A non-magnetic mini-manipulator for an MRI-based method for localization of a microelectrode tip within monkey cerebral cortex

Abstract

We previously developed a method to localize a microelectrode tip with single-voxel accuracy using 4.7 T MRI. In that study, we validated the method's localization accuracy in vitro using a phantom (in-plane resolution: 50 µm) and in vivo using anesthetized monkeys (in-plane resolution: 150 µm). In the present study, we devised a custom-made non-magnetic mini-manipulator (Narishige) that allows for the easy implementation of the localization method for electrophysiological recording from behaving monkeys. With behaving monkeys, it is important to stably retain the microelectrode and so keep the tip in the same position when monkeys are anesthetized and transferred to the MRI scanner after the recording session. We implanted a microelectrode using our mini-manipulator to assess positional stability during the transition to the MRI, which could be performed on the either the day of the recording session or the next day. Across two successive days of implantation, the position of the microelectrode tip did not change on magnetic resonance images with an in-plane resolution of 150 µm (less than ± single voxel variation across days; 0.00 ± 0.94 voxel; equivalence test, P < 0.01). This stable maintenance of the microelectrode tip position across days enables electrophysiological recording in an awake state and MRI under anesthesia to be performed even on separate days. [J Physiol Sci. 2007;57 Suppl:S71]