TY - JOUR
T1 - Right hemisphere control of visuospatial attention
T2 - Line-bisection judgments evaluated with high-density electrical mapping and source analysis
AU - Foxe, John J.
AU - McCourt, Mark E.
AU - Javitt, Daniel C.
N1 - Funding Information:
We express our sincere appreciation to Deirdre Foxe, Beth Higgins, and Dr. Micah Murray for their technical help with this study. We are most grateful to Dr. Gereon Fink and his colleagues for generously allowing us to reproduce their fMRI data in the current report. Dr. Antigona Martinez provided valuable comments on an earlier version of the manuscript for which we are indebted to her. Our thanks also go to two anonymous reviewers for their careful and constructive comments. This work was supported in part by grants from the National Institute of Mental Health (MH63434 to J.J.F.; MH49334 to D.C.J.), the National Eye Institute (EY12267 to M.E.M.), North Dakota EPSCoR (M.E.M.), the Neuropsychiatric Research Institute, Fargo, ND (M.E.M.), and the North Dakota State University Development Foundation (M.E.M.), and by generous support from the Burroughs Wellcome Fund.
PY - 2003/7/1
Y1 - 2003/7/1
N2 - The "line-bisection" task has proven an especially useful clinical tool for assessment of spatial neglect syndrome in neurological patients. Here, we investigated the neural processes involved in performing this task by recording high-density event-related potentials from 128 scalp electrodes in normal observers. We characterized a robust net negative potential from 170-400 ms poststimulus presentation that correlates with line-bisection judgments. Topographic mapping shows three distinct phases to this negativity. The first phase (∼170-190 ms) has a scalp distribution exclusively over the right parieto-occipital and lateral occipital scalp, consistent with generators in the region of the right temporo-parietal junction and right lateral occipital cortices. The second phase (∼190-240 ms) sees the emergence of a second negative focus over the right central parietal scalp, consistent with subsequent involvement of right superior parietal cortices. In the third phase (∼240-400 ms), the topography becomes dominated by this right central parietal negativity. Inverse source modeling confirmed that right hemisphere lateral occipital, inferior parietal, and superior parietal regions were the likeliest generators of the bulk of the activity associated with this effect. The line stimuli were also presented at three contrast levels (3, 25, and 100%) in order to manipulate both the latency of stimulus processing and the relative contributions from magnocellular and parvocellular inputs. Through this manipulation, we show that the line-bisection effect systematically tracks/follows the latency of the N1 component, which is considered a temporal marker for object processing in the ventral visual stream. This pattern of effects suggests that this task invokes an allocentric (object-based) form of visuospatial attention. Further, at 3% contrast, the line-bisection effect was equivalent to the effects seen at higher contrast levels, suggesting that parvocellular inputs are not necessary for successful performance of this task.
AB - The "line-bisection" task has proven an especially useful clinical tool for assessment of spatial neglect syndrome in neurological patients. Here, we investigated the neural processes involved in performing this task by recording high-density event-related potentials from 128 scalp electrodes in normal observers. We characterized a robust net negative potential from 170-400 ms poststimulus presentation that correlates with line-bisection judgments. Topographic mapping shows three distinct phases to this negativity. The first phase (∼170-190 ms) has a scalp distribution exclusively over the right parieto-occipital and lateral occipital scalp, consistent with generators in the region of the right temporo-parietal junction and right lateral occipital cortices. The second phase (∼190-240 ms) sees the emergence of a second negative focus over the right central parietal scalp, consistent with subsequent involvement of right superior parietal cortices. In the third phase (∼240-400 ms), the topography becomes dominated by this right central parietal negativity. Inverse source modeling confirmed that right hemisphere lateral occipital, inferior parietal, and superior parietal regions were the likeliest generators of the bulk of the activity associated with this effect. The line stimuli were also presented at three contrast levels (3, 25, and 100%) in order to manipulate both the latency of stimulus processing and the relative contributions from magnocellular and parvocellular inputs. Through this manipulation, we show that the line-bisection effect systematically tracks/follows the latency of the N1 component, which is considered a temporal marker for object processing in the ventral visual stream. This pattern of effects suggests that this task invokes an allocentric (object-based) form of visuospatial attention. Further, at 3% contrast, the line-bisection effect was equivalent to the effects seen at higher contrast levels, suggesting that parvocellular inputs are not necessary for successful performance of this task.
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U2 - 10.1016/S1053-8119(03)00057-0
DO - 10.1016/S1053-8119(03)00057-0
M3 - Article
C2 - 12880801
AN - SCOPUS:0042671305
SN - 1053-8119
VL - 19
SP - 710
EP - 726
JO - NeuroImage
JF - NeuroImage
IS - 3
ER -