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Understanding how behavior is controlled requires that modeling be combined with behavioral, electrophysiological, and neuroanatomical investigations. One problem in studying motor systems is that they have considerable autonomy; they are not driven solely by inputs. Choosing walking as the object of study is promising because it is a comparably simple and easy-to-elicit behavior, but it exhibits the special feature of most motor behavior—the interaction between central, autonomous components and peripheral, sensory influences. This article reviews the control of walking in stick insects, beginning with behavioral studies of single-leg control and the interleg coordinating mechanisms. These behavioral results are tested and supported by modeling the control system in an artificial neural network computer simulation and a six-legged robot. Supporting neurophysiological results also are considered. Together, the results indicate that the high flexibility and adaptability is based on a simple distributed control structure.

A system that controls the leg movement of an animal or a robot walking over irregular ground has to ensure stable support for the body and at the same time propel it forward. To do so, it has to react adaptively to unpredictable features of the environment. As part of our study of the underlying mechanisms, we present here a model for the control of the leg movement of a 6-legged walking system. The model is based on biological data obtained from the stick insect. It represents a combined treatment of realistic kinematics and biologically motivated, adaptive gait generation. The model extends a previous algorithmic model by substituting simple networks of artificial neurons for the algorithms previously used to control leg state and interleg coordination. Each system controlling an individual leg consists of three subnets. A hierarchically superior net contains two sensory and two 'premotor' units; it rhythmically suppresses the output of one or the other of the two subordinate nets. These are continuously active. They might be called the 'swing module' and the 'stance module' because they are responsible for controlling the swing (return stroke) and the stance (power stroke) movements, respectively. The swing module consists of three motor units and seven sensory units. It can produce appropriate return stroke movements for a broad range of initial and final positions, can cope with mechanical disturbances of the leg movement, and is able to react to an obstacle which hinders the normal performance of the swing movement. The complete model is able to walk at different speeds over irregular surfaces. The control system rapidly reestablishes a stable gait when the movement of the legs is disturbed.

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Background Impaired motor functions after stroke are common and negatively affect patients' activities of daily living and quality of life. In particular, hand motor function is essential for daily activities, but often returns slowly and incompletely after stroke. However, few data are available on the long-term dynamics of motor recovery and self-reported health status after stroke. The Interdisciplinary Platform for Rehabilitation Research and Innovative Care of Stroke Patients (IMPROVE) project aims to address this knowledge gap by studying the clinical course of recovery after inpatient rehabilitation. Methods In this prospective observational longitudinal multicenter study, patients were included towards the end of inpatient rehabilitation after ischemic or hemorrhagic stroke. Follow-up examination was performed at three, six, and twelve months after enrollment. Motor function was assessed by the Upper Extremity Fugl-Meyer Assessment (FMA), grip and pinch strength, and the nine-hole peg test. In addition, Patient-Reported Outcomes Measurement Information System 10-Question Short Form (PROMIS-10) was included. Linear mixed effect models were fitted to analyze change over time. To study determinants of hand motor function, patients with impaired hand function at baseline were grouped into improvers and non-improvers according to hand motor function after twelve months. Results A total of 176 patients were included in the analysis. Improvement in all motor function scores and PROMIS-10 was shown up to 1 year after inpatient rehabilitation. FMA scores improved by an estimate of 5.0 (3.7–6.4) points per year. In addition, patient-reported outcome measures increased by 2.5 (1.4–3.6) and 2.4 (1.4–3.4) per year in the physical and mental domain of PROMIS-10. In the subgroup analysis non-improvers showed to be more often female (15% vs. 55%, p = 0.0155) and scored lower in the Montreal Cognitive Assessment (25 [23–27] vs. 22 [20.5–24], p = 0.0252). Conclusions Continuous improvement in motor function and self-reported health status is observed up to 1 year after inpatient stroke rehabilitation. Demographic and clinical parameters associated with these improvements need further investigation. These results may contribute to the further development of the post-inpatient phase of stroke rehabilitation. Trial registration: The trial is registered at ClinicalTrials.gov (NCT04119479).