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Koch G, Altomare D, Benussi A, Bréchet L, Casula EP, Dodich A, Pievani M, Santarnecchi E, Frisoni GB. The emerging field of non-invasive brain stimulation in Alzheimer's disease. Brain 2024; 147:4003-4016. [PMID: 39562009 DOI: 10.1093/brain/awae292] [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: 05/29/2024] [Revised: 07/09/2024] [Accepted: 07/26/2024] [Indexed: 11/21/2024] Open
Abstract
Treating cognitive impairment is a holy grail of modern clinical neuroscience. In the past few years, non-invasive brain stimulation is increasingly emerging as a therapeutic approach to ameliorate performance in patients with cognitive impairment and as an augmentation approach in persons whose cognitive performance is within normal limits. In patients with Alzheimer's disease, better understanding of brain connectivity and function has allowed for the development of different non-invasive brain stimulation protocols. Recent studies have shown that transcranial stimulation methods enhancing brain plasticity with several modalities have beneficial effects on cognitive functions. Amelioration has been shown in preclinical studies on behaviour of transgenic mouse models for Alzheimer's pathology and in clinical studies with variable severity of cognitive impairment. While the field is still grappling with issues related to the standardization of target population, frequency, intensity, treatment duration and stimulated region, positive outcomes have been reported on cognitive functions and on markers of brain pathology. Here we review the most encouraging protocols based on repetitive transcranial magnetic stimulation, transcranial direct current stimulation, transcranial alternating current stimulation, visual-auditory stimulation, photobiomodulation and transcranial focused ultrasound, which have demonstrated efficacy to enhance cognitive functions or slow cognitive decline in patients with Alzheimer's disease. Beneficial non-invasive brain stimulation effects on cognitive functions are associated with the modulation of specific brain networks. The most promising results have been obtained targeting key hubs of higher-level cognitive networks, such as the frontal-parietal network and the default mode network. The personalization of stimulation parameters according to individual brain features sheds new light on optimizing non-invasive brain stimulation protocols for future applications.
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Affiliation(s)
- Giacomo Koch
- Experimental Neuropsychophysiology Lab, Santa Lucia Foundation IRCCS, 00179 Rome, Italy
- Department of Neuroscience and Rehabilitation, University of Ferrara and Center for Translational Neurophysiology of Speech and Communication, Italian Institute of Technology (IIT), 44121 Ferrara, Italy
| | - Daniele Altomare
- Department of Clinical and Experimental Sciences, University of Brescia, 25123 Brescia, Italy
| | - Alberto Benussi
- Neurology Unit, Department of Medical, Surgical and Health Sciences, University of Trieste, 34127 Trieste, Italy
| | - Lucie Bréchet
- Department of Basic Neurosciences, Faculty of Medicine, University of Geneva, 1205 Geneva, Switzerland
| | - Elias P Casula
- Experimental Neuropsychophysiology Lab, Santa Lucia Foundation IRCCS, 00179 Rome, Italy
- Department of System Medicine, University of Tor Vergata, 00133 Rome, Italy
| | - Alessandra Dodich
- Center for Mind/Brain Sciences (CIMeC), University of Trento, 38068 Rovereto, Italy
| | - Michela Pievani
- Laboratory Alzheimer's Neuroimaging and Epidemiology, IRCCS Istituto Centro San Giovanni di Dio Fatebenefratelli, 25123 Brescia, Italy
| | - Emiliano Santarnecchi
- Precision Neuroscience and Neuromodulation Program, Gordon Center for Medical Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, 02114 Boston, USA
| | - Giovanni B Frisoni
- Laboratory of Neuroimaging of Aging (LANVIE), University of Geneva, 1205 Geneva, Switzerland
- Geneva Memory Center, Geneva University Hospitals, 1205 Geneva, Switzerland
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Kraft JD, Hampstead BM. A Systematic Review of tACS Effects on Cognitive Functioning in Older Adults Across the Healthy to Dementia Spectrum. Neuropsychol Rev 2024; 34:1165-1190. [PMID: 37882864 PMCID: PMC11045666 DOI: 10.1007/s11065-023-09621-3] [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: 11/09/2022] [Accepted: 09/26/2023] [Indexed: 10/27/2023]
Abstract
