Positive correlation in the bisection of long and short horizontal Oppel–Kundt illusory gradients: Implications for the interpretation of the “cross-over” effect in spatial neglect

The Oppel-Kundt Illusion is Effective in Modulating Horizontal Space Representation in Humans

“…To investigate this issue, healthy participants were asked to perform, under the same illusory backgrounds, a traditional line bisection task and a landmark task in which they had to evaluate the horizontal extension of two segments composing a pre-bisected line. Consistent with the abovementioned findings (Ricci, et al, 2004;Savazzi, et al, 2007;Binetti, et al, 2011), participants mis-bisected the lines toward the denser portion of the background, a result consistent with both an illusory and a "bias of response" interpretation. The landmark task disambiguated these alternatives in favor of the illusory interpretation.…”

“…Interestingly, patients with neglect showed an improvement of their rightward bisection bias when the visual illusion induced a perceptual distortion opposite to that hypothesized to underlie neglect (i.e., illusory expansion of left space), whereas healthy participants exhibited a neglect-like bisection bias when the visual illusion induced a perceptual distortion mimicking the one hypothesized to underlie neglect (i.e., illusory contraction of the left space). Subsequent studies, employing similar versions of the Oppel-Kundt illusion, replicated and extended Ricci and coworkers' (Ricci, et al, 2004) findings, namely the displacement of the subjective midpoint towards the denser side of the illusory background in the line bisection task both in neglect patients (Savazzi, Posteraro, Veronesi, & Mancini, 2007) and healthy participants (Binetti, Aiello, Merola, Bruschini, Lecce, Macci, et al, 2011).…”

Stimulus- and state-dependence of systematic bias in spatial attention: Additive effects of stimulus-size and time-on-task

“…Anderson (1996) showed that his model can explain cross-over for long versus short lines in neglect patients, and accordingly that purely attentional accounts may provide a unitary explanation for line length effects. In contrast to such purely attentional accounts, Savazzi et al (2007Savazzi et al ( , 2008 have shown that a general left-right distortion of the mapping of external space onto an internal representation (spatial anisometry in neglect: Milner et al, 1993;Milner and Harvey, 1995;Bisiach et al, 1998Bisiach et al, , 1999 may provide the basis for a unitary explanation of the line length effects in neglect patients, and possibly pseudoneglect in healthy subjects (though see Doricchi et al, 2008 andBinetti et al, 2011 for results contrary to the space anisometry account of cross-over).…”

A rightward shift in the visuospatial attention vector with healthy aging

“…What seems to be the case is that the elderly participants show an overall rightward shift in the attentional vector, that is most pronounced for the short lines. However, the comparison of findings from healthy participants with those in neglect patients and the “crossover” literature is complicated by the large variance of line bisection performance patterns both within and across patients (Halligan et al, 1990) and common concurrent primary visual and motor deficits post-stroke (Doricchi et al, 2005; Binetti et al, 2011; Kerkhoff and Schenk, 2011). The 150 ms landmark task presentation duration employed here minimizes the influence of non-perceptual motor components such as hand use and visual scanning on bisection decisions (Milner et al, 1992; Luh, 1995; Bisiach et al, 1998; Toraldo et al, 2004).…”

“…The 150 ms landmark task presentation duration employed here minimizes the influence of non-perceptual motor components such as hand use and visual scanning on bisection decisions (Milner et al, 1992; Luh, 1995; Bisiach et al, 1998; Toraldo et al, 2004). Employing the paradigm from the current study in RH stroke neglect patients both with and without concomitant primary visual deficits would be highly informative in terms of elucidating further purely perceptual contributions to the line length effect in neglect and the potential role played by primary visual deficits in the commonly observed “crossover” effect (Doricchi et al, 2005; Binetti et al, 2011). …”