Figure 4
Rasters and peristimulus time histograms (PSTHs) constructed from DCMD responses to looming stimuli. (a) Raw continuous data from an extracellular recording of the left ventral nerve cord during presentation with the image of a 7 cm looming disk to the right eye (top). DCMD spikes were easily differentiated by their large amplitude. The projected time of collision (TOC) is marked with a vertical red line. Bursts, which comprise a minimum of two spikes occurring within 8 ms of each other, are highlighted with a vertical green line to signal the start, and horizontal lines to show the duration. PSTHs show the firing rates of the full DCMD response, spikes within bursts only, isolated spikes only, and bursts, smoothed with a 50 ms Gaussian filter. PSTHs response profile parameters included: peak firing rate (f p ) and the time of the peak relative to TOC (pt), denoted by an asterisk; peak width at half maximum (PW½M), rise phase, from the last time the histogram crosses the 99% confidence interval with a positive slope (t99) to the peak, and decay phase from the peak until it had decreased to 15% (t15). (b–e) Show rasters (top) and PSTHs (bottom) at four time points after injection with 100 ng/g IMD, 5, 17.5, 25, and 110 minutes. These panels are separated by rate type: full DCMD (b), burst spikes only (c), isolated spikes only (d), and bursts (e).
