSA exerts little effect on the organization of insular gyral responses to sympathetic components of an autonomic challenge, the Valsalva. We further assessed neural responses of insular gyri in people with OSA to a static handgrip task, which principally involves parasympathetic withdrawal. METHODS We measured insular function with blood oxygen level dependent functional MRI. We studied 48 newly-diagnosed OSA (age mean±std:46.5±9 years; AHI±std:32.6±21.1 events/hour; 36 male) and 63 healthy (47.2±8.8 years;40 male) participants. Subjects performed four 16s handgrips (1 min intervals, 80% subjective maximum strength) during scanning. fMRI time trends from five insular gyri-anterior short (ASG); mid short (MSG); posterior short (PSG); anterior long (ALG); and posterior long (PLG)-were assessed for within-group responses and between-group differences with repeated measures ANOVA (p<0.05) in combined and separate female-male models; age and resting heart-rate (HR) influences were also assessed. RESULTS Females showed greater right anterior dominance at the ASG, but no differences emerged between OSA and controls in relation to functional organization of the insula in response to handgrip. Males showed greater left anterior dominance at the ASG, but there were also no differences between OSA and controls. The males showed a group difference between OSA and controls only in the ALG. OSA males had lower left activation at the ALG compared to control males. Responses were mostly influenced by HR and age; however, age did not impact the response for right anterior dominance in females. CONCLUSIONS Insular gyri functional responses to handgrip differ in OSA vs controls in a sex-based manner, but only in laterality of one gyrus, suggesting anterior and right-side insular dominance during sympathetic activation but parasympathetic withdrawal is largely intact, despite morphologic injury to the overall structure.
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Affiliation(s)
- Amrita Pal
- UCLA School of Nursing, University of California, Los Angeles, California, United States of America
| | - Jennifer A. Ogren
- Department of Neurobiology, University of California, Los Angeles, California, United States of America
| | - Ravi S. Aysola
- Division of Pulmonary and Critical Care, David Geffen School of Medicine at UCLA, University of California, Los Angeles, California, United States of America
| | - Rajesh Kumar
- Department of Anesthesiology, University of California, Los Angeles, California, United States of America
- Department of Radiological Sciences, University of California, Los Angeles, California, United States of America
| | - Luke A. Henderson
- Department of Anatomy and Histology, Sydney Medical School, University of Sydney, Sydney, Australia
| | - Ronald M. Harper
- Department of Neurobiology, University of California, Los Angeles, California, United States of America
| | - Paul M. Macey
- UCLA School of Nursing, University of California, Los Angeles, California, United States of America
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Baker J, Kimpinski K. Evidence of Impaired Cerebellar Connectivity at Rest and During Autonomic Maneuvers in Patients with Autonomic Failure. THE CEREBELLUM 2020; 19:30-39. [PMID: 31529276 DOI: 10.1007/s12311-019-01076-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The objective of the current study was to investigate whether patients with neurogenic orthostatic hypotension (NOH) secondary to autonomic failure have impaired functional connectivity between the cerebellum and central autonomic structures during autonomic challenges. Fifteen healthy controls (61 ± 14 years) and 15 NOH patients (67 ± 6 years; p = 0.12) completed the following tasks during a functional brain MRI: (1) 5 min of rest, (2) 5 min of lower-body negative pressure (LBNP) performed at - 35 mmHg, and (3) Three, 15-s Valsalva maneuvers (VM) at 40 mmHg. Functional connectivity (Conn Toolbox V18) between central autonomic structures and discrete cerebellar regions involved in cardiovascular autonomic control, including the vermis and posterior cerebellum, was assessed using a regions-of-interest approach during rest, LBNP and VM. Functional connectivity was contrasted between controls and patients with autonomic failure. At rest, controls had significantly more intra-cerebellar connectivity and more connectivity between cerebellar lobule 9 and key central autonomic structures, including: bilateral anterior insula (TR-value: 4.84; TL-value: 4.51), anterior cingulate cortex (T-value: 3.41) and bilateral thalamus (TR-value: 3.95; TL-value: 4.51). During autonomic maneuvers, controls showed significantly more connectivity between cardiovascular cerebellar regions (lobule 9 and anterior vermis) and important autonomic regulatory sites, including the brainstem, hippocampus and cingulate: vermis-brainstem (T-value: 4.31), lobule 9-brainstem (TR-value, 5.29; TL-value, 4.53), vermis-hippocampus (T-value, 4.63), and vermis-cingulate (T-value, 4.18). Anatomical and functional studies in animals and humans substantiate a significant role for the cerebellum in cardiovascular autonomic control during postural adjustments. In the current study, patients with NOH related to autonomic failure showed evidence of reduced connectivity between cardiovascular cerebellar regions and several important central autonomic structures, including the brainstem. The cerebellum is an established structure in cardiovascular autonomic control; therefore, evidence of impaired cerebellar connectivity to other autonomic structures may further contribute to the inability to properly regulate blood pressure during postural changes in NOH patients.
