Manfred Mackeben

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Human observers fixated the center of a search array and were required to discriminate the color of an odd target if it was present. The array consisted of horizontal or vertical black or white bars. In the simple case, only orientation was necessary to define the odd target, whereas in the conjunctive case, both orientation and color were necessary. A cue(More)
Topographic characteristics of peripheral letter recognition were investigated using a sustained attention paradigm to clarify whether its deployment in the visual field is equally easy in all eight tested locations at 7.5 deg eccentricity. Target size (36 arcmin) was clearly above threshold, so that letters were easily recognized at long durations (> 500(More)
Sustained attention enhances perception in eccentric positions in the visual field, which helps patients with foveal vision loss to develop a peripheral 'preferred retinal locus' (PRL). Besides central scotoma topography, local variations of attentional performance could influence the choice of PRL location. We tested sustained attention augmenting(More)
We show that transient attention summoned by an exogenous cue shows rapid learning of the relationship between the cue and a subsequent target in a discrimination task. In experiment 1, performance was unaffected when a target always appeared in the same position on a large cue, but was degraded when the target could appear anywhere within the extent of the(More)
"Express" saccades, named for their extremely short latencies, occur more frequently in a paradigm with a "gap" in time between the disappearance of the fixation mark and the appearance of the target to be fixated. To explain this result, it has been hypothesized that movements of the eyes are preceded by movements of attention [Posner (1980) Quarterly(More)
PURPOSE To measure eccentric fixation characteristics in visual fields of patients with Stargardt's disease. METHODS The positions of fixation loci (FL) in the visual field were determined by Tübingen perimetry (TP), using the position of the blind spots in 173 patients. Altogether, 669 visual fields were measured at baseline and during follow-up. Twenty(More)
Macaque monkeys were trained to fixate a small spot while we recorded epidural steady state visual evoked potentials (SSVEP) in response to counterphase modulated sinusoidal gratings. This led to the following results: (1) the SSVEP can show either broad or narrow spatial frequency tuning, depending on electrode location, temporal frequency, contrast and(More)
Fixational eye movements in 60 eyes of 30 patients with ABCA4-associated Stargardt disease were recorded by a Scanning Laser Ophthalmoscope (SLO). The results were quantified by two new fixation quality measures expressing the eccentricity of the preferred retinal locus (PRL) non-parametrically, and fixation stability by a dynamic index. 46 eyes (77%)(More)
This analysis of time series of eye movements is a saccade-detection algorithm that is based on an earlier algorithm. It achieves substantial improvements by using an adaptive-threshold model instead of fixed thresholds and using the eye-movement acceleration signal. This has four advantages: (1) Adaptive thresholds are calculated automatically from the(More)