Correction: Energy-Optimal Electrical-Stimulation Pulses Shaped by the Least-Action Principle
Ontology highlight
ABSTRACT:
SUBMITTER:
PROVIDER: S-EPMC4264884 | biostudies-literature | 2014 Jan
REPOSITORIES: biostudies-literature
Similar Datasets
Project description:ObjectiveIdentify the optimal number of pulses necessary to achieve reliable measures of motor evoked potentials (MEPs) in transcranial magnetic stimulation (TMS) studies.MethodsRetrospective data was obtained from 54 healthy volunteers (30 men, mean age 61.7±13.1years) who as part of prior studies had completed three blocks of 30 consecutive TMS stimuli using neuronavigation. Data from four protocols were assessed: single-pulse TMS for measures of amplitude and latency of MEPs; paired-pulse TMS for short-interval intracortical inhibition (sICI) and intracortical facilitation (ICF); and single-pulse TMS to assess the effects of intermittent theta burst stimulation (iTBS). Two statistical methods were used: an internal consistency analysis and probability of inclusion in the 95% confidence interval (CI) around the mean MEPs amplitude.ResultsFor single-pulse TMS, the minimum number of pulses needed to achieve reliable amplitude and latency MEPs measures was 21 and 23, respectively. For paired-pulse TMS, the minimum number of pulses needed to achieve reliable sICI and ICF measures was 20 and 25, respectively. Finally, the minimum number of pulses needed to achieve reliable amplitude and latency MEPs measures after iTBS was 22 and 23, respectively.ConclusionsThis study provides guidelines regarding the minimum number of pulses needed to achieve reliable MEPs measurements in various study protocols using neuronavigated TMS.SignificanceResults from this study have the potential to increase the reliability and quality of future neuronavigated TMS studies.
| S-EPMC4956494 | biostudies-literature
Project description:One of the major questions in high-density transcranial electrical stimulation (TES) is: given a region of interest (ROI) and electric current limits for safety, how much current should be delivered by each electrode for optimal targeting of the ROI? Several solutions, apparently unrelated, have been independently proposed depending on how "optimality" is defined and on how this optimization problem is stated mathematically. The least squares (LS), weighted LS (WLS), or reciprocity-based approaches are the simplest ones and have closed-form solutions. An extended optimization problem can be stated as follows: maximize the directional intensity at the ROI, limit the electric fields at the non-ROI, and constrain total injected current and current per electrode for safety. This problem requires iterative convex or linear optimization solvers. We theoretically prove in this work that the LS, WLS and reciprocity-based closed-form solutions are specific solutions to the extended directional maximization optimization problem. Moreover, the LS/WLS and reciprocity-based solutions are the two extreme cases of the intensity-focality trade-off, emerging under variation of a unique parameter of the extended directional maximization problem, the imposed constraint to the electric fields at the non-ROI. We validate and illustrate these findings with simulations on an atlas head model. The unified approach we present here allows a better understanding of the nature of the TES optimization problem and helps in the development of advanced and more effective targeting strategies.
| S-EPMC7110419 | biostudies-literature
Project description:Millisecond pulses of laser light delivered to gold nanoparticles residing in close proximity to the surface membrane of neurons can induce membrane depolarization and initiate an action potential. An optocapacitance mechanism proposed as the basis of this effect posits that the membrane-interfaced particle photothermally induces a cell-depolarizing capacitive current, and predicts that delivering a given laser pulse energy within a shorter period should increase the pulse's action-potential-generating effectiveness by increasing the magnitude of this capacitive current. Experiments on dorsal root ganglion cells show that, for each of a group of interfaced gold nanoparticles and microscale carbon particles, reducing pulse duration from milliseconds to microseconds markedly decreases the minimal pulse energy required for AP generation, providing strong support for the optocapacitance mechanism hypothesis.
| S-EPMC5984948 | biostudies-literature
Project description:Peripheral nerve injuries often lead to incomplete recovery and contribute to significant disability to approximately 360,000 people in the USA each year. Stem cell therapy holds significant promise for peripheral nerve regeneration, but maintenance of stem cell viability and differentiation potential in vivo are still major obstacles for translation. Using a made-in-house 96-well vertical electrical stimulation (ES) platform, we investigated the effects of different stimulating pulse frequency, duration and field direction on human neural crest stem cell (NCSC) differentiation. We observed dendritic morphology with enhanced neuronal differentiation for NCSCs cultured on cathodes subject to 20 Hz, 100μs pulse at a potential gradient of 200 mV/mm. We further evaluated the effect of a novel cell-based therapy featuring optimized pulsatile ES of NCSCs for in vivo transplantation following peripheral nerve regeneration. 15 mm critical-sized sciatic nerve injuries were generated with subsequent surgical repair in sixty athymic nude rats. Injured animals were randomly assigned into five groups (N = 12 per group): blank control, ES, NCSC, NCSC + ES, and autologous nerve graft. The optimized ES was applied immediately after surgical repair for 1 h in ES and NCSC + ES groups. Recovery was assessed by behavioral (CatWalk gait analysis), wet muscle-mass, histomorphometric, and immunohistochemical analyses at either 6 or 12 weeks after surgery (N = 6 per group). Gastrocnemius muscle wet mass measurements in ES + NCSC group were comparable to autologous nerve transplantation and significantly higher than other groups (p < 0.05). Quantitative histomorphometric analysis and catwalk gait analysis showed similar improvements by ES on NCSCs (p < 0.05). A higher number of viable NCSCs was shown via immunochemical analysis, with higher Schwann cell (SC) differentiation in the NCSC + ES group compared to the NCSC group (p < 0.05). Overall, ES on NCSC transplantation significantly enhanced nerve regeneration after injury and repair, and was comparable to autograft treatment. Thus, ES can be a potent alternative to biochemical and physical cues for modulating stem cell survival and differentiation. This novel cell-based intervention presents an effective and safe approach for improved outcomes after peripheral nerve repair.
