Jarmo Ruohonen

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Motor and visual cortices of normal volunteers were activated by transcranial magnetic stimulation. The electrical brain activity resulting from the brief electromagnetic pulse was recorded with high-resolution electroencephalography (HR-EEG) and located using inversion algorithms. The stimulation of the left sensorimotor hand area elicited an immediate(More)
There is described a 60-channel EEG acquisition system designed for the recording of scalp-potential distributions starting just 2.5ms after individual transcranial magnetic stimulation (TMS) pulses. The amplifier comprises gain-control and sample-and-hold circuits to prevent large artefacts from magnetically induced voltages in the leads. The maximum(More)
Transcranial magnetic stimulation (TMS) is a unique method for non-invasive brain imaging. The fundamental difference between TMS and other available non-invasive brain imaging techniques is that when a physiological response is evoked by stimulation of a cortical area, that specific cortical area is causally related to the response. With other imaging(More)
Recent progress in the theory and technology of transcranial magnetic stimulation (TMS) is leading to novel approaches in brain mapping. TMS becomes a powerful functional brain mapping tool when other imaging methods are used to record TMS-evoked activity or when peripheral effects are observed as a function of stimulus location. TMS-evoked activity(More)
OBJECTIVE We have used EEG to measure effects of air- and bone-conducted sound from the coil in transcranial magnetic stimulation (TMS). METHODS Auditory-evoked potentials to TMS were recorded in three different experimental conditions: (1) the coil 2 cm above the head, (2) the coil 2 cm above the head but rigidly connected by a plastic piece to the(More)
Transcranial magnetic stimulation (TMS) is accompanied with loud clicks that evoke auditory responses in the brain, confounding several types of TMS studies. We investigated the effects of these clicks with high-resolution EEG by applying TMS pulses at 3 magnitudes, with the coil placed either at 10 or 50 mm over the subjects' vertex and recording(More)
Knowledge of the electric field that is induced in the brain or the limbs is of importance in magnetic stimulation of the nervous system. Here, an analytical model based on the reciprocity theorem is used to compare the induced electric field in unbounded, semi-infinite, spherical, and cylinder-like volume conductors. Typical stimulation coil arrangements(More)
Dissertation for the degree of Doctor of Technology to be presented with due permission for public examination and debate in Auditorium F1 The supervisor of the work was Professor Toivo Katila; I am grateful for his invaluable support. I also want to thank the instructors, Docent Risto Ilmoniemi and Professor Ferdinando Grandori. During the years 1993−1998,(More)
The activating function of peripheral nerves in magnetic stimulation is thought to be the gradient of the induced electric field component parallel to the nerve. This implies that there are several orientations of the coil that should not excite nerves. We show that these orientations, however, often yield high-amplitude and even supramaximal muscle(More)