Computational protocol: Hand Function is Altered in Individuals with a History of Illicit Stimulant Use

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Protocol publication

[…] The grip and lift task (task one) was divided into two phases: lift (dynamic) phase and hold (stationary) phase. The lift phase was defined as the period between 0s (lift onset) and 1.5s and the hold phase was defined as the period between 1.5s and 2.5s. A total of 15 parameters were measured in the lift phase and three parameters were measured in the hold phase. The variety of parameters provided information about grip strategy, kinetics and kinematics of the lifting movement, and coupling between grip force and lift force. In the lift phase, grip and lift onset were determined by first applying a 20Hz low-pass filter to the raw data followed by calculation of the rate of change in grip force (dGF/dt) and lift force (dLF/dt). Onset was defined as the time of the initial rise in the force derivative (above the noise level) that initiated the rise to the maximum derivative. This procedure was used because the change in lift force represents the first measurable mechanical event in lifting the object. Grip onset relative to lift onset (termed ‘preload duration’) and maximum rate of change in force (dGF/dtmax and dLF/dtmax) were also measured. The temporal relationship between grip force and lift force was assessed by cross-correlation of the rate of change in grip force (dGF/dt) and lift force (dLF/dt) . dLF/dt was shifted in increments of 2.5ms (sampling resolution) relative to dGF/dt until the maximum cross-correlation coefficient (ρ) was obtained (IBM SPSS Statistics 20, Armonk NY, USA). The time shift required to achieve the maximum cross-correlation coefficient represents the time difference between the change in lift force and the change in grip force, and is an index of whether the grip strategy was primarily anticipatory (i.e. grip force leads lift force, negative time shift) or reactive (i.e. grip force lags lift force, positive time shift). Other parameters that were measured in the lift phase include peak force and acceleration, time-to-peak force and acceleration, minimum lift force (degree of downward push before lifting the object), and root mean square (RMS) EMG, all of which were measured from raw traces. In the hold phase, mean grip force, grip force coefficient of variation (%), and RMS EMG were measured from raw traces. For brief MVCs, mean grip force and RMS EMG was measured over a 1s period. [...] Group data are presented as means ± standard deviation in the text and mean ± standard error of the mean in figures. One-way ANOVA was used to compare subject characteristics, MVC force, alcohol and tobacco use between groups. Non-parametric data were transformed to ranks and one-way ANOVA on ranks were performed. Post hoc discrimination was made with a Bonferroni procedure. Independent Student’s t-test was used for between-group comparison (stimulant versus cannabis) of cannabis use and the score on the agitation and irritability questions of the BDI–II. For task one and three, group data were analysed with two-way repeated measures ANOVA with gender as a covariate for comparison of group (control, stimulant, cannabis; between-subject factor) and trial (one, two, three; within-subject factor). Mauchly’s test of sphericity was performed and the Greenhouse–Geisser method was used to correct for non-sphericity (IBM SPSS Statistics 20, Armonk NY, USA). Post hoc discrimination was made with a sequential Bonferroni procedure. Spearman Rank Order correlation was used to investigate the relationship between peak grip force and drug-use characteristics (trial one only) in the stimulant group. The relation between peak grip force and maximum rate of grip force application (dGF/dtmax) was investigated with linear regression analysis (SigmaPlot 11.0; Systat Software Inc, San Jose CA, USA). Statistical significance was set at P<0.05. […]

Pipeline specifications

Software tools SPSS, SigmaPlot
Application Miscellaneous
Diseases Movement Disorders
Chemicals Cocaine, Methamphetamine