Life Sciences Commons^™

Transcranial Electrical Stimulation Motor Threshold Can Estimate Individualized Tdcs Dosage From Reverse-Calculation Electric-Field Modeling, Kevin A. Caulfield, Bashar W. Badran, William H. Devries, Philipp M. Summers, Emma Kofmehl, Xingbao Li, Jeffrey J. Borckardt, Marom Bikson, Mark S. George

Publications and Research

Background

Unique amongst brain stimulation tools, transcranial direct current stimulation (tDCS) currently lacks an easy or widely implemented method for individualizing dosage.

Objective

We developed a method of reverse-calculating electric-field (E-field) models based on Magnetic Resonance Imaging (MRI) scans that can estimate individualized tDCS dose. We also evaluated an MRI-free method of individualizing tDCS dose by measuring transcranial magnetic stimulation (TMS) motor threshold (MT) and single pulse, suprathreshold transcranial electrical stimulation (TES) MT and regressing it against E-field modeling. Key assumptions of reverse-calculation E-field modeling, including the size of region of interest (ROI) analysis and the linearity of multiple E-field …

Neuromeasure: A Software Package For Quantification Of Cortical Motor Maps Using Frameless Stereotaxic Transcranial Magnetic Stimulation, Michael B. Gerber, Alasdair C. Mclean, Samuel J. Stephen, Alex G. Chalco, Usman M. Arshad, Gary W. Thickbroom, Josh Silverstein, K. Zoe Tsagaris, Amy Kuceyeski, Kathleen Friel, Taiza E. G. Santos, Dylan J. Edwards

Publications and Research

The recent enhanced sophistication of non-invasive mapping of the human motor cortex using MRI-guided Transcranial Magnetic Stimulation (TMS) techniques, has not been matched by refinement of methods for generating maps from motor evoked potential (MEP) data, or in quantifying map features. This is despite continued interest in understanding cortical reorganization for natural adaptive processes such as skill learning, or in the case of motor recovery, such as after lesion affecting the corticospinal system. With the observation that TMS-MEP map calculation and quantification methods vary, and that no readily available commercial or free software exists, we sought to establish and make …

Sensory Abnormalities In Focal Hand Dystonia And Non-Invasive Brain Stimulation, Angelo Quartarone, Vincenzo Rizzo, Carmen Terranova, Demetrio Milardi, Daniele Bruschetta, Maria Felice Ghilardi, Paolo Girlanda

Publications and Research

It has been proposed that synchronous and convergent afferent input arising from repetitive motor tasks may play an important role in driving the maladaptive cortical plasticity seen in focal hand dystonia (FHD).This hypothesis receives support from several sources. First, it has been reported that in subjects with FHD, paired associative stimulation produces an abnormal increase in corticospinal excitability, which was not confined to stimulated muscles. These findings provide support for the role of excessive plasticity in FHD. Second, the genetic contribution to the dystonias is increasingly recognized indicating that repetitive, stereotyped afferent inputs may lead to late-onset dystonia, such as …

Maintenance Of Visual Stability In The Human Posterior Parietal Cortex, Erik Chang, Tony Ro

Publications and Research

Visual stability refers to our stable visuospatial perceptions despite the unstable visual input caused by saccades. Functional neuroimaging results, studies on patients with posterior parietal cortex (PPC) lesions, and single-unit recordings in the lateral intraparietal sulcus of primates indirectly suggest that the PPC might be a potential locus of visual stability through its involvement with spatial remapping. Here we directly explored the role of the PPC in visual stability by applying transcranial magnetic stimulation (TMS) while participants performed a perisaccadic displacement detection task. We show that TMS over the PPC but not a frontal control site alters sensitivity to displacement …

Visual Enhancing Of Tactile Perception In The Posterior Parietal Cortex, Tony Ro, Ruth Wallace, Judith Hagedorn, Alessandro Farnè, Elizabeth Pienkos

Publications and Research

The visual modality typically dominates over our other senses. Here we show that after inducing an extreme conflict in the left hand between vision of touch (present) and the feeling of touch (absent), sensitivity to touch increases for several minutes after the conflict. Transcranial magnetic stimulation of the posterior parietal cortex after this conflict not only eliminated the enduring visual enhancement of touch, but also impaired normal tactile perception. This latter finding demonstrates a direct role of the parietal lobe in modulating tactile perception as a result of the conflict between these senses. These results provide evidence for visual-to-tactile perceptual …

Transcranial Magnetic Stimulation Of The Prefrontal Cortex Delays Contralateral Endogenous Saccades, Tony Ro, Avishai Henik, Liana Machado, Robert D. Rafal

Publications and Research

The contributions of the superior prefrontal cortex (SPFC) and the superior parietal lobule (SPL) in generating voluntary endogenous and reflexive visually guided saccades were investigated using transcranial magnetic stimulation (TMS). Subjects made choice saccades to the left or right visual field in response to a central arrowhead (endogenous go signal) or a peripheral asterisk (exogenous go signal) that were presented along with a single TMS pulse at varying temporal intervals. TMS over the SPFC increased latencies for saccades made in response to an endogenous go signal toward the contralateral hemifield. No effects were observed when the go signal was exogenous …