In vivo microelectrode track reconstruction using magnetic resonance imaging

Area of Science:

• Neuroscience
• Biomedical Engineering
• Medical Imaging

Background:

• Precise anatomical localization of experimental sites is crucial for microelectrode recording and stimulation in neuroscience research.
• Current methods may lack the resolution or non-invasive nature required for detailed in vivo anatomical mapping.

Purpose of the Study:

• To develop and validate a non-invasive magnetic resonance imaging (MRI) technique for reconstructing microelectrode tracks in the brains of living animals.
• To enable more precise anatomical identification of cortical recording and stimulation sites.

Main Methods:

• Microelectrode penetrations were made in anesthetized rats.
• Metal (iron) was deposited at sites along the tracks using anodic current from the microelectrode tip.
• Gradient echo sequences in a 4.7T MRI scanner were used to visualize the metal deposits.
• MRI findings were confirmed via postmortem histology using Prussian blue staining.

Main Results:

• Metal deposits appeared as visible, hypointense punctate marks (approx. 200 microm wide) in vivo using MRI.
• MRI-visible marks were successfully created with currents as low as 1 microA (anodic) for 5 s.
• Marks remained stable in living rat brains for up to nine months.
• Both direct current and biphasic current pulses produced MRI-visible marks, with biphasic pulses causing less tissue damage.

Conclusions:

• The developed MRI technique provides precise, non-invasive anatomical information for microelectrode experiments.
• This method allows for accurate reconstruction of microelectrode tracks in living animal brains.
• The technique is sensitive, stable, and compatible with functional microstimulation protocols.