Neglect 17 combination with their connections to frontal and"where"of things.Single-cell monkey physio- regions,these neurons integrate the visual fields logical studies also support such modulation. with the tactile fields of specific body parts and with Neurons in area V4 are sensitive to specific stimuli the actions of these body parts(Gross Graziano. located within their receptive fields (Moran 1995).The parietal and frontal interconnections are Desimone.1985).Their firing increases when the anatomically segregated along a ventral-to-dorsal animal attends to that location.This stronge axis(Petrides Pandya.1984).Neurons within the response to the stimulus for which the neuron VIP sulcus are respe sive to visual stimuli within already tuned.when the animal attends to it.sug 5cm of the monkey's face (Colby.Duhamel.& gests a physiological correlate of the enhanced pe Goldberg.1993).These neurons project to area F4 eption of obiects when attention is directed to the of area 6 in the pre otor that co ation of those objects. tributes to head and mouth m nts (Fogass et al..1996:Grazi 1994)and mediate the co of very y close Conelusions and Future Directions e Na. s in the MIP sul reaching distance Grazi Convergence There is a remarkable convergence of some ideas across different disciplines with highly varied tradi- Gentilucci et al1988) and ar tions and methods.Four related ideas about spatial 994 attention and representation recur and are summa- Thi rized here. ections to as Distributed Networks arm-centere s(G et a Thes ved in the decisio Neural networks involving different and noncon- processes by whic h different kinds of movements tiguous parts of the brain mediate spatial attention are selected(Merchant,Zainos,Hernandez,Salinas. Rather than being localized to a single brain loca &Romo,1997) tion.spatial attention is mediated by the parietal and Neuron within the monkey LIP sulcu frontal and probably cingulate cortices,as well as (Duhamel,Colby,&Goldberg.1992)may be con- the basal ganglia,thalamus,and superior colliculus. nected to saccadic mechanisms of the frontal eye fields and the superior colliculus.Neurons in the Multiple Representations of Space superior colliculus are responsive to behaviorally The brain constructs multiple representations of relevant stimuli when linked to saccadic eve move space.de ments (Wurtz Goldberg.1972:Wurtz Munoz. intuitions of space as a homoge- um tha 1995).These networks probably link sensations to round tions eye movements and construct distant extrapersonal involve the body and different kinds of extrapersonal space space can be space. viewed as concentric shells around the body.close Space-Based and Object-Based Attention to the trunk,within reach of our limbs,or further away in more distant space.Extrapersonal space car Neuroimaging studies in humans have shown tha also be partitioned into retinotopic,head-centered ntion can influence and trunk-centered coordinates that all have the viewer as the primary referent.Viewer-independent ence is presumably involved in binding the "what reference frames are anchored to the spatial axescombination with their connections to frontal regions, these neurons integrate the visual fields with the tactile fields of specific body parts and with the actions of these body parts (Gross & Graziano, 1995). The parietal and frontal interconnections are anatomically segregated along a ventral-to-dorsal axis (Petrides & Pandya, 1984). Neurons within the VIP sulcus are responsive to visual stimuli within 5cm of the monkey’s face (Colby, Duhamel, & Goldberg, 1993). These neurons project to area F4 of area 6 in the premotor cortex, an area that con￾tributes to head and mouth movements (Fogassi et al., 1996; Graziano, Yap, & Gross, 1994) and may mediate the construction of very close peripersonal space. Neurons in the MIP sulcus are responsive to visual stimuli within reaching distance (Graziano & Gross, 1995). These neurons project to ventral premotor cortices that mediate visually guided arm movements (Caminiti, Ferraina, & Johnson, 1996; Gentilucci et al., 1988) and are sensitive to stimuli in arm-centered rather than retinotopic coordinates (Graziano et al., 1994). This area has direct con￾nections to the putamen, which also has such arm-centered neurons (Graziano et al., 1994). These putamenal neurons may be involved in the decision processes by which different kinds of movements are selected (Merchant, Zainos, Hernandez, Salinas, & Romo, 1997). Neurons within the monkey LIP sulcus (Duhamel, Colby, & Goldberg, 1992) may be con￾nected to saccadic mechanisms of the frontal eye fields and the superior colliculus. Neurons in the superior colliculus are responsive to behaviorally relevant stimuli when linked to saccadic eye move￾ments (Wurtz & Goldberg, 1972; Wurtz & Munoz, 1995). These networks probably link sensations to eye movements and construct distant extrapersonal space. Space-Based and Object-Based Attention Neuroimaging studies in humans have shown that visual or spatial attention can influence the pro￾cessing of objects in the ventral stream. This influ￾ence is presumably involved in binding the “what” and “where” of things. Single-cell monkey physio￾logical studies also support such modulation. Neurons in area V4 are sensitive to specific stimuli located within their receptive fields (Moran & Desimone, 1985). Their firing increases when the animal attends to that location. This stronger response to the stimulus for which the neuron is already tuned, when the animal attends to it, sug￾gests a physiological correlate of the enhanced per￾ception of objects when attention is directed to the location of those objects. Conclusions and Future Directions Convergence There is a remarkable convergence of some ideas across different disciplines with highly varied tradi￾tions and methods. Four related ideas about spatial attention and representation recur and are summa￾rized here. Distributed Networks Neural networks involving different and noncon￾tiguous parts of the brain mediate spatial attention. Rather than being localized to a single brain loca￾tion, spatial attention is mediated by the parietal and frontal and probably cingulate cortices, as well as the basal ganglia, thalamus, and superior colliculus. Multiple Representations of Space The brain constructs multiple representations of space, despite our intuitions of space as a homoge￾neous medium that surrounds us. These representa￾tions involve the body and different kinds of extrapersonal space. Extrapersonal space can be viewed as concentric shells around the body, closer to the trunk, within reach of our limbs, or further away in more distant space. Extrapersonal space can also be partitioned into retinotopic, head-centered, and trunk-centered coordinates that all have the viewer as the primary referent. Viewer-independent reference frames are anchored to the spatial axes Neglect 17