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Maryam Vaziri Pashkam, Yaoda Xu; Spatial frequency tolerant object representations in the ventral and dorsal visual processing pathways. Journal of Vision 2017;17(10):288. doi: 10.1167/17.10.288.
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© ARVO (1962-2015); The Authors (2016-present)
Object category representations have been found in both human ventral and dorsal visual processing regions. Given the differences in anatomical connections to parvo- and magno-cellular layers in LGN, the two pathways may exhibit differential sensitivity to spatial frequency. To test this idea, in this study, observers viewed blocks of images from six natural object categories and performed a one-back repetition detection task on the images. Images were shown in full spectrum, high spatial frequencies (>7 cpd), or low spatial frequencies (< 1 cpd). Using fMRI and MVPA, we examined how object category decoding would be modulated by the spatial frequency content of the images. We examined responses from topographic regions V1-V4 and IPS0-2, the object shape selective lateral occipital cortex (LO), a temporal region activated by our object stimuli, as well as superior and inferior IPS (two parietal regions previously implicated in object processing). We obtained above chance category decoding for the intact, high and low frequency images in all the regions examined. Importantly, the decoding accuracy was no different between the high and low frequency images in all the regions examined except for V4 and IPS2 where decoding was higher for the high frequency images. We also trained the classifier with high and tested it with low frequency images or vice versa and found that all regions showed robust generalization across spatial frequency. A representational similarity analysis further showed that object category representations were separated based on spatial frequency in early visual but not in dorsal and higher ventral regions. These results demonstrate that object category representations in both ventral and dorsal regions are tolerant to changes in spatial frequency and argue against a dissociation of the two pathways based on spatial frequency sensitivity.
Meeting abstract presented at VSS 2017
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