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Affiliation(s)
- Jacquie Baker
- School of Kinesiology, Western University, London, Ontario, Canada. .,Department of Clinical Neurological Sciences, University Hospital, London Health Sciences Centre, Rm. B7-140, 339 Windermere Road, London, Ontario, N6A 5A5, Canada.
| | - Kurt Kimpinski
- School of Kinesiology, Western University, London, Ontario, Canada.,Department of Clinical Neurological Sciences, University Hospital, London Health Sciences Centre, Rm. B7-140, 339 Windermere Road, London, Ontario, N6A 5A5, Canada.,Schulich School of Medicine & Dentistry, Western University, London, Ontario, Canada
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Baker J, Kimpinski K. Reduced brainstem functional connectivity in patients with peripheral autonomic failure. NEUROIMAGE-CLINICAL 2019; 23:101924. [PMID: 31491816 PMCID: PMC6617337 DOI: 10.1016/j.nicl.2019.101924] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/12/2019] [Revised: 05/31/2019] [Accepted: 06/30/2019] [Indexed: 12/30/2022]
Abstract
Autonomic homeostasis is dependent upon several brainstem nuclei, as well as several cortical and subcortical structures. Together, these sites make up, in part, the central autonomic network. Neurogenic orthostatic hypotension (NOH) is a cardinal feature of autonomic failure that occurs due to a failure to increase sympathetic efferent activity in response to postural changes. Therefore, the purpose of the current study was to investigate brainstem functional connectivity in NOH patients with peripheral autonomic lesions resulting in autonomic failure. Fifteen controls (63 ± 13 years) and fifteen Neurogenic Orthostatic Hypotension patients (67 ± 6 years; p = .2) with peripheral autonomic dysfunction completed 5-min of rest and three Valsalva maneuvers during a functional brain scan. Functional connectivity from the brainstem to cortical and subcortical structures were contrasted between patients and controls. At rest controls had significantly greater brainstem connectivity to the anterior cingulate cortex (T-value: 4.29), left anterior insula (T-value:3.31), left putamen (T-value:3.31) and bilateral thalamus (TRIGHT-value: 3.83; TLEFT-value:4.25) (p-FDR < 0.005). During Valsalva, controls showed significantly more connectivity between the brainstem and both the left anterior (cerebellum 4/5) and bilateral posterior cerebellum (cerebellar 9 and left cerebellar 6). Other cerebellar regions included brainstem-to-vermis. Other brainstem-to-cortical and subcortical regions included: bilateral putamen, posterior cingulate cortex (PCC), amygdala and medial prefrontal cortex. There was a significant negative correlation between the brainstem-cerebellar connectivity and severity of autonomic dysfunction (p < .01). During recovery phase of the Valsalva, controls had greater brainstem connectivity to the left thalamus (T-value:4.17); PCC (T-value:3.32); right putamen (T-value:3.28); right paracingulate gyrus (T-value:3.25) and left posterior cerebellum (C9) (T-value:3.21) (p-FDR < 0.05). The effect sizes for each brainstem connectivity during Valsalva and recovery ranged from moderate to strong. Patients with autonomic failure show reduced coupling between the brainstem and regions of the central autonomic network, including the cerebellum, insula, thalamus and cingulate cortices. Connectivity was associated with autonomic impairment. These findings may suggest impaired brainstem connectivity in patients with autonomic failure.
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Affiliation(s)
- Jacquie Baker
- School of Kinesiology, Western University, London, Ontario, Canada; Department of Clinical Neurological Sciences, University Hospital, London Health Sciences Centre, London, Ontario, Canada.
