How do you feel? Warm? Loved? Hurt? In danger? Isolated? As humans, we frequently “look inward” in order to guide our actions. But what bodily senses inform this “looking inwards” and how are they processed? Very thin nerve fibres arising in the skin carry specific sensations to the spinal cord, including information about pain, warmth and affective touch (e.g. the gentle caress of a loved one). Within the spinal cord these nerve fibres join highways carrying information to brain targets thought to be essential for generating feelings.
But that is not the end of the story. The sensory traffic between the spinal cord and the brain does not just travel in one direction: activity in the brain can also alter processing in the spinal cord. The ‘placebo effect’ is a good example: expecting a drug to have a beneficial effect on a painful event (e.g. being pricked by a researcher with a pin!) activates brain-to-cord connections that can prevent pain information in the skin from ever reaching the brain. This brain-down influence on the spinal cord is called descending modulation.
My PhD thesis investigated chronic pain in a rare neurological condition using MRI and found that damage in the spinal cord and changes in descending modulation both contributed to pain. Far less in known about how descending modulation might alter other (non-pain) “inward-looking” sensations, for example affective touch. An interesting question, and one I hope to answer, is how different social environments might alter processing of pain and non-pain information and whether they also effect changes at the level of the spinal cord. For example, is a gentle touch from an experimenter processed differently at the level of the spinal cord to that of a loved one? And if so, are malfunctions of this processing a feature of certain psychiatric diseases (e.g. depression and autism)?
The ESRC post-doctoral fellowship is providing me with the opportunity to publish and present my PhD findings. Excitingly, it is also providing the means to pilot spinal cord imaging techniques in Cardiff University’s world-class imaging centre (CUBRIC) that will further facilitate the exploration of social and psychological effects on spinal cord sensory processing, firstly in healthy participants and then within psychiatric disease.