Objective Measure of Imagined Hand Manipulations: An EEG Study
Christopher Donoff1, Christopher Madan1,2, Sarah Elke1, Anthony Singhal1; 1University of Alberta, 2University of Nottingham
The present study employed an objective test of imagined hand manipulations to investigate how oscillatory power changes as a function of electrode site, mental imagery accuracy, left- or right-hand stimuli, and participant handedness. In contrast to the whole-body Test of Ability in Movement Imagery (TAMI), each item in the current objective test provided five finger-movement instructions followed by four line-drawings of hands. Only one of the line-drawings was the correct final hand conformation, resulting in an objective way to measure mental imagery accuracy. EEG data was recorded using a 256-channel array while participants completed the TAMI, the novel hand-specific test inspired by the TAMI, and the Edinburgh Handedness Inventory. We were interested specifically in recording mu (8 – 13 Hz) and frontal-midline theta (4 – 8 Hz) brain oscillations, due to their involvement in motor and higher-order mental processes, respectively. Mu suppression has been observed at the onset of motoric action, indicative of an active state. Using the Better OSCillation (BOSC) detection method, the results from the hand-manipulation test depicted significantly more mu oscillations for incorrect versus correct trials, depicting the mu-suppression effect. There was also a significant increase in the amount of frontal-midline theta detected over central electrodes compared to more lateral sites. From these results, the hand-manipulation test appeared to require an increase in higher-order mental functions, such as working memory, to complete the task. This may have reduced the degree of motor-cortex region involvement, preventing any observed lateralized brain activity typically seen in movement imagery studies.
Topic Area: METHODS: Neuroimaging