Environmentally-induced changes in the brains of elderly rats.
D000367:Age Factors; D000704:Analysis of Variance; D000818:Animals; D000831:Animals, Newborn; D001522:Behavior, Animal; D001921:Brain / Q000033:anatomy & histology*; D004777:Environment; D009929:Organ Size; D051381:Rats; D012934:Social Isolation; D013997:Time Factors