To investigate whether processing underlying texture segmentation is limited when texture is not attended, we measured orientation discrimination accuracy and visual evoked potentials (VEPs) while a texture bar was cyclically alternated with a uniform texture, either attended or not. Orientation discrimination was maximum when the bar was explicitly attended, above threshold when implicitly attended, and fell to just chance when unattended, suggesting that orientation discrimination based on grouping of elements along texture boundary requires explicit attention. We analyzed tsVEPs (variations in VEP amplitude obtained by algebraic subtraction of uniform-texture from segmented-texture VEPs) elicited by the texture boundary orientation discrimination task. When texture was unattended, tsVEPs still reflected local texture segregation. We found larger amplitudes of early tsVEP components (N75, P100, N150, N200) when texture boundary was parallel to texture elements, indicating a saliency effect, perhaps at V1 level. This effect was modulated by attention, disappearing when the texture was not attended, a result indicating that attention facilitates grouping by collinearity in the direction of the texture boundary.

SM, a 21-year-old female, presents an extensive central scotoma (30 deg) with dense absolute scotoma (visual acuity = 10/100) in the macular area (10 deg) due to Stargardt's disease. We provide behavioral evidence of cortical plastic reorganization since the patient could perform several visual tasks with her poor-vision eyes better than controls, although high spatial frequency sensitivity and visual acuity are severely impaired. Between 2.5-deg and 12-deg eccentricities, SM presented (1) normal acuity for crowded letters, provided stimulus size is above acuity thresholds for single letters; (2) a two-fold sensitivity increase (d-prime) with respect to controls in a simple search task; and (3) largely above-threshold performance in a lexical decision task carried out randomly by controls. SM's hyper-vision may reflect a long-term sensory gain specific for unimpaired low spatial-frequency mechanisms, which may result from modifications in response properties due to practice-dependent changes in excitatory/inhibitory intracortical connections.

Several studies indicate long-term cognitive impairment of MDMA (ecstasy) users. In the present study we attempted to establish whether electrophysiological correlates of low-level cognitive processes present a long-term alteration, dependent on the level of use of ecstasy. We addressed this issue by investigating amplitude and latency of VEPs related to a very simple discrimination task involving sustained attention (arousal). Eight heavy-MDMA users, eight moderate-MDMA users and 18 drug-free control subjects were asked to discriminate whether the digit at the centre of the screen was 1 or 2. None of the subjects (except one) had used MDMA in the 6 months previous testing. We measured psychophysical performance and EEG, recorded in Oz and Fz during task execution. The heavy-MDMA users made significantly more errors than the other two groups (p < .05). Moreover, they presented reduced amplitude but not latency of VEPs in both Oz and Fz. The effect in Oz is present in P200 (for heavy users only, p < .05) and in P300 components (for both MDMA groups; heavy users: p < .001, moderate users: p < .0.5). In Fz, the amplitude effect is present in N250 (for heavy users only, p < .05) and in P300 components (for both MDMA groups; heavy users: p < .05, moderate users: p < .05). The three groups do not differ in early components, reflecting low-level processing. These results provide evidence of long-term electrophysiological abnormality displayed by ecstasy users and agree with the suggestion that even typical recreational doses of ecstasy are sufficient to cause long-term altered cortical activity in humans.

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A summary of eight investigations is presented, which were carried out using standardized methods, for the purpose of quantifying exposure to tasks involving repetitive movements of the upper limbs, as well as quantifying the prevalence of work-related musculoskeletal disorders (WMSDs) of the upper limbs in groups of exposed workers. A total of 462 exposed workers were examined, and the study also took into account the data pertaining to a matched reference group comprising 749 workers not exposed to any specific occupational risk. Regarding the quantification of exposure to increased risk, use was made of a concise index (OCRA index), proposed by Occhipinti, in this issue. The data resulting from the eight investigations were used for the study of measurements and models of association among the exposure variables (mainly represented by the OCRA index), as well as the effect variables represented by the prevalence of the various WMSDs of the upper limbs taken both individually and jointly. Significant associations were reported between the OCRA index and an effect indicator represented by the prevalence of all the WSMDs of the upper limbs, calculated on the number of upper limbs at risk. When a logarithmic conversion of the relative exposure (OCRA) and injury indices was carried out, a simple linear regression model resulted that seems to provide a satisfactory predictive performance of the risk of WMSDs of the upper limbs, based on the exposure index. The study confirmed the efficacy of various other models designed to predict effects based on multiple linear regression functions, in which the independent variables are represented by both the OCRA exposure index and by parameters relative to the breakdown by gender and age of the groups of exposed workers.