Measuring the attentional field throughout human visual cortex
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1
University of Wollongong, School of Psychology, Australia
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2
Medical College of Wisconsin, Department of Biophysics, United States
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3
Medical College of Wisconsin, Department of Radiology, United States
Background: The spatial topography of the attentional field (AF) is a critical feature of many models of visual attention. Previous fMRI studies of AF topography have been limited by the coarseness of the voxel sampling matrix and the presence of local susceptibility artifacts, issues that are exaggerated in higher-order areas due to their smaller surface area. Using a new technique we circumvent these issues and show that AF topography can be estimated from single voxel time-course data.
Methods: While fixating a center marker, subjects were cued to covertly attend to a target within a dartboard-like array of stimulus segments that slowly rotated about fixation. In attention runs, subjects continuously tracked a single target within the array. In sensory runs, the previously attended target was presented in isolation while subjects performed an attention task at fixation. In the attention condition, voxels with population receptive fields (pRFs) positioned along the trajectory of the target were differentially activated when the focus of attention passed over their pRF. These voxels were also activated in the sensory condition when the isolated stimulus segment passed over the pRF. Thus, the duration of fMRI activation was proportional to either (1) the width of the attentional focus or (2) the width of the stimulus segment. The empirical time-course data were fit using a model composed of the stimulus sequence, the AF, the voxel's estimated pRF, and a temporal hemodynamic response function. The resulting model parameters were used to estimate the AF topography.
Results: Responses were identified and modeled for both conditions in visual areas V1, V2, V3, V4, VO-1,2, V3AB, IPS-0,1,2,3, LO-1,2, and TO-1,2. We found that the AF scales with eccentricity and visual area. We also found that voxels in multiple visual areas exhibited attention signals that indicate a marked suppressive surround distinct from the response profile observed when measuring the sensory pRFs.
Discussion: This study demonstrates an fMRI-based technique to estimate the spatial topography of the AF from neurophysiological correlates measured throughout much of visual cortex. Recent models of visual attention indicate that the size of the AF relative to a visual stimulus and sensory pRF are central factors in determining the behavioral effects of attention. The method described here permits empirical measurement of the AF thereby providing key information for models of attention.
Acknowledgements
This research was supported by National Institute of Health Grants R01EB000843 to E. DeYoe and R01EB007827 to J. Hyde. We thank Jedidiah Mathis and Yan Ma for technical contributions and Andy Salzwedel for helpful discussions.
Keywords:
visual attention,
visual areas,
attentional field,
fMRI,
time-course analysis,
voxel based analysis
Conference:
ACNS-2013 Australasian Cognitive Neuroscience Society Conference, Clayton, Melbourne, Australia, 28 Nov - 1 Dec, 2013.
Presentation Type:
Oral
Topic:
Attention
Citation:
Puckett
AM and
DeYoe
EA
(2013). Measuring the attentional field throughout human visual cortex.
Conference Abstract:
ACNS-2013 Australasian Cognitive Neuroscience Society Conference.
doi: 10.3389/conf.fnhum.2013.212.00135
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Received:
15 Oct 2013;
Published Online:
25 Nov 2013.
*
Correspondence:
Dr. Alexander M Puckett, University of Wollongong, School of Psychology, Wollongong, NSW, Australia, pucketta@alumni.msoe.edu