Rbh. Tootell et al., THE REPRESENTATION OF THE IPSILATERAL VISUAL-FIELD IN HUMAN CEREBRAL-CORTEX, Proceedings of the National Academy of Sciences of the United Statesof America, 95(3), 1998, pp. 818-824
Previous studies of cortical retinotopy focused on influences from the
contralateral visual field, because ascending inputs to cortex are kn
own to be crossed, Here, functional magnetic resonance imaging was use
d to demonstrate and analyze an ipsilateral representation in human vi
sual cortex, Moving stimuli, in a range of ipsilateral visual field lo
cations, revealed activity: (i) along the vertical meridian in retinot
opic (presumably lower-tier) areas; and (ii) in two large branches ant
erior to that, in presumptive higher-tier areas, One branch shares the
anterior vertical meridian representation in human V3A, extending sup
eriorly toward parietal cortex, The second branch runs antero-posterio
rly along lateral visual cortex, overlying motion-selective area MT, I
psilateral stimuli sparing the region around the vertical meridian rep
resentation also produced signal reductions (perhaps reflecting neural
inhibition) in areas showing contralaterally driven retinotopy, Syste
matic sampling across a range of ipsilateral visual field extents reve
aled significant increases in ipsilateral activation in V3A and V4v, c
ompared with immediately posterior areas V3 and VP, Finally, compariso
ns between ipsilateral stimuli of different types but equal retinotopi
c extent showed clear stimulus specificity, consistent with earlier su
ggestions of a functional segregation of motion vs, form processing in
parietal vs, temporal cortex, respectively.