| | - Kurt Kimpinski
- School of Kinesiology, Western University, London, Ontario, Canada; Schulich School of Medicine & Dentistry, Western University, London, Ontario, Canada
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Sklerov M, Dayan E, Browner N. Functional neuroimaging of the central autonomic network: recent developments and clinical implications. Clin Auton Res 2018; 29:555-566. [PMID: 30470943 PMCID: PMC6858471 DOI: 10.1007/s10286-018-0577-0] [Citation(s) in RCA: 75] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2018] [Accepted: 11/07/2018] [Indexed: 12/08/2023]
Abstract
Purpose The central autonomic network (CAN) is an intricate system of brainstem, subcortical, and cortical structures that play key roles in the function of the autonomic nervous system. Prior to the advent of functional neuroimaging, in vivo studies of the human CAN were limited. The purpose of this review is to highlight the contribution of functional neuroimaging, specifically functional magnetic resonance imaging (fMRI), to the study of the CAN, and to discuss recent advances in this area. Additionally, we aim to emphasize exciting areas for future research. Methods We reviewed the existing literature in functional neuroimaging of the CAN. Here, we focus on fMRI research conducted in healthy human subjects, as well as research that has been done in disease states, to understand CAN function. To minimize confounding, papers examining CAN function in the context of cognition, emotion, pain, and affective disorders were excluded. Results fMRI has led to significant advances in the understanding of human CAN function. The CAN is composed of widespread brainstem and forebrain structures that are intricately connected and play key roles in reflexive and modulatory control of autonomic function. Conclusions fMRI technology has contributed extensively to current knowledge of CAN function. It holds promise to serve as a biomarker in disease states. With ongoing advancements in fMRI technology, there is great opportunity and need for future research involving the CAN.
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Affiliation(s)
- Miriam Sklerov
- Department of Neurology, University of North Carolina, 170 Manning Drive, CB# 7025, Chapel Hill, NC, 27599, USA.
| | - Eran Dayan
- Department of Radiology and Biomedical Research Imaging Center, University of North Carolina, 130 Mason Farm Road, CB# 7513, Chapel Hill, NC, 27599, USA
| | - Nina Browner
- Department of Neurology, University of North Carolina, 170 Manning Drive, CB# 7025, Chapel Hill, NC, 27599, USA
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Klassen SA, Limberg JK, Baker SE, Nicholson WT, Curry TB, Joyner MJ, Shoemaker JK. The role of the paravertebral ganglia in human sympathetic neural discharge patterns. J Physiol 2018; 596:4497-4510. [PMID: 30054928 PMCID: PMC6138281 DOI: 10.1113/jp276440] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2018] [Accepted: 07/23/2018] [Indexed: 12/30/2022] Open
Abstract
KEY POINTS The mechanisms affecting recruitment patterns of postganglionic sympathetic nerves remain unclear. The divergent and convergent preganglionic innervation patterns of postganglionic neurons and the presence of differently sized postganglionic nerves suggest that the ganglia may participate in modifying the discharge patterns of single sympathetic postganglionic neurons innervating the skeletal muscle circulation. Whether the ganglia affect the ordered behaviour of varying sized postganglionic sympathetic neurons in humans has not been studied. Trimethaphan infusion produced an ordered pattern of action potential (AP) de-recruitment whereby the firing of larger, low probability APs present at baseline was abolished first, followed by progressive decreased probability of smaller APs. Although integrated sympathetic bursts were no longer detected after several minutes of trimethaphan, firing of the smallest APs was detected. These data suggest the ganglia affect the distribution of firing probabilities exhibited by differently sized sympathetic neurons. The ganglia may contribute to sympathetic neural emission patterns involved in homeostatic regulation. ABSTRACT Do the ganglia contribute to the ordered behaviour of postganglionic neuronal discharge within the sympathetic nervous system? To further understand the functional organization of the sympathetic nervous system we employed the microneurographic approach to record muscle sympathetic nerve activity (MSNA) and a continuous wavelet transform to study postganglionic action potential (AP) behaviour during nicotinic blockade at the ganglia (trimethaphan camsylate, 1-7 mg min-1 ) in seven females (37 ± 5 years). Trimethaphan elicited a progressive reduction in sympathetic outflow characterized by fewer integrated bursts with decaying amplitude. Underlying trimethaphan-mediated attenuations in integrated MSNA were reductions in AP incidence (186 ± 101 to 29 ± 31 AP (100 beats)-1 ) and AP content per integrated burst (7 ± 2 to 3 ± 1 APs burst-1 ) (both P < 0.01) in the final minute of detectable bursting activity in the trimethaphan condition, compared to baseline. We observed an ordered de-recruitment of larger to smaller AP clusters active at baseline (14 ± 3 to 8 ± 2 active AP clusters, P < 0.01). Following cessation of integrated bursts in the trimethaphan condition, the smallest 6 ± 2 sympathetic AP clusters persisted to fire in an asynchronous pattern (49 ± 41 AP (100 beats)-1 ) in all participants. Valsalva's manoeuvre did not increase the incidence of these persistent APs (60 ± 42 AP (100 beats)-1 , P = 0.52), or recruit any larger APs in six of seven participants (6 ± 1 total AP clusters, P = 0.30). These data suggest that the ganglia participate in the ordered recruitment of differently sized postganglionic sympathetic nerves.
