title: Reduction of excitability ("inhibition") in the ipsilateral primary motor cortex is mirrored by fMRI signal decreases.
abstract: Functional magnetic resonance imaging (fMRI) was used to investigate how focal cortical inhibition affects the blood oxygen level-dependent (BOLD) signal. Phasic low force pinch grip reduces excitability of the ipsilateral primary motor cortex. This task was used to study BOLD signal changes during inhibition. Six right-handed normal volunteers participated in the study. They were asked to perform a right-handed pinch grip repetitively at 1 Hz and 5% of their individual maximal voluntary contraction (MVC). Data were acquired with a 1.5 Tesla Magnetom and continuous multislice T2*-weighted images. The contralateral primary motor cortex (M1) revealed an activation in the knob-shaped hand representation of the central sulcus area. More importantly, a decreased (often referred to as "negative") BOLD signal in the ipsilateral M1 was observed. We suggest phasic low force pinch grip as a reproducible, easy model of focal inhibition. Decreased cortical excitability presents as decreased BOLD signal using fMRI.
authors.affiliation: Neurologisches Universitätsklinikum, Hamburg-Eppendorf Martinistrasse 52, 20246 Hamburg, Germany.
authors.forename: Farsin
authors.initials: F
authors.lastname: Hamzei
authors.forename: Christian
authors.initials: C
authors.lastname: Dettmers
authors.forename: Reinhard
authors.initials: R
authors.lastname: Rzanny
authors.forename: Joachim
authors.initials: J
authors.lastname: Liepert
authors.forename: Christian
authors.initials: C
authors.lastname: Büchel
authors.forename: Cornelius
authors.initials: C
authors.lastname: Weiller
mesh_terms: D000328:Adult; D004574:Electromagnetic Fields; D005260:Female; D007839:Functional Laterality / Q000502:physiology*; D018737:Hand Strength / Q000502:physiology; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D009044:Motor Cortex / Q000502:physiology*; D010100:Oxygen / Q000097:blood; D013003:Somatosensory Cortex / Q000502:physiology
chemical_list: D010100:Oxygen