Temporal integration characteristics in spatial frequency identification.

Spatial frequency detection and identification performances were measured simultaneously as a function of exposure duration. Detection and identification sensitivity/duration functions appeared to be parallel over durations ranging from 10 to 1000 msec, independent of both spatial frequency and spatial frequency difference between the stimuli to be discriminated. The results are compatible with both a simultaneous or a serial processing of the two types of tasks. In the former case, detection and identification would take place at the same neural level and they would, therefore, be indistinguishable. The second alternative implies that the identification stage must have a time-constant substantially shorter than the detection stage. Both possibilities are compatible with the concept of spatial frequency labelled detectors.