title: Early exposure to dynamic environments alters patterns of motor exploration throughout the lifespan.
abstract: We assessed early rearing conditions on aging-related changes in mouse behavior. Two isolated-housing groups, running wheel (IHRW) and empty cage (IHEC), were compared against two enriched environments, static (EEST) and dynamic (EEDY), both of which included toys and other mice. For EEDY, the location of toys and sources of food and water changed daily, but remained constant for EEST. All mice, randomly assigned to one of the four groups at ∼4 weeks of age, remained in their respective environments for 25 weeks followed by single housing in empty cages. Beginning at ∼40 weeks of age, all mice were tested at monthly intervals in a plus-shaped maze in which we measured the number of arm entries and the probability of entering a perpendicular arm. Despite making significantly more arm entries than any other group, IHEC mice also were less likely to turn into the left or right arm, a sign of motor inflexibility. Both EEDY and EEST mice showed enhanced turning relative to IHRW and IHEC groups, but only EEDY mice maintained their turning performance for up to ∼100 weeks of age. EEDY and EEST mice also were unique in showing an increase in expression of the major glutamate transporter (GLT1) in striatum, but a decrease in motor cortex, suggesting a need for further assessment of environmental manipulations on long-term changes in forebrain glutamate transmission. Our behavioral results indicate that early exposure to continually changing environments, rather than socialization or exercise alone, results in life-long changes in patterns of motor exploration.
authors.affiliation: Department of Biomedical Sciences, Heritage College of Osteopathic Medicine, Ohio University, Athens, OH, USA; Ohio Musculoskeletal and Neurological Institute, Ohio University, Athens, OH, USA. Electronic address: hongs@ohio.edu.
authors.forename: S Lee
authors.initials: SL
authors.lastname: Hong
authors.affiliation: Intellectual and Developmental Disabilities Research Center, Brain Research Institute, David Geffen School of Medicine, University of California Los Angeles, USA. Electronic address: AnaEstrada@mednet.ucla.edu.
authors.forename: Ana María
authors.initials: AM
authors.lastname: Estrada-Sánchez
authors.affiliation: Department of Psychological and Brain Sciences, Indiana University, Bloomington, IN, USA. Electronic address: sjbarton@indiana.edu.
authors.forename: Scott J
authors.initials: SJ
authors.lastname: Barton
authors.affiliation: Department of Psychological and Brain Sciences, Indiana University, Bloomington, IN, USA. Electronic address: rebec@indiana.edu.
authors.forename: George V
authors.initials: GV
authors.lastname: Rebec
mesh_terms: D000367:Age Factors; D000375:Aging / Q000502:physiology*; D000704:Analysis of Variance; D000818:Animals; D002755:Choice Behavior / Q000502:physiology; D003342:Corpus Striatum / Q000378:metabolism; D004777:Environment; D027342:Excitatory Amino Acid Transporter 2 / Q000378:metabolism; D005106:Exploratory Behavior / Q000502:physiology*; D005786:Gene Expression Regulation / Q000502:physiology*; D008297:Male; D018782:Maze Learning / Q000502:physiology; D051379:Mice; D008810:Mice, Inbred C57BL; D009043:Motor Activity / Q000502:physiology*; D016548:Prosencephalon / Q000378:metabolism
chemical_list: D027342:Excitatory Amino Acid Transporter 2
keywords: Enriched environment; GLT1 expression; Isolated housing; Plus maze; Turning behavior