Anian chatteriee 18 space when asked to indicate the environm nental envi midline (Chokron Bartolom eo 1998).What has to left-sided Attention and Intention directed co ally to pro oduce this Attention and intention are tightly linked.The par adoxical behavior? extent to which perception and actions are coordi- nated in the formation and sustenance of spatial rep- Memory,Attention,and Representation resentations is remarkable.The actions themselves How does memory interact with attention to affect whether they are eye movements,head movements. online processing of stimuli in neglect?Functional or limb movements in space,are also related to imaging studies and neuronhysiological studies notions of different kinds of reference frames. suggest that there is considerable overlan betweer circuits dedicated to spatial attention and spatial Attention and Perception working memory.Monkey lesion studies indicate Attention and perception may not be as distinct an important role for spatial memories in online as is often thought.Processing of relatively early processing (Gaffan Hornak.1997).We rec stages of perception seems to be modulated by reported that memory traces of contralesional attention,although the precise boundaries between stimuli might have a disproportionate influence the two remain to be worked out. on online representations in patients with neglec (Chatteriee et al 2000)A ptual fram Unresolved Issues that tial m d a Despite this convergence of ideas,I would like to Frontal and Parietal Differences mention some issues that in my view warrant further consideration.Some questions involve research in How different are the roles of the frontal and pari- neglect directly and others involve the relationship etal cortices in spatial attention?The notion that of findings in neglect and other approaches. parietal neglect is attentional and frontal neglect is intentional has great appeal.Unfortunately,the Contralesional Hyperorientation in Negleet empirical evidence for such a clear dichotomy is mixed at best It is not even clear that these hyperorient"into contral sional space,rathe distinctions make conceptual sense.since what neglect cor tralesional space?We are used to think has been called "attentional neglect"involves eye ing of neglect as the tend ncy to oner movements and what has been called"intentional act in ipsilesional space.However,in some cases neglect"involves limb movements.Single-cell neu patients seem to be drawn contralesionally.The physiological studies suggest that ne ons withir most robust of these contralesional productive both parietal and frontal cortices mediate spatial behaviors is the crossover phenomenon,in which actions.It may be the case that the actions are mor patients bisect short lines (usually less than 4cm) ated in the tal c rtex than in the it is not to the left of the midline.However.there are other clear that on n he ral dis dramatic instances of contralesional hyperorienta tion (Chatteriee.1998).Some patients bisect lons lesion the t tal and pa ortices.Perhap and lim y be lines in contralesional space (Adair,Chatterjee ded within th Schwartz.Heilman.1998a:Kwon Heilman 1991).Some patients will point into contralesional and o of ne d h agues rsen 10 of the object itself or to axes intrinsic to the environment. Attention and Intention Attention and intention are tightly linked. The extent to which perception and actions are coordi￾nated in the formation and sustenance of spatial rep￾resentations is remarkable. The actions themselves, whether they are eye movements, head movements, or limb movements in space, are also related to notions of different kinds of reference frames. Attention and Perception Attention and perception may not be as distinct as is often thought. Processing of relatively early stages of perception seems to be modulated by attention, although the precise boundaries between the two remain to be worked out. Unresolved Issues Despite this convergence of ideas, I would like to mention some issues that in my view warrant further consideration. Some questions involve research in neglect directly and others involve the relationship of findings in neglect and other approaches. Contralesional Hyperorientation in Neglect Why do patients with right brain damage sometimes “hyperorient” into contralesional space, rather than neglect contralesional space? We are used to think￾ing of neglect as the tendency to orient toward or act in ipsilesional space. However, in some cases patients seem to be drawn contralesionally. The most robust of these contralesional productive behaviors is the crossover phenomenon, in which patients bisect short lines (usually less than 4cm) to the left of the midline. However, there are other dramatic instances of contralesional hyperorienta￾tion (Chatterjee, 1998). Some patients bisect long lines in contralesional space (Adair, Chatterjee, Schwartz, & Heilman, 1998a; Kwon & Heilman, 1991). Some patients will point into contralesional space when asked to indicate the environmental midline (Chokron & Bartolomeo, 1998). What has happened to left-sided representations or to motor systems directed contralesionally to produce this paradoxical behavior? Memory, Attention, and Representation How does memory interact with attention to affect online processing of stimuli in neglect? Functional imaging studies and neurophysiological studies suggest that there is considerable overlap between circuits dedicated to spatial attention and spatial working memory. Monkey lesion studies indicate an important role for spatial memories in online processing (Gaffan & Hornak, 1997). We recently reported that memory traces of contralesional stimuli might have a disproportionate influence on online representations in patients with neglect (Chatterjee et al., 2000). A conceptual framework that relates spatial memory and attention in influ￾encing online perception remains to be articulated. Frontal and Parietal Differences How different are the roles of the frontal and pari￾etal cortices in spatial attention? The notion that parietal neglect is attentional and frontal neglect is intentional has great appeal. Unfortunately, the empirical evidence for such a clear dichotomy is mixed at best. It is not even clear that these distinctions make conceptual sense, since what has been called “attentional neglect” involves eye movements and what has been called “intentional neglect” involves limb movements. Single-cell neu￾rophysiological studies suggest that neurons within both parietal and frontal cortices mediate spatial actions. It may be the case that the actions are more clearly segregated in the frontal cortex than in the parietal cortex. However, it is not clear that one should expect clean behavioral dissociations from lesions to the frontal and parietal cortices. Perhaps eye and limb movements may be coded within the same array of neurons, as suggested by Andersen and colleagues (Andersen, 1995a) and Pouget and Anjan Chatterjee 18