Transcranial alternating current stimulation (tACS) is a form of noninvasive brain stimulation that has experienced rapid growth within the aging population over the past decade due to its potential for modulating cognitive functioning across the "intact" to dementia spectrum. For this reason, we performed a systematic review of the literature to evaluate the efficacy of tACS on cognitive functioning in older adults, including those with cognitive impairment. Our review was completed in June 2023 using Psych INFO, Embase, PubMed, and Cochrane databases. Out of 479 screened articles, 21 met inclusion criteria and were organized according to clinical diagnoses. Seven out of nine studies targeted cognitively intact older adults and showed some type of cognitive improvement after stimulation, whereas nine out of twelve studies targeted clinical diagnoses and showed improved cognitive performance to varying degrees. Studies showed considerable heterogeneity in methodology, stimulation parameters, participant characteristics, choice of cognitive task, and analytic strategy, all of which reinforce the need for standardized reporting of tACS methods. Through this heterogeneity, multiple patterns are described, such as disease progression influencing tACS effects and the need for individualized tailoring. For clinical translation, it is imperative that the field (a) better understand the physiological effects of tACS in these populations, especially in respect to biomarkers, (b) document a causal relationship between tACS delivery and neurophysiological/cognitive effects, and (c) systematically establish dosing parameters (e.g., amplitude, stimulation frequency, number and duration of sessions, need for booster/maintenance sessions).
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Affiliation(s)
- Jacob D Kraft
- Research Program On Cognition and Neuromodulation Based Interventions, Department of Psychiatry, University of Michigan, 4250 Plymouth Rd, Ann Arbor, MI, 48105, USA.
- Department of Psychiatry &, Behavioral Health, The Ohio State University, Columbus, OH, 43210, USA.
| | - Benjamin M Hampstead
- Research Program On Cognition and Neuromodulation Based Interventions, Department of Psychiatry, University of Michigan, 4250 Plymouth Rd, Ann Arbor, MI, 48105, USA
- Mental Health Service, Neuropsychology Section, VA Ann Arbor Healthcare System, Ann Arbor, MI, 48105, USA
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Zandbagleh A, Miltiadous A, Sanei S, Azami H. Beta-to-Theta Entropy Ratio of EEG in Aging, Frontotemporal Dementia, and Alzheimer's Dementia. Am J Geriatr Psychiatry 2024; 32:1361-1382. [PMID: 39004533 DOI: 10.1016/j.jagp.2024.06.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/02/2024] [Revised: 06/25/2024] [Accepted: 06/26/2024] [Indexed: 07/16/2024]
Abstract
BACKGROUND Aging, frontotemporal dementia (FTD), and Alzheimer's dementia (AD) manifest electroencephalography (EEG) alterations, particularly in the beta-to-theta power ratio derived from linear power spectral density (PSD). Given the brain's nonlinear nature, the EEG nonlinear features could provide valuable physiological indicators of aging and cognitive impairment. Multiscale dispersion entropy (MDE) serves as a sensitive nonlinear metric for assessing the information content in EEGs across biologically relevant time scales. OBJECTIVE To compare the MDE-derived beta-to-theta entropy ratio with its PSD-based counterpart to detect differences between healthy young and elderly individuals and between different dementia subtypes. METHODS Scalp EEG recordings were obtained from two datasets: 1) Aging dataset: 133 healthy young and 65 healthy older adult individuals; and 2) Dementia dataset: 29 age-matched healthy controls (HC), 23 FTD, and 36 AD participants. The beta-to-theta ratios based on MDE vs. PSD were analyzed for both datasets. Finally, the relationships between cognitive performance and the beta-to-theta ratios were explored in HC, FTD, and AD. RESULTS In the Aging dataset, older adults had significantly higher beta-to-theta entropy ratios than young individuals. In the Dementia dataset, this ratio outperformed the beta-to-theta PSD approach in distinguishing between HC, FTD, and AD. The AD participants had a significantly lower beta-to-theta entropy ratio than FTD, especially in the temporal region, unlike its corresponding PSD-based ratio. The beta-to-theta entropy ratio correlated significantly with cognitive performance. CONCLUSION Our study introduces the beta-to-theta entropy ratio using nonlinear MDE for EEG analysis, highlighting its potential as a sensitive biomarker for aging and cognitive impairment.
