Spike finding, spike removal, and scaling of fluorescence recordings

A simple threshold-and-maximum procedure was applied for spike detection. Fluorescence traces were first high-pass filtered, and initial threshold was set at 4x noise level. This threshold was then manually adjusted. For spike removal, spikes were digitally removed and replaced with linear interpolation of the surrounding data. Linear interpolations were performed between data-points 3 ms before and 6 ms after action potential peak. To compute ΔV_m, fluorescence values were low-passed filtered (session below, ramping subthreshold membrane potential) and compared with mean fluorescence of the entire trace after spike removal (including a segment of the inter-trial interval). All fluorescence signals were normalized to spike height.