APEX1 and Cognitive impairment: Thus, for the first time we have established that fractionation of radiation causes higher degradation of grey/ white matter, inflammation and altered APE1 levels (and its localization indicating the HZE effect seems more nuclear than cytoplasmic), increased OPC, immature OL, and astrocytes in spinal cord and a very significant neuro-inflammation in brain, which likely leads to the observed significant cognitive defects.