Abstract
A permanent change of perception as a result of experience is defined as perceptual learning. It is known that the improvement is very specific, e.g. for the precise stimulus orientation and position, indicating that the underlying plastic changes are at least partly on the level of primary visual cortex (Fahle, J Vis. 2004).
Here we examined the role of task (binocular detection vs. discrimination) in different visual modalities (contrast, texture, motion, stereo, colour; see also Grimsen et al., this conference), using the same stimulus position and stimulus type. Nine healthy subjects (mean age 24.6 years) were measured on five separate days in intervals of no more than four days. At each day a four-alternative-forced-choice detection and discrimination task were utilized to identify detection and discrimination thresholds (62.5% correct responses) within each modality for each visual field quadrant using an adaptive staircase procedure.
Differences between visual field quadrants were not evident in either modality for both, detection and discrimination thresholds. Perceptual learning could be obtained for contrast, motion and colour detection but not for texture and stereo detection. In contradistinction, perceptual learning was only evident in stereo discrimination while thresholds of all other modalities were stable across the five testing days. The correlations between detection and discrimination within each modality were small but significant across subjects and days.
The results indicate that perceptual learning is highly specific across different visual modalities, as well as across different tasks within the same visual modality. The dependence of perceptual learning on early versus late selection, as well as attention mechanisms are discussed (Fahle, Philos Trans R Soc Lond B Biol Sci. 2008).
Funding: This work was supported by the German Research Foundation [BR 1691/5-1].