###### Abstract  
Paired associative stimulation (PAS) is an intervention that modulates cortical plasticity. Motor imagery (MI) is used in the rehabilitation of stroke patients. We aimed to evaluate the possible synergistic effect of associating both interventions for potentiating motor recovery poststroke. _MIPAS_ is a single-center, randomized controlled trial that enrolled 24 hemipactic poststroke participants. Three single-session interventions were tested in a crossover design: PAS/MI, PAS, and ShamPAS/MI during which the affected Extensor Caripi Radiails (ECR) muscle was targeted. During MI, the participants were instructed to imagine extending their parcite wrist. We used Sham, subthreshold stimulation during ShamPAS. Changes in ECR Motor-Evoked Potential (MEP) areas and parcite wrist Range of Motion (aROM) during active extension were compared between the interventions. We observed no significant superior effect of any intervention, neither on MEP nor on wrist aROM. A time of assessment effect was highlighted for both outcome measures, with MEP- and aROM-measured post-interventions significantly higher than those measured pre-intervention. Despite the beneficial effect of each intervention on participant parcite wrist motor function, not always associated with MEP change, our results do not highlight a specific advantage in combining PAS and MI interventions in post-stroke motor rehabilitation  
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Facilitatory corticomuscular paired associative stimulation (PAS), targeting the motor cortex and administered with an interstimulus interval (ISI) of 25 ms, is one of these NIBS interventions that relies on long-term potentiation (LTP)-like mechanisms and reproduces the process of associative motor learning by strengthening and modulating specifically the corticospinal excitability (CSE) of the targeted muscle [6]. Therefore, PAS can be considered as a NIBS intervention that is \"physiologically compatible\" with the current knowledge about the mechanisms underlying poststroke motor recovery and/or rehabilitation. Durable, reversible, and topographically specific facilitatory effects of PAS protocols have been demonstrated in healthy subjects on flexor and adbductor intrinsic finger muscles [6; 7]. In a way to be more suitable for stroke rehabilitation, the possibility to elicit a PAS effect has also been experimented on wrist extensor muscles in healthy subjects [8] and in subacute subcortical ischemic [9] and in chronic [10] stroke patients. Although the number of randomized controlled trials (RCTs) using PAS is very limited, the results obtained with PAS trials seem similar to those obtained with other NIBS techniques. Mainly, the modulation of CSE was observed after PAS intervention in healthy and stroke individuals, without a significant effect on motor performance improvement or function recovery [10; 11]. In spinal cord injury (SCI), repeated PAS has demonstrated therapeutic efficacy, with observed improvements in motor function [12; 13; 14; 15]. Limited and mostly preclinical evidence of efficacy exists in stroke patients [16; 17]. In a previous double-blinded Sham-controlled RCT, we tested and compared against Sham, a daily PAS protocol repeated over 5 days. The PAS protocol targeted the Extensor Carpi Radialis (ECR) muscle in a heterogeneous population of patients with cortical and/or subcortical strokes, mixing hemorrhagic or ischemic etiologies. We observed no significant difference in terms of CSE or motor scores, as assessed with the UE Fugl-Meyer Assessment scale (UEFMS) [18]. The absence of a difference could have been explained by the weak and variable CSE and motor effects induced by the repeated PAS intervention, also described previously [9; 10; 19], and the lack of sensitivity of the clinical scale used for motor function assessment [18]. Motor imagery (MI) is an easy-to-use and easy-to-administer intervention suitable for all stroke patients regardless of their motor deficit [20].