PurposeWe conducted a driving simulator study to investigate the effects of monitoring intersection cross traffic on gaze behaviors and responses to pedestrians by drivers with hemianopic field loss.MethodsSixteen HFL and sixteen normal vision participants completed two drives in an urban environment. At 30 intersections, a pedestrian ran across the road when the participant entered the intersection, requiring a braking response to avoid a collision. Intersections with these pedestrian events had either no cross traffic, one approaching car from the side opposite (...) the pedestrian location, or two approaching cars, one from each side at the same time.ResultsOverall, HFL drivers made more of cross-traffic on both the blind and seeing sides. They made more numerous and larger gaze scans when they fixated cars on both sides and had lower rates of unsafe responses to blind- but not seeing-side pedestrians. They were more likely to demonstrate compensatory blind-side fixation behaviors when there was no car on the seeing side. Fixation behaviors and unsafe response rates were most similar to those of NV drivers when cars were fixated on both sides.ConclusionFor HFL participants, making more scans, larger scans and safer responses to pedestrians crossing from the blind side were associated with looking at cross traffic from both directions. Thus, cross traffic might serve as a reminder to scan and provide a reference point to guide blind-side scanning of drivers with HFL. Proactively checking for cross-traffic cars from both sides could be an important safety practice for drivers with HFL. (shrink)

Blindsight is the term commonly used to describe visually guided behaviour elicited by a stimulus falling within the scotoma (blind area) caused by a lesion of the striate cortex. Such is normally held to be unconscious and to be mediated by subcortical pathways involving the superior colliculus. Blindsight is of considerable theoretical importance since it suggests that destriate man is more like destriate monkey than had been previously believed and also because it supports the classical notion of two visual systems. (...) It is also of potential clinical importance, since it has been claimed recently that systematic practice in blindsight can lead to the recovery of normal visual function in patients with cortical lesions. From a review of the literature it is concluded that all of the phenomena of blindsight can be attributed either to light scatter into unimpaired parts of the visual field or to residual vision resulting from spared striate cortex. The possible contribution f other factors is also considered. It is concluded that blindsight studies have generally failed to control for such nonblindsight interpretations partly because of poor methodology and partly because of difficulties in defining the term. (shrink)

The taxonomy proposed by Pessoa et al. should be extended to include “pathological” completion phenomena in patients with unilateral brain damage. Patients with visual field defects (hemianopias) may “complete” whole figures, while patients with parietal lobe damage may “complete” partial figures. We argue that the former may be consistent with the brain “filling-in” information, and the latter may be consistent with the brain ignoring the absence of information.

This volume provides, for the first time, multidisciplinary perspectives on the problem of awareness of deficits following brain injury. Such deficits may involve perception, attention, memory, language, or motor functions, and they can seriously disrupt an individual's ability to function. However, some brain-damaged patients are entirely unaware of the existence or severity of their deficits, even when they are easily noticed by others. In addressing these topics, contributors cover the entire range of neuropsychological syndromes in which problems with awareness of (...) deficit are observed: hemiplegia and hemianopia, amnesia, aphasia, traumatic head injury, dementia, and others. On the clinical side, leading researchers delineate the implications of awareness of deficits for rehabilitation and patient management, and the role of defense mechanisms such as denial. Theoretical discussions focus on the importance of awareness disturbances for better understanding such cognitive processes as attention, consciousness, and monitoring. (shrink)