Cover legend: Image overlay of fluorescently labeled cultured mouse hippocampal neurons transfected with green fluorescent protein and Ca_v1.3 Ca²⁺ channels (background; green and red), or densin-GFP (foreground; blue), which colocalizes with PSD-95 (red) in dendritic spines (white). Together with Ca²⁺/calmodulin-dependent protein kinase II, densin mediates a novel form of Ca²⁺-dependent facilitation. For more information, see the article by Jenkins et al. in this issue (pages 5125–5135).