Innovative Imaging of Cerebrum and Muscle (iCAM) Repeatability Study

Impairments in postural control are linked to low back pain and reductions in physical function in the elderly. Unfortunately, many techniques to assess the neural control of movement are not feasible or directly applicable to the trunk musculature. We have developed an innovative approach to study these muscles. Further development of these techniques will have applicability for the study of the physiological effects and mechanisms of many complementary and integrative health practices (e.g., mind and body approaches). Many of these approaches are used to target back pain (e.g., spinal manipulation, acupuncture) and/or involve therapeutic strategies that have a large focus on postural control (e.g., yoga, Tai Chi). Thus, developing novel and reliable techniques to study the neural control of the trunk muscles will have broad impact to the complementary and integrative health field.

Specific Aim 1. To develop a reliable neurophysiological technique to examine activity of the motor neural networks of selected trunk muscles. Approach: We have previously conducted pilot testing exploring the feasibility of obtaining high quality MRI data with various standardized trunk tasks and biofeedback variations. Once we identified the most promising tasks and MRI compatible data collection techniques, we conducted an optimization study in order to ascertain which method of task performance resulted in the highest level of image quality. We will now conduct a test-retest reliability experiment to determine the reproducibility of our targeted outcome measures. We will focus our reliability analysis on the bilateral primary sensorimotor cortex (Brodmann area 4a, 4b, 1, 2, 3a and 3b) and premotor cortex (Brodmann area 6). In addition, contrasts between two testing sessions will be completed to determine if any brain regions activated significantly more or less between sessions.

Specific Aim 2. To develop a reliable neurophysiological technique to examine spatial muscle activity of selected lumbopelvic musculature (e.g., psoas, iliacus, multifidus, erector spinae, quadratus lumborum). Approach: We have conducted pilot testing that explored the feasibility of obtaining high quality MRI data of various muscles under resting conditions as well as following different standardized tasks. We first identified the most promising muscles to evaluate and then explored which tasks (or tasks sequences) resulted in increased transverse relaxation times (T2) of these muscles. We refined our pulse sequence protocol to optimize our ability to detect an increase in T2 associated with task performance. We will now conduct a test-retest reliability experiment to determine the reproducibility of the primary outcome measures of interest (resting T2 and percent increase in T2 following task performance).

Exploratory Specific Aim 3. To examine the association of the novel neurophysiological measures from Aim 1 and 2 with classic biomechanical and muscle function measures (e.g., trunk extensor strength, trunk extensor force-matching steadiness). The neurophysiological assessments developed as a part of Aim 1 and 2 provide unique information regarding the mechanisms of motor control related to trunk musculature that have typically been very difficult to quantify. This mechanistic approach is bolstered by the ability to correlate the underlying neurophysiology of trunk function with the more traditional clinical measures of performance. Such an approach bolsters the translational capability of this investigation as the neurophysiology of low-cost clinical measures are established in addition to the development of novel intervention outcome tools.

Study Participants: Up to 50 individuals will participate in the reliability experiments. To increase the generalizability of our findings and allow for preliminary data for effect size estimates for future work, we will enroll four cohorts of study participants: healthy young adults, young adults with chronic low back pain, healthy older adults and healthy older adults with expertise in trunk muscle control (i.e., individuals with expertise in Pilates).

Expected Outcomes: We anticipate being able to demonstrate test-retest reliability utilizing two newly developed neurophysiological imaging techniques that will permit 1) examination of the activity of the motor cortical networks during an active trunk task, and 2) examination of muscle activation patterns of small and deep trunk extensor muscles that are very difficult, if not impossible, to study with more classical techniques such as electromyography. Our goal is to demonstrate an association with outcomes of these new imaging techniques with more classic neurophysiological motor outcomes for broad applicability to numerous patient populations that we believe, in the long term, will advance our understanding of trunk muscle control and function.

In this application we propose to perform the test- retest reliability experiments for the fMRI and mfMRI techniques that were previously developed in the pilot testing.