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Affiliation(s)
- Stephen A. Klassen
- Neurovascular Research LaboratoryUniversity of Western OntarioLondonOntarioCanada
- School of KinesiologyUniversity of Western OntarioLondonOntarioCanada
| | | | - Sarah E. Baker
- Department of Anesthesiology and Perioperative MedicineMayo ClinicRochesterMNUSA
| | - Wayne T. Nicholson
- Department of Anesthesiology and Perioperative MedicineMayo ClinicRochesterMNUSA
| | - Timothy B. Curry
- Department of Anesthesiology and Perioperative MedicineMayo ClinicRochesterMNUSA
| | - Michael J. Joyner
- Department of Anesthesiology and Perioperative MedicineMayo ClinicRochesterMNUSA
| | - J. Kevin Shoemaker
- Neurovascular Research LaboratoryUniversity of Western OntarioLondonOntarioCanada
- School of KinesiologyUniversity of Western OntarioLondonOntarioCanada
- Department of Physiology and PharmacologyUniversity of Western OntarioLondonOntarioCanada
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Babcock MC, Watso JC. Absent metaboreflex-induced increases in sympathetic outflow to contracting muscle. J Physiol 2018; 596:2281-2282. [PMID: 29704243 DOI: 10.1113/jp276240] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Affiliation(s)
- Matthew C Babcock
- Department of Kinesiology and Applied Physiology, University of Delaware, Newark, DE, USA
| | - Joseph C Watso
- Department of Kinesiology and Applied Physiology, University of Delaware, Newark, DE, USA
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Shoemaker JK, Klassen SA, Badrov MB, Fadel PJ. Fifty years of microneurography: learning the language of the peripheral sympathetic nervous system in humans. J Neurophysiol 2018; 119:1731-1744. [PMID: 29412776 DOI: 10.1152/jn.00841.2017] [Citation(s) in RCA: 45] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
As a primary component of homeostasis, the sympathetic nervous system enables rapid adjustments to stress through its ability to communicate messages among organs and cause targeted and graded end organ responses. Key in this communication model is the pattern of neural signals emanating from the central to peripheral components of the sympathetic nervous system. But what is the communication strategy employed in peripheral sympathetic nerve activity (SNA)? Can we develop and interpret the system of coding in SNA that improves our understanding of the neural control of the circulation? In 1968, Hagbarth and Vallbo (Hagbarth KE, Vallbo AB. Acta Physiol Scand 74: 96-108, 1968) reported the first use of microneurographic methods to record sympathetic discharges in peripheral nerves of conscious humans, allowing quantification of SNA at rest and sympathetic responsiveness to physiological stressors in health and disease. This technique also has enabled a growing investigation into the coding patterns within, and cardiovascular outcomes associated with, postganglionic SNA. This review outlines how results obtained by microneurographic means have improved our understanding of SNA outflow patterns at the action potential level, focusing on SNA directed toward skeletal muscle in conscious humans.
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Affiliation(s)
- J Kevin Shoemaker
- School of Kinesiology, University of Western Ontario , London, Ontario , Canada
| | - Stephen A Klassen
- School of Kinesiology, University of Western Ontario , London, Ontario , Canada
| | - Mark B Badrov
- School of Kinesiology, University of Western Ontario , London, Ontario , Canada
| | - Paul J Fadel
- Department of Kinesiology, University of Texas at Arlington , Arlington, Texas
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A review of human neuroimaging investigations involved with central autonomic regulation of baroreflex-mediated cardiovascular control. Auton Neurosci 2017; 207:10-21. [DOI: 10.1016/j.autneu.2017.05.008] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2016] [Revised: 03/10/2017] [Accepted: 05/13/2017] [Indexed: 12/30/2022]
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Yu ZB, Lv YB, Song LH, Liu DH, Huang XL, Hu XY, Zuo ZW, Wang Y, Yang Q, Peng J, Zhou ZH, Li HT. Functional Connectivity Differences in the Insular Sub-regions in Migraine without Aura: A Resting-State Functional Magnetic Resonance Imaging Study. Front Behav Neurosci 2017; 11:124. [PMID: 28701932 PMCID: PMC5487515 DOI: 10.3389/fnbeh.2017.00124] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2016] [Accepted: 06/13/2017] [Indexed: 11/13/2022] Open
Abstract
Objective: The objective of this study was to investigate resting-state functional connectivity (FC) differences in insular sub-regions during the interictal phase in patients with migraine without aura (MWoA). Methods: Forty-nine MWoA patients (MWoA group) and 48 healthy individuals (healthy control group) were recruited for this study. All of the subjects underwent neurological examination and magnetic resonance imaging (MRI). The MRI data were processed using Brat 1.0 software to obtain a whole-brain FC diagram and using Rest 1.8 software to obtain the FC z-score of the sub-regions of both insulas (six sub-regions on each side). Therefore, there were a total of 12 regions of interest (ROIs) that were used as seed points for the statistical analysis. Results: There was abnormal FC between the insular sub-regions and multiple brain regions in the MWoA patients compared with the healthy control group, and a clear laterality was also observed. In addition, the FC z-score of certain sub-regions was negatively correlated with the disease duration. Conclusion: Different insular sub-regions are functionally associated with different regions of the brain and therefore have different functions. In MWoA, the FC between the insular sub-regions and other brain regions was mostly reduced, while a small amount was increased; additionally, the FC may be ipsilateral with a right-side advantage. Variations in the FC of insular sub-regions can be observed as an important indicator of MWoA.
