## 1 Introduction  
Minutes after an injury to the spinal cord, structural and functional reorganization of the affected brain areas is initiated [1, 2, 3]. Deafferentation and lack of proprioception lead to remodeling processes in the brain in the sense of a negative-maladaptive neuroplasticity, and thus to a long-term reorganization of the cortical topography [3]. However, neuroplasticity is a two-way street, and as the disease progresses, there are various possibilities to either strengthen or weaken the utilized pathways. Studies on both animal models and humans indicate that cortical structures are highly adaptable after deafferentation [4; 5; 6; 7; 8; 9]. In the chronic state of the disease, exercise enhances neuroplasticity, which might modulate connectivity patterns in brain regions responsible for movement imagination and execution [10]. A transcranial magnetic stimulation (TMS) study by [PERSON] and colleagues demonstrated that cortical excitability is increased in patients with spinal cord injury (SCI) after passive cycling [10]. A further TMS study on healthy racquet players revealed the impact of specific training on brain activity. Healthy professional racquet players showed increased cortical excitability in the hand muscles that was laterally and medially shifted on the motor cortex as compared to non-professional racquet players [11]. Evidence for plastic changes in the brain due to specification of long-term sports is also given by TMS study results for healthy tennis players [12]. Moreover, motor imagery of tennis, but not golf or table tennis, resulted in increased corticospinal facilitation of the associated muscles in expert tennis players. Notably, this effect of motor imagery was not observed for novice tennis players. One possibility to intensify and support physical training is the use of motor imagery (movement imagination) that is described as a mental representation of an action without an actual motor output [13]. Also during motor imagery, increased cortical excitability could be observed in patients with SCI. EEG data revealed similar primary motor cortex activation during movement imagination and execution, while in healthy participants the activity was reduced during movement imagery [14]. [PERSON] and colleagues revealed that inhibitory processes during imagined movements of an intact limb may be weakened by SCI so that movement and imagery processes yield more similar EEG patterns in patients with SCI in comparison to healthy subjects [15]. There is evidence that movement imagination training improves motor performance, modifies brain function, and reduces pain in patients with SCI [16; 17]. Motor imagination training of the right foot resulted in increased functional magnetic resonance image (fMRI) activation of the left putamen and improved speed of movement in non-paralyzed muscles. [PERSON] and colleagues examined patients with incomplete SCI conducting a movement imagination task during high-density electroencephalography (HD-EEG) recording and found a significant decrease in connectivity between subsets of the functional sensorimotor network. The authors also discovered increased local processing, which possibly indicates an adaptive compensatory mechanism of injury-induced neuroplasticity [18]. A review showed that movement imagination of possible non-paralyzed movements was found to improve reach-to-grasp performance by increasing both tenodesis grasp capabilities and muscle strength. Additionally, movement time and trajectory variability decreased, whereas EEG, functional magnet resonance imaging, and magnetoencephalography data analysis revealed a reduction in the abnormally increased brain activity [19]. Searching the literature for EEG studies on movement imagination in patients with SCI mainly resulted in studies on brain-computer interfaces [20; 21; 22; 23]. The aim of these studies is the better understanding of EEG patterns and their discriminability between movements in patients with SCI.