Representation of the Visual Field in the Human Occipital Cortex

Abstract

To evaluate the retinotopic map of the human occipital cortex by correlating magnetic resonance imaging (MRI) findings with visual field defects in patients with occipital lobe infarcts and to assess the compatibility between our cliniconeuroimaging findings and the location of lesions predicted by the classic Holmes map and a revised map. Methods: Magnetic resonance images were obtained in 14 patients with occipital lobe infarcts. Visual field analysis was performed with tangent screen, the Goldmann perimeter, and the Humphrey Field Analyzer. Based on the pattern of visual field deficit, the location of the lesion in the mesial occipital lobe in each patient was predicted using the Holmes map and other retinotopic maps of the occipital cortex. The predicted location of the lesion was then compared with its actual location shown on MRI to assess the compatibility between our data and the other maps. These maps determine retinotopic correlates of the medial occipital lobe, but they cannot establish correlates of the striate cortex (V1). The medial occipital representation of central vision was evaluated by regression analysis. Results: The MRI correlations in this study confirmed gross estimates of the retinotopic organization of the occipital cortex. However, our findings did not correlate exactly with the Holmes map. We determined that the central 15 o of vision occupies 37% of the total surface area of the human medial occipital lobe. Based on our data, a refined retinotopic map is presented. Conclusions: The resolution of conventional MRI testifies to its considerable value in localizing occipital lobe lesions. Our findings support, and refine, the Holmes map of the human occipital cortex.

Clinical Study of the Visual Field Defects Caused by Occipital Lobe Lesions

“…However, recent studies pointed out an expansion of the area corresponding to central vision in the posterior part of the striate cortex [3,4,5,6]. Horton and Hoyt [5] indicated the underestimation of the cortical magnification of central vision in the Holmes' [2] map.…”

“…They reported that the area corresponding to the central visual field within 10° amounted to about 50% of the striate cortex, based on the correlation between the localizations of striate cortex lesions imaged by MRI and visual field defects in humans [5]. According to a study by Wong and Sharpe [4], 37% of the total surface area of the medial occipital cortex corresponded to the central 15° of vision. McFadzean et al [3] reported that the central 10° of the visual field occupied at least 50-60% of the striate cortex.…”

“…McFadzean et al [3] reported that the central 10° of the visual field occupied at least 50-60% of the striate cortex. These three studies suggested that the central visual field corresponds to the posterior half of the medial area in the striate cortex, and the peripheral visual field corresponds to the anterior half [3,4,5]. …”

“…In recent years, Horton and Hoyt [1] pointed out the underestimation of the cortical magnification of the central visual field in humans. Other recent studies also reported that the area corresponding to the central visual field expanded to the medial area in the striate cortex [3,4,5,6]. However, a comparison between the central visual field disturbances due to lesions of the occipital tip and those due to the medial area in the striate cortex has not been reported.…”

“…The map presented by Holmes [2] was widely adopted as a detailed representation of the visual field in the human striate cortex [3,4]. On this map, the central visual field was represented at the occipital tip, while the peripheral visual field was mapped anteriorly.…”