Basic NeuroscienceMR-guided stereotactic navigation

Functional magnetic resonance imaging allows precise localization of brain regions specialized for different perceptual and higher cognitive functions. However, targeting these deep brain structures for electrophysiology still remains a challenging task. Here, we propose a novel framework for MRI-stereotactic registration and chamber placement for precise electrode guidance to recording sites defined in MRI space. The proposed “floating frame” approach can be used without usage of ear bars, greatly reducing pain and discomfort common in standard stereotactic surgeries. Custom pre-surgery planning software was developed to automatically solve the registration problem and report the set of parameters needed to position a stereotactic manipulator to reach a recording site along arbitrary, non-vertical trajectories. Furthermore, the software can automatically identify blood vessels and assist in finding safe trajectories to targets. Our approach was validated by targeting different regions in macaque monkeys and rats. We expect that our method will facilitate recording in new brain areas and provide a valuable tool for electrophysiologists.

► A structured framework is proposed to solve the problem of guiding electrodes to brain regions previously identified in MR scan (or fMRI scan). ► The method is based on a set of external markers that are attached to the skull in a rigid manner. No special care needs to be taken in placing the markers, and they can be made by drilling small holes into existing acrylic head implant. ► The framework has been implemented in software, which allows unprecedented pre-surgery planning visualization capabilities, such as placing virtual chambers, grids, cannule, and electrodes. The software can assist by finding optimal trajectories to pre-selected targets. ► The software can register stereotactic coordinates and MR coordinates and report which parameters one need to set in the stereotactic manipulator to reach the target along any desirable direction. This alleviates many of the hurdles of trying to target regions that are located just below large blood vessels, by using non-vertical penetrations. ► The framework was validated the by implanting recording chambers in monkeys and rats. ► Computer simulations give predicted accuracy levels as a function of the number of markers placed, as well as the ability to infer the position of these markers.