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Affiliation(s)
- Zhi-Bo Yu
- Department of Radiology, The First Affiliated Hospital, Third Military Medical UniversityChongqing, China.,Department of Medical Imaging, PLA No.324 HospitalChongqing, China
| | - Yan-Bing Lv
- Department of General Surgery, PLA No.324 HospitalChongqing, China
| | - Ling-Heng Song
- Department of Medical Imaging, PLA No.324 HospitalChongqing, China
| | - Dai-Hong Liu
- Department of Radiology, The First Affiliated Hospital, Third Military Medical UniversityChongqing, China
| | - Xue-Ling Huang
- Department of Nursing, Chongqing Three Gorges Medical CollegeChongqing, China
| | - Xin-Yue Hu
- Department of Radiology, The First Affiliated Hospital, Third Military Medical UniversityChongqing, China
| | - Zhi-Wei Zuo
- Department of Radiology, The First Affiliated Hospital, Third Military Medical UniversityChongqing, China
| | - Yao Wang
- Department of Radiology, The First Affiliated Hospital, Third Military Medical UniversityChongqing, China
| | - Qian Yang
- Department of Radiology, The First Affiliated Hospital, Third Military Medical UniversityChongqing, China
| | - Jing Peng
- Department of Neurology, The First Affiliated Hospital, Third Military Medical UniversityChongqing, China
| | - Zhen-Hua Zhou
- Department of Neurology, The First Affiliated Hospital, Third Military Medical UniversityChongqing, China
| | - Hai-Tao Li
- Department of Radiology, The First Affiliated Hospital, Third Military Medical UniversityChongqing, China
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Cohen B, Martinelli GP, Xiang Y, Raphan T, Yakushin SB. Vestibular Activation Habituates the Vasovagal Response in the Rat. Front Neurol 2017; 8:83. [PMID: 28360882 PMCID: PMC5350135 DOI: 10.3389/fneur.2017.00083] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2016] [Accepted: 02/24/2017] [Indexed: 12/16/2022] Open
Abstract
Vasovagal syncope is a significant medical problem without effective therapy, postulated to be related to a collapse of baroreflex function. While some studies have shown that repeated static tilts can block vasovagal syncope, this was not found in other studies. Using anesthetized, male Long–Evans rats that were highly susceptible to generation of vasovagal responses, we found that repeated activation of the vestibulosympathetic reflex (VSR) with ±2 and ±3 mA, 0.025 Hz sinusoidal galvanic vestibular stimulation (sGVS) caused incremental changes in blood pressure (BP) and heart rate (HR) that blocked further generation of vasovagal responses. Initially, BP and HR fell ≈20–50 mmHg and ≈20–50 beats/min (bpm) into a vasovagal response when stimulated with Sgv\S in susceptible rats. As the rats were continually stimulated, HR initially rose to counteract the fall in BP; then the increase in HR became more substantial and long lasting, effectively opposing the fall in BP. Finally, the vestibular stimuli simply caused an increase in BP, the normal sequence following activation of the VSR. Concurrently, habituation caused disappearance of the low-frequency (0.025 and 0.05 Hz) oscillations in BP and HR that must be present when vasovagal responses are induced. Habituation also produced significant increases in baroreflex sensitivity (p < 0.001). Thus, repeated low-frequency activation of the VSR resulted in a reduction and loss of susceptibility to development of vasovagal responses in rats that were previously highly susceptible. We posit that reactivation of the baroreflex, which is depressed by anesthesia and the disappearance of low-frequency oscillations in BP and HR are likely to be critically involved in producing resistance to the development of vasovagal responses. SGVS has been widely used to activate muscle sympathetic nerve activity in humans and is safe and well tolerated. Potentially, it could be used to produce similar habituation of vasovagal syncope in humans.
