INTRODUCTION Extinction is a neurological disorder particularly frequent after cortical and subcortical right sided brain lesions (Barbieri and De Renzi, 1989; Vallar et al., 1994). First described by Anton (1899), the phenomenon of extinction implies that patients detect accurately a single contralesional stimulus but fail to detect it when presented simultaneously with a similar ipsilesional stimulus. Although a contralesional sensory impairment may co-occur, it is widely agreed that extinction reflects a higher- order deficit of spatial selective attention rather than a simple sensory deficit. Neglect and extinction disorders have been classically interpreted as the consequence of a spatial attention deficit. However, recent studies suggest the presence of temporal deficits in patients with neglect and extinction. Temporal processing deficit seems to occur independently of spatial processing impairment. These results suggest that purely spatial theories of neglect and extinction are no longer sufficient to interpret the deficits. Several recent neuropsychological evidence suggest that disorders of spatial attention like extinction and neglect also involve deficits of spatio-temporal processing (Rorden et al., 1997; di Pellegrino et al., 1997, 1998; Husain et al., 1997; Karnath et al., 2002; Cate and Behrmann, 2002; Guerrini et al., 2003). Spatio- temporal interactions had been studied in patients with left-sided visual (di Pellegrino et al., 1997; Baylis et al., 2002) and tactile extinction (Guerrini et al., 2003). In all experiments single stimuli were presented to the left or to the right hemifield while double stimuli were presented bilaterally, simultaneously or sequentially at different Stimulus Onset Asynchronies (SOAs). In all experiments, extinction was maximal when double stimuli occurred simultaneously. Performance for the contralateral stimuli improved with longer SOAs. These results not only show that a stimulus presented in the ipsilesional field interferes with the processing of a stimulus presented contralesionally, but also that the interference is independent from the sequence of the stimuli presentation. Finally, the interference is maximal at SOA 0 msec and decreases with SOA increasing. In the last few years, several studies focused on purely temporal aspects of attention mechanisms in healthy subjects as well as in patients with neglect and extinction (di Pellegrino et al., 1997, 1998; Duncan et al., 1994; Husain et al., 1997; Coull and Nobre 1998; Miniussi et al., 1999; Coull et al., 2000; Nobre, 2001; Griffin et al., 2002; Guerrini et al., 2003). There is converging evidence to indicate that competition among stimuli may depend merely on the timing of their respective occurrences and be at least partly independent from spatial variables. The classical paradigm employed to study temporal attentional mechanisms independently from spatial processing demands is the Rapid Serial Visual Cortex, (2006) 42, 17-27 RESEARCH REPORT TEMPORAL AND SPATIO-TEMPORAL ATTENTION TO TACTILE STIMULI IN EXTINCTION PATIENTS Chiara Guerrini 1 and Salvatore M. Aglioti 2 ( 1 Clinical Neuroscience Centre and Department of Psychology, University of Hull, Hull UK; 2 Department of Psychology, University “La Sapienza” and Centre of Neuropsychology Research, IRCCS, Foundation S.ta Lucia, Rome, Italy) ABSTRACT The temporal deployment of attention to tactile stimuli delivered to the same or to a symmetrical position of the body was assessed in 6 Right-Brain Damaged (RBD) patients with left tactile extinction and 6 healthy controls. Two different tasks called Temporal (T) and Spatio-Temporal (ST) extinction were used. In the T task single or double electro tactile stimuli were delivered to the same point to the left or, in separate blocks, to the right index finger. Double stimuli were separated by different Stimulus Onset Asynchronies (SOAs). In the ST task, stimuli could be single (left or right) or double (left and right). Double stimuli were delivered to the index finger of both hands simultaneously or sequentially. In both tasks subjects were asked to report the number of the stimuli they perceived. In the ST task, subjects were also requested to report the stimuli location. Results show that in both tasks RBD patients’ detection of left sided stimuli was significantly lower than of right sided stimuli detection, mainly at shortest SOAs. Moreover, detection of left sided stimuli was higher when two stimuli were delivered in sequence and in symmetrical body areas and in different sides of the space than when stimuli were delivered in sequence in the same body area. Results suggest that the interaction between spatial and temporal variables enhances the ability of tactile extinction patients to detect left sided stimuli. Key words: human, tactile, extinction, spatial attention, temporal attention