Journal
JOURNAL OF NEUROPHYSIOLOGY
Volume 105, Issue 5, Pages 2121-2131Publisher
AMER PHYSIOLOGICAL SOC
DOI: 10.1152/jn.01007.2010
Keywords
functional magnetic resonance imaging; second-order vision; adaptation; surround suppression
Categories
Funding
- National Eye Institute [EY-016165]
Ask authors/readers for more resources
Hallum LE, Landy MS, Heeger DJ. Human primary visual cortex (V1) is selective for second-order spatial frequency. J Neurophysiol 105: 2121-2131, 2011. First published February 23, 2011; doi:10.1152/jn.01007.2010.-A variety of cues can differentiate objects from their surrounds. These include first-order cues such as luminance modulations and second-order cues involving modulations of orientation and contrast. Human sensitivity to first-order modulations is well described by a computational model involving spatially localized filters that are selective for orientation and spatial frequency (SF). It is widely held that first-order modulations are represented by the firing rates of simple and complex cells (first-order neurons) in primary visual cortex (V1) that, likewise, have spatially localized receptive fields that are selective for orientation- and SF. Human sensitivity to second-order modulations is well described by a filter-rectify-filter (FRF) model, with first-and second-order filters selective for orientation and SF. However, little is known about how neuronal activity in visual cortex represents second-order modulations. We tested the FRF model by using an functional (f)MRI-adaptation protocol to characterize the selectivity of activity in visual cortex to second-order, orientation-defined gratings of two different SFs. fMRI responses throughout early visual cortex exhibited selective adaptation to these stimuli. The low-SF grating was a more effective adapter than the high-SF grating, incompatible with the FRF model. To explain the results, we extended the FRF model by incorporating normalization, yielding a filter-rectify-normalize-filter model, in which normalization enhances selectivity for second-order SF but only for low spatial frequencies. We conclude that neurons in human visual cortex are selective for second-order SF, that normalization (surround suppression) contributes to this selectivity, and that the selectivity in higher visual areas is simply fed forward from V1.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available