The importance of complex spikes in cerebellar contributions to behaviour.

点击翻译按钮获取中文摘要

The cerebellum is a major region of the brain vital for the coordination of movements. When in mammals (including humans) it is damaged ? e.g. due to stroke, genetic disorders, or tumours ? voluntary movements such as reaching to grasp an object become inaccurate and poorly timed; balance is severely disrupted; and our ability to learn new motor skills is impaired. How the internal circuitry of the cerebellum ensures that movements are performed smoothly and accurately remains unknown. Neurones called Purkinje cells are central to this function because they form the only output of the cerebellar cortex. They influence activity in the cerebellar nuclei, which, in turn, provide the output of the cerebellum, so the way in which cerebellar nuclear activity is modified by Purkinje cells is central to understanding how the cerebellum exerts its control over movement. Purkinje cells are exceptional in the mammalian brain in that they discharge two very different types of electrical impulse - simple spikes and complex spikes. The latter are thought to hold the key to cerebellar operation but their role in movement control remains a hotly debated issue. In pilot experiments we have found that complex spikes can be further categorized into two different types: spiking and non-spiking; and that the type of complex spike generated at any given time by a Purkinje cell has an effect on the on-going simple spike activity of the same cell. This has important implications for cerebellar information processing because the two types of complex spike are likely to produce distinct patterns of activity in the cerebellar nuclei, providing powerful timing signals that could underlie cerebellar contributions to coordinating movement. Using neuronal recording techniques we will determine how the two different types of complex spike: i) modify simple spike activity, and ii) influence cerebellar nuclear activity. One of the unique features of our experiments is that the neural recordings will include the natural activity patterns of complex spikes in action in animals performing a skilled reach-to-grasp movement under carefully controlled conditions. The results from this project will therefore shed light on fundamental brain processes underlying our ability to perform coordinated movements.