title: Attention influences the excitability of cortical motor areas in healthy humans.
abstract: We investigated whether human attentional processes influence the size of the motor evoked potentials (MEP) facilitation and the duration of the cortical silent period (CSP) elicited by high-frequency repetitive transcranial magnetic stimulation (rTMS). In healthy subjects we assessed the effects of 5 Hz-rTMS, delivered in trains of 10 stimuli at suprathreshold intensity over the hand motor area, on the MEP size and CSP duration in different attention-demanding conditions: "relaxed," "target hand," and "non-target hand" condition. We also investigated the inhibitory effects of 1 Hz-rTMS conditioning to the premotor cortex on the 5 Hz-rTMS induced MEP facilitation. F-waves evoked by ulnar nerve stimulation were also recorded. rTMS trains elicited a larger MEP size facilitation when the subjects looked at the target hand whereas the increase in CSP duration during rTMS remained unchanged during the three attention-demanding conditions. The conditioning inhibitory stimulation delivered to the premotor cortex decreased the MEP facilitation during the "target hand" condition, leaving the MEP facilitation during the other conditions unchanged. None of the attentional conditions elicited changes in the F wave. In healthy subjects attentional processes influence the size of the MEP facilitation elicited by high-frequency rTMS and do so through premotor-to-motor connections.
authors.affiliation: Department of Neurological Sciences, University of Rome La Sapienza, Viale dell'Università, 30, 00185 Rome, Italy.
authors.forename: Antonella
authors.initials: A
authors.lastname: Conte
authors.forename: Francesca
authors.initials: F
authors.lastname: Gilio
authors.forename: Ennio
authors.initials: E
authors.lastname: Iezzi
authors.forename: Vittorio
authors.initials: V
authors.lastname: Frasca
authors.forename: Maurizio
authors.initials: M
authors.lastname: Inghilleri
authors.forename: Alfredo
authors.initials: A
authors.lastname: Berardelli
mesh_terms: D000328:Adult; D001288:Attention / Q000502:physiology*; D003213:Conditioning, Psychological / Q000502:physiology; D003627:Data Interpretation, Statistical; D004558:Electric Stimulation; D004576:Electromyography; D019054:Evoked Potentials, Motor / Q000502:physiology; D007839:Functional Laterality / Q000502:physiology; D006225:Hand / Q000294:innervation / Q000502:physiology; D006801:Humans; D009044:Motor Cortex / Q000502:physiology*; D009473:Neuronal Plasticity / Q000502:physiology; D012016:Reference Values; D013116:Spinal Cord / Q000502:physiology; D050781:Transcranial Magnetic Stimulation; D014459:Ulnar Nerve / Q000502:physiology