scholarly journals Multi-frequency tACS has lasting effects on neural synchrony and audiovisual responses

2019 ◽  
Author(s):  
Tobias Bockhorst ◽  
Joachim Ahlbeck ◽  
Florian Pieper ◽  
Gerhard Engler ◽  
Andreas K. Engel
Keyword(s):  
Electrical Stimulation ◽  
Cortical Network ◽  
Network Activity ◽  
Oscillatory Activity ◽  
Sensory Response ◽  
Audiovisual Stimulation ◽  
Gamma Range ◽  
Baseline Activity ◽  
Transcranial Alternating Current Stimulation ◽  
Audiovisual Processing

BACKGROUND: In cortical networks, synchronized oscillatory activity of neuronal populations enables communication, and its disturbance is related to a range of pathologies. Transcranial alternating current stimulation (tACS) has been explored as a flexible, noninvasive tool for the modulation and restoration of synchronized oscillatory signals. While numerous studies have addressed cognitive or behavioural effects of electrical stimulation, the neural changes underlying the effects of tACS and their persistence after stimulation offset have remained unclear. OBJECTIVE: Here, we screened for lasting aftereffects of prolonged tACS on intrinsic network activity and audiovisual processing in the anesthetized ferret brain. METHODS: Electrical stimulation was applied via subcutaneous wire electrodes. Current waveforms were synthesized from two frequencies in the alpha or gamma range, respectively. Flashes and clicks were used for audiovisual stimulation. Electrocorticographic recordings from an extended network including occipital, temporal and parietal cortical areas were obtained before and after tACS. RESULTS: Changes in local synchrony (continuous and spike-triggered power of LFP), synchrony across recording sites (imaginary coherence) and altered dynamics of sensory response-features (peak-to-peak amplitude, extremum latency) following electrical stimulation consistently point to a synchronizing effect of tACS that can outlast stimulation offset by at least 10 min. Gamma-band tACS proved particularly effective. In line with previous reports on cross-frequency interactions, we observed effects on coherence and power of baseline activity at frequencies other than the ones targeted by tACS. These cross-frequency interactions appeared to underlie the strengthening and stabilizing effect on audiovisual responses. CONCLUSION: We demonstrate aftereffects of tACS on synchrony and stimulus processing in an extended cortical network, measured intracranially in a setting that resembles tACS stimulation in humans. The data provide direct evidence for the efficacy of tACS as a tool for sustained modulation of cortical network dynamics.

scholarly journals Chronic recording and electrochemical performance of Utah microelectrode arrays implanted in rat motor cortex

2018 ◽  
Vol 120 (4) ◽  
pp. 2083-2090 ◽  
Author(s):  
Bryan J. Black ◽  
Aswini Kanneganti ◽  
Alexandra Joshi-Imre ◽  
Rashed Rihani ◽  
Bitan Chakraborty ◽  
...  
Keyword(s):  
Electrical Stimulation ◽  
Motor Cortex ◽  
Electrochemical Performance ◽  
Failure Modes ◽  
Cortical Network ◽  
Network Activity ◽  
Rodent Models ◽  
Electrode Arrays ◽  
Chronic Recording ◽  
Wire Breakage

Multisite implantable electrode arrays serve as a tool to understand cortical network connectivity and plasticity. Furthermore, they enable electrical stimulation to drive plasticity, study motor/sensory mapping, or provide network input for controlling brain-computer interfaces. Neurobehavioral rodent models are prevalent in studies of motor cortex injury and recovery as well as restoration of auditory/visual cues due to their relatively low cost and ease of training. Therefore, it is important to understand the chronic performance of relevant electrode arrays in rodent models. In this report, we evaluate the chronic recording and electrochemical performance of 16-channel Utah electrode arrays, the current state-of-the-art in pre-/clinical cortical recording and stimulation, in rat motor cortex over a period of 6 mo. The single-unit active electrode yield decreased from 52.8 ± 10.0 ( week 1) to 13.4 ± 5.1% ( week 24). Similarly, the total number of single units recorded on all electrodes across all arrays decreased from 106 to 15 over the same time period. Parallel measurements of electrochemical impedance spectra and cathodic charge storage capacity exhibited significant changes in electrochemical characteristics consistent with development of electrolyte leakage pathways over time. Additionally, measurements of maximum cathodal potential excursion indicated that only a relatively small fraction of electrodes (10–35% at 1 and 24 wk postimplantation) were capable of delivering relevant currents (20 µA at 4 nC/ph) without exceeding negative or positive electrochemical potential limits. In total, our findings suggest mainly abiotic failure modes, including mechanical wire breakage as well as degradation of conducting and insulating substrates. NEW & NOTEWORTHY Multisite implantable electrode arrays serve as a tool to record cortical network activity and enable electrical stimulation to drive plasticity or provide network feedback. The use of rodent models in these fields is prevalent. We evaluated chronic recording and electrochemical performance of 16-channel Utah electrode arrays in rat motor cortex over a period of 6 mo. We primarily observed abiotic failure modes suggestive of mechanical wire breakage and/or degradation of insulation.