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Affiliation(s)
- Ahmad Zandbagleh
- School of Electrical Engineering (AZ), Iran University of Science and Technology, Tehran, Iran
| | - Andreas Miltiadous
- Department of Informatics and Telecommunications (AM), University of Ioannina, Arta, Greece
| | - Saeid Sanei
- Electrical and Electronic Engineering Department (SS), Imperial College London, London, UK
| | - Hamed Azami
- Centre for Addiction and Mental Health (HA), University of Toronto, Toronto, ON, Canada.
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Lee TW, Almeida S, Tramontano G. Attention improvement to transcranial alternating current stimulation at gamma frequency over the right frontoparietal network: a preliminary report. Acta Neuropsychiatr 2024:1-5. [PMID: 39355959 DOI: 10.1017/neu.2024.35] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/03/2024]
Abstract
Applying transcranial alternating current stimulation (tACS) at 40 Hz to the frontal and parietal regions, either unilaterally (left or right) or bilaterally, can improve cognitive dysfunctions. This study aimed to explore the influence of tACS at gamma frequency over right fronto-parietal (FP) region on attention. The analysis is based on retrospective data from a clinical intervention. We administered test of variables of attention (TOVA; visual mode) to 44 participants with various neuropsychiatric diagnoses before and after 12 sessions of tACS treatment. Alternating currents at 2.0 mA were delivered to the electrode positions F4 and P4, following the 10-20 EEG convention, for 20 mins in each session. We observed significant improvement across 3 indices of the TOVA, including reduction of variability in reaction time (p = 0.0002), increase in d-Prime (separability of targets and non-targets; p = 0.0157), and decrease in commission error rate (p = 0.0116). The mean RT and omission error rate largely remained unchanged. Artificial injection of tACS at 40 Hz over right FP network may improve attention function, especially in the domains of consistency in performance, target/non-target discrimination, and inhibitory control.
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Affiliation(s)
- Tien-Wen Lee
- The NeuroCognitive Institute (NCI) Clinical Research Foundation, Mount Arlington, NJ, USA
| | - Sergio Almeida
- The NeuroCognitive Institute (NCI) Clinical Research Foundation, Mount Arlington, NJ, USA
| | - Gerald Tramontano
- The NeuroCognitive Institute (NCI) Clinical Research Foundation, Mount Arlington, NJ, USA
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Paßmann S, Baselgia S, Kasten FH, Herrmann CS, Rasch B. Differential online and offline effects of theta-tACS on memory encoding and retrieval. COGNITIVE, AFFECTIVE & BEHAVIORAL NEUROSCIENCE 2024; 24:894-911. [PMID: 39085585 PMCID: PMC11390785 DOI: 10.3758/s13415-024-01204-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 07/01/2024] [Indexed: 08/02/2024]
Abstract
Theta oscillations support memory formation, but their exact contribution to the communication between prefrontal cortex (PFC) and the hippocampus is unknown. We tested the functional relevance of theta oscillations as a communication link between both areas for memory formation using transcranial alternating current stimulation (tACS). Healthy, young participants learned two lists of Dutch-German word pairs and retrieved them immediately and with a 30-min delay. In the encoding group (N = 30), tACS was applied during the encoding of list 1. List 2 was used to test stimulation aftereffects. In the retrieval group (N = 23), we stimulated during the delayed recall. In both groups, we applied tACS bilaterally at prefrontal and tempo-parietal sites, using either individualized theta frequency or 15 Hz (as control), according to a within-subject design. Stimulation with theta-tACS did not alter overall learning performance. An exploratory analysis revealed that immediate recall improved when word-pairs were learned after theta-tACS (list 2). Applying theta-tACS during retrieval had detrimental effects on memory. No changes in the power of the respective frequency bands were observed. Our results do not support the notion that impacting the communication between PFC and the hippocampus during a task by bilateral tACS improves memory. However, we do find evidence that direct stimulation had a trend for negatively interfering effects during immediate and delayed recall. Hints for beneficial effects on memory only occurred with aftereffects of the stimulation. Future studies need to further examine the effects during and after stimulation on memory formation.
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Affiliation(s)
- Sven Paßmann
- Cognitive Biopsychology and Methods, Department of Psychology, Université Fribourg, Rue P.-A.-de-Faucigny 2, 1700, Fribourg, Switzerland.
