Cortical synchronization of spontaneous trigeminal neuropathic pain monitored with in vivo optical imaging of calcium activity in freely moving mice.

Abstract

OBJECTIVE: To determine the impact of neuropathic lesion on cortical synchronization in processing spontaneous pain-like behavior. BACKGROUND: In vivo optical monitoring of neuronal activity may provide insightful mechanisms underlying the complexity of spontaneous pain-like behavior in freely moving animals. METHODS: We examined the synchronized pattern of the pyramidical neurons in anterior cingulate cortex during spontaneous grooming behavior using optical monitoring of Caactivity. A chronic constriction injury of infraorbital nerve model was performed to induce trigeminal neuropathic pain. We then analyzed the synchronized patterns of cortical population and computed Shannon entropy values to assess the uncertainty of neural coding during spontaneous pain-like behavior. RESULTS: Following nerve injury, mice exhibited significantly prolonged isolated grooming behavior compared to the control group. Our data indicate that, while neuropathic pain enhanced synchronized activity of cortical network during spontaneous grooming behavior, craniofacial nociception reduced the uncertainty of neural firing. Interestingly, this transition to a synchronized state of cortical ensembles in neuropathic pain conditions was significantly disrupted by spontaneous grooming behavior. CONCLUSION: Our findings provided a method of monitoring the synchronized activity of cortical ensemble in freely moving animals. Synchronization index may be used to decode spontaneous neuropathic pain-like behavior.