Neuronal coding of tonic pain
Final Report Abstract
Previous behavioural work has indicated that there is a tremendous variability regarding the subject’s ability to attenuate pain by means of cognitive strategies. Some subjects were be able to reduce pain via attentional shift whereas other subjects are less able to utilise this strategy. It has been hypothesised that these subjects would benefit from the application of another more suitable strategy. The present project aims to investigate whether the capability to reduce the intensity of perceived pain with a certain strategy may depend on the individual variability of cortical characteristics. The results of the project could help to provide a theoretical framework for adapting therapies individually to the needs of specific pain patients. The study resembles a clinical intervention in which a pain patient will be taught to utilise cognitive strategies to attenuate pain. During the recording of 7T MRI data, twenty participants applied three different strategies to attenuate pain: attentional shift by counting backwards, an imaginary strategy by imagining a safe and happy place as well as a cognitive reappraisal of the pain valence. As a result, all strategies obtained a significant relief of pain compared to a baseline pain condition. In contrast to the initial hypothesis, we did not find the same preference for all applied strategies; the attentional shift by counting backwards was the most effective strategy for most participants. Furthermore, behavioural data argue against a subject’s predisposition for a certain attenuation strategy. The study included participants who performed well in all tasks as well as participants that underperformed in any task. At cortical level, we revealed brain regions that reflect successful attempts to attenuate pain. These regions are distinct for the different pain attenuation strategies. This task-related networks was equally used by well-performing and poorly performing participants. We did not find any cortical activity or connectivity pattern (functional or structural) that separates the good performers from the bad performers of pain attenuation. However, in contrast to previous works, we revealed an increased connectivity for those single attempts that resulted in the lowest levels of pain. This applies even to the classical pain processing regions (e.g. insula, cingulate cortex and somatosensory cortices). The functional connectivity data would suggest that clinical treatments for pain patients should aim to increase cortico-cortical connections (particularly those from the middle insular cortex). Furthermore, we did not find any reliable cortical marker that separates over- and under-performer. This suggests that there is no common mechanism across all subjects that could be monitored and targeted in any treatment to alleviate pain. Instead, the cortical data support the concept of a subject’s unique activity pattern of pain processing and pain modulation; each patients is considered to exhibit his own pattern of pain attenuation. This pattern - the individual's signature for pain - includes brain regions that are important for all subjects but will also include regions that are important for this individual only. Future research should focus more on the variability of individually specific cortical processes (funding application submitted). The assessment of an individual's signature for pain (attenuation) may help to develop an individually tailored treatment for chronic pain. The present findings could serve as a theoretical framework for a future neurofeedback study for the treatment of chronic pain. Patients suffering from chronic pain can be trained to increase cortical connectivity in order to facilitate inhibition processes that will subsequently attenuate pain.
