Changes in glutamate receptor distribution are one of the responses to stimuli that are responsible for synaptic plasticity. Borgdorff and Choquet analyzed the lateral mobility of AMPA-type glutamate receptors, containing the GluR2 subunit, by laser-tweezer single-particle tracking. The receptors containing GluR2 exhibited periods of high and low mobility, with sites of low mobility often occurring near sites of synaptic activity. Increased intracellular calcium concentration or activation of the receptors by localized glutamate application also triggered receptor immobilization. Thus, in addition to regulating plasma membrane distribution of receptors by endocytosis and delivery, neurons may control glutamate receptor distribution by dynamically altering receptor mobility. A. J. Borgdorff, D. Choquet, Regulation of AMPA receptor lateral movements. Nature 417 , 649-653 (2002). [Online Journal]