title: Selective BOLD responses to individual finger movement measured with fMRI at 3T.
abstract: Although the gross somatotopic organization of the posterior bank of the precentral gyrus is well established, a fine scale organization of the representations of the digits of the hand has not been fully characterized. Previous neuroimaging studies have failed to find clear evidence for a specificity of digit representations in motor cortex, but rather report a distributed network of control. Reported here are the results of two experiments; in Experiment 1 a sequential finger tapping task produced strong blood oxygen level dependent (BOLD) responses in the contralateral precentral gyrus, but there was a lack of specificity for distinguishing individual representations. A randomly ordered task did accomplish this goal. In the second experiment, a randomly ordered finger-tapping task was used and the findings demonstrated BOLD responses in clusters of voxels specific to movement of a single digit. The region of interest defined for each digit comprised several noncontiguous clusters. A "selectivity index" was developed to quantify the magnitude of the BOLD response to the movement of a specific digit, relative to BOLD response associated with movement of other digits. Strong evidence of BOLD selectivity (albeit not exclusivity) was found in the hemisphere contralateral to the cued digit; however, there was no evidence for an orderly spatial topography. These findings demonstrate that a selectivity of activation is quantifiable, supports a theory of noncontiguous distribution of control, and provides a method for comparing between healthy and impaired populations and investigating changes following training or intervention.
authors.affiliation: Department of Psychology, University of Minnesota, Minneapolis, Minnesota, USA.
authors.forename: Cheryl A
authors.initials: CA
authors.lastname: Olman
authors.forename: Kristen A
authors.initials: KA
authors.lastname: Pickett
authors.forename: Michael-Paul
authors.initials: MP
authors.lastname: Schallmo
authors.forename: Teresa J
authors.initials: TJ
authors.lastname: Kimberley
mesh_terms: D000328:Adult; D001931:Brain Mapping / Q000379:methods; D005260:Female; D005385:Fingers / Q000502:physiology*; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D009044:Motor Cortex / Q000378:metabolism*; D009068:Movement / Q000502:physiology*; D010775:Photic Stimulation / Q000379:methods; D011597:Psychomotor Performance / Q000502:physiology*