title: Automatic and imperative motor activations in stimulus-response compatibility: magnetoencephalographic analysis of upper and lower limbs.
abstract: The stimulus-response (S-R) compatibility effect refers to the difference in performance due to the spatial S-R relationship in choice reaction time. We investigated the mechanism of neural activities in S-R compatibility at the level of the primary motor cortices for upper and lower limbs responses using magnetoencephalography (MEG). In the S-R compatible task, subjects were required to respond on the same side of the stimulus light using either an upper or lower limb. In the incompatible task, subjects were required to respond in the reverse manner. Premotor times of upper and lower limbs were faster for the compatible response than for the incompatible response. The neuromagnetic brain activities related to response execution were estimated using a multi-dipole model. Stimulus-locked MEG indicated that the current moments of motor dipoles for both effectors occurred bilaterally and reached the first peak at a constant delay irrespective of whether the task was compatible or incompatible. This indicates that the neural activation of the primary motor cortex is automatically synchronized with the stimulus onset. Response-locked MEG showed that the peak current moment of the motor dipole contralateral to the response was stronger for the compatible task than for the incompatible one regardless of whether the responses were made using the upper or lower limbs. The MEG results suggest that automatic motor activation facilitates imperative motor activation for a compatible response, whereas it is not sufficient to prime imperative motor activation for an incompatible response.
authors.affiliation: Division of Health Promotion and Exercise, National Institute of Health and Nutrition, Japan. kidkato@mac.com
authors.forename: Yuichiro
authors.initials: Y
authors.lastname: Kato
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Endo
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Kizuka
authors.forename: Takaaki
authors.initials: T
authors.lastname: Asami
mesh_terms: D000328:Adult; D001931:Brain Mapping; D004576:Electromyography / Q000379:methods; D007839:Functional Laterality / Q000502:physiology; D006801:Humans; D035002:Lower Extremity / Q000294:innervation / Q000502:physiology*; D015225:Magnetoencephalography; D008297:Male; D009044:Motor Cortex / Q000502:physiology*; D011597:Psychomotor Performance / Q000502:physiology; D011930:Reaction Time / Q000502:physiology* / Q000528:radiation effects; D034941:Upper Extremity / Q000294:innervation / Q000502:physiology*