West Orange, NJ. February 19, 2014. Kessler Foundation researchers have shown that discarding data from subjects with multiple sclerosis (MS) who exhibit head movement during functional magnetic resonance imaging (fMRI) may bias sampling away from subjects with lower cognitive ability. The study was published in the January issue of Human Brain Mapping. (Wylie GR, Genova H, DeLuca J, Chiaravalloti N, Sumowski JF. Functional MRI movers and shakers: Does subject-movement cause sampling bias.) Glenn Wylie, DPhil, is associate director of Neuroscience in Neuropsychology & Neuroscience Research at Kessler Foundation. He is also associate director of the Neuroimaging Center at Kessler Foundation, and an associate professor at Rutgers - New Jersey Medical School.
Because head movement during fMRI degrades data quality, data associated with severe movement is frequently discarded as a source of random error. Kessler Foundation scientists tested this assumption in 34 persons with MS by examining whether head movement was related to task difficulty and cognitive status. Cognitive status was assessed by combining performance on a working memory and processing speed task.
"We found an interaction between task difficulty and cognitive status," explained Dr. Wylie. "As task difficulty increased, there was a linear increase in movement that was larger among subjects with lower cognitive ability." Healthy controls showed similar, though far smaller, effects. This finding indicates that discarding data with severe movement artifact may bias MS samples such that only subjects with less-severe cognitive impairment are included in the analyses. However, even if such data are not discarded outright, subjects who move more will contribute less to the group-level results because of the poor quality of their data.
It is important for researchers to be aware of this potential bias. "Some newer scanners can correct for motion," noted Dr. Wylie. "Another approach is to monitor each subject's motion parameters and ensure that an adequate number of subjects with low cognition are included. Recruiting a large number of subjects may ensure inclusion of a sufficient number of people with low cognition/low movement. It is however, a costly option."
Funded by the National MS Society (RG3330A1/3; PP1364); NIH (HD060765-01); Kessler Foundation
About MS Research at Kessler Foundation
Kessler Foundation's cognitive rehabilitation research in MS is funded by grants from the National Institutes of Health, National MS Society, NJ Commission of Brain Injury Research, Consortium of MS Centers, and Kessler Foundation. Under the leadership of John DeLuca, PhD, senior VP for Research & Training, and Nancy Chiaravalloti, PhD, director of Neuropsychology & Neuroscience Research, scientists have made important contributions to the knowledge of cognitive decline in MS. Clinical studies span new learning, memory, executive function, attention and processing speed, emotional processing, employment and cognitive fatigue. Research tools include innovative applications of neuroimaging, iPADs, and virtual reality. Among recent findings are the benefits of cognitive reserve and aerobic exercise; correlation between cognitive performance and outdoor temperatures; efficacy of short-term cognitive rehabilitation using modified story technique; factors related to risk for unemployment, and the correlation between memory improvement and cerebral activation on fMRI. Foundation research scientists have faculty appointments at Rutgers New Jersey Medical School. The opening of the Neuroimaging Center at Kessler Foundation in 2013 has greatly expanded the Foundation's capability for neuroscience research.
About Kessler Foundation
Kessler Foundation, a major nonprofit organization in the field of disability, is a global leader in rehabilitation research that seeks to improve cognition, mobility and long-term outcomes, including employment, for people with neurological disabilities caused by diseases and injuries of the brain and spinal cord. Kessler Foundation leads the nation in funding innovative programs that expand opportunities for employment for people with disabilities. For more information, visit KesslerFoundation.org. facebook.com/KesslerFoundation