INTRODUCTION In the present work we tried to establish whether Mental Rotation (MR) is determined by the type of stimulus (Tomasino et al. , 2003; Rumiati et al., 2001; Kosslyn et al., 1998) or the strategy used (Kosslyn et al., 2001). Tomasino et al. (2003) have reported a double dissociation in MR tasks, following right (RH) or left (LH) hemispheric lesions: LH patients are selectively impaired in MR tasks involving body parts, while RH patients are impaired in MR tasks of stimuli other than body parts. However, this hemispheric specialization based on the type of stimulus is in contrast with a neuroimaging study demonstrating that the same LH areas activated when subjects mentally rotated hands, were activated also when they performed MR of 3-D cubes as a consequence of their own hand turning the stimuli (i.e. the motor strategy, Kosslyn et al., 2001). By contrast left motor regions were not enhanced when the MR was performed by imagining the consequences of an external force (an electric motor) manipulating the 3-D cubes (i.e., the visual strategy). Here we aimed at providing neuropsychological evidence supporting that such visual and motor transformations are dissociable as a consequence of brain damage to the fronto (motor and premotor)- parietal region of the RH or the LH respectively. Patients were asked to adopt a motor strategy and, in a different block, a visual strategy. In order to apply a motor strategy a patient had to imagine turning the stimulus with his/her own hand; the visual strategy was applied when MR of hand shapes and 3-D cubes was based on the object’s reference frame. Independent of the stimulus to be rotated, LH patients were expected to make more errors than RH patients in applying the motor strategy with hands as well as with 3-D cubes. It is known from neuropsychological (Tomasino et al., 2003; Rumiati et al., 2001; Sirigu et al., 1996) and functional imaging findings (Kosslyn et al., 2001; 1998; Ganis et al., 2000; Parsons and Fox, 1998) that the LH sustains tasks that require actual and simulated movements (Decety et al. , 1994). In contrast, MR using a visual strategy should result more difficult for RH than LH patients. Indeed neuropsychological observations suggest that the RH is competent for spatial operations (Bricolo et al., 2000; Ratcliff, 1979). METHOD Subjects Table I contains information concerning the patients who took part in the study. Four patients were selected for having a lesion affecting parietal and/or premotor areas, two in the LH (MT and CD) and two in the RH (BR and CR). Note that all of them performed normally on two tests assessing Cortex, (2004) 40, 197-199 ABSTRACT EFFECTS OF STRATEGIES ON MENTALROTATION PERFORMED BY UNILATERALBRAIN DAMAGED PATIENTS Barbara Tomasino 1 , Lorenza Vorano 2 , Miran Skrap 3 , Gianluigi Gigli 4 and Raffaella I. Rumiati 1 ( 1 Programme in Neuroscience, Scuola Internazionale Superione di Studi Avanzati, Trieste, Italy; 2 Istituto Regionale di Medicina Fisica e Riabilitazione Gervasutta, Udine; Italy; 3 Azienda Ospedaliera S. Maria della Misericordia, Unità Operativa di Neurochirurgia, Udine, Italy; 4 Azienda Ospedaliera S. Maria della Misericordia, Unità Operativa di Neurologia, Udine, Italy) TABLE I Neuropsychological profile of RH– and LH– brain damaged patients Patient MT CD BR CR Sex M F F M Age 50 80 51 71 Education 13 8 13 5 Site of Lesion L P, FTP L TP R PM R P Intelligence WAIS 93 94 n.a. n.a. Language AAT aphasic aphasic – – Visual processing Test 1 20/20 19/20 20/20 20/20 (VOSP) Test 2 20/20 18/20 20/20 19/20 L-R discrimination 24/24 24/24 24/24 24/24 Praxis Imitation 45/72 45/72 72/72 69/72 Body Schema Pointing & normal normal normal normal imitation 1 Lesion sites: L = Left, R = Right, F = Frontal, T = Temporal, P = Parietal, PM = Premotor. 2 The figures in bold refer to scores below the cut-off.