Track-weighted functional connectivity in the sensory discrimination network correlates with haptic performance: a preliminary study in stroke.

Research Report
Population: Adult

Alexandra L Borstad, PhD, PT, NCS, Research Assistant Professor, The Ohio State University

Petra Schmalbrock, PhD, Associate Professor-Radiology, The Ohio State University

Deborah Nichols-Larsen, PhD, PT, Director-School of Health and Rehabilitation Sciences, The Ohio State University

Keywords: Plasticity, Stroke, Somatosensation, MRI

Purpose/Hypothesis: Complex haptic tasks such as sensory discrimination require efficient processing between multiple brain areas. Novel methods which combine the structural and functional imaging such as, track-weighted functional connectivity (TW-FC) proposed by Calamante and colleagues, may be sensitive to, and inform our understanding of, the neural correlates of haptic performance. The purpose of this preliminary study was to 1) measure the test re-test reliability of TW-FC 2) to compare TW-FC in the sensory discrimination network in stroke and control participants. We hypothesized that 1) TW-FC would be reliable sensitive to between group differences and 2) TW-FC would correlate with sensory discrimination performance.

Subjects: Ten community-dwelling individuals with hemiparesis as a result of chronic stroke, with mild to moderate deficits in upper extremity function and 10 age, gender and handedness neurotypical controls provided written consent to participate in this IRB approved study. The mean (SD) age was 67(10) years for post-stroke and 65(10) for controls. Chronicity was 27(26) months.

Materials/Methods: Somatosensory function was evaluated, using monofilaments and the Hand Active Sensation Test (HASTe) a measure of haptic performance. The 6-item Wolf was used to measure motor performance. Brush discrimination fMRI was used for the functional connectivity, sixty-direction diffusion images for whole brain fiber tracking. Data was obtained on a 3Tesla Philips scanner. Track-weighed functional connectivity images were generated and quantified using a region of interest method.

Results: Between group differences were not statistically significant for either somatosensory measure. HASTe scores and TW-FC values were normally distributed. Paired t-tests revealed no between group differences for the three TW-FC ROI’s examined: white matter, sensory discrimination network or the whole brain. TW-FC of the white matter was significantly related to age (r=0.62, p=0.003), lesion volume (r=0.65.p=0.044), chronicity (r=0.81,p=0.004), and right HASTe scores (r=0.65, p=0.002) but was not related to touch perception, 6-item Wolf, or brain volume. TW-FC was 1.9% different across ROI’s described by Willats, 2014. Conclusions: This preliminary study suggests the TW-FC method, which fuses functional connectivity and structural brain information into a single quantifiable image, is sensitive to neural differences related to haptic performance. TW-FC may be superior to other connectivity methods for longitudinal analysis as the test-retest differences were low. Future work with TW-FC should expand to include examining connectivity between specific, spatially extended regions in functional networks.

Borstad, Alexandra L, PhD, PT, NCS; Schmalbrock, Petra , PhD; Nichols-Larsen, Deborah S, PhD, PT. Track-weighted functional connectivity in the sensory discrimination network correlates with haptic performance: a preliminary study in stroke.. Poster Presentation. IV STEP Conference, American Physical Therapy Association, Columbus, OH, July 17, 2016. Online.