Abstract
Circuit compensation is often observed in patients with acute ischemic stroke, suggesting the importance of the interaction between brain regions. Also, contextual fear memory is an association between multisensory contexts and fearful stimuli, for which the interaction between the hippocampus and the amygdala is believed to be critical. To understand how focal ischemia in one region could influence the other region, we used a modified photo-thrombosis to induce focal ischemia in the hippocampus or the amygdala or both in freely-moving rats. We found that the learning curve and short-term memory were not affected in the rats although focal ischemia was induced 5 hrs before learning in either the hippocampus or the amygdala; these were impaired by the induction of ischemia in both the regions. Furthermore, the learning curve and short-term memory were impaired when ischemia was induced 24 hrs before learning in either the hippocampus or the amygdala when the synaptic transmission was altered in one region due to ischemia in the other region. These results suggest that the circuit compensation between the hippocampus and the amygdala is critical for fear memory acquisition.
Significance Statement
Contextual fear memory needs the interconnection between the hippocampus and the amygdala. However, it is unclear whether and how the two regions produce circuit compensation under an ischemic situation. Here, we employed the developing of ischemia in the hippocampus or the amygdala or both in freely moving rats. We found that memory acquisition was not affected 5 hrs post-ischemia, but it was impaired 24 hrs post-ischemia when the synaptic transmission was impaired in one region due to ischemia in the other region. Furthermore, ischemia in both brain regions impaired memory acquisition. These results indicate a circuit compensation between the hippocampus and the amygdala in memory acquisition if one with ischemia does not affect the function of the other.
Footnotes
The authors declare no competing interests.
This study was supported by the Natural Science Foundation of China (31100775 and 31371141 to Q.X.Z., U15022058 to L.X., 31860272 to P.G., and 31861143037 to both L.X. and G.R.-L.), and Strategic Priority Research Program of the Chinese Academy of Sciences (XDB32020000 to L.X.), and Department of Science and Technology Program of Yunnan Province (2016HA002 to L.X.), and External Cooperation Program BIC of the Chinese Academy of Sciences (GJHZ1549 to G.R.-L.), and Youth Innovation Promotion Association of the Chinese Academy of Sciences (2013250 to Q.X.Z.).
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