- Department of Neurology, University Medicine Greifswald, Greifswald, Germany.
| | - Sandrine Baselgia
- Cognitive Biopsychology and Methods, Department of Psychology, Université Fribourg, Rue P.-A.-de-Faucigny 2, 1700, Fribourg, Switzerland
| | - Florian H Kasten
- Centre de Recherche Cerveau & Cognition, CNRS, Toulouse, France
- Université Toulouse III Paul Sabatier, Toulouse, France
| | - Christoph S Herrmann
- Experimental Psychology Lab, Department of Psychology, Carl Von Ossietzky Universität, Oldenburg, Germany
| | - Björn Rasch
- Cognitive Biopsychology and Methods, Department of Psychology, Université Fribourg, Rue P.-A.-de-Faucigny 2, 1700, Fribourg, Switzerland
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Ghezeljeh FK, Kazemi R, Rostami R, Zandbagleh A, Khomami S, Vandi FR, Hadipour AL. Female Cerebellum Seems Sociable; An iTBS Investigation. CEREBELLUM (LONDON, ENGLAND) 2024; 23:1783-1794. [PMID: 38530595 DOI: 10.1007/s12311-024-01686-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 03/11/2024] [Indexed: 03/28/2024]
Abstract
The cerebellum has been shown to be engaged in tasks other than motor control, including cognitive and affective functions. Prior neuroimaging studies have documented the role of this area in social cognition and despite these findings, no studies have yet examined the causal relationship between the cerebellum and social cognition. This study aimed to investigate the role of the cerebellum in empathy and theory of mind (ToM) in a randomized, placebo-controlled, double-blind, parallel study. 32 healthy participants were assigned to either a sham or active group. For the active group, an intermittent theta-burst stimulation (iTBS) protocol at 100% of the motor threshold was applied to the cerebellum, while the control group received sham stimulation. An eyes-closed EEG session, the Empathy Quotient (EQ) test, and the Reading the Mind in the Eyes Test (RMET) were administered before and after the iTBS session. The results demonstrated differences in cognitive empathy, ToM, and a decrease in the activity of the default mode network (DMN) between the active and sham groups in females. Females also showed a decrease in the activity of the affective empathy network and connectivity in the DMN. We conclude that cognitive empathy and ToM are associated with cerebellar activity, and due to sex-related differences in the cortical organization of this area which is modulated by sex hormones, the stimulation of the cerebellum in males and females yields different results.
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Affiliation(s)
| | - Reza Kazemi
- Faculty of Entrepreneurship, University of Tehran, Farshi Moghadam (16 St.), North Kargar Ave., Tehran, Iran.
| | - Reza Rostami
- Department of Psychology, University of Tehran, Tehran, Iran
| | - Ahmad Zandbagleh
- School of Electrical Engineering, Iran University of Science and Technology, Tehran, Iran
| | - Sanaz Khomami
- Department of Psychology, West Tehran Branch, Islamic Azad University, Tehran, Iran
| | | | - Abed L Hadipour
- Department of Cognitive Sciences, University of Messina, Messina, Italy
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Zandbagleh A, Sanei S, Azami H. Implications of Aperiodic and Periodic EEG Components in Classification of Major Depressive Disorder from Source and Electrode Perspectives. SENSORS (BASEL, SWITZERLAND) 2024; 24:6103. [PMID: 39338848 PMCID: PMC11436117 DOI: 10.3390/s24186103] [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: 08/28/2024] [Revised: 09/16/2024] [Accepted: 09/20/2024] [Indexed: 09/30/2024]
Abstract
Electroencephalography (EEG) is useful for studying brain activity in major depressive disorder (MDD), particularly focusing on theta and alpha frequency bands via power spectral density (PSD). However, PSD-based analysis has often produced inconsistent results due to difficulties in distinguishing between periodic and aperiodic components of EEG signals. We analyzed EEG data from 114 young adults, including 74 healthy controls (HCs) and 40 MDD patients, assessing periodic and aperiodic components alongside conventional PSD at both source and electrode levels. Machine learning algorithms classified MDD versus HC based on these features. Sensor-level analysis showed stronger Hedge's g effect sizes for parietal theta and frontal alpha activity than source-level analysis. MDD individuals exhibited reduced theta and alpha activity relative to HC. Logistic regression-based classifications showed that periodic components slightly outperformed PSD, with the best results achieved by combining periodic and aperiodic features (AUC = 0.82). Strong negative correlations were found between reduced periodic parietal theta and frontal alpha activities and higher scores on the Beck Depression Inventory, particularly for the anhedonia subscale. This study emphasizes the superiority of sensor-level over source-level analysis for detecting MDD-related changes and highlights the value of incorporating both periodic and aperiodic components for a more refined understanding of depressive disorders.
