Abstract
Both theoretical and experimental evidence suggests that duration perception is mediated preferentially by the color-blind but high temporally sensitive luminance pathway. In this experiment we tested whether color modulated stimuli and high spatial frequency luminance modulated stimuli, which are known to be relayed mostly by the slow parvocellular system, are able to elicit reliable sense of duration. We show that ramped color modulated stimuli seem to last less than luminance modulated stimuli matched for visibility. The effect is large, about 200 ms and is constant at all durations tested (range 500–1100 ms). However, high spatial frequency luminance stimuli obtain duration matches similar to those of low spatial frequency luminance modulated stimuli. The results at various levels of contrast and temporal smoothing indicate that equiluminant stimuli have higher contrast thresholds to activate the mechanisms which time visual stimuli. Overall the results imply that both the magnocellular and the parvocellular systems access reliably the timing mechanisms with a difference only in the way these are engaged.
Highlights
Despite subjective time is a perceptual dimension that transcends each sensory modality, recent evidence is showing that the estimation of brief temporal intervals is computed by multiple parallel temporal units deeply rooted in sensory processes (Buonomano and Merzenich, 1995; Ivry and Spencer, 2004; Mauk and Buonomano, 2004; Johnston et al, 2006; Johnston, 2010)
PERCEIVED DURATION IN THE MAGNOCELLULAR AND PARVOCELLULAR SYSTEMS Figure 1 shows the results when subjects had to compare the duration of a color modulated stimulus to that of a reference luminance modulated stimulus
In both subjects the data points lie above the diagonal indicating that subjects needed a longer presentation of the color modulated stimulus to match the duration of a reference luminance modulated stimulus
Summary
Despite subjective time is a perceptual dimension that transcends each sensory modality, recent evidence is showing that the estimation of brief temporal intervals is computed by multiple parallel temporal units deeply rooted in sensory processes (Buonomano and Merzenich, 1995; Ivry and Spencer, 2004; Mauk and Buonomano, 2004; Johnston et al, 2006; Johnston, 2010). Not least perceived timing depends on very basic stimulus features (such as speed, contrast, size), indicating that the network for temporal processing extends to and is in partial overlap with purely sensory processes (Roelofs and Zeeman, 1951; Brown, 1995; Terao et al, 2008; Cicchini and Morrone, 2009) All of these notions go hand in hand with the concept that even small neuronal ensembles, not specialized for temporal processing, are able to encode the passage of time (Buonomano and Merzenich, 1995; Yamazaki and Tanaka, 2005; Karmarkar and Buonomano, 2007)
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