Biomedical subjects

S Pfaff

Publications and source records attributed to S Pfaff.

4 recordsLinked to original sources

PubMed2000

Evidence for multistability in the visual perception of pigeons.

Perceptual multistability refers to cases where perception alternates between two or more interpretations of an unchanging sensory stimulus. In a first experiment we trained eight pigeons to discriminate horizontal and vertical apparent motion stimuli and then presented a multistable display. In five cases their behavior showed alternations similar to human experiments. In a second experiment we varied the aspect ratio of the display in order to support the hypothesis of a percept-driven nature of the switching behavior. The pecking rates and mean phase durations varied as predicted. This is the first evidence of visual multistability in animals confronted with classical ambiguous figures. The data suggest a stochastic mechanism.

Adaptation, Physiological↗

PubMed1998

Neuronal diversification: development of motor neuron subtypes.

Recent progress has been made in defining the developmental mechanisms that contribute to the diversification of motor neuron subtypes, which differ in transcription factor gene expression and synaptic connections. These studies suggest that progenitor cells acquire specific motor neuron identities through the coordinate actions of multiple factors. Current evidence suggests that Sonic hedgehog initiates a common pathway for motor neuron differentiation, while positionally distributed factors act to assign subtype identities.

Animals↗

PubMed1992

Perioperative antibiotic prophylaxis: the importance of timing.

1. Although prophylactic antibiotics have demonstrated efficacy in surgical procedures, they can fail because, generally, an inappropriate agent is used or the agent is inappropriately administered. 2. The timing of administration is important. Studies indicate that to reduce the risk of infection, high levels of antibiotic must be present in the bloodstream and tissues at the time of the incision. 3. Nurses play a central role in ensuring the proper timing of the administration of prophylactic antibiotics. Improvement in the timing of administration will reduce both morbidity and institutional costs.

Anti-Bacterial Agents↗

PubMed1991

Attractors and perceptual field dynamics of homogeneous stimulus areas.

The phenomenon of the wandering point on a blank sheet of paper in serial reproductions is the starting point of an investigation of the perceptual field structure of homogeneous stimulus areas; 609 stimulus points distributed regularly in 21 rows and 29 columns on a DIN A4 sheet were presented successively to 10 subjects and had to be reproduced immediately afterwards in order to establish empirical vector fields. These were subjected to vector-analytic procedures. A method for the decomposition of the measured vector fields into partitions from gradient potentials and circulation potentials is demonstrated. The gradient potentials of the empirical vector fields revealed a highly regular structure with four point attractors near the corners of the sheet. A model calculation of the wandering point in this potential landscape showed results comparable to the empirical phenomenon. The results are discussed in favor of Gestalt theory and against direct perception.

Attention↗