Stories

Dr. Steven Beyea and Dr. Timothy Bardouille have published a new paper. See full text. 

Highlights

• Most visual response characteristics do not differ between MEG systems.
• There is a latero-medial bias in the localization of the primary visual cortex.
• The median difference in localization between systems is 10.5 mm.

Abstract

Objectives

When using MEG for pre-surgical mapping it is critically important that reliable estimates of functional locations, such as the primary visual cortex (V1) can be provided. Several different models of MEG systems exist, each with varying software and hardware configurations, and it is not currently known how the system type contributes to variability in V1 localization.

Patients and Methods

In this study, participants underwent MEG sessions using two different systems (Vector View and CTF) during which they were presented with a repeating grating stimulus to the lower-left visual quadrant to generate a visual evoked field (VEF). The location, amplitude and latency of the VEF source was compared between systems for each participant.

Results

No significant differences were found in latency and amplitude between systems, however, a significant bias in the latero-medial position of the localization was present. The median inter-system Euclidian distance between V1 localization across participants was 10.5 mm.

Conclusions

Overall, our results indicate that mapping of V1 can be reliably reproduced within approximately one centimetre by different MEG systems.

Significance

This result provides knowledge of the useful limits on the reliability of localization which can be taken into consideration in clinical practice.