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Jimoh Z, Marouf A, Zenke J, Leung AWS, Gomaa NA. Functional Brain Regions Linked to Tinnitus Pathology and Compensation During Task Performance: A Systematic Review. Otolaryngol Head Neck Surg 2023; 169:1409-1423. [PMID: 37522290 DOI: 10.1002/ohn.459] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2023] [Revised: 06/24/2023] [Accepted: 07/11/2023] [Indexed: 08/01/2023]
Abstract
OBJECTIVE To systematically search the literature and organize relevant advancements in the connection between tinnitus and the activity of different functional brain regions using functional magnetic resonance imaging (fMRI). DATA SOURCES MEDLINE (OVID), EMBASE (OVID), CINAHL (EBSCO), Web of Science, ProQuest Dissertations & Theses Global, Cochrane Database of Systematic Reviews, and PROSPERO from inception to April 2022. REVIEW METHODS Studies with adult human subjects who suffer from tinnitus and underwent fMRI to relate specific regions of interest to tinnitus pathology or compensation were included. In addition, fMRI had to be performed with a paradigm of stimuli that would stimulate auditory brain activity. Exclusion criteria included non-English studies, animal studies, and studies that utilized a resting state magnetic resonance imaging or other imaging modalities. RESULTS The auditory cortex may work to dampen the effects of central gain. Results from different studies show variable changes in the Heschl's gyrus (HG), with some showing increased activity and others showing inhibition and volume loss. After controlling for hyperacusis and other confounders, tinnitus does not seem to influence the inferior colliculus (IC) activation. However, there is decreased connectivity between the auditory cortex and IC. The cochlear nucleus (CN) generally shows increased activation in tinnitus patients. fMRI evidence indicates significant inhibition of thalamic gating. Activating the thalamus may be of important therapeutic potential. CONCLUSION Patients with tinnitus have significantly altered neuronal firing patterns, especially within the auditory network, when compared to individuals without tinnitus. Tinnitus and hyperacusis commonly coexist, making differentiation of the effects of these 2 phenomena frequently difficult.
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Affiliation(s)
- Zaharadeen Jimoh
- Faculty of Science, University of Alberta, Edmonton, Alberta, Canada
| | - Azmi Marouf
- Department of Otolaryngology-Head and Neck Surgery, Case Western Reserve School of Medicine and University Hospitals Cleveland Medical Center, Cleveland, Ohio, USA
| | - Julianna Zenke
- Division of Otolaryngology-Head and Neck Surgery, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada
| | - Ada W S Leung
- Department of Occupational Therapy, Neuroscience, and Mental Health Institute, Faculty of Rehabilitation Sciences, University of Alberta, Edmonton, Alberta, Canada
| | - Nahla A Gomaa
- Division of Otolaryngology-Head and Neck Surgery, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada
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Adhikari Y, Ma CG, Chai Z, Jin X. Preventing development of post-stroke hyperexcitability by optogenetic or pharmacological stimulation of cortical excitatory activity. Neurobiol Dis 2023; 184:106233. [PMID: 37468047 DOI: 10.1016/j.nbd.2023.106233] [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: 02/20/2023] [Revised: 06/30/2023] [Accepted: 07/16/2023] [Indexed: 07/21/2023] Open
Abstract
Stroke is the most common cause of acquired epilepsy, but treatment for preventing the development of post-stroke epilepsy is still unavailable. Since stroke results in neuronal damage and death as well as initial loss of activity in the affected brain region, homeostatic plasticity may be trigged and contribute to an increase in network hyperexcitability that underlies epileptogenesis. Correspondingly, enhancing brain activity may inhibit hyperexcitability from enhanced homeostatic plasticity and prevent post-stroke epileptogenesis. To test these hypotheses, we first used in vivo two-photon and mesoscopic imaging of activity of cortical pyramidal neurons