Neural Substrates of Cognitive Load Changes During a Motor Task in Subjects with Stroke

Journal of Neurologic Physical Therapy - 2008-08-01Kimberley TJ, Lewis S, Strand C, Rice BD, Hall S, Slivnik P10.1097/NPT.0b013e318183d716
Purpose: A critical component to rehabilitation is the degree to which we challenge patients to facilitate learning without providing excessive competition for cognitive resources. The purpose of this study was to examine brain activation and motor performance during changes in cognitive load in a continuous motor task in subjects with stroke (n = 7) and healthy subjects (n = 17).Methods: Subjects participated in a joystick drawing task during
Functional Magnetic Resonance Imaging

Functional Magnetic Resonance Imaging (fMRI)

A functional neuroimaging procedure using MRI technology that measures brain activity by detecting changes associated with blood flow. This technique relies on the fact that cerebral blood flow and neuronal activation are coupled. When an area of the brain is in use, blood flow to that region also increases.[citation needed] The primary form of fMRI uses the blood-oxygen-level dependent (BOLD) contrast, discovered by Seiji Ogawa. This is a type of specialized brain and body scan used to map neural activity in the brain or spinal cord of humans or other animals by imaging the change in blood flow (hemodynamic response) related to energy use by brain cells. Since the early 1990s, fMRI has come to dominate brain mapping research because it does not require people to undergo shots, surgery, or to ingest substances, or be exposed to ionising radiation, etc.
. Subjects attempted to continuously draw a square under three conditions of varying cognitive demands.Results: In subjects with stroke, results showed significantly less activation in contralateral primary motor area when the task did not require working memory demands and no change when the condition required online visual feedback processing. Bilaterally, the premotor cortex also demonstrated a significant decrease in activation when the task did not require working memory and then an increase in activation when online visual feedback processing was required. Despite these changes in activation, the accuracy of performance was maintained across the three conditions. Healthy subjects demonstrated no significant differences in activation between conditions.Conclusion: These data suggest that the sensorimotor areas investigated have the greatest demand when the task requires working memory, but that only the bilateral premotor area has increased demands when online visual feedback processing is required. Use of working memory and visual feedback should be carefully considered when designing rehabilitation programs to balance challenging patients with overwhelming their potentially limited cognitive resources.