BACKGROUND:　Physical　exercises　have　been　shown　to　be　a　surprisingly　effective　strategy　to　take　advantage　of　the　brain＇s　natural　capacity　for　plasticity,　and　prevent　brain　degeneration　in　mouse　histological　studies.　In　vivo　magnetic　resonance　microscopy　(MRM)　provides　highly　resolved　anatomical　images　and　allows　quantitative　assessment　of　brain　atrophy　in　the　aged　mouse　model.　OBJECTIVE:　The　aim　of　the　present　study　was　to　investigate,　through　the　effects　of　10　weeks　voluntary　wheel　running,　the　mouse＇s　brain　atrophy.　METHODS:　Sixteen　C57BL/6J　mice,　aged　21　months,　were　randomized　to　the　exercise　or　sedentary　group.　Each　mouse　was　scanned　in　a　7.0-T　MRM　scanner　at　two　time　points:　22　months　old　baseline　and　a　follow-up　three　months　later.　Multi-atlas　based　brain　segmentation　approach　was　used　to　obtain　volumes　of　39　brain　regions.　RESULTS:　The　results　showed　that　mice　in　the　exercise　group　had　less　brain　atrophy　compared　with　the　mice　in　the　sedentary　group.　CONCLUSIONS:　The　results　provide　new　insights　into　exercise　induced　brain　plasticity　in　aged　animals.