Consistent with this, sensory experience in adults alters the density of inhibitory corticocortical connections, which is increased www.selleckchem.com/products/ldk378.html by overstimulation as seen ultrastructurally (Knott et al., 2002) and decreased after deprivation as observed via glutamic acid decarboxylase staining or GABA receptor radiolabeling (Akhtar and Land, 1991 and Fuchs and Salazar, 1998). Future studies, such as minimal stimulation of TC axons and paired

recordings from connected cortical cells in vitro, are needed to assess the relative contributions of thalamocortical strengthening, inhibitory synapse weakening or pruning, and their induction times to L4 synchrony. Changes in L4 synchrony may partially explain why trimming suppresses L2/3 responses during adolescence but not adulthood (Glazewski and Fox,

1996). Our results clearly show that innocuous, nondestructive sensory experience during adulthood induces large-scale changes in thalamocortical axons. This contradicts the idea that adult plasticity has a purely cortical locus and raises the possibility that the structure of other subcortical regions might remain in flux throughout life. Subcortical connections, such as primary afferents traversing the spinal cord or brainstem fibers ascending to thalamus, may be more plastic than currently thought. While largely stable in their branching patterns and size, axons from superficial and deep cortical layers as well as nonprimary thalamic nuclei continuously elongate and retract short branches in wild-type hypoxia-inducible factor pathway animals (De Paola et al., 2006). Our study indicates that axons from primary thalamic nuclei exhibit similar ongoing structural dynamics. Changes in sensory experience, whether by experimental manipulation (e.g., trimming) or in the natural environment, probably stabilize and destabilize axonal bouton/branch turnover, slowly sculpting out new axonal morphology and patterns of connectivity.

Rapid spine turnover is known to exist on dendritic trees with otherwise stable morphology in motor, somatosensory, and visual cortices (Grutzendler et al., 2002, Trachtenberg et al., 2002 and Xu et al., 2009). Ergoloid Our study indicates that experience-induced plasticity involves not only synaptic strengthening/weakening and fine-scale formation/pruning of synapses but also gross axonal remodeling. We conclude that thalamocortical input to cortex remains plastic in adulthood, raising the possibility that the axons of other subcortical structures might also remain in flux throughout life. All procedures were approved by the Columbia University Institutional Animal Care and Use Committee. Twenty-eight adult (weight 200–500 g, mean 290 g) Wistar rats (Hilltop Laboratories) were used for anatomy experiments. All whiskers except two (D2 and D3) on the right side of the face were trimmed to a length of <1 mm every second day, without anesthesia, for 13–27 days prior to cell filling.