in Thy1-GCaMP6 transgenic mice to determine longitudinal changes in excitatory activity after a photothrombotic ischemic stroke. At 3-days post-stroke, there was a significant loss of neuronal activity in the peri-injury area as indicated by reductions in the frequency of calcium spikes and percentage of active neurons, which recovered to baseline level at day 7, supporting a homeostatic activity regulation of the surviving neurons in the peri-injury area. We further used optogenetic stimulation to specifically stimulate activity of pyramidal neurons in the peri-injury area of Thy-1 channelrhodopsin transgenic mice from day 5 to day 15 after stroke. Using pentylenetetrazole test to evaluate seizure susceptibility, we showed that stroke mice are more susceptible to Racine stage V seizures (time latency 54.3 ± 12.9 min) compared to sham mice (107.1 ± 13.6 min), but optogenetic stimulation reversed the increase in seizure susceptibility (114.0 ± 9.2 min) in mice with stroke. Similarly, administration of D-cycloserine, a partial N-methyl-d-aspartate (NMDA) receptor agonist that can mildly enhance neuronal activity without causing post-stroke seizure, from day 5 to day 15 after a stroke significantly reversed the increase in seizure susceptibility. The treatment also resulted in an increased survival of glutamic acid decarboxylase 67 (GAD67) positive interneurons and a reduced activation of glial fibrillary acidic protein (GFAP) positive reactive astrocytes. Thus, this study supports the involvement of homeostatic activity regulation in the development of post-stroke hyperexcitability and potential application of activity enhancement as a novel strategy to prevent post-stroke late-onset seizure and epilepsy through regulating cortical homeostatic plasticity.
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Affiliation(s)
- Yadav Adhikari
- Stark Neurosciences Research Institute, Indiana University School of Medicine, Indianapolis, IN, USA; Schepens Eye Research Institute, Department of Ophthalmology, Harvard Medical School, Boston, MA, USA.
| | - Cun-Gen Ma
- Shanxi Key Laboratory of Innovative Drug for the Treatment of Serious Diseases Basing on the Chronic Inflammation/Neurobiology Research Center, Shanxi University of Chinese Medicine, Jinzhong, Shanxi, China
| | - Zhi Chai
- Shanxi Key Laboratory of Innovative Drug for the Treatment of Serious Diseases Basing on the Chronic Inflammation/Neurobiology Research Center, Shanxi University of Chinese Medicine, Jinzhong, Shanxi, China
| | - Xiaoming Jin
- Stark Neurosciences Research Institute, Indiana University School of Medicine, Indianapolis, IN, USA; Department of Anatomy, Cell Biology and Physiology, Indiana University School of Medicine, Indianapolis, IN, USA
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3
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Issa NP, Nunn KC, Wu S, Haider HA, Tao JX. Putative roles for homeostatic plasticity in epileptogenesis. Epilepsia 2023; 64:539-552. [PMID: 36617338 PMCID: PMC10015501 DOI: 10.1111/epi.17500] [Citation(s) in RCA: 11] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2022] [Revised: 01/04/2023] [Accepted: 01/05/2023] [Indexed: 01/09/2023]
Abstract
Homeostatic plasticity allows neural circuits to maintain an average activity level while preserving the ability to learn new associations and efficiently transmit information. This dynamic process usually protects the brain from excessive activity, like seizures. However, in certain contexts, homeostatic plasticity might produce seizures, either in response to an acute provocation or more chronically as a driver of epileptogenesis. Here, we review three seizure conditions in which homeostatic plasticity likely plays an important role: acute drug withdrawal seizures, posttraumatic or disconnection epilepsy, and cyclic seizures. Identifying the homeostatic mechanisms active at different stages of development and in different circuits could allow better targeting of therapies, including determining when neuromodulation might be most effective, proposing ways to prevent epileptogenesis, and determining how to disrupt the cycle of recurring seizure clusters.
