Diversity of spike-frequency adaptation, sAHP amplitude, and gain change by noise in pyramidal neurons. A–C, Left plots show voltage traces of firing during the first 500 ms of noiseless current steps, middle plots show AHPs after 30 spikes at 50 Hz, and right plots are f–I relationships with noise (σ = 4) and without noise (σ = 0). Solid lines are fits to the f–I relationships with noise, as described in Figure 2. A, Layer 2/3 pyramidal neuron with slow spike-frequency adaptation (left), large sAHP (middle), and gain increase by noise (right). B, Layer 5 pyramidal neuron with no slow adaptation, a very small sAHP, and little gain change by noise. C, Another layer 5 pyramidal neuron with slow adaptation, a large sAHP, and gain increase by noise. D, Distribution of sAHP amplitude in layer 2/3 pyramidal cells (top) and layer 5 pyramidal cells (bottom). E, Scatter plot showing the relationship between sAHP amplitude and the additive effect of noise. The solid line is the linear regression for all data points. The small negative correlation between these measures was not significant. L2/3, Layer 2/3; L5, layer 5. F, Relationship between sAHP amplitude and gain change by noise, showing a significant positive correlation.