Reticulospinal Function in Health and Recovery from Lesion

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When we move, the brain sends commands to the spinal cord via a number of separate pathways. Neural circuits within the spinal cord then interpret these commands to activate muscles, and generate the required movements. Two very important pathways are called the corticospinal tract (CST) and the reticulospinal tract (RST). In primates such as man, the CST appears to be more important in controlling movement than in lower species, and this has led to considerable research concentrating on it. By contrast, we know much less about the RST. What commands are sent via the RST? How are they ?read out? by the spinal cord? How does this differ from the CST? These are the questions that this project seeks to address.We will make recordings of the electrical activity of single nerve cells in the cerebral cortex (origin of the CST), reticular formation (origin of the RST), and spinal cord, in monkeys trained to perform a reach and grasp task. Using modern methods, we will be able to characterise in detail how these different centres cooperate to control a voluntary movement.Whilst this information is important in itself if we are to understand the brain, it is also highly relevant to understanding disease. Conditions such as stroke, or spinal cord injury, can interrupt the pathways linking brain and spinal cord. In the months following such damage, most patients show some recovery. It is likely that surviving pathways reconfigure to take over some of the function which is normally performed by the damaged pathways. In the second part of this project, we will interrupt the CST on one side of the brain in monkeys, and wait for them to recover. We will then repeat the single nerve cell recordings carried out in the healthy animals. In this way, we will be able to determine precisely how the RST connections, and the spinal cord?s response to them, change to allow the animal to recover. Understanding this process in its fine details will give us new insights into functional recovery. The knowledge which we gain may suggest better strategies for rehabilitation, allowing doctors and physiotherapists to work with the brain?s own recovery processes to achieve better outcomes.