Effects of aging on interference control in selective attention and working memory.

Working memory decay in advanced age has been attributed to a concurrent decrease in the ability to control interference. The present study contrasted a form of interference control in selective attention that acts upon the perception of external stimuli (access) with another form that operates on internal representations in working memory (deletion), in order to determine both of their effects on working memory efficiency in younger and older adults. Additionally, we compared memory performance under these access and deletion functions to performance in their respective control conditions. The results indicated that memory accuracy improved in both age groups from the access functions, but that only young adults benefited from the deletion functions. In addition, intrusion effects in the deletion condition were larger in older than in younger adults. The ability to control the irrelevant perception- and memory-elicited interference did not decline in general with advancing age; rather, the control mechanisms that operate on internal memory representations declined specifically.

Specificity and generalization of perceptual learning in low myopia.

PURPOSE: In this study we investigated in observers with low myopia: (i) the pattern of lateral interactions between stimuli activating early cortical analyzers and its modulation by perceptual learning (PL), and (ii) whether PL transferred to untrained stimuli and tasks and whether it exhibits interocular transfer. METHOD: Participants (seven adults with low myopia) performed 12 training sessions. Participants were trained on a contrast detection task of a central Gabor target flanked by two co-oriented and co-aligned high contrast Gabor patches. Target-to-flankers separation along the vertical axis was varied from 2 wavelengths (λ) to 8λ. RESULTS: The results showed that before PL facilitatory lateral interactions in the myopic eye were reduced in strength, but PL increased contrast sensitivity and improved facilitatory lateral interactions. However, PL did not transfer to different local/global orientations and lower spatial frequencies. On the other hand, PL resulted in an enhancement of the contrast sensitivity function (CSF) and of the uncorrected visual acuity (UCVA) both in the trained and untrained eye. CONCLUSIONS: Such improvements seem to be associated to a modulation of lateral interactions between target and flankers and it is likely to take place at a level in which the inputs from the two eyes converge.

The effect of visual experience on texture segmentation without awareness.

The effect of visual experience is usually investigated through active (task dependent) training in a discrimination task. In contrast, the current work explored the psychophysical and electrophysiological correlates of passive (task independent) visual experience in texture segmentation by using an inattentional blindness-like paradigm (Mack et al., 1992). The psychophysical and electrophysiological responses to a segmented line-texture bar, with texture elements oriented either congruently (parallel) or noncongruently (orthogonal) to bar orientation, were collected after both short and long passive experience, with the texture presented on the background while subjects performed a primary task. Subjects were not able to distinguish the orientation of the bar (psychophysical results) after either short or long passive experience. However, the short experience produced an electrophysiological correlate of texture segmentation (N150), and the amplitude of this component was greater for the parallel bar, demonstrating that it reflected not simply local orientation discontinuities but also texture boundary-surface orientation congruency. This configurational effect in texture segmentation, which occurred without awareness during passive viewing, disappeared when the subjects had previously discriminated the orientation of the bar and when experience was lengthened, probably as a consequence of adaptation. Our study provides the first ERP evidence that boundary-surface relations are available during short passive visual experiences of very salient texture images and are suppressed by long experience, probably because of adaptation.

The aesthetic experience of 'contour binding'.

To find the diagnostic spatial frequency information in different painting styles (cubism, impressionism and realism), we have compared sensitivity (d') in distinguishing signal (subject of the painting) from noise with normal, high-pass and low-pass filtered images at long (150 ms) and short (30 ms) exposure. We found that for cubist-style images, d' increases with high-pass filtering compared with normal and low-pass filtered images, but decreases with low-pass filtering compared with normal images. These results indicate that channels with high spatial resolution provide the diagnostic information to solve the binding problem. Sensitivity for images in impressionist style was instead reduced by both low- and high-pass filtering. This indicates that both high and low spatial frequency channels play a role in solving the binding problem, suggesting the involvement of large collator units that group the response of small channels tuned to the same orientation. The difference between realism, which shows higher sensitivity for low-frequency filtering at short durations and cubism in which the binding problem is solved by high spatial frequency channels, has a corresponding difference in aesthetic judgment: the probability of judging a painting as 'intriguing' is larger with low-pass filtering than with high-pass filtering in realism, while the opposite is true for cubism. This suggests that the aesthetic experience is available during early processing of an image, and could preferentially influence high-level categorization of the subject of a painting.