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Affiliation(s)
- Ahmad Zandbagleh
- School of Electrical Engineering, Iran University of Science and Technology, Tehran 16846-13114, Iran;
| | - Saeid Sanei
- Electrical and Electronic Engineering Department, Imperial College London, London SW7 2AZ, UK;
| | - Hamed Azami
- Centre for Addiction and Mental Health, University of Toronto, Toronto, ON M6J 1H1, Canada
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Wynn SC, Marshall TR, Nyhus E. Utilizing tACS to enhance memory confidence and EEG to predict individual differences in brain stimulation efficacy. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.05.27.596015. [PMID: 38854074 PMCID: PMC11160642 DOI: 10.1101/2024.05.27.596015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2024]
Abstract
The information transfer necessary for successful memory retrieval is believed to be mediated by theta and gamma oscillations. These oscillations have been linked to memory processes in electrophysiological studies, which were correlational in nature. In the current study, we used transcranial alternating current stimulation (tACS) to externally modulate brain oscillations to examine its direct effects on memory performance. Participants received sham, theta (4 Hz), and gamma (50 Hz) tACS over frontoparietal regions while retrieving information in a source memory paradigm. Linear regression models were used to investigate the direct effects of oscillatory non-invasive brain stimulation (NIBS) on memory accuracy and confidence. Our results indicate that both theta and gamma tACS altered memory confidence. Specifically, theta tACS seemed to lower the threshold for confidence in retrieved information, while gamma tACS appeared to alter the memory confidence bias. Furthermore, the individual differences in tACS effects could be predicted from electroencephalogram (EEG) measures recorded prior to stimulation, suggesting that EEG could be a useful tool for predicting individual variability in the efficacy of NIBS.
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Affiliation(s)
- Syanah C Wynn
- Neuroimaging Center, Johannes Gutenberg University Medical Center Mainz, Mainz, Germany
- Department of Psychology and Program in Neuroscience, Bowdoin College, Brunswick, ME, United States
- Centre for Human Brain Health, School of Psychology, University of Birmingham, Birmingham, UK
| | - Tom R Marshall
- Centre for Human Brain Health, School of Psychology, University of Birmingham, Birmingham, UK
| | - Erika Nyhus
- Department of Psychology and Program in Neuroscience, Bowdoin College, Brunswick, ME, United States
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Chen R, Huang L, Wang R, Fei J, Wang H, Wang J. Advances in Non-Invasive Neuromodulation Techniques for Improving Cognitive Function: A Review. Brain Sci 2024; 14:354. [PMID: 38672006 PMCID: PMC11048722 DOI: 10.3390/brainsci14040354] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2024] [Revised: 03/27/2024] [Accepted: 03/30/2024] [Indexed: 04/28/2024] Open
Abstract
Non-invasive neuromodulation techniques are widely utilized to study and improve cognitive function, with the aim of modulating different cognitive processes. For workers performing high-intensity mental and physical tasks, extreme fatigue may not only affect their working efficiency but may also lead to cognitive decline or cognitive impairment, which, in turn, poses a serious threat to their physical health. The use of non-invasive neuromodulation techniques has important research value for improving and enhancing cognitive function. In this paper, we review the research status, existing problems, and future prospects of transcranial direct current stimulation (tDCS), transcranial alternating current stimulation (tACS), transcranial magnetic stimulation (TMS), and transcutaneous acupoint stimulation (TAS), which are the most studied physical methods in non-invasive neuromodulation techniques to improve and enhance cognition. The findings presented in this paper will be of great reference value for the in-depth study of non-invasive neuromodulation techniques in the field of cognition.
