Effects of 56Fe-particle cranial radiation on hippocampus-dependent cognition depend on the salience of the environmental stimuli

Jacob Raber, Susanna Rosi, Ayanabha Chakraborti, Kelly Fishman, Catherine Dayger, Matthew J. Davis, Laura Villasana, John R. Fike

Research output: Contribution to journalArticle

14 Scopus citations


Ionizing radiation reduces the numbers of neurons expressing activity-regulated cytoskeleton-associated protein (Arc) in the hippocampal dentate gyrus (DG). It is currently unclear if that change relates to cognitive function. We assessed the effects of 1 Gy of head-only 56Fe-particle irradiation on hippocampus-dependent and hippocampus-independent fear conditioning and determined how those changes related to Arc expression within the DG. Irradiated mice that did not receive tone-shock pairings on day 1 showed less freezing in the same context on a second day and a lower fraction of Arc-expressing neurons in the free (lower) blade of the DG than sham-irradiated mice. Those data suggested reduced hippocampus-dependent spatial habituation learning. Changes in Arc expression in the free blade correlated positively with freezing in mice that did not receive tone-shock pairings. However, irradiated mice that did receive tone-shock pairings showed enhanced contextual freezing but a reduced percentage of Arc-expressing neurons in the enclosed (upper) blade. Changes in Arc expression correlated negatively with freezing in mice that received tone-shock pairings. In animals receiving cued fear conditioning, radiation did not affect cognitive performance or the fractions of Arc-expressing neurons. While the relationship between Arc expression and cognitive performance is complex, our data suggest that radiation effects on hippocampus-dependent cognition might depend on the prominence (salience) of environmental stimuli and blade-specific Arc expression.

Original languageEnglish (US)
Pages (from-to)521-526
Number of pages6
JournalRadiation research
Issue number4
StatePublished - Oct 1 2011


ASJC Scopus subject areas

  • Biophysics
  • Radiation
  • Radiology Nuclear Medicine and imaging

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