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Affiliation(s)
- Bernard Cohen
- Department of Neurology, Icahn School of Medicine at Mount Sinai , New York, NY , USA
| | - Giorgio P Martinelli
- Department of Neurology, Icahn School of Medicine at Mount Sinai , New York, NY , USA
| | - Yongqing Xiang
- Department of Computer and Information Science, Brooklyn College, City University of New York , New York, NY , USA
| | - Theodore Raphan
- Department of Computer and Information Science, Brooklyn College, City University of New York , New York, NY , USA
| | - Sergei B Yakushin
- Department of Neurology, Icahn School of Medicine at Mount Sinai , New York, NY , USA
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15
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Borsook D, Veggeberg R, Erpelding N, Borra R, Linnman C, Burstein R, Becerra L. The Insula: A "Hub of Activity" in Migraine. Neuroscientist 2016; 22:632-652. [PMID: 26290446 PMCID: PMC5723020 DOI: 10.1177/1073858415601369] [Citation(s) in RCA: 98] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The insula, a "cortical hub" buried within the lateral sulcus, is involved in a number of processes including goal-directed cognition, conscious awareness, autonomic regulation, interoception, and somatosensation. While some of these processes are well known in the clinical presentation of migraine (i.e., autonomic and somatosensory alterations), other more complex behaviors in migraine, such as conscious awareness and error detection, are less well described. Since the insula processes and relays afferent inputs from brain areas involved in these functions to areas involved in higher cortical function such as frontal, temporal, and parietal regions, it may be implicated as a brain region that translates the signals of altered internal milieu in migraine, along with other chronic pain conditions, through the insula into complex behaviors. Here we review how the insula function and structure is altered in migraine. As a brain region of a number of brain functions, it may serve as a model to study new potential clinical perspectives for migraine treatment.
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Affiliation(s)
- David Borsook
- Pain/Analgesia Imaging Neuroscience (P.A.I.N.) Group, Department of Anesthesia, Boston Children's Hospital, Center for Pain and the Brain, Harvard Medical School, Waltham, MA, USA
- Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA, USA
- Departments of Psychiatry and Radiology, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA, USA
| | - Rosanna Veggeberg
- Pain/Analgesia Imaging Neuroscience (P.A.I.N.) Group, Department of Anesthesia, Boston Children's Hospital, Center for Pain and the Brain, Harvard Medical School, Waltham, MA, USA
| | - Nathalie Erpelding
- Pain/Analgesia Imaging Neuroscience (P.A.I.N.) Group, Department of Anesthesia, Boston Children's Hospital, Center for Pain and the Brain, Harvard Medical School, Waltham, MA, USA
| | - Ronald Borra
- Pain/Analgesia Imaging Neuroscience (P.A.I.N.) Group, Department of Anesthesia, Boston Children's Hospital, Center for Pain and the Brain, Harvard Medical School, Waltham, MA, USA
| | - Clas Linnman
- Pain/Analgesia Imaging Neuroscience (P.A.I.N.) Group, Department of Anesthesia, Boston Children's Hospital, Center for Pain and the Brain, Harvard Medical School, Waltham, MA, USA
| | - Rami Burstein
- Department of Anesthesia, Beth Israel Deaconess Hospital, Harvard Medical School, Boston, MA, USA
| | - Lino Becerra
- Pain/Analgesia Imaging Neuroscience (P.A.I.N.) Group, Department of Anesthesia, Boston Children's Hospital, Center for Pain and the Brain, Harvard Medical School, Waltham, MA, USA
- Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA, USA
- Departments of Psychiatry and Radiology, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA, USA
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Chang C, Raven EP, Duyn JH. Brain-heart interactions: challenges and opportunities with functional magnetic resonance imaging at ultra-high field. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2016; 374:rsta.2015.0188. [PMID: 27044994 PMCID: PMC4822447 DOI: 10.1098/rsta.2015.0188] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 02/05/2016] [Indexed: 05/24/2023]
Abstract
Magnetic resonance imaging (MRI) at ultra-high field (UHF) strengths (7 T and above) offers unique opportunities for studying the human brain with increased spatial resolution, contrast and sensitivity. However, its reliability can be compromised by factors such as head motion, image distortion and non-neural fluctuations of the functional MRI signal. The objective of this review is to provide a critical discussion of the advantages and trade-offs associated with UHF imaging, focusing on the application to studying brain-heart interactions. We describe how UHF MRI may provide contrast and resolution benefits for measuring neural activity of regions involved in the control and mediation of autonomic processes, and in delineating such regions based on anatomical MRI contrast. Limitations arising from confounding signals are discussed, including challenges with distinguishing non-neural physiological effects from the neural signals of interest that reflect cardiorespiratory function. We also consider how recently developed data analysis techniques may be applied to high-field imaging data to uncover novel information about brain-heart interactions.
