MEG-SIM: a web portal for testing MEG analysis methods using realistic simulated and empirical data

MEG and EEG measure electrophysiological activity in the brain with exquisite temporal resolution. Because of this unique strength relative to noninvasive hemodynamic-based measures (fMRI, PET), the complementary nature of hemodynamic and electrophysiological techniques is becoming more widely recognized (e.g., Human Connectome Project). However, the available analysis methods for solving the inverse problem for MEG and EEG have not been compared and standardized to the extent that they have for fMRI/PET. A number of factors, including the non-uniqueness of the solution to the inverse problem for MEG/EEG, have led to multiple analysis techniques which have not been tested on consistent datasets, making direct comparisons of techniques challenging (or impossible). Since each of the methods is known to have their own set of strengths and weaknesses, it would be beneficial to quantify them. Toward this end, we are announcing the establishment of a website containing an extensive series of realistic simulated data for testing purposes ( http://cobre.mrn.org/megsim/ ). Here, we present: 1) a brief overview of the basic types of inverse procedures; 2) the rationale and description of the testbed created; and 3) cases emphasizing functional connectivity (e.g., oscillatory activity) suitable for a wide assortment of analyses including independent component analysis (ICA), Granger Causality/Directed transfer function, and single-trial analysis.

Effects of ultraviolet radiation on the pathogenesis of Mycobacterium lepraemurium infection in mice

The purpose of this study was to determine whether exposing mice to ultraviolet radiation (UVR) would alter the pathogenesis of infection with Mycobacterium lepraemurium (MLM), which causes a chronic, progressive, lethal disease in susceptible mouse strains. BALB/c mice were irradiated on dorsal skin with various doses of UVR from FS40 sunlamps 3 days before infection with MLM in the hind footpad. The course of disease was followed by assessing the number of acid-fast bacteria in the footpad, regional lymph node and spleen, and measuring the size of the lesion at the site of MLM infection at various times after infection. Mice were also tested periodically for a delayed-type hypersensitivity (DTH) response by injecting MLM antigen into the uninfected footpad and measuring footpad swelling 24 hours later. Mice treated with a single high dose of UVR (45 kJ/m2) had significantly more bacteria in the infected footpad, lymph node and spleen than unirradiated control animals. They also had larger lesions at the site of MLM infection and exhibited significant suppression of the DTH response at 3 and 6 months after infection. Injection of mice s.c. in the footpad with MLM 3d after 45 kJ/m2 UVR reduced the median survival time from 391 to 305 d and after i.v. infection from 171 to 139 d. Dose-response studies indicated that exposing mice to 2.3 kJ/m2 of UVR, which is approximately 1 minimal erythemal dose for this strain, suppressed the DTH response by 50% at 3 months after infection.(ABSTRACT TRUNCATED AT 250 WORDS)