title: Phasic stabilization of motor output after auditory and visual distractors.
abstract: To maintain steady motor output, distracting sensory stimuli need to be blocked. To study the effects of brief auditory and visual distractors on the human primary motor (M1) cortex, we monitored magnetoencephalographic (MEG) cortical rhythms, electromyogram (EMG) of finger flexors, and corticomuscular coherence (CMC) during right-hand pinch (force 5-7% of maximum) while 1-kHz tones and checkerboard patterns were presented for 100 ms once every 3.5-5 s. Twenty-one subjects (out of twenty-two) showed statistically significant ∼20-Hz CMC. Both distractors elicited a covert startle-like response evident in changes of force and EMG (∼50% of the background variation) but without any visible movement, followed by ∼1-s enhancement of CMC (auditory on average by 75%, P < 0.001; visual by 33%, P < 0.05) and rolandic ∼20-Hz rhythm (auditory by 14%, P < 0.05; visual by 11%, P < 0.01). Directional coupling of coherence from muscle to the M1 cortex (EMG→MEG) increased for ∼0.5 s at the onset of the CMC enhancement, but only after auditory distractor (by 105%; P < 0.05), likely reflecting startle-related proprioceptive afference. The 20-Hz enhancements occurred in the left M1 cortex and were for the auditory stimuli preceded by an early suppression (by 7%, P < 0.05). Task-unrelated distractors modulated corticospinal coupling at ∼20 Hz. We propose that the distractors triggered covert startle-like responses, resulting in proprioceptive afference to the cortex, and that they also transiently disengaged the subject's attention from the fine-motor task. As a result, the corticospinal output was readjusted to keep the contraction force stable.
authors.affiliation: Brain Research Unit, Department of Neuroscience and Biomedical Engineering, Aalto University, AALTO, Espoo, Finland.
authors.forename: Harri
authors.initials: H
authors.lastname: Piitulainen
authors.affiliation: Brain Research Unit, Department of Neuroscience and Biomedical Engineering, Aalto University, AALTO, Espoo, Finland.
authors.forename: Mathieu
authors.initials: M
authors.lastname: Bourguignon
authors.affiliation: Brain Research Unit, Department of Neuroscience and Biomedical Engineering, Aalto University, AALTO, Espoo, Finland.
authors.forename: Eero
authors.initials: E
authors.lastname: Smeds
authors.affiliation: Laboratoire De Cartographie Fonctionnelle Du Cerveau, UNI-ULB Neuroscience Institute, Université Libre De Bruxelles (ULB), Bruxelles, Belgium.
authors.forename: Xavier
authors.initials: X
authors.lastname: De Tiège
authors.affiliation: Brain Research Unit, Department of Neuroscience and Biomedical Engineering, Aalto University, AALTO, Espoo, Finland.|MEG Core and Advanced Magnetic Imaging (AMI) Centre, Aalto NeuroImaging, Aalto University, AALTO, Espoo, Finland.
authors.forename: Veikko
authors.initials: V
authors.lastname: Jousmäki
authors.affiliation: Brain Research Unit, Department of Neuroscience and Biomedical Engineering, Aalto University, AALTO, Espoo, Finland.
authors.forename: Riitta
authors.initials: R
authors.lastname: Hari
mesh_terms: D000161:Acoustic Stimulation; D000328:Adult; D001931:Brain Mapping; D004576:Electromyography; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005260:Female; D005385:Fingers / Q000294:innervation; D018737:Hand Strength / Q000502:physiology*; D006801:Humans; D007537:Isometric Contraction; D008279:Magnetic Resonance Imaging; D015225:Magnetoencephalography; D008297:Male; D009044:Motor Cortex / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology; D010775:Photic Stimulation; D055815:Young Adult
keywords: cortex-muscle coherence; isometric contraction; magnetoencephalography; sensorimotor cortex; sensorimotor integration; startle reflex