Object substitution masking and it's relationship with visual crowding

Object substitution masking (OSM) occurs when the perceptibility of a brief target is reduced by a trailing surround mask typically composed of four dots. Camp et al. (Journal of Experimental Psychology: Human Perception and Performance, 41, 940–957, 2015) found that crowding a target by adding adjacent flankers, in addition to OSM, had a more deleterious effect on performance than expected based on the combined individual effects of crowding and masking alone. The current experiments test why OSM and crowding interact in this way. In three experiments, target-flanker distance is manipulated whilst also varying mask duration in a digit identification task. The OSM effect—as indexed by the performance difference between unmasked and masked conditions—had a quadratic function with respect to target-flanker distance. Results suggest it is OSM affecting crowding rather than the converse: Masking seems to amplify crowding at intermediate target-distractor distances at the edge of the crowding interference zone. These results indicate that OSM and crowding share common mechanisms. The effect of OSM is possibly a consequence of changes to the types of feature detectors which are pooled together for target identification when that target must compete for processing with a trailing mask in addition to competition from adjacent flankers

Patients with hemi-spatial neglect are more prone to limb spasticity, but this does not prolong their hospital stay.

Objective: To determine whether stroke patients who suffer from hemi-spatial neglect tend to stay in hospital longer because they are prone to limb spasticity. Design: Retrospective analysis of in-patient medical notes. Setting: In-patient neuro-rehabilitation unit of a regional UK teaching hospital Participants: All 106 patients admitted to the neuro-rehabilitation unit between 2008-2010 who had suffered a stroke, as confirmed by CT or MRI. Intervention: Not applicable. Main Outcome Measures: Statistical coincidence of hemi-spatial neglect and spasticity; Length of hospital stay. Results: Chi-square analyses indicated that individuals with left neglect were nearly a third more likely to develop spasticity than those without neglect (87% vs. 57%), while nearly one half of those with left-sided spasticity showed neglect (44% vs. 13%). Individuals with neglect stayed in hospital 45 days longer than those without neglect, but the presence/absence of spasticity did not affect length of stay. Conclusions: The results provide the first statistical evidence that neglect and limb spasticity tend to co-occur post-stroke, though it is only the former that significantly prolongs stay. Diagnostic value aside, these results are important because they tell us that the treatment of neglect should not be overshadowed by efforts to reduce co-morbid spasticity. Despite its poor prognosis, hemi-spatial neglect continues to receive little targeted therapy in some units