Biophysical determinants of transcranial magnetic stimulation: effects of excitability and depth of targeted area.

Safe and effective transcranial magnetic stimulation (TMS) requires accurate intensity calibration. Output is typically calibrated to individual motor cortex excitability and applied to nonmotor brain areas, assuming that it captures a site nonspecific factor of excitability. We tested this assumption by correlating the effect of TMS at motor and visual cortex. In 30 participants, we measured motor threshold (MT) and phosphene threshold (PT) at the scalp surface and at coil-scalp distances of 3.17, 5.63, and 9.03 mm. We also modeled the effect of TMS in a simple head model to test the effect of distance. Four independent tests confirmed a significant correlation between PT and MT. We also found similar effects of distance in motor and visual areas, which did not correlate across participants. Computational modeling suggests that the relationship between the effect of distance and the induced electric field is effectively linear within the range of distances that have been explored empirically. We conclude that MT-guided calibration is valid for nonmotor brain areas if coil-cortex distance is taken into account. For standard figure-of-eight TMS coils connected to biphasic stimulators, the effect of cortical distance should be adjusted using a general correction factor of 2.7% stimulator output per millimeter

Biophysical determinants of transcranial magnetic stimulation : effects of excitability and depth of targeted area

Safe and effective transcranial magnetic stimulation (TMS) requires accurate intensity calibration. Output is typically calibrated to individual motor cortex excitability and applied to nonmotor brain areas, assuming that it captures a site nonspecific factor of excitability. We tested this assumption by correlating the effect of TMS at motor and visual cortex. In 30 participants, we measured motor threshold (MT) and phosphene threshold (PT) at the scalp surface and at coil-scalp distances of 3.17, 5.63, and 9.03 mm. We also modeled the effect of TMS in a simple head model to test the effect of distance. Four independent tests confirmed a significant correlation between PT and MT. We also found similar effects of distance in motor and visual areas, which did not correlate across participants. Computational modeling suggests that the relationship between the effect of distance and the induced electric field is effectively linear within the range of distances that have been explored empirically. We conclude that MT-guided calibration is valid for nonmotor brain areas if coil-cortex distance is taken into account. For standard figure-of-eight TMS coils connected to biphasic stimulators, the effect of cortical distance should be adjusted using a general correction factor of 2.7% stimulator output per millimeter

Asc-Seurat: analytical single-cell Seurat-based web application

Background: Single-cell RNA sequencing (scRNA-seq) has revolutionized the study of transcriptomes, arising as a powerful tool for discovering and characterizing cell types and their developmental trajectories. However, scRNA-seq analysis is complex, requiring a continuous, iterative process to refine the data and uncover relevant biological information. A diversity of tools has been developed to address the multiple aspects of scRNA-seq data analysis. However, an easy-to-use web application capable of conducting all critical steps of scRNA-seq data analysis is still lacking. We present Asc-Seurat, a feature-rich workbench, providing an user-friendly and easy-to-install web application encapsulating tools for an all-encompassing and fluid scRNA-seq data analysis. Asc-Seurat implements functions from the Seurat package for quality control, clustering, and genes differential expression. In addition, Asc-Seurat provides a pseudotime module containing dozens of models for the trajectory inference and a functional annotation module that allows recovering gene annotation and detecting gene ontology enriched terms. We showcase Asc-Seurat's capabilities by analyzing a peripheral blood mononuclear cell dataset. Conclusions: Asc-Seurat is a comprehensive workbench providing an accessible graphical interface for scRNA-seq analysis by biologists. Asc-Seurat significantly reduces the time and effort required to analyze and interpret the information in scRNA-seq datasets

Comparative incidence rates of mild adverse effects to transcranial magnetic stimulation

Objectives Past research has largely neglected to investigate mild adverse effects (MAEs) to transcranial magnetic stimulation (TMS), including headache and nausea. Here we explored the relationship between MAEs, participant characteristics (age and gender) and protocol parameters, including mode of application, coil geometry, stimulated brain region, TMS frequency, TMS intensity, and active vs. sham stimulation. Methods Data from 1270 standard post-monitoring forms was obtained from 113 healthy participants. Analyses aimed to identify the risk factors associated with MAE reports and specific symptoms. Results The overall rate of MAEs across TMS sessions was ∼5%, with ∼78% of symptoms occurring post-session. Initial TMS sessions were followed by a higher MAE incidence rate relative to later testing sessions. No associations between participant characteristics, TMS frequency, or intensity were observed. Conclusions TMS-related MAEs are relatively common and may be exacerbated by initial expectations or anxieties of participants. A significant proportion of MAEs may reflect reporting of coincidental phenomena that are unrelated to TMS. Recommendations for future safety studies are proposed and monitoring documentation is provided. Significance Our findings illustrate the importance of standardized monitoring of MAEs. Such research aids our understanding of how MAEs arise and may lead to interventions for reducing their incidence

Comparative incidence rates of mild adverse effects to transcranial magnetic stimulation

Objectives: Past research has largely neglected to investigate mild adverse effects (MAEs) to transcranial magnetic stimulation (TMS), including headache and nausea. Here we explored the relationship between MAEs, participant characteristics (age and gender) and protocol parameters, including mode of application, coil geometry, stimulated brain region, TMS frequency, TMS intensity, and active vs. sham stimulation. Methods: Data from 1270 standard post-monitoring forms was obtained from 113 healthy participants. Analyses aimed to identify the risk factors associated with MAE reports and specific symptoms. Results: The overall rate of MAEs across TMS sessions was similar to 5%, with similar to 78% of symptoms occurring post-session. Initial TMS sessions were followed by a higher MAE incidence rate relative to later testing sessions. No associations between participant characteristics, TMS frequency, or intensity were observed. Conclusions: TMS-related MAEs are relatively common and may be exacerbated by initial expectations or anxieties of participants. A significant proportion of MAEs may reflect reporting of coincidental phenomena that are unrelated to TMS. Recommendations for future safety studies are proposed and monitoring documentation is provided. Significance: Our findings illustrate the importance of standardized monitoring of MAEs. Such research aids our understanding of how MAEs arise and may lead to interventions for reducing their incidence. (C) 2012 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved