Focusing narrowly or broadly attention when judging categorical and coordinate spatial relations: a MEG study

Lateralized pointing does not cause a cognitive bias

Lateralized pointing has been shown to cause not only a shift in visuo-motor midline, but also a shift in non-lateralized spatial attention. Non-lateralized cognitive consequences of lateralized pointing have been reported for local and global visuospatial processing. Here, we evaluate these findings and examine this effect for categorical and coordinate spatial relation processing, for which the attentional processes are thought to be highly similar to local and global visuospatial processing, respectively. Participants performed a commonly used working memory task to assess categorical and coordinate spatial relation processing. Lateralized pointing with either the left or the right hand, to either the left or the right side was introduced as a manipulation, as well as a new control condition without any pointing. Performance on the spatial relation task was measured before and after pointing. The results suggest that non-lateralized consequences of lateralized pointing cannot be generalized to other cognitive tasks relying on attentional processing. Further examination of lateralized pointing is recommended before drawing further conclusions concerning its impact on non-lateralized cognition.

Differential neural activity patterns for spatial relations in humans: a MEG study

Children learn the words for above-below relations earlier than for left-right relations, despite treating these equally well in a simple visual categorization task. Even as adults--conflicts in congruency, such as when a stimulus is depicted in a spatially incongruent manner with respect to salient global cues--can be challenging. Here we investigated the neural correlates of encoding and maintaining in working memory above-below and left-right relational planes in 12 adults using magnetoencephalography in order to discover whether above-below relations are represented by the brain differently than left-right relations. Adults performed perfectly on the task behaviorally, so any differences in neural activity were attributed to the stimuli's cognitive attributes. In comparing above-below to left-right relations during stimulus encoding, we found the greatest differences in neural activity in areas associated with space and movement. In comparing congruent to incongruent trials, we found the greatest differential activity in premotor areas. For both contrasts, brain areas involved in the encoding phase were also involved in the maintenance phase, which provides evidence that those brain areas are particularly important in representing the relational planes or congruency types throughout the trial. When comparing neural activity associated with the relational planes during working memory, additional right posterior areas were implicated, whereas the congruent-incongruent contrast implicated additional bilateral frontal and temporal areas. These findings are consistent with the hypothesis left-right relations are represented differently than above-below relations.

Hemispheric lateralization in top-down attention during spatial relation processing: a Granger causal model approach

Magnetoencephalography was recorded during a matching-to-sample plus cueing paradigm, in which participants judged the occurrence of changes in either categorical (CAT) or coordinate (COO) spatial relations. Previously, parietal and frontal lobes were identified as key areas in processing spatial relations and it was shown that each hemisphere was differently involved and modulated by the scope of the attention window (e.g. a large and small cue). In this study, Granger analysis highlighted the patterns of causality among involved brain areas--the direction of information transfer ran from the frontal to the visual cortex in the right hemisphere, whereas it ran in the opposite direction in the left side. Thus, the right frontal area seems to exert top-down influence, supporting the idea that, in this task, top-down signals are selectively related to the right side. Additionally, for CAT change preceded by a small cue, the right frontal gyrus was not involved in the information transfer, indicating a selective specialization of the left hemisphere for this condition. The present findings strengthen the conclusion of the presence of a remarkable hemispheric specialization for spatial relation processing and illustrate the complex interactions between the lateralized parts of the neural network. Moreover, they illustrate how focusing attention over large or small regions of the visual field engages these lateralized networks differently, particularly in the frontal regions of each hemisphere, consistent with the theory that spatial relation judgements require a fronto-parietal network in the left hemisphere for categorical relations and on the right hemisphere for coordinate spatial processing.