Recent data have highlighted some unexpected and potentially concerning effects of cosmic
radiation exposure on the brain. Animal models subjected to charged particles ranging from
protons to the heavier ionized nuclei in the galactic cosmic rays have revealed that such
exposures lead to neurocognitive complications involving a range of associated pathologies.
Importantly, space relevant doses ≤50 cGy of nearly any ion has now been found to elicit
neuroinflammation, the degradation of mature neurons throughout the brain, and
impairments in learning and memory along with a host of mood disorders. Even more
concerning for NASA, is that the majority of these cosmic radiation-induced disruptions in CNS
functionality do not appear to resolve even over the course of 1 year following exposure.
Recent models have now suggested that astronauts engaged in deep space travel may incur
up to 40% of their total dose in the form of pions. Pion doses were found to increase with
enhanced shielding thickness, and point to the need to more fully understand the potential
risks associated with pion exposures. Past clinical data has found them relatively ineffective at
enhancing cancer cell kill, but in the setting of a highly interconnected network such as the
brain, spallation reactions associated with negative and even positive pions may prove
particularly deleterious. In the frame of a collaborative study between the CHUV, University
of California Irvine (UCI) and Paul Scherrer Institute (PSI), mice were exposed to a pion beam
possessing an approximate kinetic energy 150 MeV (both negative and positive pions) to a
total dose of ~20cGy. Cognitive studies revealed short and delayed deficits in hippocampal &
cortical learning and memory after exposure to 20 cGy negative pions whereas anxiety-like
behavior was not affected. 20cGy positive pions mainly affected delayed hippocampal &
cortical learning. My master thesis aimed at understanding the molecular basis of the pion-
induced cognitive dysfunction using RNA profiling. Bio-informatic analysis of the libraries and
qRT-PCR enabled us to identify 4 potential targets involved in Pion-mediated cognitive
decrements. Interestingly, the genes identified were found to control synapse and vascular
functions in the brain. More studies will be needed to decipher if/how these genes are
markers of the congnitive defects or if they are causal.