Structural basis for the role of inhibition in facilitating adult brain plasticity.

Although inhibition has been implicated in mediating plasticity in the adult brain, the underlying mechanism remains unclear. Chen and colleagues show that experience drives structural remodeling of superficial layer 2/3 interneurons in an input- and circuit-specific manner, with up to 16% of branch tips undergoing remodeling. Visual deprivation initially induces dendritic branch retractions, and this is accompanied by a loss of inhibitory inputs onto neighboring pyramidal cells. The authors find a decrease in inhibitory tone. The antidepressant fluoxetine gives similar results. This is visualized as providing a permissive environment for further structural adaptation, including addition of new synapse-bearing branch tips. The authors suggest that therapeutic approaches that reduce inhibition, when combined with an instructive stimulus, could facilitate restructuring of mature circuits impaired by damage or disease, improving function and perhaps enhancing cognitive abilities.
Chen JL, Lin WC, Cha JW, So PT, Kubota Y, Nedivi E. Nature Neuroscience doi:10.1038/nn.2799 [Epub ahead of print 10 April 2011].
http://www.nature.com/neuro/journal/vaop/ncurrent/full/nn.2799.html