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

Abstract

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.

Local–global interference is modulated by age, sex and anterior corpus callosum size

“…Interference may emerge from at least three sources: the stimulus content at global and local levels, i.e., when local and global stimuli are incongruent compared with when they are congruent (Kotchoubey et al, 1997;Proverbio et al, 1998); from response conflict when feature processing at the unattended level suggests a different response from the attended stimulus attribute Malinowski et al, 2002;Volberg and Hübner, 2004;Weissman et al, 2003); or from sequential processing when the target location switches between local and global levels in two consecutive trials (level switching) (Han et al, 2000a;Schatz and Erlandson, 2003). Behaviorally, interference effects are usually defined as costs in response time (RT) and facilitation effects as benefits in RTs.…”

“…Thus, stimulus position is most likely responsible for different findings in RT studies usually using a lateral stimulus presentation in contrast to ERP studies with central presentations. The competition hypothesis (Han et al, 2002;Volberg and Hübner, 2004) assumes that with central stimulation both hemispheres have simultaneous access to the same visual information and the specialized hemisphere assigns more resources to a given local or global target level bringing hemispheric differences for local and global feature processing to light. With lateralized presentations visual information has to cross over to the cerebral hemisphere ipsilateral to the stimulated visual hemifield.…”

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

“…Hübner and Malinowksi 2002), event-related potentials studies (ERP, e.g. Volberg and Hübner 2004), and brain imaging studies (e.g. Heinze et al 1998).…”

Local and global auditory processing: Behavioral and ERP evidence

“…Many studies employing selective or divided attention tasks, central or lateralized presentation of stimuli, and varied or consistent information at unattended levels report no evidence of lateralized processing for local versus global information (Han et al, 1997(Han et al, , 1999Han & He, 2003;Han et al, 2000a;Heinze et al, 1998;Johannes et al, 1996). However, there is some evidence for lateralization -in the predicted direction -of later components (N250 and P300) under conditions of divided attention (Heinze et al, 1998;Heinze & Münte, 1993), when information at the other level could result in response conflicts (Volberg & Hübner, 2004), when level to be attended was cued immediately before presentation (Yamaguchi, Yamagata, & Kobayashi, 2000), and when targets were compared to nontargets at the two levels (Proverbio, Minniti, & Zani, 1998). Evidence for lateralization of earlier ERP components (P100) has only been reported for a paradigm in which the information at the unattended level was invariable and unrelated to the discrimination task (Evans, Shedden, Hevenor, & Hahn, 2000).…”