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Affiliation(s)
- Ruijuan Chen
- School of Life Sciences, Tiangong University, Tianjin 300387, China; (R.C.); (H.W.)
| | - Lengjie Huang
- School of Electronics & Information Engineering, Tiangong University, Tianjin 300387, China; (L.H.); (R.W.); (J.F.)
| | - Rui Wang
- School of Electronics & Information Engineering, Tiangong University, Tianjin 300387, China; (L.H.); (R.W.); (J.F.)
| | - Jieying Fei
- School of Electronics & Information Engineering, Tiangong University, Tianjin 300387, China; (L.H.); (R.W.); (J.F.)
| | - Huiquan Wang
- School of Life Sciences, Tiangong University, Tianjin 300387, China; (R.C.); (H.W.)
| | - Jinhai Wang
- School of Life Sciences, Tiangong University, Tianjin 300387, China; (R.C.); (H.W.)
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Braun JA, Patel M, Henderson LA, Dawood T, Macefield VG. Electrical stimulation of the ventromedial prefrontal cortex modulates muscle sympathetic nerve activity and blood pressure. Cereb Cortex 2024; 34:bhad422. [PMID: 37950875 DOI: 10.1093/cercor/bhad422] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2023] [Revised: 10/13/2023] [Accepted: 10/15/2023] [Indexed: 11/13/2023] Open
Abstract
We recently showed that transcranial alternating current stimulation of the dorsolateral prefrontal cortex modulates spontaneous bursts of muscle sympathetic nerve activity, heart rate, and blood pressure (Sesa-Ashton G, Wong R, McCarthy B, Datta S, Henderson LA, Dawood T, Macefield VG. Stimulation of the dorsolateral prefrontal cortex modulates muscle sympathetic nerve activity and blood pressure in humans. Cereb Cortex Comm. 2022:3:2tgac017.). Stimulation was delivered between scalp electrodes placed over the nasion and electroencephalogram (EEG) electrode site F3 (left dorsolateral prefrontal cortex) or F4 (right dorsolateral prefrontal cortex), and therefore the current passed within the anatomical locations underlying the left and right ventromedial prefrontal cortices. Accordingly, we tested the hypothesis that stimulation of the left and right ventromedial prefrontal cortices would also modulate muscle sympathetic nerve activity, although we predicted that this would be weaker than that seen during dorsolateral prefrontal cortex stimulation. We further tested whether stimulation of the right ventromedial prefrontal cortices would cause greater modulation of muscle sympathetic nerve activity, than stimulation of the left ventromedial prefrontal cortices. In 11 individuals, muscle sympathetic nerve activity was recorded via microelectrodes inserted into the right common peroneal nerve, together with continuous blood pressure, electrocardiogram, and respiration. Stimulation was achieved using transcranial alternating current stimulation, +2 to -2 mA, 0.08 Hz, 100 cycles, applied between electrodes placed over the nasion, and EEG electrode site FP1, (left ventromedial prefrontal cortices) or FP2 (right ventromedial prefrontal cortices); for comparison, stimulation was also applied over F4 (right dorsolateral prefrontal cortex). Stimulation of all three cortical sites caused partial entrainment of muscle sympathetic nerve activity to the sinusoidal stimulation, together with modulation of blood pressure and heart rate. We found a significant fall in mean blood pressure of ~6 mmHg (P = 0.039) during stimulation of the left ventromedial prefrontal cortices, as compared with stimulation of the right. We have shown, for the first time, that transcranial alternating current stimulation of the ventromedial prefrontal cortices modulates muscle sympathetic nerve activity and blood pressure in awake humans at rest. However, it is unclear if this modulation occurred through the same brain pathways activated during transcranial alternating current stimulation of the dorsolateral prefrontal cortex.
