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Action potentials have been shown to shunt synaptic charge to a degree that depends on their waveform. In this way, they participate in synaptic integration, and thus in the probability of generating succeeding action potentials, in a shape-dependent way. Here we test whether the different action potential waveforms produced during dynamical stimulation in a single cortical neuron carry information about the conductance stimulus history. When pyramidal neurons in rat visual cortex were driven by a conductance stimulus that resembles natural synaptic input, somatic action potential waveforms showed a large variability that reliably signaled the history of the input for up to 50 ms before the spike. The correlation between stimulus history and action potential waveforms had low noise, resulting in information rates that were three to four times larger than for the instantaneous spike rate. The reliable correlation between stimulus history and spike waveforms then acts as a local encoding at the single-cell level. It also directly affects neuronal communication as different waveforms influence the production of succeeding spikes via differential shunting of synaptic charge. Modeling was used to show that slow conductances can implement memory of the stimulus history in cortical neurons, encoding this information in the spike shape.

Structured illumination microscopy in thick fluorescent samples is a challenging task. The out-of-focus fluorescence background deteriorates the illumination pattern and the reconstructed images suffer from influence of noise. We present a combination of structured illumination microscopy with line scanning. This technique reduces the out-of-focus fluorescence background, which improves the modulation and the quality of the illumination pattern and therefore facilitates the reconstruction. We present super-resolution, optically sectioned images of a thick fluorescent sample, revealing details of the specimen's inner structure.

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Excitatory postsynaptic currents (EPSCs) in most mammalian central neurons have a fast alpha-amino-3-hydroxy-5-methyl-4-isoazole-proprionic acid (AMPA) receptor-mediated component, lasting a few milliseconds, and a slow N-methyl-D-aspartic acid (NMDA)-receptor-mediated component, lasting hundreds of milliseconds. The time course of the AMPA phase is crucial in the integrative function of neurons, but measuring it accurately is often confounded by cable filtering between the recording electrode and the synapse. We describe a method for recovering the AMPA phase of individual EPSCs by determining the impulse response of the cable filter from single NMDA channel transitions in the slow tails of the same EPSC, then deconvolving the measured AMPA current. Using simulations, we show that filtering of an AMPA conductance transient in a voltage-clamped dendrite behaves in an almost perfectly linear fashion. Expressions are derived for the time course of single channel transitions and the AMPA phase filtered through a voltage-clamped cable or a single exponential filter, using a kinetic model for AMPA receptor activation. Fitting these expressions to experimental records directly estimates the underlying kinetics of the AMPA phase. Example measurements of spontaneous EPSCs in cultured nonpyramidal rat cortical neurons yielded rising time constants of 0.2-0.8 ms, and decay time constants of 1.3-2 ms at 23-25 degrees C.