http://academic.oup.com/milmed/article-pdf/146/7/506/24126715/milmed-146-7-506.pdf

Goodman and Gilman's The Pharmacological Basis of Therapeutics

Meta- and paracontrast reveal differences between contour- and brightness-processing mechanisms.

Midazolam amnesia and dual-process models of the word-frequency mirror effect

A majority of dyslexic children have been found in many studies to show a deficiency of early vision, also called transient deficit. A series of four experiments was conducted to test whether or not the performance in different tasks is affected by a transient deficit. However, no clear evidence of a transient deficit was found, although the reliability of the measurements was high and the power of the statistical tests was adequate. All previous findings regarding the transient deficit can be explained by a reduced amplitude of the transient response. The same factor also accounts for a large part of the interindividual variability in this study. The failure to find a transient deficit in dyslexic children is explained only in part by language and preselection, and the outcome challenges the generality of previous findings.

Is there a deficit of early vision in dyslexia

How features are attributed to objects is one of the most puzzling issues in the neurosciences. A deeply entrenched view is that features are perceived at the locations where they are presented. Here, we show that features in motion displays can be systematically attributed from one location to another although the elements possessing the features are invisible. Furthermore, features can be integrated across locations. Feature mislocalizations are usually treated as errors and limits of the visual system. On the contrary, we show that the nonretinotopic feature attributions, reported herein, follow rules of grouping precisely suggesting that they reflect a fundamental computational strategy and not errors of visual processing.

The flight path of the phoenix--the visible trace of invisible elements in human vision.

Metakontrast: ein berühmtes, aber schwer messbares Phänomen

Psychophysical experiments in humans have revealed similar characteristics of visual receptive fields as were found in cats and monkeys from retinal ganglion cell recordings. In addition, in some retinal ganglion cells of cats the GABA antagonist bicuculline decreases the activity of the inhibitory surround. These findings led to two predicitions: 1) benzodiazepines will selectively increase the inhibitory surround of human visual receptive fields, 2) after dark adaptation, no free GABA will be available in the synapses and benzodiazepines will have no effect on the visual system. Characteristics of human receptive fields were determined by subthreshold summation: the contrast threshold of a vertical line was measured dependent on the distance of two parallel flanking lines whose contrast was below threshold. Both hypotheses were confirmed: the threshold in the inhibitory region of receptive fields was specifically increased in a dose-dependent manner by midazolam PO (7.5 mg: P < 0.05; 15 mg: P < 0.01). In dark-adapted subjects no effect of midazolam was found. Control experiments with atropine (1 mg IV), sulpiride (100 mg IM), and levodopa (100 mg PO) showed no specific effect. The visual system may be a model to bridge the gap between animal and human psychopharmacology.

F. Walder

Papers

Metakontrast: ein berühmtes, aber schwer messbares Phänomen

Specific effects of the benzodiazepine midazolam on visual receptive fields in light and dark adapted human subjects.