NEUROCASE 2012, iFirst, 1–19 Perceptual and response-related components of unilateral neglect may evolve independently of one another: Evidence from five single-case studies Alessio Toraldo 1 , Marcella Laiacona 2 , Rossella Pagani 3 , Alessandra Mandelli 4 , and Erminio Capitani 4,5 1 DSU, Psychology Section, Pavia University, Pavia, Italy 2 Salvatore Maugeri Foundation, Neurology Unit, Veruno Medical Center, IRCCS, Veruno, Italy 3 Rehabilitation Unit, San Paolo Hospital, Milan, Italy 4 Health Science Department, Università degli Studi di Milano, Milan, Italy 5 Neurology Unit, San Paolo Hospital, Milan, Italy The Milner Landmark Task allows the disentanglement of perceptual and response-related components of unilat- eral neglect. If these two components reflect separate functional systems, then cases should be observed in which the two components evolve differently across time. To test this hypothesis we surveyed a continuous series of 21 right hemisphere stroke patients. Five patients from the sample were affected by unilateral neglect at the outset and could be submitted to repeated administrations of the Landmark task in the first weeks post stroke. Two ver- sions of the task were used, Landmark-Manual and Landmark-Verbal, differing in the type of response required. Two patients showed independent changes in the perceptual and the response-related component of neglect, hence confirming the view of separate functional systems underlying them. Dissociations between the task versions were found, witnessing a role of the type of response. Unexpectedly, one patient showed an initial leftward deviation of the subjective midpoint of the stimulus line, which later reversed to a classical rightward deviation. We interpreted such a pattern in terms of co-existing “productive” and “negative” components of perceptual neglect. Keywords: Unilateral neglect; Neglect evolution; Landmark test; Input-related neglect; Output-related neglect; Paradoxical neglect. Unilateral neglect is not a unitary entity (Di Bartolomeo & Chockron, 2001). For a satisfactory classification of neglect patients one should specify whether the deficit concerns personal, peri-personal or extra-personal space (Bisiach, 1999) and whether it differently affects perceptual and response-related components. In this study we will focus on the latter dichotomy, with special reference to the sponta- neous evolution that follows acute brain damage. Address correspondence to Alessio Toraldo, Dipartimento di Psicologia, Università di Pavia, Piazza Botta 11, 27100, Pavia, Italy. (E-mail: alessio.toraldo@unipv.it). This project was partially supported by a Milan University FIRST Grant and by a PRIN Grant to EC. No conflict of interest affects this manuscript. We thank one of the reviewers for his/her thoughtful comments. The suggestion to distinguish between perceptual and response components of neglect was put for- ward by Watson, Miller, and Heilman (1978) and became the subject of many subsequent enquiries. “Perceptual neglect” prevents the patient from col- lecting and correctly representing information aris- ing from the contralesional side and conveyed along one or more input channels (e.g., visual, tactile, and so on), independently of the ability to direct a c  2012 Taylor & Francis http://www.tandfonline.com http://dx.doi.org/10.1080/13554794.2012.741257