Veronelli, L. 1, 2 , Vallar, G. 1, 3 , Marinelli, C. V. 4, 5 , Primativo, S. 4, 5 & Arduino, L. S. 6, 7
1 Department of Psychology, University of Milano-Bicocca, Milan, Italy
2 Department of Neuro Rehabilitative Sciences, Casa Di Cura Privata del Policlinico, Milan, Italy
3 IRCCS Istituto Auxologico Italiano, Milan, Italy
4 Department of Psychology, University of Rome La Sapienza, Rome, Italy
5 Neuropsychological Research Centre, IRCCS Foundation Hospital Santa Lucia, Rome, Italy
6 Department Of Psychology, LUMSA University, Rome, Italy
7 ISTC-CNR, Rome, Italy
In a line bisection task, right-brain damaged patients with unilateral spatial neglect (USN) set the midline to the right with respect to the objective midpoint, while unimpaired participants (UP) show a reversed bias (‘pseudoneglect’). In a recent study with UP, Arduino, Previtali and Girelli (2010) demonstrated that length differently affects the bisection of lines and orthographic stimuli, suggesting that different mechanisms may be involved in word and line bisection. The present study investigated these stimulus-dependent biases in USN patients. In Experiment 1 eleven patients and matched controls were asked to bisect words of different lengths (5-13 letters) and comparable lines. Experiment 2 focused on ortho-phonological features, requiring the bisection of words with different final sequences (stressed on the penultimate or antepenultimate syllable). Despite an overall rightward error modulated by stimulus length, in a few patients the directional biases for words and lines conjured up a double dissociation (Exp. 1), supporting the existence of partially independent mechanisms in word and line bisection. Results from Experiment 2 indicate that the final part of a word could be used by USN patients as a cue during bisection. Globally, both visuo-spatial and lexical mechanisms seem to influence the bisection of word in USN patients.