Spatial-Orientation Priming Impedes Rather than Facilitates the Spontaneous Control of Hand-Retraction Speeds in Patients with Parkinson’s Disease

Abstract

BackgroundOften in Parkinson’s disease (PD) motor-related problems overshadow latent non-motor deficits as it is difficult to dissociate one from the other with commonly used observational inventories. Here we ask if the variability patterns of hand speed and acceleration would be revealing of deficits in spatial-orientation related decisions as patients performed a familiar reach-to-grasp task. To this end we use spatial-orientation priming which normally facilitates motor-program selection and asked whether in PD spatial-orientation priming helps or hinders performance.MethodsTo dissociate spatial-orientation- and motor-related deficits participants performed two versions of the task. The biomechanical version (DEFAULT) required the same postural- and hand-paths as the orientation-priming version (primed-UP). Any differences in the patients here could not be due to motor issues as the tasks were biomechanically identical. The other priming version (primed-DOWN) however required additional spatial and postural processing. We assessed in all three cases both the forward segment deliberately aimed towards the spatial-target and the retracting segment, spontaneously bringing the hand to rest without an instructed goal.Results and ConclusionsWe found that forward and retracting segments belonged in two different statistical classes according to the fluctuations of speed and acceleration maxima. Further inspection revealed conservation of the forward (voluntary) control of speed but in PD a discontinuity of this control emerged during the uninstructed retractions which was absent in NC. Two PD groups self-emerged: one group in which priming always affected the retractions and the other in which only the more challenging primed-DOWN condition was affected. These PD-groups self-formed according to the speed variability patterns, which systematically changed along a gradient that depended on the priming, thus dissociating motor from spatial-orientation issues. Priming did not facilitate the motor task in PD but it did reveal a breakdown in the spatial-orientation decision that was independent of the motor-postural path.

The rates of change of the stochastic trajectories of acceleration variability are a good predictor of normal aging and of the stage of Parkinson's disease

“…One reason for this is that this quantity relates to the magnitude of the maximum acceleration vector which in recent work we have found to be a good predictor of the break down between movements that are automatically performed and movements that are performed under voluntary control, in PD. We have also found it to be a good predictor of early latent cognitive impairments in PD (Yanovich et al, 2013). Another reason is that the maximum deviations are most likely collected at highest motions where the accelerometer activity is at its highest (as opposed to when the person is resting and the phone is not moving much).…”

“…Current traditional statistical techniques (e.g., significant hypothesis testing) have proven inadequate to tackle the heterogeneity of the disease, the manifestation of its symptoms, and to evaluate the response to drug treatments or deep brain stimulation (DBS) (Yanovich et al, 2013). The golden standard in scientific research of the Social and the Health sciences is to homogenize the samples a priori, hand pick the groups with as similar as possible features to test some hypothesis on the effect of some treatment in relation to controls.…”

“…At shorter time scales our methods (Torres and Jose, 2012) can identify external influences in the rate of change of the stochastic signal so as to highlight the external source(s) of sensory guidance and context that most likely tend to drive the signal toward more predictive than toward more random and noisier stochastic regimes. The new statistical techniques used in this paper to analyze the mobile phone accelerometer data have been previously applied to sports (Torres, 2011, 2013), autism detection (Torres, 2012; Torres et al, 2013a), autism therapeutic interventions (Torres et al, 2013b), and reach-to-grasp in PD (Yanovich et al, 2013). …”

Strategies to develop putative biomarkers to characterize the female phenotype with autism spectrum disorders

“…Distributional analyses were performed on both sets of parameters. In prior work, we had discovered that the two-parameter, continuous gamma family of probability distributions captures with high confidence the continuum of human motor signatures in both typical and compromised systems (Torres 2011(Torres , 2013aTorres et al 2013a;Yanovich et al 2013). Thus we used the gamma plane here to plot (shape, scale) the gamma parameters for each individual, as they were experimentally estimated with 95% confidence intervals.…”

“…Some of these may impact movement and could be reflected in the continuous flow of motions, including the spontaneous segments of natural behaviors. Some of the well-known peripheral issues include problems with the autonomic nervous system, involving the enteric (gastro-intestinal) subsystems of the PNS (Ashwood et al 2003;Buie et al 2010;de Magistris et al 2010;Kushak et al 2011;MacFabe et al 2011;Mazurek et al 2013;Molloy and Manning-Courtney 2003); problems with sleep and the circadian rhythms are also common (Bourgeron 2007;Glickman 2010); and unusual and unpredictable pain and temperature dysregulation are well documented, particularly in autism of known etiology (Bandstra et al 2012;Dubois et al 2010;Klintwall et al 2011;Nader et al 2004;Tordjman et al 2009;Zeidan-Chulia et al 2011). These are, however, often down-played and interpreted as "co-morbid," secondary symptoms in the face of more obvious differences in the development of social and communicative skills.…”