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要旨:
Functional magnetic resonance imaging (fMRI) is commonly used to study the operational organization of the brain, although the relationship between the measured fMRI signal and underlying neural activity remains unclear. In this study, we propose a novel approach utilizing an intracortical electrophysiology setup, enabling simultaneous recording of neural signals during fMRI measurements at a high field strength of 14.1 Tesla. While existing silicon-based NeuroNexus and Pt/Ir electrodes are effective up to 7 Tesla, our aim is to develop new electrodes with improved MRI characteristics for higher field strengths. By combining materials with complementary properties, we designed electrodes using the excellent conductivity and susceptibility properties of copper, in conjunction with polyurethane insulation and additional stabilizing fibers. We conducted susceptibility tests comparing established and prototype electrodes using gradient echo imaging, demonstrating reduced imaging artifacts with the prototype electrode (von Raven et al. SfN 2022). Biocompatibility tests performed on U-87 MG glioblastoma cells revealed that the prototype electrode did not cause significant cell death, unlike pure copper wires (figure 1a-d). The imaging artefact caused by the prototype electrode, consisting of a copper wire of 25µmØ and stabilization fibers using a gradient echo sequence was less than 200µmØ (figure 2). Noise level recorded by the electrophysiology setup during simultaneous echo planar imaging was less than 300µV at the input (figure 3). The use of insulated copper wire attached to stabilization fibers offers a promising alternative to conventional electrodes, particularly at higher field strengths. Animal experiments utilizing these electrodes could provide valuable functional information, and advanced post-processing techniques may further reduce gradient-induced noise. This approach of combining different materials in electrode design to minimize susceptibility artifacts and enhance signal quality holds potential for future clinical applications.
