Upper Limb Asymmetry in the Sense of Effort Is Dependent on Force Level

Abstract

Previous studies have shown that asymmetries in upper limb sensorimotor function are dependent on the source of sensory and motor information, hand preference and differences in hand strength. Further, the utilization of sensory and motor information and the mode of control of force may differ between the right hand/left hemisphere and left hand/right hemisphere systems. To more clearly understand the unique contribution of hand strength and intrinsic differences to the control of grasp force, we investigated hand/hemisphere differences when the source of force information was encoded at two different force levels corresponding to a 20 and 70% maximum voluntary contraction or the right and left hand of each participant. Eleven, adult males who demonstrated a stronger right than left maximum grasp force were requested to match a right or left hand 20 or 70% maximal voluntary contraction reference force with the opposite hand. During the matching task, visual feedback corresponding to the production of the reference force was available and then removed when the contralateral hand performed the match. The matching relative force error was significantly different between hands for the 70% MVC reference force but not for the 20% MVC reference force. Directional asymmetries, quantified as the matching force constant error, showed right hand overshoots and left undershoots were force dependent and primarily due to greater undershoots when matching with the left hand the right hand reference force. Findings further suggest that the interaction between internal sources of information, such as efferent copy and proprioception, as well as hand strength differences appear to be hand/hemisphere system dependent. Investigations of force matching tasks under conditions whereby force level is varied and visual feedback of the reference force is available provides critical baseline information for building effective interventions for asymmetric (stroke-related, Parkinson’s Disease) and symmetric (Amyotrophic Lateral Sclerosis) upper limb recovery of neurological conditions where the various sources of sensory – motor information have been significantly altered by the disease process.

Isometric Force Matching Asymmetries Depend on the Position of the Left Hand Regardless of Handedness

“…The total amount of the requested force had a relevant effect on the performance, increasing the difference between the two hands and its variability. Further, the bias error highlighted that the left hand applied more force than the right for the lower target force, but this effect was decreased and even inverted for the higher target force, consistently with previous results in sequential [8,9] and concurrent [10] matching task. The results of the present study extend the previous findings, highlighting that this effect was not influenced by the handedness.…”

“…the performance seemed to be influenced by the specialization of the brain hemisphere, evolving independently from handedness. The significant effect of the left hand position in right-handed individuals [11] was supported by the dichotomous model [3] observed in motor [7] and force tasks [8,9]. This model suggests that during bimanual activities, the dominant right arm relies more on visual feedback, while the non-dominant left arm on proprioceptive feedback.…”

“…According to this theory, the dominant arm, in bimanual reaching and position matching tasks, relies more on visual feedback, whereas the non-dominant arm relies more on proprioceptive feedback. This model could also explain results on the sense of effort [8] and grasp force [9] in bimanual tasks. However, to the best of our knowledge the handedness effect on behavioral asymmetries has not been evaluated in bimanual force control tasks with both hands are actively engaged toward a common goal.…”

Clinical and Electrophysiological Hints to TMS in De Novo Patients with Parkinson’s Disease and Progressive Supranuclear Palsy

“…In this context, pioneer neuroanatomical studies showed that the dominant hemisphere may have higher corticospinal tract density [ 77 , 78 ], although the neurophysiology underlying brain asymmetries is still controversial, with some authors suggesting that the dominant hemisphere exhibits larger cortical representation areas with lower excitability [ 79 ], while others report the opposite [ 80 , 81 ], or even no difference [ 82 , 83 , 84 ]. It has been recently demonstrated that a laterality asymmetry possibly leads to a more pronounced MEP distribution on the dominant hemisphere compared to the non-dominant side in healthy right-handers [ 85 ], and that patients with motor and movement disorders exhibit disruptions of motor unit recruitment and discharge patterns [ 86 , 87 , 88 , 89 ], which may affect dominant and non-dominant sides differently [ 90 ]. However, the lack of similar data in PSP precludes a better understanding of laterality asymmetries in these patients and stimulates further studies on this intriguing topic.…”

Impaired Modulation of Motor and Functional Performance in Patients after Total Knee Arthroplasty: A Prospective Observational Study

“…Modulation of motor output has been reported to depend on central and peripheral processes in relation to sense of force or tension and sense of effort [5]. Sense of force originates from articular, muscular, and cutaneous receptors, whereas sense of effort arises from the perception of descending motor commands [6][7][8]. However, the contribution of these two mechanisms on performance modulation ability remains controversial, especially in patients with musculoskeletal impairments (e.g., end-stage knee osteoarthritis) or after surgery (e.g., total knee arthroplasty), for whom muscle and/or joint damages generate a discrepancy between sense of force and sense of effort [5,9,10].…”