fMRI of human visual cortex

Engel, Stephen A.; Rumelhart, David E.; Wandell, Brian A.; Lee, Adrian T.; Glover, Gary H.; Chichilnisky, E. J.; Shadlen, Michael N.

doi:10.1038/369525a0

Cited by 940 publications

(790 citation statements)

References 7 publications

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“…The left column in the figure illustrates the high-resolution data that can be obtained in monkeys with invasive techniques; the right column illustrates the quality of data that can be obtained in the human cortex with non-invasive imaging. Large-scale maps of the visual field (or 'retinotopic maps'), which were first described physiologically in the primary visual cortex in macaques 127,128 , were obtained in humans with fMRI more than a decade ago 129,130 (see figure, part a). At a finer scale, physiological studies carried out long ago determined that cortical area V1 in non-human primates contains oculardominance columns, which are elongated regions approximately 0.5 mm wide in which neurons receive input that is dominated by one eye 131,132 (see figure, part b, left-hand panel).…”

Section: Box 1 | Recent Advances Through Functional Mrimentioning

confidence: 99%

Interpreting fMRI data: maps, modules and dimensions

2008

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Neuroimaging research over the past decade has revealed a detailed picture of the functional organization of the human brain. Here we focus on two fundamental questions that are raised by the detailed mapping of sensory and cognitive functions and illustrate these questions with findings from the object-vision pathway. First, are functionally specific regions that are located close together best understood as distinct cortical modules or as parts of a larger-scale cortical map? Second, what functional properties define each cortical map or module? We propose a model in which overlapping continuous maps of simple features give rise to discrete modules that are selective for complex stimuli.Advances in brain imaging technology (especially functional MRI (fMRI)) have radically improved our understanding of the functional organization of the human brain (BOX 1). In this Review we describe the organization of the ventral visual pathway, which is characterized by strong selectivity for particular object categories (for example, faces and bodies) at the level of both individual neurons and larger cortical regions. We then consider two central questions: whether this organization reflects maps or modules, and what properties are mapped. In each case we derive clues from the literature on the primary sensory cortex, in which cortical maps have been studied extensively using electrophysiology in animals. We find that apparently modular cortical regions, such as orientation columns and face-selective regions, might be parts of larger maps, and show that it is a substantial challenge to determine the basic properties and dimensions that describe functional organization most parsimoniously. We then propose a new framework that reconciles the existence of graded cortical maps and distinct functional modules. In this framework, the strong category selectivity that exists for faces and other objects might arise from the nonlinear combination of multiple correlated maps for simpler stimulus properties. The ventral visual pathwayThe ventral visual pathway comprises a large cortical region that occupies the ventral and lateral surfaces of the occipital and temporal lobes (FIG. 1). A substantial proportion of fMRI voxels in this pathway are 'object-selective' -that is, they respond more strongly when people view images of objects than when people view scrambled versions of these objects or texture patterns. This object-selective region is often referred to as the lateral occipital complex (LOC) 1 . The LOC has little selectivity for particular stimulus categories 2-4 , but several regions of NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript cortex near the LOC are selective for particular object categories: they respond at least twice as strongly to their 'preferred' stimuli than to other stimuli. For example, in essentially all humans cortical regions can be found that respond selectively to faces (the fusiform face area (FFA) 5,6 and, in many individuals, the occipital face area (OFA)) 7,8 , to pl...

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Section: Box 1 | Recent Advances Through Functional Mrimentioning

confidence: 99%

Interpreting fMRI data: maps, modules and dimensions

2008

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“…Standard stimuli were used to create polar-angle and eccentricity maps of the visual cortex (Engel et al, 1994;Sereno et al, 1995;DeYoe et al, 1996;Engel et al, 1997). Rotating wedge and expanding annulus sections of a radial dynamic checkerboard were used for the phase-encoded retinotopic mapping (Figs.…”

Section: Visual Stimulimentioning

confidence: 99%

“…This method was made possible by the finding that time delays (or phase lags) of the cortical activity elicited by slowly expanding circular patterns depend on visual field location (Engel et al, 1994). Sereno et al (1995) were the first to map visual areas using this phase-encoded method and both expanding rings and rotating wedge stimuli.…”

Section: Introductionmentioning

confidence: 99%

Automatic volumetric segmentation of human visual retinotopic cortex

et al. 2003

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Previous identification of early visual cortical areas in humans with phase-encoded retinotopic mapping techniques have relied on an accurate cortical surface reconstruction. Here a 3D phase-encoded retinotopic mapping technique that does not require a reconstruction of the cortical surface is demonstrated. The visual field sign identification is completely automatic and the method directly supplies volumes for a region-of-interest analysis, facilitating the application of cortical mapping to a wider population. A validation of the method is provided by simulations and comparison to cortical surface-based methodology.

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“…Stimuli for retinotopic mapping of eccentricity [Engel et al, 1994;Hadjikhani et al, 1998;Sereno et al, 1995) were slowly expanding thin rings made of flickering arcs with random color distribution generated using a Silicon Graphics O 2 workstation with GL graphics library functions. The thin rings were segmented in 20 randomly colored sectors alternating at 4 Hz flickering frequency.…”

Section: Retinotopic Mappingmentioning

confidence: 99%

Influence of EEG electrodes on the BOLD fMRI signal

Bonmassar¹,

Hadjikhani²,

Ives³

et al. 2001

Human Brain Mapping

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Measurement of the EEG during fMRI scanning can give rise to image distortions due to magnetic susceptibility, eddy currents or chemical shift artifacts caused by certain types of EEG electrodes, cream, leads, or amplifiers. Two different creams were tested using MRS and T2* measurements, and we found that the one with higher water content was superior. This study introduces an index that quantifies the influence of EEG equipment on the BOLD fMRI signal. This index can also be used more generally to measure the changes in the fMRI signal due to the presence of any type of device inside (or outside) of the field of view (e.g., with fMRI and diffuse optical tomography, infrared imaging, transcranial magnetic stimulation, ultrasound imaging, etc.). Quantitative noise measurements are hampered by the normal variability of functional activation within the same subject and by the different slice profiles obtained when inserting a subject multiple times inside a MR imaging system. Our measurements account for these problems by using a matched filtering of cortical surface maps of functional activations. The results demonstrate that the BOLD signal is not influenced by the presence of EEG electrodes when using a properly constructed MRI compatible recording cap.

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fMRI of human visual cortex

Cited by 940 publications

References 7 publications

Interpreting fMRI data: maps, modules and dimensions

Interpreting fMRI data: maps, modules and dimensions

Automatic volumetric segmentation of human visual retinotopic cortex

Influence of EEG electrodes on the BOLD fMRI signal

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