Space-based bias of covert visual attention in complex regional pain syndrome

This topical update reports recent progress in the international effort to develop a more accurate and valid diagnostic criteria for complex regional pain syndrome (CRPS). The diagnostic entity of CRPS (published in the International Association for the Study of Pain's Taxonomy monograph in 1994; International Association for the Study of Pain [IASP]) was intended to be descriptive, general, and not imply etiopathology, and had the potential to lead to improved clinical communication and greater generalizability across research samples. Unfortunately, realization of this potential has been limited by the fact that these criteria were based solely on consensus and utilization of the criteria in the literature has been sporadic at best. As a consequence, the full potential benefits of the IASP criteria have not been realized. Consensus-derived criteria that are not subsequently validated may lead to over- or underdiagnosis, and will reduce the ability to provide timely and optimal treatment. Results of validation studies to date suggest that the IASP/CRPS diagnostic criteria are adequately sensitive; however, both internal and external validation research suggests that utilization of these criteria causes problems of overdiagnosis due to poor specificity. This update summarizes the latest international consensus group's action in Budapest, Hungary to approve and codify empirically validated, statistically derived revisions of the IASP criteria for CRPS.

Spatial selective attention is widely considered to be right hemisphere dominant. Previous functional magnetic resonance imaging studies, however, have reported bilateral blood-oxygenation-level-dependent responses in dorsal frontoparietal regions during anticipatory shifts of attention to a location (Kastner et al., 1999; Corbetta et al., 2000; Hopfinger et al., 2000). Right-lateralized activity has mainly been reported in ventral frontoparietal regions for shifts of attention to an unattended target stimulus (Arrington et al., 2000; Corbetta et al., 2000). However, clear conclusions cannot be drawn from these studies because hemispheric asymmetries were not assessed using direct voxelwise comparisons of activity in left and right hemispheres. Here, we used this technique to measure hemispheric asymmetries during shifts of spatial attention evoked by a peripheral cue stimulus and during target detection at the cued location. Stimulus-driven shifts of spatial attention in both visual fields evoked right-hemisphere dominant activity in temporoparietal junction (TPJ). Target detection at the attended location produced a more widespread right hemisphere dominance in frontal, parietal, and temporal cortex, including the TPJ region asymmetrically activated during shifts of spatial attention. However, hemispheric asymmetries were not observed during either shifts of attention or target detection in the dorsal frontoparietal regions (anterior precuneus, medial intraparietal sulcus, frontal eye fields) that showed the most robust activations for shifts of attention. Therefore, right hemisphere dominance during stimulus-driven shifts of spatial attention and target detection reflects asymmetries in cortical regions that are largely distinct from the dorsal frontoparietal network involved in the control of selective attention.

Our ability to interact with the immediate surroundings depends not only on an adequate representation of external space but also on our ability to represent the location of objects with respect to our own body and especially to our hands. Indeed, electrophysiological studies in monkeys revealed multimodal neurons with spatially corresponding tactile and visual receptive fields in a number of brain areas, suggesting a representation of visual peripersonal space with respect to the body. In this functional magnetic resonance imaging study, we localized areas in human intraparietal sulcus (IPS) and lateral occipital complex (LOC) that represent nearby visual space with respect to the hands (perihand space), by contrasting the response to a ball moving near-to versus far-from the hands. Furthermore, by independently manipulating sensory information about the hand, in the visual (using a dummy hand) and proprioceptive domains (by changing the unseen hand position), we determined the sensory contributions to the representation of hand-centered space. In the posterior IPS, the visual contribution was dominant, overriding proprioceptive information. Surprisingly, regions within LOC also displayed visually dominant, hand-related activation. In contrast, the anterior IPS was characterized by a proprioceptive representation of the hand, as well as showing tactile hand-specific activation, suggesting a homology with monkey parietal hand-centered areas. We therefore suggest that, whereas cortical regions within the posterior IPS and LOC represent hand-centered space in a predominantly visual manner, the anterior IPS uses multisensory information in representing perihand space.