AUTHOR=Bolzoni Francesco , Esposti Roberto , Marchese Silvia M. , Pozzi Nicoló G. , Ramirez-Pasos Uri E. , Isaias Ioannis U. , Cavallari Paolo 

TITLE=Disrupt of Intra-Limb APA Pattern in Parkinsonian Patients Performing Index-Finger Flexion

JOURNAL=Frontiers in Physiology

VOLUME=Volume 9 - 2018

YEAR=2018

URL=https://www.frontiersin.org/journals/physiology/articles/10.3389/fphys.2018.01745

DOI=10.3389/fphys.2018.01745

ISSN=1664-042X

ABSTRACT=Voluntary movements induce postural perturbations which are counteracted by Anticipatory Postural Adjustments (APAs). These actions are known to build up long fixation chains toward available support points (inter-limb APAs), so as to grant whole body equilibrium. Moreover, recent studies highlighted that APAs also build-up short fixation chains, within the same limb where a distal segment is moved (intra-limb APAs), aimed at stabilizing the proximal segments. The neural structures generating intra-limb APAs still need investigations; the present study aims to compare focal movement kinematics and intra-limb APA latencies and pattern between healthy subjects and parkinsonian patients, assuming the latter as a model of basal ganglia dysfunction.
Intra-limb APAs that stabilize the arm when the index-finger is briskly flexed were recorded in 13 parkinsonian patients and in 10 age-matched healthy subjects.
Index-finger movement was smaller in parkinsonian patients vs. healthy subjects (p = 0.01) and more delayed with respect to the onset of the prime mover Flexor Digitorum Superficialis (FDS, p < 0.0001). In agreement with the literature, in all healthy subjects the FDS activation was preceded by an inhibitory intra-limb APA in Biceps Brachii (BB) and Anterior Deltoid (AD), and almost simultaneous to an excitatory intra-limb APA in Triceps Brachii (TB). In parkinsonian patients, no significant differences were found for TB and AD intra-limb APA timings, however only 4 patients showed an inhibitory intra-limb APA in BB, while other 4 did not show any BB intra-limb APAs and 5 actually developed a BB excitation. The frequency of occurrence of normal sign, lacking and inverted BB APAs was different in healthy vs. parkinsonian participants (p = 0.0016). The observed alterations in index-finger kinematics and intra-limb APA pattern in parkinsonian patients suggest that basal ganglia, in addition to shaping the focal movement, may also contribute to intra-limb APA control.