Integration of concurrent sensory signals in the human spinal cord and brain.

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Pain is a sensory function supported by the peripheral and central nervous systems. These include nociceptors, the spinal cord and the brain. Nociception and pain constitute an alarm system to detect threat to body tissues, which trigger protective neural processes and behaviours. These neural processes and behaviours are critical for the integrity of the body. Nociceptive stimuli trigger motor reflexes, such as the nociceptive flexion reflex (NFR), which allows the withdrawal of a limb. This automatic response is produced by the spinal cord and is generally followed by pain perception. In turn, pain triggers behavioural responses that are coordinated by the brain and adapted to the contextual demands. In this proposal, we will investigate how the spinal cord and brain integrate multiple nociceptive stimuli to produce adapted motor reflexes and cerebral responses. When competing stimuli are processed by the brain, cognitive functions allow to select and prioritize information from these stimuli. The so-called bottom-up processes give salient stimuli a stronger neuronal representation. For instance, nociceptive stimuli are intrinsically salient and capture attention. However, attentional capture may be influenced by so-called top-down processes. Top-down selection is determined by cognitive goals represented in working memory. Cognitive goals determine which stimuli are task relevant (attentional set). For instance, a nociceptive stimulus may be selected to prioritize a protective behaviour in response to pain perception at the expense of task performance. Conversely, pain perception can be inhibited by cognitive processes if task execution is prioritized. The balance between these bottom-up and top-down processes is critical for optimal behavioural performance, behavioural adaptation and even survival. In this proposal, we will investigate how stimulus saliency and cognitive functions alter the cerebral integration of concurrent nociceptive stimuli. To investigate our research questions, we will conduct experiments to examine spinal cord and brain activity evoked by electrical and laser stimuli that produce touch or pain sensation. Spinal cord activity will be measured with reflexes measured as muscle activity in the legs and brain activity will be measured as electrical signals recorded with electroencephalography. This research program will contribute to the understanding of spinal and cerebral mechanisms underlying nociceptive integration and responses. This is essential to better understand pain, motor reflexes and how stimulus saliency and cognition may affect these processes. This knowledge will provide solid bases to understand pain as an adaptive function of the nervous system in healthy individuals and in the long term may improve treatments to patients with chronic pain.