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Affiliation(s)
- Naoum P. Issa
- Comprehensive Epilepsy Center, Department of Neurology, 5841 S. Maryland Ave., MC 2030, University of Chicago, Chicago, IL 60637
| | | | - Shasha Wu
- Comprehensive Epilepsy Center, Department of Neurology, 5841 S. Maryland Ave., MC 2030, University of Chicago, Chicago, IL 60637
| | - Hiba A. Haider
- Comprehensive Epilepsy Center, Department of Neurology, 5841 S. Maryland Ave., MC 2030, University of Chicago, Chicago, IL 60637
| | - James X. Tao
- Comprehensive Epilepsy Center, Department of Neurology, 5841 S. Maryland Ave., MC 2030, University of Chicago, Chicago, IL 60637
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Aghdash SN, Foroughi G. Chemical Kindling as an Experimental Model to Assess the Conventional Drugs in the Treatment of Post-traumatic Epilepsy. CNS & NEUROLOGICAL DISORDERS DRUG TARGETS 2023; 22:1417-1428. [PMID: 36443981 DOI: 10.2174/1871527322666221128155813] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/28/2022] [Revised: 09/06/2022] [Accepted: 09/09/2022] [Indexed: 11/30/2022]
Abstract
BACKGROUND Traumatic brain injury (TBI) is one of the leading causes of morbidity and mortality today, which will surpass many infectious diseases in the coming years/decades. Posttraumatic epilepsy (PTE) is one of the most common debilitating consequences of TBI. PTE is a secondary, acquired epilepsy that causes recurrent, spontaneous seizures more than a week after TBI. The extent of head injury in individuals who develop PTE is unknown; however, trauma is thought to account for 20% of symptomatic epilepsy worldwide. Understanding the mechanisms of epilepsy following TBI is crucial for the discovery of new anticonvulsant drugs for the treatment of PTE, as well as for improving the quality of life of patients with PTE. OBJECTIVE This review article explains the rationale for the usage of a chemical model to access new treatments for post-traumatic epilepsy. RESULTS There are multiple methods to control and manage PTE. The essential and available remedy for the management of epilepsy is the use of antiepileptic drugs. Antiepileptic drugs (AEDs) decrease the frequency of seizures without affecting the disease's causality. Antiepileptic drugs are administrated for the prevention and treatment of PTE; however, 30% of epilepsy patients are drug-resistant, and AED side effects are significant in PTE patients. There are different types of animal models, such as the liquid percussion model, intracortical ferric chloride injection, and cortical subincision model, to study PTE and neurophysiological mechanisms underlying the development of epilepsy after head injury. However, these animal models do not easily mimic the pathological events occurring in epilepsy. Therefore, animal models of PTE are an inappropriate tool for screening new and putatively effective AEDs. Chemical kindling is the most common animal model used to study epilepsy. There is a strong similarity between the kindling model and different types of human epilepsy. CONCLUSION Today, researchers use experimental animal models to evaluate new anticonvulsant drugs. The chemical kindling models, such as pentylenetetrazol, bicuculline, and picrotoxin-induced seizures, are important experimental models to analyze the impact of putative antiepileptic drugs.
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Affiliation(s)
- Simin Namvar Aghdash
- Department of Biology, Faculty of Basic Sciences, Azarbaijan Shahid Madani University, Tabriz, Iran
| | - Golsa Foroughi
- Department of Biology, Faculty of Basic Sciences, Azarbaijan Shahid Madani University, Tabriz, Iran
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5
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Invasive cortical stimulation. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2021; 159:23-45. [PMID: 34446248 DOI: 10.1016/bs.irn.2021.03.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The field of neuromodulation, at its essence, aims to apply electrical stimulation to the brain to ameliorate various pathology. Many methods of applying this stimulation exist, including invasive and non-invasive means. In the realm of invasive stimulation, stimulation of the cortex remains one of the earliest techniques investigated, yet one of the most underutilized today. Evidence for the efficacy of direct invasive cortical stimulation continues to mount, especially in recent years. In this chapter we will review the evidence for the use of invasive cortical stimulation as it applies to neuropathic pain, epilepsy, psychiatric disease, movement disorders, tinnitus, and post-stroke recovery, as well explore some potential mechanisms and future directions of the technique.
