Organic solvent exposure and contrast sensitivity: comparing men and women

The goal of this study was to compare the visual contrast sensitivity (CS) of men and women exposed and not exposed to organic solvents. Forty-six volunteers of both genders aged between 18 and 41 years (mean±SD=27.72±6.28) participated. Gas station attendants were exposed to gas containing 46.30 ppm of solvents at a temperature of 304±274.39 K, humidity of 62.25±7.59% and ventilation of 0.69±0.46 m/s (a passive gas chromatography-based sampling method was used considering the microclimate variables). Visual CS was measured via the psychophysical method of two-alternative forced choice using vertical sinusoidal gratings with spatial frequencies of 0.2, 0.5, 1.0, 2.0, 5.0, 10.0, and 16.0 cpd (cycles per degree) and an average luminance of 34.4 cd/m2. The results showed that visual CS was significantly lower (P<0.05) in the following groups: i) exposed men compared to unexposed men at frequencies of 0.2, 0.5, 1.0, and 2.0 cpd; ii) exposed women compared to unexposed women at a frequency of 5.0 cpd; and iii) exposed women compared to exposed men at a frequency of 0.5 cpd, even at exposures below the tolerance limit (300 ppm). These results suggest that the visual CS of exposed men was impaired over a wider range of spatial frequencies than that of exposed women. This difference may have been due to the higher body fat content of women compared to that of men, suggesting that body fat in women can serve as a protective factor against neurotoxic effects.

Attentional selection of levels within hierarchically organized figures is mediated by object-files.

Objects frequently have a hierarchical organization (tree-branch-leaf). How do we select the level to be attended? This has been explored with compound letters: a global letter built from local letters. One explanation, backed by much empirical support, is that attentional competition is biased toward certain spatial frequency (SF) bands across all locations and objects (a SF filter). This view assumes that the global and local letters are carried respectively by low and high SF bands, and that the bias can persist over time. Here we advocate a complementary view in which perception of hierarchical level is determined by how we represent letters in object-files. Although many properties bound to an object-file (i.e., position, color, even shape) can mutate without affecting its persistence over time, we posit that same object-file cannot be used to store information from different hierarchical levels. Thus, selection of level would be independent from locations but not from the way objects are represented at each moment. These views were contrasted via an attentional blink paradigm that presented letters within compound figures, but only one level at a time. Attending to two letters in rapid succession was easier if they were at the same-compared to different-levels, as predicted by both accounts. However, only the object-file account was able to explain why it was easier to report two targets on the same moving object compared to the same targets on distinct objects. The interference of different masks on target recognition was also easier to predict by the object-file account than by an SF filter. The methods introduced here allowed us to investigate attention to hierarchical levels and to object-files within the same empirical framework. The data suggests that SF information is used to structure the internal organization of object representations, a process understood best by integrating object-file theory with previous models of hierarchical perception.

Lateral visual hemifield asymmetry and sex differences in recognizing low and high spatial frequency filtered faces

The present study investigated whether low and high spatial frequency filtered images of faces were recognized differently when briefly presented in the right and the left visual fields of men and women. The method of confidence rating was applied to assess pooled Receiver Operating Characteristic curves based on z scores and the d´ parameter of Signal Detection Theory for recognition indices, in addition to response times. The results showed that men better recognized low spatial frequency filtered faces than high spatial frequency filtered faces in both visual fields, suggesting that both the right and left hemispheres in males prioritize low spatial frequencies to recognize faces. The results for women were similar to men only when the faces were shown in the left visual field. When the faces were presented in the right visual field, women better recognized high spatial frequency filtered faces, suggesting that the left hemisphere in females prioritizes high spatial frequencies, whereas the right hemisphere in females prioritizes low spatial frequencies to recognize faces...

Lateral visual hemifield asymmetry and sex differences in recognizing low and high spatial frequency filtered faces

The present study investigated whether low and high spatial frequency filtered images of faces were recognized differently when briefly presented in the right and the left visual fields of men and women. The method of confidence rating was applied to assess pooled Receiver Operating Characteristic curves based on z scores and the d´ parameter of Signal Detection Theory for recognition indices, in addition to response times. The results showed that men better recognized low spatial frequency filtered faces than high spatial frequency filtered faces in both visual fields, suggesting that both the right and left hemispheres in males prioritize low spatial frequencies to recognize faces. The results for women were similar to men only when the faces were shown in the left visual field. When the faces were presented in the right visual field, women better recognized high spatial frequency filtered faces, suggesting that the left hemisphere in females prioritizes high spatial frequencies, whereas the right hemisphere in females prioritizes low spatial frequencies to recognize faces.(AU)