scholarly journals Sustained neural rhythms reveal endogenous oscillations supporting speech perception

PLoS Biology ◽  
2021 ◽  
Vol 19 (2) ◽  
pp. e3001142
Author(s):  
Sander van Bree ◽  
Ediz Sohoglu ◽  
Matthew H. Davis ◽  
Benedikt Zoefel
Keyword(s):  
Electrical Stimulation ◽  
Speech Perception ◽  
Oscillatory Activity ◽  
Neural Oscillations ◽  
Evoked Responses ◽  
Sustained Effects ◽  
Brain Responses ◽  
Underlying Principle ◽  
Transcranial Alternating Current Stimulation ◽  
Neural Entrainment

Rhythmic sensory or electrical stimulation will produce rhythmic brain responses. These rhythmic responses are often interpreted as endogenous neural oscillations aligned (or “entrained”) to the stimulus rhythm. However, stimulus-aligned brain responses can also be explained as a sequence of evoked responses, which only appear regular due to the rhythmicity of the stimulus, without necessarily involving underlying neural oscillations. To distinguish evoked responses from true oscillatory activity, we tested whether rhythmic stimulation produces oscillatory responses which continue after the end of the stimulus. Such sustained effects provide evidence for true involvement of neural oscillations. In Experiment 1, we found that rhythmic intelligible, but not unintelligible speech produces oscillatory responses in magnetoencephalography (MEG) which outlast the stimulus at parietal sensors. In Experiment 2, we found that transcranial alternating current stimulation (tACS) leads to rhythmic fluctuations in speech perception outcomes after the end of electrical stimulation. We further report that the phase relation between electroencephalography (EEG) responses and rhythmic intelligible speech can predict the tACS phase that leads to most accurate speech perception. Together, we provide fundamental results for several lines of research—including neural entrainment and tACS—and reveal endogenous neural oscillations as a key underlying principle for speech perception.

scholarly journals Sustained neural rhythms reveal endogenous oscillations supporting speech perception

2020 ◽  
Author(s):  
Sander van Bree ◽  
Ediz Sohoglu ◽  
Matthew H Davis ◽  
Benedikt Zoefel
Keyword(s):  
Electrical Stimulation ◽  
Speech Perception ◽  
Oscillatory Activity ◽  
Neural Oscillations ◽  
Evoked Responses ◽  
Sustained Effects ◽  
Brain Responses ◽  
Underlying Principle ◽  
Transcranial Alternating Current Stimulation ◽  
Intelligible Speech

AbstractRhythmic sensory or electrical stimulation will produce rhythmic brain responses. These rhythmic responses are often interpreted as endogenous neural oscillations aligned to the stimulus rhythm. However, stimulus-aligned brain responses can also be explained as a sequence of evoked responses, which only appear regular due to the rhythmicity of the stimulus, without necessarily involving underlying neural oscillations. To distinguish evoked responses from true oscillatory activity, we tested whether rhythmic stimulation produces oscillatory responses which continue after the end of the stimulus. Such sustained effects provide evidence for true involvement of neural oscillations. In Experiment 1, we found that rhythmic intelligible, but not unintelligible speech produces oscillatory responses in magnetoencephalography (MEG) which outlast the stimulus at parietal sensors. In Experiment 2, we found that transcranial alternating current stimulation (tACS) leads to rhythmic fluctuations in speech perception outcomes which continue after the end of electrical stimulation. We further report that the phase relation between electroencephalography (EEG) and rhythmic intelligible speech can predict the tACS phase that leads to most accurate speech perception. Together, our results lay the foundation for a new account of speech perception which includes endogenous neural oscillations as a key underlying principle.

scholarly journals Altered network properties in C9ORF72 repeat expansion cortical neurons are due to synaptic dysfunction

2021 ◽  
Vol 16 (1) ◽  
Author(s):  
Emma M. Perkins ◽  
Karen Burr ◽  
Poulomi Banerjee ◽  
Arpan R. Mehta ◽  
Owen Dando ◽  
...  
Keyword(s):  
Synaptic Plasticity ◽  
Synaptic Vesicle ◽  
Cortical Neurons ◽  
Electrode Array ◽  
Repeat Expansion ◽  
Cortical Network ◽  
Synaptic Function ◽  
Network Activity ◽  
Cortical Function ◽  
Network Function

