Small effects of smoking on visual spatiotemporal processing

Peer reviewedPublisher PD

Spatial and temporal aspects of visual backward masking in children and young adolescents

We thank Marc Repnow for his help setting up the experiments. In addition, we thank two anonymous reviewers for their very thoughtful and helpful comments. This work was supported by the Volkswagen Foundation project “Between Europe and the Orient—A Focus on Research and Higher Education in/on Central Asia and the Caucasus” and by the VELUX Foundation project “Perception, Cognition and Healthy Brain Aging.”Peer reviewedPublisher PD

Specific Gestalt principles cannot explain (un)crowding

The standard physiological model has serious problems accounting for many aspects of vision, particularly when stimulus configurations become slightly more complex than the ones classically used, e.g., configurations of Gabors rather than only one or a few Gabors. For example, as shown in many publications, crowding cannot be explained with most models crafted in the spirit of the physiological approach. In crowding, a target is neighbored by flanking elements, which impair target discrimination. However, when more flankers are added, performance can improve for certain flanker configurations (uncrowding), which cannot be explained by classic models. As was shown, aspects of perceptual organization play a crucial role in uncrowding. For this reason, we tested here whether known principles of perceptual organization can explain crowding and uncrowding. The answer is negative. As shown with subjective tests, whereas grouping is indeed key in uncrowding, the four Gestalt principles examined here did not provide a clear explanation to this effect, as variability in performance was found between and within categories of configurations. We discuss the philosophical foundations of both the physiological and the classic Gestalt approaches and sketch a way to a happy marriage between the two

Sex-related differences in vision are heterogeneous

Despite well-established sex differences for cognition, audition, and somatosensation, few studies have investigated whether there are also sex differences in visual perception. We report the results of fifteen perceptual measures (such as visual acuity, visual backward masking, contrast detection threshold or motion detection) for a cohort of over 800 participants. On six of the fifteen tests, males significantly outperformed females. On no test did females significantly outperform males. Given this heterogeneity of the sex effects, it is unlikely that the sex differences are due to any single mechanism. A practical consequence of the results is that it is important to control for sex in vision research, and that findings of sex differences for cognitive measures using visually based tasks should confirm that their results cannot be explained by baseline sex differences in visual perception

Effects of alcohol on the time course of visual information processing in woman

Alcohol is one of the most commonly consumed drugs in the world. While the effects of alcohol on cognitive and psychomotor skills have been well studied, little research has examined alcohol's effects on visual processing. In the present study, we evaluated the influence of a moderate dose of alcohol (0.4 g/kg) on visual processing; using a backward masking technique, shine-through (Herzog & Koch, 2001). A vernier was presented for a short time and followed by a grating comprising 25 or 5 elements. In order to control for the interaction of sex with effects of alcohol, participation was limited to females. 19 healthy volunteers, aged between 20 and 40 years (N=11 received alcohol; N=8 received placebo), participated. We found that alcohol deteriorated visual processing by a factor of. In addition, we showed that all subjects were sensitive to variations in the spatial and temporal layout of the mask, irrespective of whether alcohol was provided or not

Time course of visual information processing in adolescents

Visual backward masking is a well suited technique to investigate intact and deficient visual information processing. Whereas visual backward masking has been studied extensively in adult populations, there is only a limited number of investigations in adolescents. Subjects were 17 adolescents (age 10-13 years) and 15 adults (18 -32 years) with normal or correct to normal vision. A vernier was presented followed by a masking grating of either 25 or 5 elements. A spatial inhomogeneous 'gap grating' and a temporal inhomogeneous grating were used as well. Performance with the 25 and 5 element grating was strongly deteriorated in adolescents indicating immature visual processing. However, both adolescents and adults were very sensitive to temporal and spatial in homogeneities in the mask indicating intact and complex spatio-temporal processing. Adolescents were retested one year later. The masking deficits of the adolescents had largely disappeared. We suggest that this improvement is associated with an age-related development of specific or non-specific (motivation, attention) factors. The work was supported by Volkswagen Foundation

How alcohol intake affects visual temporal processing

Alcohol affects vision. However, the influence of alcohol on visual processing is largely unknown. Here, we investigated the effects of alcohol on visual spatiotemporal processing. We employed a visual paradigm, the shine through backward masking paradigm, in which a vernier is either presented alone or followed by a variety of mask. We investigated performance for women at blood alcohol levels of 0 mg/kg, 400 mg/kg and 600 mg/kg and for men at 0 mg/kg, 400 mg/kg and 800 mg/kg. When the vernier was presented alone, vernier offset discrimination was not affected by alcohol. When the vernier was followed by a mask, stimulus onset asynchronies (SOAs) between target and mask were significantly longer after alcohol intake. However, as a second experiment showed, spatial and temporal processing per se were not impaired by alcohol. In addition, spatial processing was not affected by moderate alcohol consumption. Hence, moderate consumption of alcohol does not affect visual processing per se. We propose that the longer SOAs after alcohol intake are related to changes in mechanisms of target stabilization rather than changes in spatial and temporal sensitivity as has been previously suggested. (c) 2012 Elsevier Ltd. All rights reserved

Early visual processing deficits in the elderly: anterior increases and posterior decreases of electrical source activity

We compared temporal processing in elderly and young controls using EEG and electrical neuroimaging. Subjects discriminated the offset direction of Vernier stimuli in four conditions: Vernier only, mask only, Vernier immediately followed by a mask, and Vernier followed by a mask after a 150 ms SOA. The elderly showed a markedly decreased performance when the Vernier was immediately followed by a mask. Statistical analysis of the electrical sources in this condition showed decreased activity in occipital and fusiform areas at around stimulus onset, and increased activity in right inferior parietal area cortex (BA40) at around 170 ms. Hence, ongoing electrical activity in higher level visual areas is decreased in the elderly, while parietal cortex shows evoked increases that may reflect increased spatial attention. Across the four stimulus conditions elderly showed a distinct EEG scalp topography at around 150 ms that was not observed in young controls. In addition, elderly showed markedly decreased responses at around the N1 latency. Electrical source imaging across the stimulus conditions around this latency revealed decreased electrical activity in the precuneus and cingulate cortex, and increased activity in the inferior parietal, the medial and superior frontal gyrus, as well as in the caudate nucleus. Results are in line with the posterior–anterior shift account of aging and show that a reorganization is apparent around stimulus onset, as well as in visual processing before 200 ms