Cortical and subcortical activation during mental imagery of locomotion: A functional MRI investigation

Abstract

The purpose of this research study was to compare how imagery strategy affected brain activation patterns during mental imagery (MI) of bilateral foot movements and walking. Eleven healthy subjects (4 males, 7 females) were 39–64 years old. Subjects self-rated imagery ability with Movement Imagery Questionnaire (MIQ). Subjects were trained using imagery strategies and provided with a visual context (video of hallway) for imagined walking practice. On return visit for brain imaging, executed and imagined speeds of gait were assessed to determine chronometric consistency. Functional Magnetic Resonance Images were acquired on a 1.5T scanner (GE LX Horizon Echospeed) using a blocked paradigm. Of the total of five tasks, the subjects performed an imagined walking task using visual imagery (VI) and kinesthetic imagery (KI). They also performed executed bilateral foot movements (Ex FM) and imagined bilateral foot movements using KI (KI FM), and VI (VI FM). Significantly activated voxels were identified using Statistical Parametric Mapping 1999 (SPM99) in the following regions of Interest (ROls): Anterior cingulate (AC), posterior cingulate (PC), sensorimotor cortex (SMC), supplemental motor area (SMA), dorsolateral prefrontal cortex (DLPFC), parietal lobe (PL). SPM Group data for tasks and task subtractions were analyzed at p ≤ 0.001 with 20 voxel clustering. The laterality index was also calculated for each ROI. Group results revealed Ex FM produced greater bilateral (left >right) activation in SMC and left SMA than imagined FM. KI Walk produced minimal, but slightly more activation than VI Walk. KI strategy activated similar ROls irrespective of task. Group subtractions for tasks produced no differences in activation for imagined walking or FM tasks. These preliminary descriptive findings suggest that imagery strategy modified cortical representation, but task seemed to have a greater influence on activation patterns than strategy for foot movements. Bilateral activation was expected with bilateral motor tasks, but lateralization may be related to the type of imagery and/or the task. The tasks chosen may require little cortical activation, due to their automatic nature. These findings provide the foundation for further research investigating the use of mental practice of walking as an adjunct to physical rehabilitation for the recovery of walking.