Patient and oncologist expectations of functional prognosis among older adults with acute myeloid leukemia.

The acquisition of a new motor skill task is defined as the process by which movements become progressively more accurate through practice and interaction with the environment (Willingham ; Cheung et al. ; Doyon et al. ). This incremental process begins with a rapid initial phase, during which task repetition within a single session induces specific changes in movement control, ultimately enabling precise execution of the new motor skill (Doyon and Benali ). These early changes in movement control reflect neural plasticity at both cortical and subcortical levels, ensuring the coordinated activation of synergistic muscles required for the intended movement (Dayan and Cohen ; Ungerleider et al. ; Ziemann et al. ; Stefan et al. ; Aizenstein et al. ; Hikosaka et al. ; Doyon et al. ; Floyer-Lea and Matthews ; Cheung et al. ). For instance, the early learning phase is dominated by cerebellar activity, with peak activation of the primary motor cortex linked with error correction (Lohse et al. ). Thus, research on functional and neural circuitry adaptations at the supraspinal level has significantly advanced our understanding of motor skill learning mechanisms. Spinal mechanics underlying voluntary movement generation have also been explored in the context of motor skill learning (Ely et al. ; Kinany et al. ; Vahdat et al. ; Landelle et al. ). Neural inputs transmitted from spinal and supraspinal sources to spinal motor neurons consist of independent synaptic inputs, as well as synaptic inputs shared across the entire pool (Negro and Farina ; Castronovo et al. ; Enoka and Farina ; Farina and Negro ). Due to the spread of shared inputs, the motor neuron pool functions as a selective linear filter, canceling out in the neural drive input components that are not common to all motor neurons. As a result, the cumulative spike train of action potentials received by the muscle (Farina and Negro ), is primarily determined by the common synaptic inputs (Hug et al. a; Negro et al. ; Thompson et al. ; Farina et al. ; Negro et al. ). Therefore, investigating changes in the neural drive provides direct information on alterations in the strength of common synaptic inputs to alpha motor neurons. Building on this concept, a recent study investigated how the acquisition of a force-matching task influences the low-frequency oscillations of shared synaptic inputs to alpha motor neurons (Cabral et al. ), which are key determinants of force generation and variability (Enoka and Farina ; Hug et al. a; Farina and Negro ; Negro et al. ). The findings revealed that the short-term acquisition of the task was associated with reductions in physiological tremor oscillations within the shared synaptic inputs, with these reductions correlating with improvements in performance. Additionally, compelling evidence suggested that learning a new motor task may modulate presynaptic inhibition by reducing H-reflex excitability, potentially facilitating motor sequence consolidation within spinal circuits (Lungu et al. ; Giboin et al. ; Perez et al. ). However, previous research has primarily focused on individual muscles controlling a single joint. How shared synaptic inputs are transmitted across synergistic muscles and modulated during skill acquisition remains unclear. Therefore, the aim of this study was to investigate whether the short-term acquisition of a motor task is mediated by changes in the common synaptic inputs to motor neurons of synergistic muscle. We investigated this issue in the vastus lateralis (VL) and vastus medialis (VM) muscles, which act synergistically with the rest of the quadriceps group during knee extension. This synergistic pair is particularly relevant because VM and VL are believed to receive a high proportion of shared synaptic input during voluntary isometric contractions (Laine et al. ). However, they are anatomically and functionally distinct. Due to differences in muscle architecture (Flandry and Hommel ; Blazevich et al. ), the VL has a greater potential for force generation (Lin et al. ; Lieber et al. ). Therefore, we consider it relevant to investigate whether these architectural and functional differences would lead to distinct modulation of common synaptic inputs during the short-term acquisition of a motor task. We hypothesized that the acquisition of a new skill training task would be similar across synergistic muscles and that the effects of neural drive oscillations on the overall force output would mainly depend on the different anatomical conformation of the muscles, the mechanical constraints, and the functions they perform.