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D L Mitov

Publications and source records attributed to D L Mitov.

3 recordsLinked to original sources
PubMed2005

Temporal summation and reaction times for detecting gratings.

The effects of the duration of presentation of stimuli on the reaction time for detection of gratings of different spatial frequencies were studied. The product of contrast and duration (the contrast "energy") was kept constant for each duration. These experiments showed that at near-threshold "energies," reaction times did not change with increases in the duration to 15 and 30 msec at low and high spatial frequencies respectively. At high contrast "energies," this critical duration was identical (15 msec) for both low and high spatial frequencies. The effects of the duration of a linearly increasing front for grating presentation on detection reaction times were also studied. Increases in the duration of the front (to 60 msec) significantly lengthened the reaction time at low spatial frequencies at all contrast levels studied. Conversely, at high spatial frequencies, a significant increase in the reaction time was seen only at high contrast levels. These results suggest that reaction time depends on two types of mechanisms (phasic and tonic) at near-threshold contrast and one type (phasic) at high contrast.

Contrast Sensitivity↗
PubMed2003

[Temporal summation and reaction time for grid detection].

We studied the stimulus-duration effect on the reaction time (RT) to gratings with different spatial frequencies. At each duration value, the product of the contrast and the duration, i.e. the contrast "energy" was kept constant. We found that at near-threshold "energy" levels the RT was constant for up to 15 ms at lower spatial frequencies and up to 30 ms at higher spatial frequencies. At higher "energy" levels, this critical interval was the same (up to 15 ms) for both lower and higher spatial frequencies. The effect of the duration of gradual onset of the stimulus on RT was also studied. An increase of onset duration (up to 60 ms) at low spatial frequencies substantially delayed reaction time for the contrasts under study. Conversely, at high spatial frequencies, this effect was present only for gratings with a high contrast. These results suggest that reaction time is determined by two types of mechanisms (transient and sustained) at a near threshold contrast, and by one type (transient) mechanism at higher contrasts.

Contrast Sensitivity↗