The feeling of what (does not) happen: A multimodal neurobehavioural account of somatosensory misperceptions

Sometimes our bodily sensations do not always reflect sensory reality. For example, how many times have you felt itchy or even scratched yourself when watching TV programmes where people have insects crawling over their hands and faces? In this case we know that the insects are not actually on us but the ability to recognise what is a 'true' bodily event vs. a 'false' one has implications for many common and distressing unexplained medical symptoms such as itch, numbness, tickling or tingling sensations and even some forms of pain. The purpose of our research is to find better biological markers of these bodily symptoms and help explain how the brain can 'create' bodily sensations in the absence of any actual physical input.
In five experimental studies we will use state-of-the-art brain imaging techniques to measure the activity of the brain before the person actually reports feeling touch or thinks they have been touched in cases when no touch has even been applied to them. We will measure the brain's response before the stimulation occurs and we will measure the person's own behavioural response indicating whether they think they have been touched or not. We will then compare the brain response to the 'true' (i.e., when touch has occurred) vs. 'false' (i.e., when it didn't) bodily event. In another study we will ask people to focus their attention on their own internal bodily sensations (such as their heartbeat) to see whether this increases the number of false bodily events reported by people and changes their brain response in a predictable way. In the final study, we will use a method that allows us to directly stimulate the brain to see whether this changes the number of false bodily events that people report in a predictable way, thus giving us a likely cause, based on differences in brain function, as to why some people experience a higher number of bodily symptoms that don't seem to have any physical cause.
Based on evidence from our previous studies we predict that people who show a particular pattern of brain activity (involving the medial frontal and parietal regions at the centre of the brain) will say they feel touch (even when they haven't been touched) more than other people who have the opposite pattern of brain activity (involving lateral frontal and parietal regions at the outer edges of the brain). These regions in the middle of the brain have been linked to studies involving pain and hallucinations but this will be the first time they have been linked to creating bodily symptoms and the first time anyone has recorded their activity before the person is actually touched. By measuring this activity we aim to be able to predict who is more likely to be susceptible to experiencing these false bodily sensations and in the future be able to help them by developing more effective treatments that target these overactive parts of the brain and stop them producing symptoms like itch and pain.
The outcomes of this research have the potential to benefit a wide variety of people, from basic scientists to people with medical conditions. We will know more about the brain after completing this project, which will help other scientists to understand the brain and its role in controlling bodily awareness. It will also give us more information on the possible causes of some medical conditions such as some forms of itch, numbness and pain, which at the moment are difficult to treat because there doesn't seem to be anything physically wrong with the body. Ultimately, this research will provide us with a better understanding of the brain systems responsible for bodily awareness and improved methods for measuring these systems, which can then be used to develop more effective treatments for people with medically unexplained somatic conditions.

A major goal of cognitive neuroscience is to explain the causal links between brain function and behaviour. This novel research project brings together experts in neuroscience, psychology and engineering to determine the role of pre-stimulus brain activity in the subsequent detection of near-threshold tactile events particularly when an absent tactile event is misperceived as being present. In three work packages we will extend the behavioural, EEG and fMRI approaches used successfully in our previous work to develop an overarching model of the influence of baseline neural activity on somatosensory perception using a signal detection approach. We predict that the correct detection of touch will be preceded by activity in lateral fronto-parietal (lFP) brain regions, involved in monitoring external events, whereas the misperception of touch will be preceded by activity in medial fronto-parietal (mFP) regions, involved in monitoring internal bodily sensations. We will then use interoceptive and exteroceptive attention tasks to increase the 'top-down' influence from these frontal brain regions on somatosensory perception. We predict that focussing on internal bodily sensations (counting heartbeats) prior to the task will activate mFP (and insula) cortex and increase the number of tactile misperceptions more than focussing on external tactile sensations. In the final phase of the research we will directly stimulate somatosensory cortex (using transcranial Direct Current Stimulation) to determine the causal role of intrinsic neural activity on tactile perception. We predict that applying stimulation at a frequency that increases resting alpha-oscillatory activity will increase the number of tactile misperceptions, thereby establishing a causal link between intrinsic neural activity and somatosensory perception. Overall, the outcomes of this research will reveal the fundamental role of dynamic brain networks and oscillatory activity in bodily consciousness.

The primary goal of our research is to impact on the scientific study of brain-body interactions by contributing experimental brain data to validate recent theoretical models of brain function and systems approaches to the biosciences. It will stimulate collaboration between interdisciplinary scientists who are interested in furthering the scientific discovery of brain function and its role in human behaviour including enhancing quality of life, health and well-being. Through dissemination of our results at national and international conferences and in high-impact peer-reviewed journals we will benefit other academic researchers in neuroimaging, electrophysiology, behavioural and cognitive neuroscience, and experimental psychology by demonstrating the role of intrinsic brain activity in perception and behaviour. Our findings also have significant implications for measuring, understanding and improving the treatment of a variety of medical conditions that defy a physical explanation for their cause. 'Medically unexplained' symptoms (such as some forms of musculoskeletal pain, itch, and gastrointestinal problems) are a common and conceptually difficult area of research but of huge importance. Over one quarter of primary care patients in England have these symptoms and because they cause similar levels of disability as disease if not treated properly they can have serious social and economic consequences. By improving the predictive neural markers of somatic awareness we will deepen our scientific understanding of the underlying biological and cognitive mechanisms of these conditions leading to more powerful tools for their treatment. Our on-going collaborations and local collaborative opportunities provide specific pathways to impact for the proposed work. We will host a series of workshops and seminars with clinical psychologists specialising in the treatment of medially unexplained symptoms and the effectiveness of interventions for chronic pain and pain clinicians in the North West, with whom we have long-standing collaborations. We will disseminate the findings and discuss ways in which our detailed understanding of how the brain mediates the perception of bodily events can be used to develop novel therapeutic strategies developed through experimentation, by implementation of a translational medicine framework. We will also discuss the findings with a patient user-group who we regularly consult to gain feedback on the importance and benefits of research to clinical conditions. This information will also be used in the longer-term to provide up-to-date knowledge for decision-making by charities such as Arthritis Research UK, BackCare and the Pain Relief Foundation and potential policy makers. We will also increase public understanding of these conditions through our outreach activities to non-academic audiences and through research-led teaching of undergraduate and postgraduate students at our respective institutions. Dr Poliakoff is the Public Engagement Officer for Psychological Sciences at the University of Manchester. She has co-organised many events involving hands-on activities about the brain and senses for the public at different venues. Dr Lloyd has previously presented at the British Association for the Advancement of Science on sensory illusions, co-hosted a Royal Society Summer Science Exhibition 'Fooling the Senses' and worked with the British media. All senior researchers involved in the project will share their technical skills with the post-doctoral research fellow and other research students to advance professional development of cognitive neuroscience methods and application in the UK.