The effect of lateralization bias of pain on pain, anxiety and cognition in mice.

The transmission of pain signals through the spinal cord can cause structural and functional changes in the brain, which may contribute to diverse symptoms. Since the early 19th century, researchers have been studying hemispheric asymmetries in the brain and their effects across different species. However, it remains unclear whether pain-related emotional and cognitive changes are differently affected by left- and right-sided pain. To address this question, we conducted a study comparing the performance of chronic neuropathic mice with left or right spared nerve injury (SNI) in various behavioral tests. We evaluated their behaviors in the open field (OF), Y-maze, novel object recognition, and fear conditioning tests, and compared their performance to that of sham mice. Compared with sham mice, SNI mice manifested mechanical allodynia. In the OF test, SNI-L mice showed an increased anxiety-like profile compared to the other groups. Both left- and right- sided SNI mice showed cognitive deficits to a similar degree in memory tasks. Our results revealed that unilateral chronic neuropathic pain differentially affected anxiety condition, but not pain threshold and cognitive function.