Rasmus Kragh Nielsen

Effect of Early and Late Rehabilitation Onset in a Chronic Rat Model of Ischemic Stroke— Assessment of Motor Cortex Signaling and Gait Functionality Over Time

The aim of the present study was to investigate the effects of ischemic stroke and onset of subsequent rehabilitation of gait function in rats. Nine male Sprague-Dawley rats were instrumented with a 16-channel intracortical (IC) electrode array. An ischemic stroke was induced within the hindlimb area of the left motor cortex. The rehabilitation consisted of a repetitive training paradigm over 28 days, initiated on day one (“Early-onset”, 5 rats) and on day seven, (“Late-onset”, 4 rats). Data were obtained from IC microstimulation tests, treadmill walking tests, and beam walking tests. Results revealed an expansion of the hindlimb representation within the motor cortex area and an increased amount of cortical firing rate modulation for the “Early-onset” group but not for the “Late-onset” group. Kinematic data revealed a significant change for both intervention groups. However, this difference was larger for the “Early-onset” group. Results from the beam walking test showed functional performance deficits following stroke which returned to pre-stroke level after the rehabilitative training. The results from the present study indicate the existence of a critical time period following stroke where onset of rehabilitative training may be more effective and related to a higher degree of true recovery.

Rehabilitation Technologies Application in Stroke and Traumatic Brain Injury Patients

Neurorehabilitation plays a crucial role in the multidisciplinary management of brain injury patients. Emergent therapies based on rehabilitation technologies such as robots, bci, FES, and virtual reality could facilitate cognitive and sensorimotor recovery by supporting and motivating patients to practice-specific tasks on high repetitive levels during different stages of rehabilitation. Robots have become a promising task-oriented tool intended to restore upper limb function and a more normal gait pattern. Virtual reality environments by providing powerful sensorimotor feedback and increasing user interaction with a virtual scenario could improve gait, balance, and upper limb motor function. This chapter will provide an overview on the rationale of introducing rehabilitation technologies-based therapies into clinical settings and discuss their evidence for effectiveness, safety, and value for stroke and traumatic brain injury patients. In addition, recommendations for goal setting and practice of training based on disease-related symptoms and functional impairment are summarized together with reliable functional assessments.

Low-Frequency Intracortical Electrical Stimulation Decreases Sensorimotor Cortex Hyperexcitability in the Acute Phase of Ischemic Stroke

Ischemic stroke causes a series of complex pathophysiological events in the brain. Electrical stimulation of the brain has been considered as a novel neuroprotection intervention to save the penumbra. However, the effect on the cells’ responsiveness and their ability to survive has yet to be established. The objective of the present study was to investigate the effects of low-frequency intracortical electrical stimulation (lf-ICES) applied to the ischemia-affected sensorimotor cortex immediately following ischemic stroke. Twenty male Sprague-Dawley rats were instrumented with an intracortical microelectrode array (IC MEA) and a cuff-electrode around the sciatic nerve. Photothrombosis intervention was performed within the sensorimotor cortex and the electrophysiological changes were assessed by analysis of the neural responses to stimulation of the sciatic nerve. Neuroprotection intervention consisted of eight 23 min lf-ICES blocks applied to the IC MEA during the initial 4 h following photothrombosis. Our results revealed that the area and magnitude of the sensorimotor cortex response significantly increased if ischemic stroke was allowed to progress uninterrupted, whereas this was not observed for the group of rats subjected to lf-ICES. Our findings indicate that low-frequency electrical stimulation is able to minimize hyperexcitability and may therefore be a candidate as neuroprotection intervention in the future.

Novel Approach for Investigation of Neuronal Alterations Following Ischemic Stroke in a Rat Model

Ischemic stroke is a complex pathological trauma involving a multitude of detrimental processes. Due to the complexity of both the neural networks in the brain and the pathological process following stroke, novel methods to obtain knowledge about ischemic stroke are needed. One recently suggested model is to utilize intracortical (IC) microwire electrode-arrays to record from ischemic cortical tissue. In the present work we report on refinements made to the model, including design of a novel IC electrode-array and methods for quantification and analysis of the obtained IC recordings. IC recordings were obtained from one Sprague-Dawley rat prior to induction of ischemic stroke and in a follow-up period of 150 min post-stroke. The results showed that the refinements of the model resulted in a more intuitive way of interpreting the progression of ischemic stroke. Future enhancements of the model should concern features that focus on the spatial dynamics within the ischemia affected neural networks. In addition to assisting in generating knowledge about the pathology of ischemic stroke the model may be useful for optimization of rehabilitative electrical stimulation protocols.