Npgrj_nmeth_873 369..375

Sensory stimuli trigger complex patterns of neuronal action potentials in the brain. Measurement of these patterns is important for understanding the way the brain processes information. There are currently no efficient techniques to visualize patterns of highfrequency action potentials. Because individual action potentials result in transient increases in intracellular Ca2+, fluorescent calcium sensors are often used as an indirect readout of these spikes. Because of the slow decay of Ca2+ signals, however, Ca2+ remains elevated during high-frequency firing, making it difficult to determine the underlying changes in firing rate. Yaksi and Friedrich now report a signal-processing method that uses deconvolution to accurately determine changes in action potential firing rate that underlie Ca2+ signals visualized by two-photon microscopy in whole brain. Article p377, News and Views p344