Old, similar, or new: Hippocampal-dependent pattern separation performance in fibromyalgia

Abstract

In addition to chronic musculoskeletal pain, people with fibromyalgia often have memory deficits. Pattern separation is a neurological process that may be related to the memory deficits observed in people with fibromyalgia. Greater hippocampal activation has been associated with pattern separation deficits outside of fibromyalgia and has been observed in people with fibromyalgia. However, the relationship between hippocampal activation and pattern separation deficits in people with fibromyalgia is still unclear. Thus, this study aimed to examine the relationship between hippocampal activation and pattern separation in fibromyalgia. We hypothesized that participants with fibromyalgia would have worse pattern separation performance and greater hippocampal activation compared to healthy controls and that greater hippocampal activation would be correlated with worse pattern separation performance in participants with fibromyalgia. Sixteen participants (five with fibromyalgia and 11 healthy controls) completed the Mnemonic Similarity Task (MST) during functional magnetic resonance imaging (fMRI) scanning and were included in the final analyses. We observed that participants with fibromyalgia had worse pattern separation performance and greater hippocampal activation compared to healthy controls. Further, worse pattern separation performance was correlated with greater hippocampal activation in participants with fibromyalgia. While these findings are preliminary, they suggest that people with fibromyalgia still show pattern separation deficits, even when the hippocampus is working harder.