| S-EPMC6201278 | biostudies-literature
Project description:Optimizing direct electrical stimulation for the treatment of neurological disease remains difficult due to an incomplete understanding of its physical propagation through brain tissue. Here, we use network control theory to predict how stimulation spreads through white matter to influence spatially distributed dynamics. We test the theory's predictions using a unique dataset comprising diffusion weighted imaging and electrocorticography in epilepsy patients undergoing grid stimulation. We find statistically significant shared variance between the predicted activity state transitions and the observed activity state transitions. We then use an optimal control framework to posit testable hypotheses regarding which brain states and structural properties will efficiently improve memory encoding when stimulated. Our work quantifies the role that white matter architecture plays in guiding the dynamics of direct electrical stimulation and offers empirical support for the utility of network control theory in explaining the brain's response to stimulation.
| S-EPMC6849479 | biostudies-literature
Project description:Electron Nuclear DOuble Resonance (ENDOR) is based on the measurement of nuclear transition frequencies through detection of changes in the polarization of electron transitions. In Davies ENDOR, the initial polarization is generated by a selective microwave inversion pulse. The rectangular inversion pulses typically used are characterized by a relatively low selectivity, with full inversion achieved only for a limited number of spin packets with small resonance offsets. With the introduction of pulse shaping to EPR, the rectangular inversion pulses can be replaced with shaped pulses with increased selectivity. Band-selective inversion pulses are characterized by almost rectangular inversion profiles, leading to full inversion for spin packets with resonance offsets within the pulse excitation bandwidth and leaving spin packets outside the excitation bandwidth largely unaffected. Here, we explore the consequences of using different band-selective amplitude-modulated pulses designed for NMR as the inversion pulse in ENDOR. We find an increased sensitivity for small hyperfine couplings compared to rectangular pulses of the same bandwidth. In echo-detected Davies-type ENDOR, finite Fourier series inversion pulses combine the advantages of increased absolute ENDOR sensitivity of short rectangular inversion pulses and increased sensitivity for small hyperfine couplings of long rectangular inversion pulses. The use of pulses with an almost rectangular frequency-domain profile also allows for increased control of the hyperfine contrast selectivity. At X-band, acquisition of echo transients as a function of radiofrequency and appropriate selection of integration windows during data processing allows efficient separation of contributions from weakly and strongly coupled nuclei in overlapping ENDOR spectra within a single experiment.
| S-EPMC5376364 | biostudies-literature
Project description:In an ongoing debate on the physical nature of the action potential (AP), one group adheres to the electrical model of Hodgkin and Huxley, while the other describes the AP as a nonlinear acoustic pulse propagating within an interface near a transition. However, despite remarkable similarities, acoustics remains a non-intuitive mechanism for APs for the following reason. While acoustic pulses are typically associated with the propagation of density, pressure and temperature variation, APs are most commonly measured electrically. Here, we show that this discrepancy is lifted upon considering the electrical and chemical aspects of the interface, in addition to its mechanical properties. Specifically, we demonstrate how electrical and pH aspects of acoustic pulses emerge from an idealized description of the lipid interface, which is based on classical physical principles and contains no fit parameters. The pulses that emerge from the model show similarities to APs not only in qualitative shape and scales (time, velocity and voltage), but also demonstrate saturation of amplitude and annihilation upon collision.
| S-EPMC6408356 | biostudies-literature
Project description:The field of spintronics involves the study of both spin and charge transport in solid-state devices. Ultrafast magnetism involves the use of femtosecond laser pulses to manipulate magnetic order on subpicosecond time scales. We unite these phenomena by using picosecond charge current pulses to rapidly excite conduction electrons in magnetic metals. We observe deterministic, repeatable ultrafast reversal of the magnetization of a GdFeCo thin film with a single sub-10-ps electrical pulse. The magnetization reverses in ~10 ps, which is more than one order of magnitude faster than any other electrically controlled magnetic switching, and demonstrates a fundamentally new electrical switching mechanism that does not require spin-polarized currents or spin-transfer/orbit torques. The energy density required for switching is low, projecting to only 4 fJ needed to switch a (20 nm)3 cell. This discovery introduces a new field of research into ultrafast charge current-driven spintronic phenomena and devices.
| S-EPMC5669611 | biostudies-literature
Project description:It is unclear how nanosecond electrical pulses affect gene expression. We used microarrays to identify how cells respond to this specific type of stress
2016-02-16 | GSE77906 | GEO
Project description:It is unclear how nanosecond electrical pulses affect gene expression. We used microarrays to identify how cells respond to this specific type of stress HDFA cells were exposed to 100, 10 nanosecond duration pulses at 150 kV/cm. Gene expression was analyzed 4 hrs post exposure
2016-02-16 | E-GEOD-77906 | biostudies-arrayexpress