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Focal application of a strong static magnetic field over the human scalp induces measurable local changes in brain function. Whether it also induces distant effects across the brain and how these local and distant effects collectively affect motor behavior remains unclear. Here we applied transcranial static magnetic field stimulation (tSMS) over the supplementary motor area (SMA) in healthy subjects. At a behavioral level, tSMS increased the time to initiate movement while decreasing errors in choice reaction-time tasks. At a functional level, tSMS increased SMA resting-state fMRI activity and bilateral functional connectivity between the SMA and both the paracentral lobule and the lateral frontotemporal cortex, including the inferior frontal gyrus. These results suggest that tSMS over the SMA can induce behavioral aftereffects associated with modulation of both local and distant functionally-connected cortical circuits involved in the control of speed-accuracy tradeoffs, thus offering a promising protocol for cognitive and clinical research.

Focal application of a strong static magnetic field over the human scalp induces measurable local changes in brain function. Whether it also induces distant effects across the brain and how these local and distant effects collectively affect motor behavior remains unclear. Here we applied transcranial static magnetic field stimulation (tSMS) over the supplementary motor area (SMA) in healthy subjects. At a behavioral level, tSMS increased the time to initiate movement while decreasing errors in choice reaction-time tasks. At a functional level, tSMS increased SMA resting-state fMRI activity and bilateral functional connectivity between the SMA and both the paracentral lobule and the lateral frontotemporal cortex, including the inferior frontal gyrus. These results suggest that tSMS over the SMA can induce behavioral aftereffects associated with modulation of both local and distant functionally-connected cortical circuits involved in the control of speed-accuracy tradeoffs, thus offering a promising protocol for cognitive and clinical research.

Ablative neurosurgery has been used to treat Parkinson's disease for many decades. MRI-guided focused ultrasound allows focal lesions to be made in deep brain structures without skull incision. We investigated the safety and preliminary efficacy of unilateral subthalamotomy by focused ultrasound in Parkinson's disease.

[Abstract] Objective. The application of transcranial static magnetic field stimulation (tSMS) in humans reduces the excitability of the motor cortex for a few minutes after the end of stimulation. However, when tSMS is applied in humans, the cortex is at least 2 cm away, so most of the strength of the magnetic field will not reach the target. The main objective of the study was to measure the strength and reproducibility of static magnetic fields produced by commercial neodymium magnets. Methods. We measured the strength and reproducibility of static magnetic fields produced by four different types of neodymium cylindrical magnets using a magnetic field-to-voltage transducer. Results. Magnetic field strength depended on magnet size. At distances <1.5 cm, the magnetic field strength was affected by the presence of central holes (potentially useful for recording electroencephalograms). At distances >1.5 cm, the measurements made on the cylinder axis and 1.5 cm off the axis were comparable. The reproducibility of the results (i.e., the consistency of the field strength across magnets of the same size) was very high. Conclusions. These measurements offer a quantitative empirical reference for developing devices useful for tSMS protocols in both humans and animals.

Electrodo para registro de señales bioeléctricas y su procedimiento de fabricación. Electrodo (1) para el registro de las señales bioleléctricas de un paciente, que comprende: una matriz plana (2), que tiene una cara interior (2a) y una cara exterior(2b); al menos un soporte metálico (3) unido a la cara interior (2a) de la matriz plana (2); al menos una pieza elástica porosa (4), impregnada por una dispersión inorgánica conductora de la electricidad, que tiene una superficie de fijación (4b) fijada al soporte metálico (3) y una superficie de contacto (4a) para establecer contacto eléctrico con el cráneo del paciente.

Fast ripples are a type of transient high-frequency oscillations recorded from the epileptogenic regions of the hippocampus and the temporal cortex of epileptic humans and rodents. These events presumably reflect hypersynchronous bursting of pyramidal cells. However, the oscillatory spectral content of fast ripples varies from 250 to 800 Hz, well above the maximal firing frequency of most hippocampal pyramidal neurons. How such high-frequency oscillations are generated is therefore unclear. Here, we combine computational simulations of fast ripples with multisite and juxtacellular recordings in vivo to examine the underlying mechanisms in the hippocampus of epileptic rats. We show that populations of bursting cells firing individually at 100-400 Hz can create fast ripples according to two main firing regimes: (1) in-phase synchronous firing resulting in >pure> fast ripples characterized by single spectral peaks that reflect single-cell behavior and (2) out-of-phase firing that results in >emergent> fast ripples. Using simulations, we found that fast ripples generated under these two different regimes can be quantitatively separated by their spectral characteristics, and we took advantage of this separability to examine their dynamics in vivo.We found that in-phase firing can reach frequencies up to 300 Hz in the CA1and up to 400Hzin the dentate gyrus. The organization of out-of-phase firing is determined by firing delays between cells discharging at low frequencies. The two firing regimes compete dynamically, alternating randomly from one fast ripple event to the next, and they reflect the functional dynamic organization of the different regions of the hippocampus. Copyright © 2010 the authors.

Electrodo para registro de señales bioeléctricas y su procedimiento de fabricación. Electrodo (1) para el registro de las señales bioleléctricas de un paciente, que comprende: una matriz plana (2), que tiene una cara interior (2a) y una cara exterior (2b); al menos un soporte metálico (3) unido a la cara interior (2a) de la matriz plana (2); al menos una pieza elástica porosa (4), impregnada por una dispersión inorgánica conductora de la electricidad, que tiene una superficie de fijación (4b) fijada al soporte metálico (3) y una superficie de contacto (4a) para establecer contacto eléctrico con el cráneo del paciente.

[EN] Electrode (1) for recording the bioelectromagnetic signals of a patient, that comprises: a flat matrix (2), that has an interna1 (2a) and an externa1 face (2b); at least one metal support (3) connected to the internal face (2a) of the flat matrix (2); at least one porous elastic part (4), impregnated with an inorganic electrically conductive dispersion, that has a fixing surface (4b) fixed to the metal support (3) and a contact surface (4a) to establish an electrical contact with the patient's skull., [ES] Electrodo (1) para el registro de las señales bioleléctricas de un paciente, que comprende: una matriz plana (2), que tiene una cara interior (2a) y una cara exterior(2b); al menos un soporte metálico (3) unido a la cara interior (2a) de la matriz plana (2); al menos una pieza elástica porosa (4), impregnada por una dispersión inorgánica conductora de la electricidad, que tiene una superficie de fijación (4b) fijada al soporte metálico (3) y una superficie de contacto (4a) para establecer contacto eléctrico con el cráneo del paciente.