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Thomas J. McKeeff, David A. Remus, Frank Tong; Decreased temporal processing capacity for objects as a function of ascending the ventral visual pathway. Journal of Vision 2004;4(8):514. doi: 10.1167/4.8.514.
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© ARVO (1962-2015); The Authors (2016-present)
Humans exhibit limited capacities for object recognition when required to process large amounts of visual information in a short period of time. Behavioral studies have shown that object recognition for serially presented stimuli is impaired as temporal presentation rates approach 8–10 items per second. One possible explanation for these processing limitations is that higher visual areas, important for object recognition, are limited in temporal processing capacity because of the need to integrate information from earlier areas. Here, we used fMRI to investigate the temporal processing capacities of visual areas along the ventral pathway: V1 through V4, the Fusiform Face Area (FFA) and the Parahippocampal Place Area (PPA). Subjects viewed serial sequences of faces or houses at rates of 2.3, 4.7, 9.4, 18.8, or 37.5 items per second. Subjects were required to discriminate which of two target images appeared in the presentation stream while maintaining central fixation throughout the task. Each subject also performed separate retinotopy scans as well as FFA and PPA localizers, allowing for independent delineation of visual areas. Peaks in the temporal frequency tuning function were calculated for each visual area. As the visual pathway was ascended, there was a significant decrease in peak temporal frequency tuning with V1 and V2 peaking at approximately 16 items/sec, VP and V4 at 8 items/sec, and FFA and PPA at 4 items/sec. The response properties of the FFA and PPA appeared to match behavioral performance, with decrements in object recognition emerging as presentation rates exceeded 4.7 items/sec. Overall, these data suggest that limitations in rapid object recognition may result from the processing limitations of higher visual areas rather than early or intermediate visual areas.
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