Correlated Size Variations Measured in Human Visual Cortex V1/V2/V3 with Functional MRI - Brain Informatics - page 36

Correlated Size Variations Measured in Human Visual
Cortex V1/V2/V3 with Functional MRI
Tianyi Yan 1 , Fengzhe Jin 3 , and Jinglong Wu 1,2
1 Graduate School of Natural Science and Technology, Okayama University
3-1-1 Tsushima-naka, Okayama, Japan
2 International WIC Institute, Beijing University of
Technology, Beijing, China
[e-mail]
3 Design Department of Transportation Systems Works Transportation
Division Toyo Denki Seizo K.K., Japan
Abstract. The retinotopic characteristics on human peripheral vision are still
not well known. The position, surface area and visual field representation of
human visual areas V1, V2 and V3 were measured using fMRI in 8 subjects (16
hemispheres). Cortical visual field maps of the 120deg were measured using ro-
tating wedge and expanding ring stimuli. The boundaries between areas were
identified using an automated procedure to fit an atlas of the expected visual
field map to the data. All position and surface area measurements were made
along the boundary between white matter and gray matter. In this study, we de-
veloped a new visual presentation system widest view (60 deg of eccentricity).
The wide-view visual presentation system was made from nonmagnetic optical
fibers and a contact lens, so can use in general clinical fMRI condition and the
cost is lower. We used the newly wide view visual presentation system, the rep-
resentation of the visual field in areas V1, V2 and V3 spans about 2223
mm^2,1679 mm^2 and 1690 mm^2 .
1 Introduction
The number of neurons in human visual cortex far exceeds the number in many other
species that depend on vision. For example, the surface area of macaque monkey
visual cortex is probably no more than 20% that of human visual cortex, although the
cortical neuronal density is similar. This species difference in the number of cells in
visual cortex cannot be explained by how these species encode the visual world. The
monkey samples the retinal image at a higher resolution. There are 1.5 million optic
nerve fibers from each eye in macaque and only 1 million such fibers in humans [1].
The large size of human visual cortex is likely not a result of an increase in the supply
of information but, rather, due to an increase in visual processing and the organization
and delivery of information to other parts of cortex, such as those devoted to language
and reading. Given these differences in visual cortex size, it would not be surprising
that many features of human visual cortex are not present in closely related primate
systems [2].