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

2013 ◽  
Vol 109 (2) ◽  
pp. 437-444 ◽  
Author(s):  
Mark G. Stokes ◽  
Anthony T. Barker ◽  
Martynas Dervinis ◽  
Frederick Verbruggen ◽  
Leah Maizey ◽  
...  
Keyword(s):  
Transcranial Magnetic Stimulation ◽  
Magnetic Stimulation ◽  
Head Model ◽  
Brain Areas ◽  
Motor Cortex Excitability ◽  
Visual Areas ◽  
Phosphene Threshold ◽  
A Site ◽  
The Relationship ◽  
Individual Motor

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.

scholarly journals Top-down control of visual cortex by the frontal eye fields through oscillatory realignment

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Domenica Veniero ◽  
Joachim Gross ◽  
Stephanie Morand ◽  
Felix Duecker ◽  
Alexander T. Sack ◽  
...  
Keyword(s):  
Visual Cortex ◽  
Transcranial Magnetic Stimulation ◽  
Visual Perception ◽  
Magnetic Stimulation ◽  
Single Pulse ◽  
Frontal Eye Fields ◽  
Phase Reset ◽  
Top Down ◽  
Visual Areas ◽  
Beta Frequency

AbstractVoluntary allocation of visual attention is controlled by top-down signals generated within the Frontal Eye Fields (FEFs) that can change the excitability of lower-level visual areas. However, the mechanism through which this control is achieved remains elusive. Here, we emulated the generation of an attentional signal using single-pulse transcranial magnetic stimulation to activate the FEFs and tracked its consequences over the visual cortex. First, we documented changes to brain oscillations using electroencephalography and found evidence for a phase reset over occipital sites at beta frequency. We then probed for perceptual consequences of this top-down triggered phase reset and assessed its anatomical specificity. We show that FEF activation leads to cyclic modulation of visual perception and extrastriate but not primary visual cortex excitability, again at beta frequency. We conclude that top-down signals originating in FEF causally shape visual cortex activity and perception through mechanisms of oscillatory realignment.

scholarly journals Transcranial Magnetic Stimulation as a Tool to Investigate Motor Cortex Excitability in Sport

2021 ◽  
Vol 11 (4) ◽  
pp. 432
Author(s):  
Fiorenzo Moscatelli ◽  
Antonietta Messina ◽  
Anna Valenzano ◽  
Vincenzo Monda ◽  
Monica Salerno ◽  
...  
Keyword(s):  
Transcranial Magnetic Stimulation ◽  
Motor Cortex ◽  
Magnetic Stimulation ◽  
Motor Coordination ◽  
Cortical Excitability ◽  
Non Invasive ◽  
Motor Cortex Excitability ◽  
Invasive Method ◽  
And Control ◽  
The Impact

Transcranial magnetic stimulation, since its introduction in 1985, has brought important innovations to the study of cortical excitability as it is a non-invasive method and, therefore, can be used both in healthy and sick subjects. Since the introduction of this cortical stimulation technique, it has been possible to deepen the neurophysiological aspects of motor activation and control. In this narrative review, we want to provide a brief overview regarding TMS as a tool to investigate changes in cortex excitability in athletes and highlight how this tool can be used to investigate the acute and chronic responses of the motor cortex in sport science. The parameters that could be used for the evaluation of cortical excitability and the relative relationship with motor coordination and muscle fatigue, will be also analyzed. Repetitive physical training is generally considered as a principal strategy for acquiring a motor skill, and this process can elicit cortical motor representational changes referred to as use-dependent plasticity. In training settings, physical practice combined with the observation of target movements can enhance cortical excitability and facilitate the process of learning. The data to date suggest that TMS is a valid technique to investigate the changes in motor cortex excitability in trained and untrained subjects. Recently, interest in the possible ergogenic effect of non-invasive brain stimulation in sport is growing and therefore in the future it could be useful to conduct new experiments to evaluate the impact on learning and motor performance of these techniques.

The Relationship Between Transcranial Magnetic Stimulation, Sleep and Plasticity

2020 ◽  
Vol 87 (9) ◽  
pp. S345-S346
Author(s):  
Michael Centorino ◽  
Laura Bajor ◽  
Praveen Gootam ◽  
Risa Nikase-Richardson ◽  
Frank Kozel
Keyword(s):  
Transcranial Magnetic Stimulation ◽  
Magnetic Stimulation ◽  
The Relationship
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