brain and spinal fMRI

Magnetic resonance imaging (MRI) that is able to demonstrate where the brain is functioning (fMRI) has been developed over more than 20 years and has had a significant impact on our understanding of brain function and our ability to detect changes as a result of injury. The focus of research in my lab builds upon important new developments that enable fMRI to be applied in the spinal cord and brainstem. This work significantly enhances the benefit of fMRI for neuroscience research, and will eventually support clinical assessments. One key advantage of adding spinal cord fMRI to conventional brain fMRI is the ability to study distributed networks, such as related to pain or central sensitization, across the entire CNS from the cord to the cortex.

Technical challenges exist, but the key challenges have been overcome or significantly reduced, by adapting fMRI methods for this region

Current projects are focussed on 1) investigating pain processing and how it is regulated by the body in healthy people, 2) understanding how pain processing is altered in cases of chronic pain and after changes due to injury or disease, and 3) investigating how the spinal cord and brainstem functions are coordinated during the resting state. Many of the current projects involve combined brain, brainstem, and spinal cord functional MRI.

Pain serves an important purpose; to encourage us to avoid or prevent injury, and to protect an injured area of the body while it heals. Pain is the net result of the sensations that we feel, and our emotional response to those sensations, and so it can vary with the situation, or our mood, or illness or previous injuries. Important advances in our understanding of pain have shown that the brain and brainstem send signals to the spinal cord to increase or decrease pain depending on the situation. For example, in an emergency situation a person may not notice their own injuries while they are removing themselves and other people from danger, but, after this threatening situation has ended, they may then feel considerable pain because of their injuries. In everyday life we also feel pain differently, depending on our mood or attention focus or even when we listen to music. It is believed that this system to regulate pain may be imbalanced in cases of chronic pain.

Our results show that the state of the spinal cord is continuously regulated, as opposed to the regulation being a reaction to a noxious sensation or injury. This is important for our understanding of how effects such as mood or attention focus alter pain, and phenomena such as the placebo effect.

We can now investigate this complete network that regulates pain, in people.

Magnetic resonance imaging of neuronal function in the human spinal cord has been developed to the point that it can accurately demonstrate neural activity in response to a variety of sensory, motor, and emotional/cognitive stimuli. It has also been demonstrated to detect changes as a result of traumatic injury and multiple sclerosis.

Methods have been developed to overcome (or at least reduce) the key challenges of 1) magnetic field differences in different materials (bone, tissue, air), 2) the small physical dimensions of the spinal cord, and 3) movement caused by the heart beat and breathing (called "physiological noise"). The methods have been demonstrated to be highly effective.

Software has been developed specifically for spinal cord and brainstem fMRI analysis, and is freely available here. This includes methods to reduce image artifacts, correct for movement, carry out the analysis, and convert the results into a spatially normalized form that is the same for every person. Group analysis to characterize consistent features of how spinal cord and brainstem function are affected by injury, or disease, or normal differences in responses to different sensations and pain can also be carried out. In addition, software has been developed to carry out analyses to identify connectivity between regions that are working as part of a network.

BELOW: Example of the most sophisticated connectivity methods that have been applied to the spinal cord and brainstem to date. This figure shows the connectivity between brainstem and spinal cord regions before, during, and after the application of a noxious heat stimulus. Participants had been trained, and were familiar with the heat pain and the timing of the study   The connectivity was calculated using structural equation modeling (SEM).
Published in "Continuous Descending Modulation of the Spinal Cord Revealed by Functional MRI", Stroman et. al., 2016.

This research is supported by: