Introduction: Combined transcranial magnetic stimulation/electro- encephalography (TMS/EEG) was used to study the activation of cortical regions to a variety of focused sub- and suprathreshold magnetic pulses over the left primary motor cortex (M1) in order to study the intracortical mechanisms of oscillatory activity. Methods: In two experiments a total of three TMS conditions were performed in 5 healthy subjects with respect to the individual rest motor threshold (RMT): (1) baseline unconditioned single pulse 120%; (2) intracortical inihibition (ICI, 3ms) paired-pulse TMS and finally (3) transcallosal stimulation over the left and right M1 were also executed. We evaluated the cortical reactions to magnetic stimulation using event-related power transformations of delta, theta alpha and beta rhythms, that reflected regional oscillatory activity of different neural assembles. Results: The single and paired pulse TMS over M1 revealed a reduced in power of oscillations in both hemispheres for both rapid rhythms (alpha and beta) in the initial period immediately after the TMS with a rebound of activity after 500ms from the magnetic stimulus. While we observe a increase in power lasts between 500ms to 900ms for the slow rhythms (delta and theta). The new finding is that decrease in oscillatory activity was noted mainly after inhibitory paired TMS (3ms interstimulus intervals) in alpha band diffused over bilateral frontal and central electrodes. While paired stimulation induces for the beta activity a decrease in power followed by a rapid rebound, while induces an increase of the delta and theta activity. Transcallosal stimulation between the to motor areas at 10ms of interstimulus intervals induces similar pattern for alpha and beta rhythms and for the delta and theta rhythms with more diffusion over the frontal areas and both motor areas. Conclusions: The new method of wavelet analysis based on the time frequency analysis induces new investigation of the modulation of the brain oscillatory activity after perturbational approach. The main findings are consistent with the possibility that the human motor system may be based on network-like oscillatory cortical activity and might be modulated by single and paired magnetic pulses applied to M1, suggesting a phenomenon of resetting.
|Titolo:||Short lasting modulation of brain oscillatory activity induced by intracortical and transcallosal paired TMS over the motor areas detected by the time frequency analysis|
|Data di pubblicazione:||2011|
|Appare nelle tipologie:||04.02 Abstract in Atti di convegno|