Direct detection of neural activity in vitro using magnetic resonance electrical impedance tomography (MREIT)

• Published in: NeuroImage (Orlando, Fla.) Vol. 161; pp. 104 - 119
• Main Authors: Sadleir, Rosalind J., Fu, Fanrui, Falgas, Corey, Holland, Stephen, Boggess, May, Grant, Samuel C., Woo, Eung Je
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.11.2017; Elsevier Limited
• Subjects: Action potential; Action Potentials - drug effects; Action Potentials - physiology; Animals; Aplysia; Aplysia californica; Blood flow; Butyrates - pharmacology; Chlorides; Electric Impedance; Electrical impedance; Excitotoxicity; Experiments; fMRI; Functional magnetic resonance imaging; Ganglia; Ganglia, Invertebrate - diagnostic imaging; Ganglia, Invertebrate - drug effects; Hydrocarbons, Fluorinated - pharmacology; In Vitro Techniques; Magnetic fields; Magnetic Resonance Imaging - methods; Medical imaging; Methods; Microelectrode array; MREIT; MRI; Neuroimaging; Neurons - drug effects; Neurons - physiology; Neurotoxins - pharmacology; NMR; Noise; Nuclear magnetic resonance; Potassium chloride; Seawater; Tomography; MREIT; Aplysia; fMRI; Action potential; Microelectrode array; MRI
• ISSN: 1053-8119; 1095-9572; 1095-9572
• DOI: 10.1016/j.neuroimage.2017.08.004

We describe a sequence of experiments performed in vitro to verify the existence of a new magnetic resonance imaging contrast — Magnetic Resonance Electrical Impedance Tomography (MREIT) —sensitive to changes in active membrane conductivity. We compared standard deviations in MREIT phase data from spontaneously active Aplysia abdominal ganglia in an artificial seawater background solution (ASW) with those found after treatment with an excitotoxic solution (KCl). We found significant increases in MREIT treatment cases, compared to control ganglia subject to extra ASW. This distinction was not found in phase images from the same ganglia using no imaging current. Further, significance and effect size depended on the amplitude of MREIT imaging current used. We conclude that our observations were linked to changes in cell conductivity caused by activity. Functional MREIT may have promise as a more direct method of functional neuroimaging than existing methods that image correlates of blood flow such as BOLD fMRI. [Display omitted] •A new, direct MRI technique for imaging neural activity was validated.•Significant changes in ganglion images were observed after excitotoxic treatment.•Method was demonstrated in-vitro, but scales to entire brains.