title: On the regularity of preparatory activity preceding movements with the dominant and non-dominant hand: a readiness potential study.
abstract: The readiness potential (RP), a slow negative electroencephalographic pre-movement potential, was reported to commence earlier for movements with the non-dominant left hand than with the dominant right hand. Latencies in these reports were always calculated from averaged RPs, whereas onset times of individual trials remained inaccessible. The aim was to use a new statistical approach to examine whether a few left hand trials with very early pre-movement activity disproportionally affect the onset of the average. We recorded RPs in 28 right-handed subjects while they made self-paced repetitive unilateral movements with their dominant and non-dominant hand. Skewness, a measure of distribution asymmetry, was analysed in sets of single-trial RPs to discriminate between a symmetric distribution and an asymmetric distribution containing outlier trials with early onset. Results show that for right hand movements skewness has values around zero across electrodes and pre-movement intervals, whereas for left hand movements skewness has initially negative values which increase to neutral values closer to movement onset. This indicates a symmetric (e.g., Gaussian) distribution of onset times across trials for simple right hand movements, whereas cortical activation preceding movements with the non-dominant hand is characterised by outlier trials with early onset of negativity. These findings may explain differences in the averaged brain activation preceding dominant versus non-dominant hand movements described in previous electrophysiological/neuroimaging studies. The findings also constrain mental chronometry, a technique that makes conclusions upon the time and temporal order of brain processes by measuring and comparing onset times of averaged electroencephalographic potentials evoked by these processes.
authors.affiliation: Department of Neurology, Medical University of Vienna, Wahringer Gurtel 18-20, 1090 Wien, Austria. georg.dirnberger@weizmann.ac.il
authors.forename: Georg
authors.initials: G
authors.lastname: Dirnberger
authors.forename: Cornelia
authors.initials: C
authors.lastname: Duregger
authors.forename: Gerald
authors.initials: G
authors.lastname: Lindinger
authors.forename: Wilfried
authors.initials: W
authors.lastname: Lang
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D003265:Contingent Negative Variation / Q000502:physiology*; D004569:Electroencephalography; D004576:Electromyography; D005260:Female; D007839:Functional Laterality / Q000502:physiology*; D006225:Hand; D006801:Humans; D033182:Intention; D008297:Male; D009068:Movement / Q000502:physiology*; D011597:Psychomotor Performance; D011930:Reaction Time; D013997:Time Factors; D055815:Young Adult