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6
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Altered brain responses to emotional facial expressions in tinnitus patients. PROGRESS IN BRAIN RESEARCH 2021; 262:189-207. [PMID: 33931179 DOI: 10.1016/bs.pbr.2021.01.026] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Tinnitus, the phantom perception of sound, is a frequent disorder that can lead to severe distress and stress-related comorbidity. The pathophysiological mechanisms involved in the etiology of tinnitus are still under exploration. Electrophysiological and functional neuroimaging studies provide increasing evidence for abnormal functioning in auditory but also in non-auditory, e.g., emotional, brain areas. In order to elucidate alterations of affective processing in patients with chronic tinnitus, we used functional magnetic resonance imaging (fMRI) to measure neural responses to emotionally expressive and neutral faces. Twelve patients with chronic tinnitus and a group of 11 healthy controls, matched for age, sex, hearing loss and depressive symptoms were investigated. While viewing emotionally expressive faces compared to neutral faces brain activations in the tinnitus patients differed from those of the controls in a cluster that encompasses the amygdala, the hippocampus and the parahippocampal gyrus bilaterally. Whereas in controls affective faces induced higher brain activation in these regions than neutral faces, these regions in tinnitus patients were deactivated. Our results (1) provide evidence for alterations of affective processing of facial expressions in tinnitus patients indicating general domain-unspecific dysfunctions in emotion processing and (2) indicate the involvement of medial temporal areas in the pathophysiology of tinnitus.
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7
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Korai SA, Ranieri F, Di Lazzaro V, Papa M, Cirillo G. Neurobiological After-Effects of Low Intensity Transcranial Electric Stimulation of the Human Nervous System: From Basic Mechanisms to Metaplasticity. Front Neurol 2021; 12:587771. [PMID: 33658972 PMCID: PMC7917202 DOI: 10.3389/fneur.2021.587771] [Citation(s) in RCA: 34] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2020] [Accepted: 01/04/2021] [Indexed: 12/19/2022] Open
Abstract
Non-invasive low-intensity transcranial electrical stimulation (tES) of the brain is an evolving field that has brought remarkable attention in the past few decades for its ability to directly modulate specific brain functions. Neurobiological after-effects of tES seems to be related to changes in neuronal and synaptic excitability and plasticity, however mechanisms are still far from being elucidated. We aim to review recent results from in vitro and in vivo studies that highlight molecular and cellular mechanisms of transcranial direct (tDCS) and alternating (tACS) current stimulation. Changes in membrane potential and neural synchronization explain the ongoing and short-lasting effects of tES, while changes induced in existing proteins and new protein synthesis is required for long-lasting plastic changes (LTP/LTD). Glial cells, for decades supporting elements, are now considered constitutive part of the synapse and might contribute to the mechanisms of synaptic plasticity. This review brings into focus the neurobiological mechanisms and after-effects of tDCS and tACS from in vitro and in vivo studies, in both animals and humans, highlighting possible pathways for the development of targeted therapeutic applications.
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Affiliation(s)
- Sohaib Ali Korai
- Division of Human Anatomy - Laboratory of Neuronal Networks, University of Campania "Luigi Vanvitelli", Naples, Italy
| | - Federico Ranieri
- Neurology Unit, Department of Neurosciences, Biomedicine and Movement Sciences, University of Verona, Verona, Italy
| | - Vincenzo Di Lazzaro
- Neurology, Neurophysiology and Neurobiology Unit, University Campus Bio-Medico, Rome, Italy
| | - Michele Papa
- Division of Human Anatomy - Laboratory of Neuronal Networks, University of Campania "Luigi Vanvitelli", Naples, Italy.,ISBE Italy, SYSBIO Centre of Systems Biology, Milan, Italy
| | - Giovanni Cirillo
- Division of Human Anatomy - Laboratory of Neuronal Networks, University of Campania "Luigi Vanvitelli", Naples, Italy.,Neurology Unit, Department of Neurosciences, Biomedicine and Movement Sciences, University of Verona, Verona, Italy
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8
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Wang ML, Song Y, Liu JX, Du YL, Xiong S, Fan X, Wang J, Zhang ZD, Mao LQ, Ma FR. Role of the caudate-putamen nucleus in sensory gating in induced tinnitus in rats. Neural Regen Res 2021; 16:2250-2256. [PMID: 33818509 PMCID: PMC8354105 DOI: 10.4103/1673-5374.310692] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Tinnitus can be described as the conscious perception of sound without external stimulation, and it is often accompanied by anxiety, depression, and insomnia. Current clinical treatments for tinnitus are ineffective. Although recent studies have indicated that the caudate-putamen nucleus may be a sensory gating area involved in noise elimination in tinnitus, the underlying mechanisms of this disorder are yet to be determined. To investigate the potential role of the caudate-putamen nucleus in experimentally induced tinnitus, we created a rat model of tinnitus induced by intraperitoneal administration of 350 mg/kg sodium salicylate. Our results revealed that the mean spontaneous firing rate of the caudate-putamen nucleus was increased by sodium salicylate treatment, while dopamine levels were decreased. In addition, electrical stimulation of the caudate-putamen nucleus markedly reduced the spontaneous firing rate of neurons in the primary auditory cortex. These findings suggest that the caudate-putamen nucleus plays a sensory gating role in sodium salicylate-induced tinnitus. This study was approved by the Institutional Animal Care and Use Committee of Peking University Health Science Center (approval No. A2010031) on December 6, 2017.
