About the role of visual field defects in pure alexia

Pure alexia is an acquired reading disorder characterized by a disproportionate prolongation of reading time as a function of word length. Although the vast majority of cases reported in the literature show a right-sided visual defect, little is known about the contribution of this low-level visual impairment to their reading difficulties. The present study was aimed at investigating this issue by comparing eye movement patterns during text reading in six patients with pure alexia with those of six patients with hemianopic dyslexia showing similar right-sided visual field defects. We found that the role of the field defect in the reading difficulties of pure alexics was highly deficit-specific. While the amplitude of rightward saccades during text reading seems largely determined by the restricted visual field, other visuo-motor impairments-particularly the pronounced increases in fixation frequency and viewing time as a function of word length-may have little to do with their visual field defect. In addition, subtracting the lesions of the hemianopic dyslexics from those found in pure alexics revealed the largest group differences in posterior parts of the left fusiform gyrus, occipito-temporal sulcus and inferior temporal gyrus. These regions included the coordinate assigned to the centre of the visual word form area in healthy adults, which provides further evidence for a relation between pure alexia and a damaged visual word form area. Finally, we propose a list of three criteria that may improve the differential diagnosis of pure alexia and allow appropriate therapy recommendations.

Indigene Prepräsentation im "neuen" Venezolanischen Fernsehen

Das Fernsehen hat sich in vielen Gesellschaften dieser Erde zum dominierenden Medium entwickelt und ist Gegenstand andauernder Auseinandersetzungen zwischen externer Einflussnahme und journalistischer Autonomie. Im Falle Venezuelas haben die jüngsten politischen Transformationen auch innerhalb der Medienlandschaft zu massiven Veränderungen geführt. Auf Initiative der Regierung Chávez wurden mehrere staatliche Sender gegründet, die das emanzipatorische Ziel einer Demokratisierung des Fernsehens propagieren. Das "neue" Fernsehen verspricht eine "neue" Sichtweise, ausgehend von dem Konzept einer partizipativen Repräsentation, das eine weitgehende Integration aller VenezolanerInnen, vor allem der zuvor benachteiligten Klassen, auf praktischer und inhaltlicher Ebene vorsieht. Unter ihnen auch die indigenen Gruppen des Landes, die vormals entweder weitgehend ausgeblendet, oder durch klischeehafte Inhalte und klassische Stereotypen repräsentiert wurden. Welcher Platz wird nun den Indigenen im "neuen" venezolanischen Fernsehen zuteil? Wie findet Repräsentation statt und wann kann von partizipativer Repräsentation gesprochen werden? Das sind die Fragen, denen ich anhand eines Fallbeispiels aus der Perspektive der visuellen Anthropologie in diesem Beitrag nachgehen möchte.

Real-time computer-based visual feedback improves visual acuity in downbeat nystagmus - a pilot study.

BACKGROUND Patients with downbeat nystagmus syndrome suffer from oscillopsia, which leads to an unstable visual perception and therefore impaired visual acuity. The aim of this study was to use real-time computer-based visual feedback to compensate for the destabilizing slow phase eye movements. METHODS The patients were sitting in front of a computer screen with the head fixed on a chin rest. The eye movements were recorded by an eye tracking system (EyeSeeCam®). We tested the visual acuity with a fixed Landolt C (static) and during real-time feedback driven condition (dynamic) in gaze straight ahead and (20°) sideward gaze. In the dynamic condition, the Landolt C moved according to the slow phase eye velocity of the downbeat nystagmus. The Shapiro-Wilk test was used to test for normal distribution and one-way ANOVA for comparison. RESULTS Ten patients with downbeat nystagmus were included in the study. Median age was 76 years and the median duration of symptoms was 6.3 years (SD +/- 3.1y). The mean slow phase velocity was moderate during gaze straight ahead (1.44°/s, SD +/- 1.18°/s) and increased significantly in sideward gaze (mean left 3.36°/s; right 3.58°/s). In gaze straight ahead, we found no difference between the static and feedback driven condition. In sideward gaze, visual acuity improved in five out of ten subjects during the feedback-driven condition (p = 0.043). CONCLUSIONS This study provides proof of concept that non-invasive real-time computer-based visual feedback compensates for the SPV in DBN. Therefore, real-time visual feedback may be a promising aid for patients suffering from oscillopsia and impaired text reading on screen. Recent technological advances in the area of virtual reality displays might soon render this approach feasible in fully mobile settings.