Electrophyisology Recording in Functional MRI (fMRI) Environments using TDT

This document is a hardware and software instructional reference for conducting electrophysiology recordings in Functional MRI (fMRI) environments using TDT hardware and software.

The challenge of using both modalities simultaneously is that the electrophysiology recording system can introduce imaging artifacts, and the MRI system introduces artifacts on the electrophysiology system. The purpose of this guide is to discuss proper hardware/software setup to minimize these artifacts.

This guide will not go into any meaningful details about electrode placement or implantation surgery, and assumes you can record clean signals outside of the fMRI environment.

Motivation

Electrophysiology and fMRI are two very different types of recording modalities. The first is recording electrical activity from the brain of a subject. The data is filtered for both fast neural/spiking activity and longer term activity of local field potentials (LFP). The subject can be head-fixed or freely moving.

In fMRI the subject is head-fixed and restrained in a tube. It measures changes in blood flow and relies on the fact that blood flow and neuronal activity are coupled. The activity is on a longer time scale, from several seconds to minutes. This looks at the whole brain as opposed to a very small section of the brain.

Combining the two recording methodologies provides a better understanding of the underlying architecture of the brain. You can use the electrophysiology to validate the fMRI data by determining a correlation between fMRI signals and LFP or spiking data. You can also record both neural activity and fMRI activity from multiple sites to see time course of signals in the brain.

You can use the electrophysiology data to validate the blood-oxygen-level dependent (BOLD) signal in fMRI. Integrating the two helps you understand the relationship between BOLD and neural responses to stimulus, and elucidate the underlying neural activity driving the BOLD response.