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Cognitive flexibility and long-term depression (LTD) are impaired following β-catenin stabilization in vivo

Significance Complex learning and memory are believed to require the weakening or elimination of synapses in the brain, a process mediated by adhesion molecules, which maintain synapse strength and stability. In the present study, we examine in vivo the effects of stabilization of β-catenin, an intracellular protein that is a component of the cadherin adhesion complex. We find that stabilization of β-catenin in the brain prevents normal activity-dependent downscaling of synapse strength, resulting in a striking impairment in cognitive flexibility. These results demonstrate that β-catenin plays an important role in learning and memory and that aberrant increases in synaptic adhesion can have detrimental effects on cognitive function. The cadherin/β-catenin adhesion complex is a key mediator of the bidirectional changes in synapse strength which are believed to underlie complex learning and memory. In the present study, we demonstrate that stabilization of β-catenin in the hippocampus of adult mice results in significant impairments in cognitive flexibility and spatial reversal learning, including impaired extinction during the reversal phase of the Morris water maze and deficits in a delayed nonmatch to place T-maze task. In accordance with these deficits, β-catenin stabilization was found to abolish long-term depression by stabilizing cadherin at the synaptic membrane and impairing AMPA receptor endocytosis, while leaving basal synaptic transmission and long-term potentiation unaffected. These results demonstrate that the β-catenin/cadherin adhesion complex plays an important role in learning and memory and that aberrant increases in synaptic adhesion can have deleterious effects on cognitive function.