A behavioural and electrophysiological investigation into the priming effects of motor imagery on lower limb responses.

Imagined movements (MI) are a complex behaviour, borne of the neural circuitry and cognitions shared with real actions. They have been implemented in many clinical and elite performance programmes, although these programme outcomes are inconsistent. Applying current models of MI to understand these inconsistencies is confounded by an ineffective discrimination between effects of MI on performance and those of simple preparation for action (MP). Critically, empirical comparisons have yet to be drawn between MI and MP. This thesis presents the results of four behavioural studies and one electroencephalographic (EEG) study which attempted to resolve neurocognitive aspects of this confound. In Experiment 1 (n=18), participants prepared for a lower limb response, or imagined then responded in a repeated measures design. Response time congruency priming was significantly larger following MI than MP, driven by increased costs. Three follow-up experiments were conducted. First (n=16), it was shown that the enhanced priming effect did not depend on optimal temporal preparation. Second (n=13), these effects were also present following imagination and preparation of finger responses. Third (n=21), non-motor cognitive load was manipulated in an additional task, and indicated that the MI priming effects could not be explained more simply as a distracting secondary task. A hypothetical view derived from this data was proposed, suggesting that MI priming can interact with normal MP processes by amplifying the gain of information received from proprioceptive channels prior to response, thus enhancing the difference between correctly and incorrectly primed responses compared to MP alone. Using EEG, the final experiment (n=11) showed the MI priming effect held up when controlling for unwanted muscular activation, and that it may be due to stronger corticomotor activity following MI, supporting the hypothetical view. This thesis therefore provides an integrative neurocognitive perspective on the role of MI in enhancing real performance at short time-scales