# Perspectives and Challenges in Robotic Neurorehabilitation
###### Abstract  
The development of robotic devices for rehabilitation is a fast-growing field. Nowadays, thanks to novel technologies that have improved robots' capabilities and offered more cost-effective solutions, robotic devices are increasingly being employed during clinical practice, with the goal of boosting patients' recovery. Robotic rehabilitation is also widely used in the context of neurological disorders, where it is often provided in a variety of different fashions, depending on the specific function to be restored. Indeed, the effect of robot-aided neurorehabilitation can be maximized when used in combination with a proper training regimen (based on motor control paradigms) or with non-invasive brain machine interfaces. Therapy-induced changes in neural activity and behavioral performance, which may suggest underlying changes in neural plasticity, can be quantified by multimodal assessments of both sensorimotor performance and brain/muscular activity pre/post or during intervention. Here, we provide an overview of the most common robotic devices for upper and lower limb rehabilitation and we describe the aforementioned neurorehabilitation scenarios. We also review assessment techniques for the evaluation of robotic therapy. Additional exploitation of these research areas will highlight the crucial contribution of rehabilitation robotics for promoting recovery and answering questions about reorganization of brain functions in response to disease. electrophysiological recordings; end-effector robot; exoskeleton; neuroimaging; robotic rehabilitation; sensorimotor assessment +
Footnote †: journal: Applied  
In the last decades, innovative robotic technologies have been developed in order to effectively help clinicians during the neurorehabilitation process. The term \"robotic technology\" in this application domain refers to any mechatronic device with a certain degree of intelligence that can physically intervene on the behavior of the patient, optimizing and speeding up his/her sensorimotor recovery. The two key capabilities of these robots are: (1) Assessing the human sensorimotor function; and (2) re-training the human brain in order to improve the patient's quality of life. However, most of the studies in this field have been focused more on the development of the devices, whereas less effort was made on maximizing their efficacy for promoting recovery. The main challenge consists of designing effective training modalities, supported by appropriate control strategies. Thus, each robotic device supports a pre-defined training modality depending on the low-level control strategy implemented and also on the residual abilities of each patient. Usually, most of the rehabilitation devices implement a passive training modality (robot-driven, position control strategy), where the robot imposes the trajectories, and an active training modality (patient-driven), where the robot modulates its trajectory in response to the subject's intention to move [7; 8]. However, among all the different training modalities, the most relevant is the assistive one. Assistive controllers help participants to move their impaired limbs according to the desired postures during grasping, reaching, or walking, reflecting the strategy adopted by conventional physical and occupational therapy (active assistive training mode). Specifically, among the assistive strategies, the assistance-as-needed is widely employed because it reduces the patient risk of relying only on the robot to accomplish the rehabilitative task. Indeed, over-assistance could decrease the level of participation and, as a consequence, also the chance to induce neuroplastic changes [9]. This is called the \"slacking\" effect, and can be formally defined as a reduction of voluntary movement control when the patient undergoes repetitive passive mobilization of the limbs [10]. In addition to the assistance-as-needed strategy, to avoid the slacking effect, challenge-based controllers are used to make tasks more difficult or stimulating.