Environmental Factors Promoting Neural Plasticity: Insights from Animal and Human Studies

Table 1

Structural and functional effects of environmental enrichment (EE).

Sample		EE condition	Functional Effects (behavioral effects)	Structural Effects (molecular and cellular effects)	Refs.
Effects of EE on healthy rodents
Wistar rats		EE from weaning for 2.5/3 months	Precocious development of spatial cognitive map; enhanced spatial memory and cognitive flexibility	Increases dendritic length and spine density in frontal and parietal pyramidal neuron apical and basal arborizations; synaptogenesis; increases of BDNF levels in the hippocampus and cerebellum	[14, 23, 35–37, 40]
Wistar rats; C57BL/6J mice		Maternal and paternal EE: a transgenerational model	In pups: accelerated acquisition of complex motor behaviors; decreased anxiety-related behaviors	In pups: high expression of neurotrophin in cerebellar and striatal areas; low ACTH levels	[38–41]
Neuroprotective effects of EE on neurodegeneration
Neurodegenerative disorders	HD mouse models	Running exercise about from 4 weeks of age	Partially delayed onset of motor symptoms and cognitive deficits (memory/executive functions)	Altered BDNF mRNA levels	[10, 15, 42–45]
		EE about from 4 weeks of age	Delayed onset of motor symptoms and cognitive deficits (memory/executive functions)	Decreased cortical and striatal volume loss; ameliorated deficit in neurogenesis; increased neurotrophin expression; enhanced CB1 receptor levels
	PD mouse models	Running exercise from 6 weeks	Attenuated motor impairment, reduced anxiety behavior	Decreased loss of striatal DA	[10, 15, 46–49]
	AD mouse/rat models	Intensive locomotor training	Increases performances in spatial memory tasks	Decreased beta-amyloid plaques	[10, 15, 24–27, 50–57, 62]
		EE from weaning for 2.5/3 months; EE for 2 months at different age	Enhanced spatial memory and executive functions (cognitive flexibility)	Decreased beta-amyloid plaques; increased levels of neurotrophic substances; increased spine number and density in pyramidal neurons
Aging		EE and locomotor training in middle age	Preservation of spatial abilities in old age	Changes in hippocampal astrocytes; hippocampal neurogenesis	[58–61]

EE refers to a complex stimulation of experiences. BDNF: brain-derived neurotrophic factor; NGF: nerve growth factor; ACTH: adrenocorticotropic hormone; HD: huntington’s disease; PD: parkinson’s disease; AD: alzheimer’s disease; DA: dopamine.