Abstract Background Physiological disturbances in cortical network excitability and plasticity are established and widespread in amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) patients, including those harbouring the C9ORF72 repeat expansion (C9ORF72RE) mutation – the most common genetic impairment causal to ALS and FTD. Noting that perturbations in cortical function are evidenced pre-symptomatically, and that the cortex is associated with widespread pathology, cortical dysfunction is thought to be an early driver of neurodegenerative disease progression. However, our understanding of how altered network function manifests at the cellular and molecular level is not clear. Methods To address this we have generated cortical neurons from patient-derived iPSCs harbouring C9ORF72RE mutations, as well as from their isogenic expansion-corrected controls. We have established a model of network activity in these neurons using multi-electrode array electrophysiology. We have then mechanistically examined the physiological processes underpinning network dysfunction using a combination of patch-clamp electrophysiology, immunocytochemistry, pharmacology and transcriptomic profiling. Results We find that C9ORF72RE causes elevated network burst activity, associated with enhanced synaptic input, yet lower burst duration, attributable to impaired pre-synaptic vesicle dynamics. We also show that the C9ORF72RE is associated with impaired synaptic plasticity. Moreover, RNA-seq analysis revealed dysregulated molecular pathways impacting on synaptic function. All molecular, cellular and network deficits are rescued by CRISPR/Cas9 correction of C9ORF72RE. Our study provides a mechanistic view of the early dysregulated processes that underpin cortical network dysfunction in ALS-FTD. Conclusion These findings suggest synaptic pathophysiology is widespread in ALS-FTD and has an early and fundamental role in driving altered network function that is thought to contribute to neurodegenerative processes in these patients. The overall importance is the identification of previously unidentified defects in pre and postsynaptic compartments affecting synaptic plasticity, synaptic vesicle stores, and network propagation, which directly impact upon cortical function.

scholarly journals Neuromodulation of Astrocytic K+ Clearance

2021 ◽  
Vol 22 (5) ◽  
pp. 2520
Author(s):  
Alba Bellot-Saez ◽  
Rebecca Stevenson ◽  
Orsolya Kékesi ◽  
Evgeniia Samokhina ◽  
Yuval Ben-Abu ◽  
...  
Keyword(s):  
Oscillatory Behavior ◽  
Network Activity ◽  
Oscillatory Activity ◽  
Extracellular Potassium ◽  
Uptake Mechanism ◽  
Kir Channels ◽  
Neuronal Network Activity ◽  
Clearance Process ◽  
Spatial Buffering ◽  
The Impact

Potassium homeostasis is fundamental for brain function. Therefore, effective removal of excessive K+ from the synaptic cleft during neuronal activity is paramount. Astrocytes play a key role in K+ clearance from the extracellular milieu using various mechanisms, including uptake via Kir channels and the Na+-K+ ATPase, and spatial buffering through the astrocytic gap-junction coupled network. Recently we showed that alterations in the concentrations of extracellular potassium ([K+]o) or impairments of the astrocytic clearance mechanism affect the resonance and oscillatory behavior of both the individual and networks of neurons. These results indicate that astrocytes have the potential to modulate neuronal network activity, however, the cellular effectors that may affect the astrocytic K+ clearance process are still unknown. In this study, we have investigated the impact of neuromodulators, which are known to mediate changes in network oscillatory behavior, on the astrocytic clearance process. Our results suggest that while some neuromodulators (5-HT; NA) might affect astrocytic spatial buffering via gap-junctions, others (DA; Histamine) primarily affect the uptake mechanism via Kir channels. These results suggest that neuromodulators can affect network oscillatory activity through parallel activation of both neurons and astrocytes, establishing a synergistic mechanism to maximize the synchronous network activity.

Sham transcranial electrical stimulation and its effects on corticospinal excitability: a systematic review and meta-analysis

2018 ◽  
Vol 29 (2) ◽  
pp. 223-232 ◽  
Author(s):  
Thusharika D. Dissanayaka ◽  
Maryam Zoghi ◽  
Michael Farrell ◽  
Gary F. Egan ◽  
Shapour Jaberzadeh
Keyword(s):  
Systematic Review ◽  
Electrical Stimulation ◽  
Meta Analysis ◽  
Random Noise ◽  
Corticospinal Excitability ◽  
Transcranial Electrical Stimulation ◽  
Placebo Effects ◽  
Randomized Controlled ◽  
Transcranial Random Noise Stimulation ◽  
Transcranial Alternating Current Stimulation

AbstractSham stimulation is used in randomized controlled trials (RCTs) to assess the efficacy of active stimulation and placebo effects. It should mimic the characteristics of active stimulation to achieve blinding integrity. The present study was a systematic review and meta-analysis of the published literature to identify the effects of sham transcranial electrical stimulation (tES) – including anodal and cathodal transcranial direct current stimulation (a-tDCS, c-tDCS), transcranial alternating current stimulation (tACS), transcranial random noise stimulation (tRNS) and transcranial pulsed current stimulation (tPCS) – on corticospinal excitability (CSE), compared to baseline in healthy individuals. Electronic databases – PubMed, CINAHL, Scopus, Science Direct and MEDLINE (Ovid) – were searched for RCTs of tES from 1990 to March 2017. Thirty RCTs were identified. Using a random-effects model, meta-analysis of a-tDCS, c-tDCS, tACS, tRNS and tPCS studies showed statistically non-significant pre-post effects of sham interventions on CSE. This review found evidence for statically non-significant effects of sham tES on CSE.

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