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Affiliation(s)
- Meng-Lin Wang
- Department of Otolaryngology Head and Neck Surgery, Peking University Third Hospital, Beijing, China
| | - Yu Song
- Department of Otolaryngology Head and Neck Surgery, Peking University Third Hospital, Beijing, China
| | - Jun-Xiu Liu
- Department of Otolaryngology Head and Neck Surgery, Peking University Third Hospital, Beijing, China
| | - Ya-Li Du
- Department of Otolaryngology Head and Neck Surgery, Peking University Third Hospital, Beijing, China
| | - Shan Xiong
- Department of Otolaryngology Head and Neck Surgery, Peking University Third Hospital, Beijing, China
| | - Xin Fan
- Department of Otolaryngology Head and Neck Surgery, Peking University Third Hospital, Beijing, China
| | - Jiang Wang
- Department of Otolaryngology Head and Neck Surgery, Peking University Third Hospital, Beijing, China
| | - Zhi-Di Zhang
- Department of Otolaryngology Head and Neck Surgery, Peking University Third Hospital, Beijing, China
| | - Lan-Qun Mao
- Beijing National Laboratory for Molecular Sciences, Key Laboratory of Analytical Chemistry for Living Biosystems, Institute of Chemistry, the Chinese Academy of Sciences, Beijing, China
| | - Fu-Rong Ma
- Department of Otolaryngology Head and Neck Surgery, Peking University Third Hospital, Beijing, China
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9
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Basso L, Boecking B, Brueggemann P, Pedersen NL, Canlon B, Cederroth CR, Mazurek B. Gender-Specific Risk Factors and Comorbidities of Bothersome Tinnitus. Front Neurosci 2020; 14:706. [PMID: 33071718 PMCID: PMC7539146 DOI: 10.3389/fnins.2020.00706] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2020] [Accepted: 06/11/2020] [Indexed: 11/13/2022] Open
Abstract
Objective This study aims to identify gender-specific risk factors associated with the presence of bothersome tinnitus (compared with non-bothersome tinnitus), including sociodemographic and lifestyle factors, tinnitus-associated phenomena (hearing loss, traumatic experiences, sleep disturbances), and physical as well as mental comorbidities. Methods We conducted a cross-sectional study using survey data from the Swedish LifeGene cohort containing information on self-reported tinnitus (N = 7615). We (1) analyzed risk factor and comorbidity frequencies, (2) computed multivariate logistic regression models to identify predictors of bothersome tinnitus within both genders, and (3) moderated logistic regression models to compare effects between genders. Results (1) The majority of factors that differed in frequencies between bothersome and non-bothersome tinnitus were equal for both genders. Women with bothersome tinnitus specifically reported higher rates of cardiovascular disease, thyroid disease, epilepsy, fibromyalgia, and burnout, and men with bothersome tinnitus reported higher rates of alcohol consumption, Ménière's disease, anxiety syndrome, and panic (compared with non-bothersome tinnitus, respectively). (2) Across both genders, multivariate logistic regression analyses revealed significant associations between bothersome tinnitus and age, reduced hearing ability, hearing-related difficulties in social situations, and reduced sleep quality. In women, bothersome tinnitus was specifically associated with cardiovascular disease and epilepsy; in men, with lower education levels and anxiety syndrome. (3) Moderated logistic regression analyses revealed that the effects of low education and anxiety syndrome were present in men, but not in women, whereas the effects of age, reduced hearing ability and related difficulties, cardiovascular disease, epilepsy, and burnout were not gender specific. Conclusion Irrespective of gender, bothersome tinnitus is associated with higher age, reduced hearing ability, hearing-related difficulties, cardiovascular disease, epilepsy, and burnout. Gender-specific effects comprise low levels of education and the presence of anxiety syndrome for men. These findings need to be interpreted with caution, yet they suggest the presence of gender-specific biopsychosocial influences in the emergence or maintenance of bothersome tinnitus. Future studies ought to investigate the underlying mechanisms of the observed relationships.