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Affiliation(s)
- Catie Chang
- Advanced Magnetic Resonance Imaging Section, Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892, USA
| | - Erika P Raven
- Advanced Magnetic Resonance Imaging Section, Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892, USA Center for Functional and Molecular Imaging, Georgetown University Medical Center, Washington, DC 20007, USA
| | - Jeff H Duyn
- Advanced Magnetic Resonance Imaging Section, Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892, USA
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Macey PM, Ogren JA, Kumar R, Harper RM. Functional Imaging of Autonomic Regulation: Methods and Key Findings. Front Neurosci 2016; 9:513. [PMID: 26858595 PMCID: PMC4726771 DOI: 10.3389/fnins.2015.00513] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2015] [Accepted: 12/22/2015] [Indexed: 01/06/2023] Open
Abstract
Central nervous system processing of autonomic function involves a network of regions throughout the brain which can be visualized and measured with neuroimaging techniques, notably functional magnetic resonance imaging (fMRI). The development of fMRI procedures has both confirmed and extended earlier findings from animal models, and human stroke and lesion studies. Assessments with fMRI can elucidate interactions between different central sites in regulating normal autonomic patterning, and demonstrate how disturbed systems can interact to produce aberrant regulation during autonomic challenges. Understanding autonomic dysfunction in various illnesses reveals mechanisms that potentially lead to interventions in the impairments. The objectives here are to: (1) describe the fMRI neuroimaging methodology for assessment of autonomic neural control, (2) outline the widespread, lateralized distribution of function in autonomic sites in the normal brain which includes structures from the neocortex through the medulla and cerebellum, (3) illustrate the importance of the time course of neural changes when coordinating responses, and how those patterns are impacted in conditions of sleep-disordered breathing, and (4) highlight opportunities for future research studies with emerging methodologies. Methodological considerations specific to autonomic testing include timing of challenges relative to the underlying fMRI signal, spatial resolution sufficient to identify autonomic brainstem nuclei, blood pressure, and blood oxygenation influences on the fMRI signal, and the sustained timing, often measured in minutes of challenge periods and recovery. Key findings include the lateralized nature of autonomic organization, which is reminiscent of asymmetric motor, sensory, and language pathways. Testing brain function during autonomic challenges demonstrate closely-integrated timing of responses in connected brain areas during autonomic challenges, and the involvement with brain regions mediating postural and motoric actions, including respiration, and cardiac output. The study of pathological processes associated with autonomic disruption shows susceptibilities of different brain structures to altered timing of neural function, notably in sleep disordered breathing, such as obstructive sleep apnea and congenital central hypoventilation syndrome. The cerebellum, in particular, serves coordination roles for vestibular stimuli and blood pressure changes, and shows both injury and substantially altered timing of responses to pressor challenges in sleep-disordered breathing conditions. The insights into central autonomic processing provided by neuroimaging have assisted understanding of such regulation, and may lead to new treatment options for conditions with disrupted autonomic function.
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Affiliation(s)
- Paul M Macey
- UCLA School of Nursing, University of California at Los AngelesLos Angeles, CA, USA; Brain Research Institute, University of California at Los AngelesLos Angeles, CA, USA
| | - Jennifer A Ogren
- Department of Neurobiology, University of California at Los Angeles Los Angeles, CA, USA
| | - Rajesh Kumar
- Brain Research Institute, University of California at Los AngelesLos Angeles, CA, USA; Department of Anesthesiology, University of California at Los AngelesLos Angeles, CA, USA; Department of Radiological Sciences, David Geffen School of Medicine at University of California at Los AngelesLos Angeles, CA, USA; Department of Bioengineering, University of California at Los AngelesLos Angeles, CA, USA
| | - Ronald M Harper
- Brain Research Institute, University of California at Los AngelesLos Angeles, CA, USA; Department of Neurobiology, University of California at Los AngelesLos Angeles, CA, USA
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Sheng X, Chen M, Huang B, Liu J, Zhou L, Bao M, Li S. Cardioprotective effects of low-level carotid baroreceptor stimulation against myocardial ischemia-reperfusion injury in canine model. J Interv Card Electrophysiol 2016; 45:131-40. [DOI: 10.1007/s10840-015-0094-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/15/2015] [Accepted: 12/22/2015] [Indexed: 12/26/2022]
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Cheshire WP. Highlights in clinical autonomic neurosciences: Brain volume and autonomic regulation. Auton Neurosci 2014; 183:4-7. [PMID: 24862160 DOI: 10.1016/j.autneu.2014.05.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Advances in volumetric magnetic resonance imaging (MRI) technology are beginning to provide structural correlates to functional dysautonomic syndromes in the brain. This paper highlights several interesting recent discoveries in which measurable variations in general or regional subcortical or cortical brain volume corresponded to changes in blood pressure or heart rate. Although these MRI findings currently lack diagnostic value in routine clinical practice, they may provide important clues to the pathophysiology of autonomic disorders and to links between autonomic and cognitive disorders. If validated by further studies, they also have potential implications for the management of orthostatic hypotension, particularly when combined with hypertension.
