title: Detection and identification of near-threshold visual patterns.
abstract: For a number of visual dimensions--spatial frequency, orientation, spatial position, and direction of motion (at velocities higher than 1 or 2 deg/sec)--experimental results at near-threshold contrasts can be explained by assuming that multiple mechanisms selectively sensitive along that dimension exist and have labeled outputs. For the temporal-position dimension, analogous experimental results can be explained by assuming that each mechanism's output at a particular time depends only on the recent past and is labeled. For the eye-of-origin dimension, however, although the evidence suggests selectively sensitive mechanisms (at least at some spatial and temporal frequencies), these mechanisms seem not to have labeled outputs. For the temporal-frequency dimension (at any fixed spatial frequency), evidence suggests that there are not narrowly tuned mechanisms although there may be very broadly tuned ones.
mesh_terms: D001288:Attention; D004193:Discrimination Learning; D005556:Form Perception; D006801:Humans; D009039:Motion Perception; D009949:Orientation; D010364:Pattern Recognition, Visual; D011601:Psychophysics; D012684:Sensory Thresholds; D013028:Space Perception