Group study of an 'undercover' test for visuospatial neglect: Invisible cancellation can reveal more neglect than standard cancellation

Visual neglect is a relatively common deficit after brain damage, particularly strokes. Cancellation tests provide standard clinical measures of neglect severity and deficits in daily life. A recent single-case study introduced a new variation on standard cancellation. Instead of making a visible mark on each target found, the patient made invisible marks (recorded with carbon paper underneath, for later scoring). Such invisible cancellation was found to reveal more neglect than cancellation with visible marks. Here we test the generality of this. Twenty three successive cases with suspected neglect each performed cancellation with visible or invisible marks. Neglect of contralesional targets was more pronounced with invisible marks. Indeed, about half of the patients only showed neglect in this version. For cases showing more neglect with invisible marks, stronger neglect of contralesional targets correlated with more revisits to ipsilesional targets for making additional invisible marks upon them. These results indicate that cancellation with invisible marks can reveal more neglect than standard cancellation with visible marks, while still providing a practical bedside test. Our observations may be consistent with recent proposals that demands on spatial working memory (required to keep track of previously found items only when marked invisibly) can exacerbate spatial neglect

Attentional load and sensory competition in human vision: Modulation of fMRI responses by load fixation during task-irrelevant stimulation in the peripheral visual field.

Perceptual suppression of distractors may depend on both endogenous and exogenous factors, such as attentional load of the current task and sensory competition among simultaneous stimuli, respectively. We used functional magnetic resonance imaging (fMRI) to compare these two types of attentional effects and examine how they may interact in the human brain. We varied the attentional load of a visual monitoring task performed on a rapid stream at central fixation without altering the central stimuli themselves, while measuring the impact on fMRI responses to task-irrelevant peripheral checkerboards presented either unilaterally or bilaterally. Activations in visual cortex for irrelevant peripheral stimulation decreased with increasing attentional load at fixation. This relative decrease was present even in V1, but became larger for successive visual areas through to V4. Decreases in activation for contralateral peripheral checkerboards due to higher central load were more pronounced within retinotopic cortex corresponding to 'inner' peripheral locations relatively near the central targets than for more eccentric 'outer' locations, demonstrating a predominant suppression of nearby surround rather than strict 'tunnel vision' during higher task load at central fixation. Contralateral activations for peripheral stimulation in one hemifield were reduced by competition with concurrent stimulation in the other hemifield only in inferior parietal cortex, not in retinotopic areas of occipital visual cortex. In addition, central attentional load interacted with competition due to bilateral versus unilateral peripheral stimuli specifically in posterior parietal and fusiform regions. These results reveal that task-dependent attentional load, and interhemifield stimulus-competition, can produce distinct influences on the neural responses to peripheral visual stimuli within the human visual system. These distinct mechanisms in selective visual processing may be integrated within posterior parietal areas, rather than earlier occipital cortex

Exploring How Industrial Designers Can Contribute to Scientific Research

This paper describes the initial findings of an empirical study exploring how industrial designers might be able to support scientists in their research activities. The paper compares and contrasts the findings of a literature review, a series of interviews with scientists and three case studies in which designers collaborated with scientific teams at a university. It reflects on the designers’ contribution to research and highlights potential barriers and enablers to collaboration. In addition to the expected contribution of designers to supporting commercialisation of technology, the research demonstrated the potential for industrial design to have an impact on research itself. When involved earlier in the scientific research process, designers can challenge the research direction and support scientists in demonstrating, communicating and exploring potential future applications

The Opportunity Spectrum -- Concept and Behavioral Information in Outdoor Recreation Resource Supply Inventories: Background and Application

The paper describes an outdoor recreation resource (ORR) Supply Inventory and Classification (SIC) System that is being developed for multiple use natural resource planning. Four previously developed ORR SIC’s on which this system was built are described briefly. A general model for natural resource planning is presented to show how the proposed ORR SIC fits into a larger planning framework. The proposed SIC System is described and its application for regional and unit planning is explained. Relationships between OR consumers\u27 preferences for specific types of satisfying experiences and their preferences for specific attributes of the physical, social, and managerial settings are translated into specific and objective criteria proposed for inventorying and classifying lands as to their potential for providing particular types of OR opportunities on the spectrum

