Central versus peripheral retinotopic and temporal frequency sensitivities of human visual areas measured using fMRI

Using functional magnetic resonance imaging (fMRI) we have researched the variation in response magnitude, in each visual areas (V1-V3), as a function of visual retintotopic areas (V1-V3) and temporal frequency (TF). Each visual area was identified in each subject using a combination of retinotopic mapping fMRI and cortical flattening techniques. A checkerboard was used as the stimulus in the study in which we TF was 2, 4, 8, 16Hz. It was hypothesized the peripheral stimulation would lead to faster onset latencies, as well as preferentially activae doral stream visual areas relative to central field stimulation. For the experiment we constructed fMRI amplitude tuning curves, averaged across subjects, for each visual area. The tuning curves that resulted are consistent with the known physiological properties of cells in the corresponding macaque visual areas, previous functional imaging studies, and in the case of VI, the psychophysically determined contrast sensitivity functions for temporal frequency. And retinotopic mapping is a key property of organization of human occipital cortex. The retinotopic organization of the central visual field of visual areas V1/V2/V3 has been well estimated. We also used functional magnetic resonance Imaging (fMRI) to measure the retinotopic mapping of the peripheral visual field (eccentricity up to 60deg). We estimate the locations of the visual areas in 0∼60deg and the result is coincident with the anatomical studies. Visual areas VI, V2, V3 showed more direction sensitivity at low temporal frequencies in the central visual area, while there was the same signal change in the peripheral visual areas.