Nociceptive input to cerebellar pathways and its behavioural significance

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All living creatures have to deal with pain - it's an unpleasant, but vital experience that safeguards animal welfare and ultimately, survival. Pain is a warning, a signal that you need to do something. Normally you have two choices: either move away and escape serious injury; or, if you're already hurt, you simply have to cope with the pain. Your brain recognises the difference between these two kinds of pain and works out the best bodily response. Escaping pain means that an animal has to rapidly get up and go. It has to run, jump, perhaps fly or swim to get away from the threat - this is an active response to escapable pain. To escape the pain animals have to move and movement requires increased muscular activity. When muscles go to work in an emergency they demand increases in blood pressure, heart rate and breathing to fuel them with extra oxygen and nutrients. In contrast, there is no escaping the pain of a stomach ache. When you move, the pain stays with you - all that can be done is to endure it, to try and cope with it. This is a passive response to inescapable pain. The best thing to do is to try and protect the injured tissues, which means 'lying low', keeping movement to a minimum - the opposite of an active response. To be effective, active and passive responses to pain are complex and they need body and brain to work together in a highly co-ordinated way. It is the body that responds to pain, but it is the brain that co-ordinates the respective changes in movement and in heart and lung functions. It is likely that escapable and inescapable pain is each controlled by its own separate connections within the brain. We have good evidence that this is the way that brain circuits control changes in blood pressure, but much less is known about the brain circuits that control changes in bodily movement in response to these different kinds of pain. The key aim of the present work is to find out whether different types of pain activate different circuits within the brain that control movement. In particular, we will focus on brain circuits leading to the cerebellum, the major controller of body movement in mammals. We will chart pain pathways within the brain that lead to the cerebellum and we will find out whether different pathways are activated by escapable pain (e.g. pain paths arising from the skin), as opposed to those activated by inescapable pain (e.g. pain paths arising from the guts). Also, by recording the electrical signals of individual brain cells, we will find out if painful and non painful signals are sent to the cerebellum by the same route. Pain also causes stress and anxiety, which affect the way in which an animal responds to, and copes with, pain. Stress activates parts of the brain that alter incoming pain signals, which in turn change the animal's response to pain. The final part of our study will see if the 'stress and anxiety' brain centres can alter the flow of information in pain pathways leading to the cerebellum.