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Affiliation(s)
- William P Cheshire
- Department of Neurology, Mayo Clinic, 4500 San Pablo Rd., Jacksonville, FL 32224, USA.
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20
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Linz D, Ukena C, Mahfoud F, Neuberger HR, Böhm M. Atrial Autonomic Innervation. J Am Coll Cardiol 2014; 63:215-24. [DOI: 10.1016/j.jacc.2013.09.020] [Citation(s) in RCA: 87] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/11/2013] [Revised: 09/03/2013] [Accepted: 09/10/2013] [Indexed: 10/26/2022]
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Linz D, Mahfoud F, Schotten U, Ukena C, Neuberger HR, Wirth K, Böhm M. Effects of electrical stimulation of carotid baroreflex and renal denervation on atrial electrophysiology. J Cardiovasc Electrophysiol 2013; 24:1028-33. [PMID: 23638844 DOI: 10.1111/jce.12171] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/19/2013] [Revised: 04/02/2013] [Accepted: 04/02/2013] [Indexed: 11/29/2022]
Abstract
INTRODUCTION This study was designed to compare the effect of electrical baroreflex stimulation (BRS) at an intensity used in hypertensive patients and renal denervation (RDN) on atrial electrophysiology. BRS and RDN reduce blood pressure and global sympathetic drive in patients with resistant hypertension. Whereas RDN decreases sympathetic renal afferent nerve activity, leading to decreased central sympathetic drive, BRS modulates autonomic balance by activation of the baroreflex, resulting in both reduced sympathetic drive and increased vagal activation. Increased vagal tone potentially shortens atrial refractoriness resulting in a stabilization of reentry circuits perpetuating atrial fibrillation (AF). METHODS AND RESULTS In normotensive anesthetized pigs (n = 12), we compared the acute effect of BRS and RDN on blood pressure, atrial effective refractory period (AERP), and inducibility of AF. Electrical BRS was titrated to result in comparable heart rate and blood pressure reduction compared to irreversible RDN. BRS resulted in a rapid and pronounced shortening of AERP (from 162 ± 8 milliseconds to 117 ± 16 milliseconds, P = 0.001) associated with increased AF-inducibility from 0% to 82%. This shortening in AERP was completely reversible after stopping BRS. After administration of atropine, AF-inducibility during BRS was attenuated. Ventricular repolarization was not modulated by BRS. In RDN, AF was not inducible; however, it did not prevent BRS-induced shortening of AERP. CONCLUSION RDN and BRS resulting in comparable blood pressure and heart rate reductions differently influence atrial electrophysiology. Vagally mediated shortening of AERP, resulting in increased AF-inducibility, was observed with BRS but not with RDN.
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Affiliation(s)
- Dominik Linz
- Universitätsklinikum des Saarlandes, Klinik für Innere Medizin III, Homburg/Saar, Germany
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James C, Henderson L, Macefield VG. Real-time imaging of brain areas involved in the generation of spontaneous skin sympathetic nerve activity at rest. Neuroimage 2013; 74:188-94. [PMID: 23485741 DOI: 10.1016/j.neuroimage.2013.02.030] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2013] [Revised: 02/13/2013] [Accepted: 02/15/2013] [Indexed: 11/16/2022] Open
Abstract
In thermoneutral conditions resting skin sympathetic nerve activity (SSNA) is related to the level of arousal and emotional state. The brain regions responsible for the generation of spontaneous SSNA are not known. In the present study we used concurrent recordings of SSNA and brain activity in awake humans to identify cortical and subcortical areas involved in the generation of spontaneous SSNA in 13 healthy subjects. Blood oxygen level dependent signal intensity increases covaried with SSNA in the left thalamus in the region of the ventromedial nucleus, the left posterior and right anterior insula, the right orbitofrontal cortex, the right frontal cortex, and bilaterally in the mid-cingulate cortex and precuneus. Functional connectivity analysis revealed a strong positive coupling between the right orbitofrontal cortex and the right anterior insula. Furthermore, signal intensity changes within the precuneus were temporally coupled to the left anterior and posterior insula, cerebellum, cingulate cortex and thalamus. It has been hypothesized that these brain regions monitor the internal state of the body and may regulate emotional state changes. Our results show that the activities within these regions are also correlated to spontaneous fluctuations in SSNA.
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Affiliation(s)
- Cheree James
- School of Medicine, University of Western Sydney, Sydney, NSW 2751, Australia
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