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Affiliation(s)
- Laura Basso
- Tinnitus Center, Charité - Universitätsmedizin Berlin, Berlin, Germany
| | - Benjamin Boecking
- Tinnitus Center, Charité - Universitätsmedizin Berlin, Berlin, Germany
| | - Petra Brueggemann
- Tinnitus Center, Charité - Universitätsmedizin Berlin, Berlin, Germany
| | - Nancy L Pedersen
- Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden
| | - Barbara Canlon
- Laboratory of Experimental Audiology, Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden
| | - Christopher R Cederroth
- Laboratory of Experimental Audiology, Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden.,National Institute for Health Research (NIHR) Nottingham Biomedical Research Centre, Nottingham University Hospitals NHS Trust, Nottingham, United Kingdom.,Hearing Sciences, Division of Clinical Neuroscience, School of Medicine, University of Nottingham, Nottingham, United Kingdom
| | - Birgit Mazurek
- Tinnitus Center, Charité - Universitätsmedizin Berlin, Berlin, Germany
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10
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Different Effects of Transcranial Direct Current Stimulation on Leg Muscle Glucose Uptake Asymmetry in Two Women with Multiple Sclerosis. Brain Sci 2020; 10:brainsci10080549. [PMID: 32823504 PMCID: PMC7465960 DOI: 10.3390/brainsci10080549] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2020] [Revised: 08/11/2020] [Accepted: 08/12/2020] [Indexed: 12/17/2022] Open
Abstract
Asymmetrical lower limb strength is a significant contributor to impaired walking abilities in people with multiple sclerosis (PwMS). Transcranial direct current stimulation (tDCS) may be an effective technique to enhance cortical excitability and increase neural drive to more-affected lower limbs. A sham-controlled, randomized, cross-over design was employed. Two women with MS underwent two 20 min sessions of either 3 mA tDCS or Sham before 20 min of treadmill walking at a self-selected speed. During walking, the participants were injected with the glucose analogue, [18F] fluorodeoxyglucose (FDG). Participants were then imaged to examine glucose metabolism and uptake asymmetries in the legs. Standardized uptake values (SUVs) were compared between the legs and asymmetry indices were calculated. Subject 2 was considered physically active (self-reported participating in at least 30 min of moderate-intensity physical activity on at least three days of the week for the last three months), while Subject 1 was physically inactive. In Subject 1, there was a decrease in SUVs at the left knee flexors, left upper leg, left and right plantar flexors, and left and right lower legs and SUVs in the knee extensors and dorsiflexors were considered symmetric after tDCS compared to Sham. Subject 2 showed an increase in SUVs at the left and right upper legs, right plantar flexors, and right lower leg with no muscle group changing asymmetry status. This study demonstrates that tDCS may increase neural drive to leg muscles and decrease glucose uptake during walking in PwMS with low physical activity levels.
