On 25 February Carolina Murd will defence her doctoral thesis "Mechanisms of processing visual motion information: Psychophysical, bioelectrical and transcranial magnetic stimulation investigations" in the Council of the Faculty of the Social Sciences and Education.
Professor Talis Bachmann, University of Tartu
Senior Researcher Kairi Kreegipuu, University of Tartu
Professor Jochen Müsseler, RWTH Aachen University, Germany
Motion perception is one of the most important functions of our visual system, enabling us to adapt and survive in the frequently changing environment. The mechanisms processing and using motion information are quite complex and often influenced by motivational aspects such as attention. The present doctoral dissertation deals with three main topics that are related to motion perception. First, it is examined how people perceive moving objects in comparison to stationary ones and whether a new experimental design with two objects moving in opposite direction reveals new information about the flash-lag effect. Second, it is observed, by using different task setups and measuring the bioelectrical activity of the brain, how and in which conditions does the presence of motion influence colour change perception in the moving object. Third part of the dissertation is dedicated to motion after-effect and how it is influenced by selective attention and brain stimulation. The main results found were as follows: 1) when people are presented with two objects moving in opposite direction and one of them has to be compared with briefly presented stationary flash, the mislocalization of the moving object it greater, 2) motion enhances the detection of the colour change in the moving object, but this enhancing effect is both task- and object-specific and not reflected in the bioelectrical activity of the brain, 3) both selective attention and brain stimulation influence the perceived duration of motion after-effect, but the direction of these influences depends on the experimental instruction and on the temporal characteristics of attending. In summary, motion perception is an integrative process that is based on different psychological and neurophysiological processes. The present dissertation has contributed to investigating these processes.