Cover picture: Optical recording of synaptic NMDA receptor activation in an acute hippocampal slice. CA1 pyramidal cells (background image) are loaded with a mixture of calcium-sensitive (green) and calcium-insensitive (red) dye. The stochastic responses of several synapses to extracellular stimulation of the presynaptic axons are revealed by the increase in fluorescence intensity of the calcium-sensitive dye (yellow spines). Ten separate trials are shown in separate frames. For details, see the article by Nimchinsky et al. in this issue (pages 2054–2064).