STATE-DEPENDENT COMPRESSION OF S1 POPULATION GEOMETRY DURING CFA-INDUCED PERSISTENT PAIN

Persistent pain is accompanied by altered sensory perception, yet how chronic inflammation reshapes cortical population representations remains unclear. We asked whether complete Freund’s adjuvant (CFA)-induced inflammatory pain is associated with a remapping of activity geometry in primary somatosensory cortex (S1), potentially biasing processing toward more state-like signaling. Using in vivo two-photon calcium imaging in awake mice, we recorded S1 neurons during graded von Frey stimulation before and after CFA. Under baseline conditions, population responses showed relatively rich structure and supported differentiation of stimulus intensity. After CFA, responses became more constrained in population space, with reduced apparent dimensionality and changes in correlation structure. These effects were not readily explained by uniform changes at the single-neuron level, suggesting a greater contribution of shared population activity. Population-level analyses (e.g., eigenspectra) were consistent with stronger low-dimensional organization after CFA and less distinct separation among stimulus-intensity responses. Together, these findings suggest that inflammatory pain is accompanied by compression of S1 population activity, which may limit feature-specific sensory discrimination and motivates further study of network-state and upstream contributions.