Placticing attention in contrast discrimination tasks
Y. Tanaka and D. Sagi (2000) Investigative Ophthalmology and Visual Science (ARVO abstract) 40(4) pp751.

Purpose: To test effects of temporal cueing (attention) on contrast discrimination. Methods: Contrast discrimination thresholds were measured for a foveal Gabor Signal (GS; sigma=lambda=0.15deg, fixed location) as a function of pedestal contrast (TvC function), with and without temporal cueing. In the 2 interval-forced-choice task, a random time delay (450-900 ms) was introduced before a first stimulus interval (90 ms), as well as a second random delay (1710-2160 ms) prior to a second stimulus interval (90 ms), producing temporal uncertainty. Temporal cues (two peripheral crosses, 90 ms) preceded each stimulus by 450~ms, where optimal facilitation in threshold was observed. First discrimination was tested with temporal uncertainty (4 sessions, no-cue condition), followed by discrimination with time-locked cue presentation (4 sessions, cue condition ), and subsequent temporal uncertainty condition (4-8 sessions). Results: In the first no-cue condition, contrast discrimination thresholds showed a typical dipper (facilitation: 0.26±0.08 log units) followed by a continuous increase of discrimination threshold with contrast (log-log linear slope=0.84±0.08, average±SE, n=5 observers). Temporal cueing yielded a decrease of slope to 0.59±0.06 associated with a shift of the TvC function rightwards by 0.31±0.13 log units (with c -> DeltaC(c)=DeltaC(0)), and a decrease of absolute threshold (DeltaC(0)) by 0.20±0.04 log units. In the final no-cue condition, the improved slope and shift were preserved (slope: 0.48±0.11, shift: 0.45±0.12 log units). The changes of TvC function persisted for several months. No learning was observed in experiments using no-cue condition only. Conclusions: These results demonstrate (1) attention effects on contrast discrimination, possibly modulating self-inhibitory processes, and that (2) attentional priming combined with practice can produce long-term plasticity.