The cerebellum is the largest motor structure within the CNS, and as a result, has been the focus of intensive investigation. Studies indicate that the cerebellum is intimately involved with sensory-motor integration for the maintenance and performance of smooth and accurate movements. Many observations of cerebellar function have been obtained from work on in vivo animal models. For example, detailed anatomical and electrophysiological studies in anaesthetized or decerebrate animals have revealed how information from peripheral receptors in muscle, skin and joints is forwarded to the cerebellum, in addition to the ‘wiring’ of the mammalian cerebellum in relation to other areas of the CNS concerned with the programming and management of voluntary movement (e.g. the inferior olive, pontine nuclei, red nucleus and motor cortex). Moreover, studies in awake animals have demonstrated the modulation of cerebellar neuronal discharge patterns during the execution and coordination of movements. In addition, the ability to manipulate the ionic environment and high mechanical stability of in vitro brain slice preparations has provided important details of the cellular mechanisms and synaptic events involved in cerebellar function. These preparations, however, exclude neuronal connections with other areas of the CNS as well the rest of the body. Given that many studies have demonstrated that normal cerebellar function is dependent on maintaining its connections with other brain structures (especially the inferior olive), we have therefore developed a non-pulsatile, perfused hindbrain and upper body preparation (PHBP) to study the neuronal mechanisms of the intact cerebellum in situ. Previously, a similar preparation (lacking a cerebellum) has been used to examine brainstem mechanisms that underlie cardio-respiratory control (Paton, 1996; Potts et al. 2000). All surgical and experimental procedures were approved and performed in accordance with local animal welfare guidelines. In the experimental procedure Wistar rats of either sex weighing between 85-120 g (4-6 weeks of age) are deeply anaesthetized with halothane and bisected below the diaphragm. The upper body is perfused via the descending aorta with a Ringer solution gassed with 95%O₂-5%CO₂ mixture via a double lumen cannula at a pressure of 75-80 mmHg, and brain temperature is maintained at 33°C. Perfusion pressure is monitored via the second lumen of the cannula. The flow rate of the perfusate is altered until phrenic nerve activity monitored via a suction electrode displayed a eupnoeic (ramp-like) pattern. To illustrate the viability of the cerebellum in the PHBP a number of procedures will be carried out during the demonstration: (i) Electrical stimuli will be applied to the surface of the cerebellar cortex and the brachial plexus to evoke parallel fibre and cerebellar field potentials respectively. (ii) Microstimulation of nucleus interpositus will be used to evoke EMG activity in an ipsilateral forelimb muscle (e.g. biceps brachii). And (iii) extracellular recordings will be made from single cerebellar neurones with high impedance glass-insulated tungsten microelectrodes (3-5 MΩ).