title: How does environmental enrichment reduce repetitive motor behaviors? Neuronal activation and dendritic morphology in the indirect basal ganglia pathway of a mouse model.
abstract: Repetitive motor behaviors are observed in many neurodevelopmental and neurological disorders (e.g., autism spectrum disorders, Tourette syndrome, fronto-temporal dementia). Despite their clinical importance, the neurobiology underlying these highly stereotyped, apparently functionless behaviors is poorly understood. Identification of mechanisms that mediate the development of repetitive behaviors will aid in the discovery of new therapeutic targets and treatment development. Using a deer mouse model, we have shown that decreased indirect basal ganglia pathway activity is associated with high levels of repetitive behavior. Environmental enrichment (EE) markedly attenuates the development of such aberrant behaviors in mice, although mechanisms driving this effect are unknown. We hypothesized that EE would reduce repetitive motor behaviors by increasing indirect basal ganglia pathway function. We assessed neuronal activation and dendritic spine density in basal ganglia of adult deer mice reared in EE and standard housing. Significant increases in neuronal activation and dendritic spine densities were observed only in the subthalamic nucleus (STN) and globus pallidus (GP), and only for those mice that exhibited an EE-induced decrease in repetitive motor behavior. As the STN and GP lie within the indirect pathway, these data suggest that EE-induced attenuation of repetitive motor behaviors is associated with increased functional activation of the indirect basal ganglia pathway. These results are consistent with our other findings highlighting the importance of the indirect pathway in mediating repetitive motor behaviors.
authors.affiliation: Department of Psychology, University of Florida, Gainesville, FL, USA. Electronic address: abechard@ufl.edu.
authors.forename: Allison R
authors.initials: AR
authors.lastname: Bechard
authors.affiliation: Department of Psychology, University of Florida, Gainesville, FL, USA.
authors.forename: Nadia
authors.initials: N
authors.lastname: Cacodcar
authors.affiliation: Department of Pharmacology, University of Florida, Gainesville, FL, USA.
authors.forename: Michael A
authors.initials: MA
authors.lastname: King
authors.affiliation: Department of Psychology, University of Florida, Gainesville, FL, USA; Department of Psychiatry, McKnight Brain Institute, University of Florida, Gainesville, FL, USA.
authors.forename: Mark H
authors.initials: MH
authors.lastname: Lewis
mesh_terms: D000818:Animals; D001479:Basal Ganglia / Q000502:physiology*; D001522:Behavior, Animal / Q000502:physiology*; D003712:Dendrites; D004195:Disease Models, Animal; D004777:Environment; D005260:Female; D008297:Male; D051379:Mice; D009434:Neural Pathways / Q000502:physiology*; D010542:Peromyscus; D013239:Stereotyped Behavior / Q000502:physiology*; D020531:Subthalamic Nucleus / Q000503:physiopathology
keywords: Animal models; Basal ganglia circuitry; Cytochrome oxidase; Deer mice; Golgi-Cox histochemistry; Subthalamic nucleus