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Affiliation(s)
- Joe A Braun
- Baker Heart and Diabetes Institute, 75 Commerical Road, Melbourne, VIC 3004, Australia
- Department of Neuroscience, Monash University, 99 Commercial Road, Melbourne, VIC 3004, Australia
| | - Mariya Patel
- Baker Heart and Diabetes Institute, 75 Commerical Road, Melbourne, VIC 3004, Australia
- Baker Department of Cardiometabolic Health, The University of Melbourne, Grattan Street, Parkville, VIC 3010, Australia
| | - Luke A Henderson
- School of Medical Sciences (Neuroscience), Brain and Mind Centre, The University of Sydney, 94 Mallett Street, Sydney, NSW 2006, Australia
| | - Tye Dawood
- Baker Heart and Diabetes Institute, 75 Commerical Road, Melbourne, VIC 3004, Australia
- Baker Department of Cardiometabolic Health, The University of Melbourne, Grattan Street, Parkville, VIC 3010, Australia
| | - Vaughan G Macefield
- Baker Heart and Diabetes Institute, 75 Commerical Road, Melbourne, VIC 3004, Australia
- Department of Neuroscience, Monash University, 99 Commercial Road, Melbourne, VIC 3004, Australia
- Baker Department of Cardiometabolic Health, The University of Melbourne, Grattan Street, Parkville, VIC 3010, Australia
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Löffler BS, Stecher HI, Meiser A, Fudickar S, Hein A, Herrmann CS. Attempting to counteract vigilance decrement in older adults with brain stimulation. FRONTIERS IN NEUROERGONOMICS 2023; 4:1201702. [PMID: 38234473 PMCID: PMC10790873 DOI: 10.3389/fnrgo.2023.1201702] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/06/2023] [Accepted: 11/23/2023] [Indexed: 01/19/2024]
Abstract
Introduction Against the background of demographic change and the need for enhancement techniques for an aging society, we set out to repeat a study that utilized 40-Hz transcranial alternating current stimulation (tACS) to counteract the slowdown of reaction times in a vigilance experiment but with participants aged 65 years and older. On an oscillatory level, vigilance decrement is linked to rising occipital alpha power, which has been shown to be downregulated using gamma-tACS. Method We applied tACS on the visual cortex and compared reaction times, error rates, and alpha power of a group stimulated with 40 Hz to a sham and a 5-Hz-stimulated control group. All groups executed two 30-min-long blocks of a visual task and were stimulated according to group in the second block. We hypothesized that the expected increase in reaction times and alpha power would be reduced in the 40-Hz group compared to the control groups in the second block (INTERVENTION). Results Statistical analysis with linear mixed models showed that reaction times increased significantly over time in the first block (BASELINE) with approximately 3 ms/min for the SHAM and 2 ms/min for the 5-Hz and 40-Hz groups, with no difference between the groups. The increase was less pronounced in the INTERVENTION block (1 ms/min for SHAM and 5-Hz groups, 3 ms/min for the 40-Hz group). Differences among groups in the INTERVENTION block were not significant if the 5-Hz or the 40-Hz group was used as the base group for the linear mixed model. Statistical analysis with a generalized linear mixed model showed that alpha power was significantly higher after the experiment (1.37 μV2) compared to before (1 μV2). No influence of stimulation (40 Hz, 5 Hz, or sham) could be detected. Discussion Although the literature has shown that tACS offers potential for older adults, our results indicate that findings from general studies cannot simply be transferred to an old-aged group. We suggest adjusting stimulation parameters to the neurophysiological features expected in this group. Next to heterogeneity and cognitive fitness, the influence of motivation and medication should be considered.
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Affiliation(s)
- Birte S. Löffler
- Assistance Systems and Medical Device Technology, Department of Health Services Research, Carl von Ossietzky University Oldenburg, Oldenburg, Germany
| | - Heiko I. Stecher
- Experimental Psychology Lab, Department of Psychology, European Medical School, Cluster of Excellence “Hearing4all”, Carl von Ossietzky University Oldenburg, Oldenburg, Germany
| | - Arnd Meiser
- Experimental Psychology Lab, Department of Psychology, European Medical School, Cluster of Excellence “Hearing4all”, Carl von Ossietzky University Oldenburg, Oldenburg, Germany
| | - Sebastian Fudickar
- Assistance Systems and Medical Device Technology, Department of Health Services Research, Carl von Ossietzky University Oldenburg, Oldenburg, Germany
| | - Andreas Hein
- Assistance Systems and Medical Device Technology, Department of Health Services Research, Carl von Ossietzky University Oldenburg, Oldenburg, Germany
| | - Christoph S. Herrmann
- Experimental Psychology Lab, Department of Psychology, European Medical School, Cluster of Excellence “Hearing4all”, Carl von Ossietzky University Oldenburg, Oldenburg, Germany
- Research Center Neurosensory Science, Carl von Ossietzky University Oldenburg, Oldenburg, Germany
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