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11
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Workman CD, Kamholz J, Rudroff T. Increased leg muscle fatigability during 2 mA and 4 mA transcranial direct current stimulation over the left motor cortex. Exp Brain Res 2020; 238:333-343. [PMID: 31919540 DOI: 10.1007/s00221-019-05721-w] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2019] [Accepted: 12/30/2019] [Indexed: 12/21/2022]
Abstract
Transcranial direct current stimulation (tDCS) using intensities ≤ 2 mA on physical and cognitive outcomes has been extensively investigated. Studies comparing the effects of different intensities of tDCS have yielded mixed results and little is known about how higher intensities (> 2 mA) affect outcomes. This study examined the effects of tDCS at 2 mA and 4 mA on leg muscle fatigability. This was a double-blind, randomized, sham-controlled study. Sixteen healthy young adults underwent tDCS at three randomly ordered intensities (sham, 2 mA, 4 mA). Leg muscle fatigability of both legs was assessed via isokinetic fatigue testing (40 maximal reps, 120°/s). Torque- and work-derived fatigue indices (FI-T and FI-W, respectively), as well as total work performed (TW), were calculated. FI-T of the right knee extensors indicated increased fatigability in 2 mA and 4 mA compared with sham (p = 0.01, d = 0.73 and p < 0.001, d = 1.61, respectively). FI-W of the right knee extensors also indicated increased fatigability in 2 mA and 4 mA compared to sham (p = 0.01, d = 0.57 and p < 0.001, d = 1.12, respectively) and 4 mA compared with 2 mA (p = 0.034, d = 0.37). tDCS intensity did not affect TW performed. The 2 mA and 4 mA tDCS intensities increased the fatigability of the right knee extensors in young, healthy participants, potentially from altered motor unit recruitment/discharge rate or cortical hyperexcitability. Despite this increase in fatigability, the TW performed in both these conditions was not different from sham.
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Affiliation(s)
- Craig D Workman
- Department of Health and Human Physiology, University of Iowa, E432 Field House, Iowa City, IA, 52242, USA
| | - John Kamholz
- Department of Neurology, University of Iowa Hospitals and Clinics, Iowa City, IA, USA
| | - Thorsten Rudroff
- Department of Health and Human Physiology, University of Iowa, E432 Field House, Iowa City, IA, 52242, USA.
- Department of Neurology, University of Iowa Hospitals and Clinics, Iowa City, IA, USA.
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12
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Workman CD, Kamholz J, Rudroff T. Transcranial Direct Current Stimulation (tDCS) to Improve Gait in Multiple Sclerosis: A Timing Window Comparison. Front Hum Neurosci 2019; 13:420. [PMID: 31849628 PMCID: PMC6893177 DOI: 10.3389/fnhum.2019.00420] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2019] [Accepted: 11/13/2019] [Indexed: 12/18/2022] Open
Abstract
Unilateral weakness of the lower limb is a hallmark of multiple sclerosis (MS) and a significant contributor to the progressive worsening of walking ability. There are currently no effective rehabilitation strategies targeting strength asymmetries and/or gait impairments in people with MS (PwMS). Transcranial direct current stimulation (tDCS) has improved motor outcomes in various populations, but the effect of tDCS on gait in PwMS and the ideal timing window of tDCS application are still unknown. This study investigated the effects of tDCS, either before or during a 6 min walk test (6MWT), on the distance walked and gait characteristics in PwMS. Twelve participants were recruited and randomly assigned into BEFORE or DURING groups (both n = 6). The BEFORE group received stimulation before performing a 6MWT (sham/2 mA, 13 min). The DURING group received stimulation only during a 6MWT (sham/2 mA, 6 min). Stimulation was over the more MS-affected primary motor cortex (M1). Distance walked and gait characteristics of the walk were the primary and secondary outcomes. The results indicated a significant decrease in distance walked in the DURING group (p = 0.026) and a significant increase in gait velocity in the BEFORE group (p = 0.04). These changes were accompanied by trends (p < 0.1) in distance walked, gait velocity, and stride length. Overall, the results of this study suggest that tDCS performed before a 6MWT might be more effective than tDCS during a 6MWT and that a single session of tDCS may not be sufficient to influence gait. Clinical Trial Registration: www.ClinicalTrials.gov, identifier #NCT03757819.
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Affiliation(s)
- Craig D Workman
- Department of Health and Human Physiology, University of Iowa, Iowa City, IA, United States
| | - John Kamholz
- Department of Neurology, Carver College of Medicine, University of Iowa Hospitals and Clinics, Iowa City, IA, United States
| | - Thorsten Rudroff
- Department of Health and Human Physiology, University of Iowa, Iowa City, IA, United States.,Department of Neurology, Carver College of Medicine, University of Iowa Hospitals and Clinics, Iowa City, IA, United States
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