Biomedical subjects

Gregor Volberg

Publications and source records attributed to Gregor Volberg.

3 recordsLinked to original sources

PubMed2006

Do the hemispheres differ in their preparation for global/local processing?

It has recently been suggested that hemispheric differences for global and local processing already occur in response to visual pre-cues that direct attention to a specific level. However, in the supporting studies cue information was confounded with the form of the cues. In order to dissolve the confound, we compared event-related brain potentials towards cues differing in form with those towards identically formed color cues. As a result, hemispheric differences were found only for the former cue type. The data thus show that the mere cue information does not produce hemispheric asymmetries associated with global/local target stimulus processing.

Adult↗

PubMed2005

The integration of object levels and their content: a theory of global/local processing and related hemispheric differences.

This article presents and tests the authors' integration hypothesis of global/local processing, which proposes that at early stages of processing, the identities of global and local units of a hierarchical stimulus are represented separately from information about their respective levels and that, therefore, identity and level information have to be integrated at later stages. It further states that the cerebral hemispheres differ in their capacities for these binding processes. Three experiments are reported in which the integration hypothesis was tested. Participants had to identify a letter at a prespecified level with the viewing duration restricted by a mask. False reporting of the letter at the nontarget level was predicted to occur more often when the integration of identity and level could fail. This was the case. Moreover, visual-field effects occurred, as expected. Finally, a multinomial model was constructed and fitted to the data.

Adult↗

PubMed2004

On the role of response conflicts and stimulus position for hemispheric differences in global/local processing: an ERP study.

It is widely assumed that the local and global levels of hierarchical stimuli are processed more efficiently in the left and right cerebral hemispheres, respectively. However, corresponding effects were not observed under all circumstances. In ERP studies, they occurred more often with centrally presented stimuli than with laterally presented ones, whereas reaction-time studies revealed that a response conflict between the levels is relevant. The present study examines which of these two factors is more important by presenting conflicting and non-conflicting stimuli to the left or right visual field and recording ERPs as well as collecting behavioral data. If a central stimulus position is crucial, then no effects should show up. Contrary to this prediction, the expected hemispheric differences were observed in the behavioral data as well as in the later occurring (N2 and P3) ERP amplitudes. However, in all variables, the effects were more pronounced for conflicting stimuli. The results suggest that response conflicts are more important for obtaining hemispheric differences in global/local processing than a central stimulus presentation. This is interpreted in the way that hemispheric differences vary with respect to the stimulus representation that is needed to select a proper response.

Adult↗