The Oppel-Kundt illusion (OKI) consists of the perception of a filled space as larger than an empty space of the same size. Here, we used a modified version of that illusion composed of a gradient of vertical lines whose spacing decreased progressively from one side to the other: space is expected to be perceived as larger where the lines are more compressed. We tested the hypothesis that a horizontal stimulus presented in a space perceived as larger will produce faster RTs by asking forty-four healthy subjects to respond as quickly as possible to lateralized stimuli (horizontal bars, vertical bars and circles) presented on different backgrounds (control condition: evenly spaced vertical lines or an empty space; illusory conditions: vertical lines progressively compressed to the right or the left). Subjects' RTs were reliably faster for horizontal stimuli presented on the space perceived as larger than on the space perceived as smaller. To verify that this effect was actually due to a size illusion, the same subjects were asked to adjust the size of the stimuli presented on the same backgrounds as to make them equal to a reference stimulus. For horizontal stimuli, subjects produced adjustments in accordance with the predicted effect of the illusion. Together, these data show that the OKI produces a distortion of space that extends to stimuli placed in front of it and that RTs are influenced by the perceived and not the physical size of the stimuli. Implications for neural bases of illusions and for spatial neglect are discussed.

Object The aim of this study was to explore the feasibility of intraoperative visuospatial mapping with the same criteria currently used to define essential language areas. Methods The authors compared surgical procedures in 2 patients with similar tumors (Grade II oligodendroglioma in the right parietal lobe) undergoing awake, image-assisted surgery for lesion removal with intraoperative neurophysiological monitoring. The line bisection task was used in both patients but with different criteria. Results In the first case, the authors respected any area, even within the tumor, where significant interference was found (a stimulation-induced error in 2 of 3 applications defined an essential area). In the second case, they removed 1 essential area located in the tumor and recorded an uneventful clinical response soon thereafter. They continued to monitor the patient without stimulation and stopped the resection when the patient was close to the criteria valid for defining spatial neglect. The signs of spatial neglect were present for 3 days postoperatively and then cleared spontaneously. Subtotal tumor removal was achieved in both cases. Conclusions Evidence in the present study reveals that areas for visuospatial functions cannot be assessed with the same criteria used for language functions, since essential areas located in the tumor can be safely removed.

Patients with neglect fail to report, respond to, or orient to stimuli presented on the opposite side of the brain lesion. Spatial neglect is a multi-componential syndrome and many of its symptoms and signs need specific testing to detect their different clinical manifestations. Given that neglect has a dramatic effect on the outcome of these patients, it is of paramount importance for accurate assessment all its manifestations. Thus, the purpose of this study is to assess visuo-spatial functions with a newly-built neuropsychological battery to determine the incidence of visuo-spatial disorders and spatial neglect in patients with right brain tumour. We tested 14 patients undergoing tumour resection, both pre-operatively and post-operatively. Pre-operatively, we found an incidence of 42.86% for visuo-spatial deficits and of 14.29% specifically for spatial neglect. This incidence increases post-operatively to 57.14% for visuo-spatial deficits and to 42.86% specifically for spatial neglect. The present study has important implications for a better knowledge of the spatial disorders in patients with right-brain tumour, thus providing a clearer picture on the everyday life problems faced by these patients, both within the family and in working contexts.

It is commonly said that tall people look thinner. Here, we asked whether an illusion exists such that the taller of two equally wide stimuli looks thinner, and conversely whether the thinner of two equally tall stimuli looks taller. In five experiments, participants judged the horizontal or vertical extents of two identical bodies, rectangles, or cylinders that differed only in their vertical or horizontal extents. Our results confirmed the folk wisdom that being tall makes you look thinner. We similarly found that being thin makes you look taller, although this effect was less pronounced. The same illusion was present for filled rectangles and cylinders, but it was consistently stronger for both photographs and silhouettes of the human body, raising the question of why the human form should be more prone to this illusion.

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