Thus, input from both hemifields reaches each hemisphere. In fact, in albinism three different resulting cortical organization patterns have been reported. The geniculostriate projection can be reordered resulting in a contiguous retinotopic map of both visual hemifields (“Boston” pattern); alternatively, reordering can be absent with intracortical suppression inducing a lack of behavioral sensitivity of the temporal retina (“Midwestern” pattern)

or without suppression retaining sensitivity (“True Albino” pattern). While the former organization patterns of the visual cortex appear to be reserved to nonprimate models of albinism, the latter is found in both nonprimates and primates (Guillery et al., 1984; Hoffmann et al., 2003). PI3K Inhibitor Library datasheet Our aim was to resolve the organization pattern in human achiasma. We investigated two of these extremely rare achiasmic subjects. Three types of investigations were performed using 1.5, 3, and 7 Tesla MRI: (1) optimized retinotopic mapping (DeYoe et al., 1996; Engel et al., 1994, 1997; Hoffmann et al., 2009; Sereno et al.,

1995; Wandell et al., 2007), (2) characterization of the population GDC-0199 in vitro receptive field (pRF) properties (Dumoulin and Wandell, 2008), and (3) diffusion-tensor imaging (DTI) and tractography to investigate white matter integrity (Sherbondy et al., 2008a, 2008b). Our results indicate that the abnormal visual input in human achiasma does not induce a sizable topographic reorganization in the geniculostriate projection or of the occipital callosal connections. We propose that reorganization of intracortical architecture in the visual system underlies the ability to cope with these abnormal inputs. In subject AC1, visual hemifield representations on the cortical surface were obtained separately for each visual hemifield and eye using fMRI-based retinotopic mapping (DeYoe et al., 1996; Engel et al., 1994, 1997; Hoffmann et al., 2009; Sereno et al., 1995; Wandell et al., 2007). Mapping of either visual hemifield Tolmetin yielded dominant responses on the occipital lobe ipsilateral to

the stimulated eye (Figures 1 and S1). Figure 1 illustrates that stimulation of the right eye revealed orderly eccentricity maps of both hemifields on the right hemisphere only (Figure 1B). Moreover, opposite visual hemifields were represented as a cortical superposition of mirror-symmetrical visual field positions. Accordingly, the phase maps obtained for stimulation in opposite hemifields were highly correlated (Figure 1C) and the borders of the early visual areas were identical for the representation of the contralateral and the ipsilateral visual hemifield as derived from polar angle maps (Figure S1). Similar results were obtained on the left hemisphere for stimulation of the left eye (Figure S1).