Measuring Mental Imagery

Abstract

Mental imagery describes the cognitive ability to form internal representations of our sensorimotor experiences. It follows that there are different types of mental imagery, such as visual, auditory, kinesthetic, motor, and spatial. The work presented here sought to further develop and validate a novel objective measure of motor imagery. Specifically, does this novel questionnaire require motor imagery processes for successful completion. If so, the nature of ‘hands’ being the contents of an individual’s movement imagery would suggest that hand-dominance effects could be observed. The first study described in Chapter 1 hypothesized that given a sufficient sample of right-handed participants and trials of both right- and left-hand stimuli, right-handed participants should perform better on right-hand trials than left-hand trials. A pencil-and-paper hand-version of the Test of Ability in Movement Imagery was administered to 79 right-handed participants, and a significant right-handedness effect was observed. Given the results in Chapter 1, a follow-up study utilizing a computerized version of the pencil-and-paper hand-imagery questionnaire was administered to 22 right-handed and 18 left-handed participants, while electroencephalography data was recorded. We hypothesized that mu oscillations, which are suppressed at the onset and duration of both real and simulated action, would produce contralateral event-related desynchronization (suppression) to the hand in which finger movements were being mentally simulated. Further, we expected a handedness effect to also be detected electrophysiologically, such that right-handed participants would display greater mu suppression over electrode site C3 (left cerebral hemisphere), whereas left-handed participants would display greater mu suppression over electrode site C4 (right cerebral hemisphere). Oscillatory analysis depicted a significant increase of frontal-midline theta and posterior alpha power during correct versus error trials. This pattern of results suggests participants employed spatial working memory to successfully complete the task. Taking the results from the two studies together, insight is gained regarding the factors of experimental design determining the qualities of spatial imagery attended to by participants.