Sources on the anterior and posterior banks of the central sulcus identified from magnetic somatosensory evoked responses using Multi-Start Spatio-Temporal localization

Abstract

A Multi‐Start Spatio‐Temporal (MSST) multidipole localization algorithm was used to study sources on the anterior and posterior banks of the central sulcus localized from early somatosensory magnetoencephalography (MEG) responses. Electrical stimulation was applied to the right and left median nerves of 8 normal subjects. Two sources, one on the anterior and one on the posterior bank of the central sulcus, were localized from 16 data sets (8 subjects, 2 hemispheres). Compared with the more traditional practice of single‐dipole fits to peak latencies, MSST provided more reliable source locations. The temporal dynamics of the anterior and posterior central sulcus sources, obtained using MSST, showed considerable temporal overlap. In some cases, the two sources appeared synchronous. On the other hand, in the traditional single‐dipole peak‐latency fit approach, there is no time course other than a focal dipole moment activated only at the selected peak latency. The same group of subjects also performed a motor task involving index‐finger lifting; the anterior central sulcus source obtained from electrical median nerve stimulation localized to the same or similar region in the primary motor area identified from the finger‐lift task. The physiological significance of the anterior central sulcus source is discussed. The findings suggest that one can test the integrity of cortical tissue in the region of primary motor cortex using electrical somatosensory stimulation. Hum. Brain Mapping 11:59–76, 2000. © 2000 Wiley‐Liss, Inc.

Movement-related changes in cortical excitability: A steady-state SEP approach

“…This result fits well with the ssSEP attenuation in the time window of the ADAN, supporting an interpretation of the ADAN as activity of the premotor cortex associated with the selection and/or covert activation of a motor response (Gherri et al, 2007;Mathews et al, 2006;. It should be noted, however, that there is continuing debate about precentral contributions to the generation of SEPs (Huang et al, 2000;Waberski et al, 1999;Wasaka et al, 2003). Hence, it cannot be ruled out that instead of being mediated by an efferent signal to the somatosensory cortex, the attenuation of SEPs occurs through a more direct mechanism within the motor cortex.…”

Homeostatic Metaplasticity in the Human Somatosensory Cortex

“…This suggests that homeostatic metaplasticity constitutes a general principle in the human cerebral cortex to maintain synaptic strength in a physiological range. It is commonly accepted that both the N20 and the P25 components of the median nerve somatosensory evoked potential are generated in the posterior bank of the central sulcus, corresponding to Brodmann's area 3b (Huang et al, 2000;Mauguiere et al, 1999;Lee & Seyal, 1998;Urbano et al, 1997;McLaughlin & Kelly, 1993;Allison et al, 1989). Therefore, it can be assumed that changes in the P25 component indicate excitability changes in the primary somatosensory cortex.…”

An automatic MEG low-frequency source imaging approach for detecting injuries in mild and moderate TBI patients with blast and non-blast causes

“…To increase the reliability of the MEG-MR co-registration, approximately 80 points on the scalp were digitized with the Polhemus system, in addition to the three landmarks, and those points were co-registered onto the scalp surface of the MR images. Based on our experience with MEG median-nerve task that is well-known to produce reliable responses at the primary somatosensory cortex for hand representations that are associated with unique anatomical landmarks (Huang et al, 2000(Huang et al, , 2006, the MEG-MR co-registration error is expected to be less than 3 mm. The T1-weighted images were also used to extract the innermost skull surface (SEGLAB software developed by Elekta/Neuromag).…”