Abstract
It has been suggested that visual adaptation-based duration compression (Johnston, Arnold, & Nishida, 2006, Current Biology, 16(5):472–9; Bruno & Johnston, 2010, Frontiers in Psychology, 1(170): 1–8) might be related to the shortening of the temporal impulse response in M neurons (Kaplan & Benardete, 2001, Progress in Brain Research, 134:17–34). The temporal impulse response lengthens (by around 30%) and neural latencies increase at low light levels (Kelly, 1961, Journal of the Optical Society of America, 51:422–9; Peterson, Ohzawa, & Freeman, 2001, Visual Neuroscience, 18: 203–8) suggesting visual duration may appear to expand in the dark. We first measured a progressive shift and reduction of the occurrence of an apparent motion reversal as we decreased the luminance level, indicating a lengthening of the temporal impulse response (Takeuchi & DeValois, 2009, Vision Research, 49(8):801–9). We then measured perceived duration at these luminance levels (0.75, 3 and 50 cd/m2) after 25 minutes of dark adaptation. We asked subjects to compare the relative duration of a flickering Gaussian blob with that of an amplitude-modulated (AM) tone after equating the apparent contrast and the apparent temporal frequency of the visual flicker at the different light levels (relative to an AM tone with variable frequency). While the temporal frequency estimates did not substantially differ across luminance levels (the visual stimulus appeared to flicker at a higher rate than the AM tone), duration seemed to be expanded at the lowest luminance level (0.75 cd/m2) relative to the highest (50 cd/m2) by approximately 60 ms. Thus we have shown reduced luminance is associated with both a lengthening of the temporal impulse response and a duration expansion, linking the two, and providing further evidence for a relationship between changes in the tuning of the neurons in the early stages of the magnocellular pathway and time perception.