Hemispheric differences in frontal and parietal influences on human occipital cortex: direct confirmation with concurrent TMS-fMRI

We used concurrent TMS-fMRI to test directly for hemispheric differences in causal influences of the right or left fronto-parietal cortex on activity (BOLD signal) in the human occipital cortex. Clinical data and some behavioral TMS studies have been taken to suggest right-hemisphere specialization for top-down modulation of vision in humans, based on deficits such as spatial neglect or extinction in lesioned patients, or findings that TMS to right (vs. left) fronto-parietal structures can elicit stronger effects on visual performance. But prior to the recent advent of concurrent TMS and neuroimaging, it was not possible to directly examine the causal impact of one (stimulated) brain region upon others in humans. Here we stimulated the frontal or intraparietal cortex in the left or right hemisphere with TMS, inside an MR scanner, while measuring with fMRI any resulting BOLD signal changes in visual areas V1-V4 and V5/MT+. For both frontal and parietal stimulation, we found clear differences between effects of right- versus left-hemisphere TMS on activity in the visual cortex, with all differences significant in direct statistical comparisons. Frontal TMS over either hemisphere elicited similar BOLD decreases for central visual field representations in V1-V4, but only right frontal TMS led to BOLD increases for peripheral field representations in these regions. Hemispheric differences for effects of parietal TMS were even more marked: Right parietal TMS led to strong BOLD changes in V1-V4 and V5/MT+, but left parietal TMS did not. These data directly confirm that the human frontal and parietal cortex show right-hemisphere specialization for causal influences on the visual cortex

The Serendipitous Discovery of a Group or Cluster of young Galaxies at z=2.40 in Deep Hubble Space Telescope WFPC2 Images

We report the serendipitous discovery of a group or cluster of young galaxies at $z\simeq$2.40 in a 24-orbit HST/WFPC2 exposure of the field around the weak radio galaxy 53W002. Potential cluster members were identified on ground-based narrow-band redshifted Ly$\alpha$ images and confirmed via spectroscopy. In addition to the known weak radio galaxy 53W002 at z=2.390, two other objects were found to have excess narrow-band Ly$\alpha$ emission at $z\simeq$2.40. Both have been spectroscopically confirmed, and one clearly contains a weak AGN. They are located within one arcminute of 53W002, or $\sim0.23h_{100}^{-1}$Mpc ($q_o$=0.5) at $z\simeq$2.40, which is the physical scale of a group or small cluster of galaxies. Profile fitting of the WFPC2 images shows that the objects are very compact, with scale lengths $\simeq$0\farcs 1 ($\simeq0.39h_{100}^{-1}$kpc), and are rather faint (luminosities < L*), implying that they may be sub-galactic sized objects. We discuss these results in the context of galaxy and cluster evolution and the role that weak AGN may play in the formation of young galaxies.Comment: Accepted for publication in The Astrophysical Journal (Letters). 13 pages of gzip compressed and uuencoded PS. Figures are available at http://www.phys.unsw.edu.au/~spd/bib.htm

Saccades to a remembered location elicit spatially specific activation in human retinotopic visual cortex

The possible impact upon human visual cortex from saccades to remembered target locations was investigated using functional magnetic resonance imaging (fMRI). A specific location in the upper-right or upper-left visual quadrant served as the saccadic target. After a delay of 2,400 msec, an auditory signal indicated whether to execute a saccade to that location (go trial) or to cancel the saccade and remain centrally fixated (no-go). Group fMRI analysis revealed activation specific to the remembered target location for executed saccades, in the contralateral lingual gyrus. No-go trials produced similar, albeit significantly reduced, effects. Individual retinotopic mapping confirmed that on go trials, quadrant-specific activations arose in those parts of ventral V1, V2, and V3 that coded the target location for the saccade, whereas on no-go trials, only the corresponding parts of V2 and V3 were significantly activated. These results indicate that a spatial-motor saccadic task (i.e., making an eye movement to a remembered location) is sufficient to activate retinotopic visual cortex spatially corresponding to the target location, and that this activation is also present (though reduced) when no saccade is executed. We discuss the implications of finding that saccades to remembered locations can affect early visual cortex, not just those structures conventionally associated with eye movements, in relation to recent ideas about attention, spatial working memory, and the notion that recently activated representations can be "refreshed" when needed