Abstract Background: Opium-dependence having different effects on the nervous system is a common problem, especially in the Middle East and Iran. The aim of this study is evaluating the effects of opium-dependence on visual evoked potential (VEP) in men. Methods: Thirty subjects with both chronic cigarette smoking and opium-dependence (group 1) and 30 subjects with only chronic ciga...

It has been found that humans are able to distinguish colours without luminance cues by about 2-4 months of age and that sensitivity to colour difference develops during childhood, reaching a peak around adolescence. This prolonged period of maturation is reflected by improvements in psychophysical threshold measures and by the VEP characteristics of morphology, latency and amplitude. An intra-...

In a previous report we described how the state of attention of the subject was an important factor in determining the amplitude of the visual evoked response (VER). Stabilization of the response is an obvious desideratum in any attempt at studying the visual system with the aid of the VER. The present report deals with attempts to stabilize the VER by achieving a constant level of attention. T...

The Test of Visual-Perceptual Skills (TVPS) was used to determine if children with cerebral palsy demonstrated problems in visual perception on a motor-free visual perception test. Twenty-four children with cerebral palsy and 24 normal children, all of normal intelligence, were given the TVPS. Results showed that children with cerebral palsy attained significantly lower mean perceptual quotient...

Visual analog scales (VASs) have long been used as a method of measuring preferences for health outcomes. They are easy and inexpensive to implement, can be administered quickly, and lend themselves to self-completion. Over time, however, disturbing questions have emerged concerning the validity of the VAS approach. This article reviews briefly the history, theory, practice, problems, and advan...

[This corrects the article DOI: 10.1371/journal.pntd.0004672.].