Co-registration of cortical magnetic stimulation and functional magnetic resonance imaging

Abstract

Functional magnetic resonance imaging (fMRI) and transcranial magnetic stimulation (TMS) are noninvasive techniques recently used to investigate cortical motor physiology. However, these modalities measure different phenomena, and in studies of human motor control they have given inconsistent results. We have developed a reproducible technique which co-registers TMS and fMRI, using a frameless method. In four normal subjects, the TMS map and fMRI activation were present on the primary motor cortex contralateral to the target hand, with some extension into primary sensory cortex. fMRI activation alone was also present in the medial motor cortex bilaterally and in the sensorimotor cortex ipsilateral to the target hand. This technique allows a more comprehensive evaluation of the physiologic events involved in motor control.

Effects of Right Parietal Transcranial Magnetic Stimulation on Object Identification and Orientation Judgments

“…These points were then used by the navigation software to compute an estimated brain volume in Talairach space, by means of a warping procedure applied to a generic MRI volume (the Montreal Neurological Institute template). The precision of this neuronavigation method is within millimeters (Bastings et al, 1998) and is comparable to the spatial resolution of the TMS at motor threshold intensity (Herwig et al, 2001). Talairach coordinates for the stimulation sites (the P4 and the vertex locations described above) were estimated in a group of five individuals and their mean location is pictured in Figure 2.…”

Event-related TMS over the right posterior parietal cortex induces ipsilateral visuo-spatial interference

“…This cortical impact point was considered as the site where TMS was maximal. Depending on the cortical region of interest, co-registration accuracy of a few mm is attainable [23].…”

Registration and Visualization of Transcranial Magnetic Stimulation on MR Images

“…Thirdly, those 5 registrations were used to determine the location of several MRI-visible markers. The mean error was found to be 3.8mm while the same test using our implementation of Basting's [1] method lead to an error of 9.7mm. Finally, the reproducibility of the method was assessed by computing the CoGs of the MEPs on the brain surface using the 5 registrations.…”

“…Wang [5] and Bastings [1] use a magnetic field (MF) digitizer to acquire points on the scalp surface. Wang attaches the MF transmitter on the patient's head while Basting uses two receivers, one fixed on the patient to track head motion and one mobile to acquire the data.…”