Synaptic plasticity is considered an essential process for the formation and maintenance of memory.In the talk I will describe experiments that directly observe changes at synapses in live animals using time lapse two-photon microscopy.It had been assumed for decades that cognitive deficits within the aging brain result from reduced synaptic density and plasticity.By imaging axonal arbors and boutons in the aged brain, we surprisingly find the opposite, i.e.,dramatically increased rates of synapse formation, elimination, and destabilization in specific cortical circuits.This observation suggests that learning and memory deficits in the aged brain may arise not through an inability to form new synapses but rather through decreased synaptic tenacity.