Bilateral visual field maps in a patient with only one hemisphere

Abstract

In mammals smooth retinotopic maps of the visual field are formed along the visual processing pathway whereby the left visual field is represented in the right hemisphere and vice versa. The reorganization of retinotopic maps in the lateral geniculate nucleus (LGN) of the thalamus and early visual areas (V1-V3) is studied in a patient who was born with only one cerebral hemisphere. Before the seventh week of embryonic gestation, the development of the patient's right cerebral hemisphere terminated. Despite the complete loss of her right hemisphere (di-and telencephalon) at birth, the patient's remaining hemisphere has not only developed maps of the contralateral (right) visual hemifield but, surprisingly, also maps of the ipsilateral (left) visual hemifield. Retinal ganglion-cells changed their predetermined crossing pattern in the optic chiasm and grew to the ipsilateral LGN. In the visual cortex, islands of ipsilateral visual field representations were located along the representations of the vertical meridian. In V1, smooth and continuous maps from contra-and ipsilateral hemifield overlap each other, whereas in ventral V2 and V3 ipsilateral quarter field representations invaded small distinct cortical patches. This reveals a surprising flexibility of the self-organizing developmental mechanisms responsible for map formation.functional MRI ͉ retinotopic mapping ͉ achiasmatic ͉ cortical lesion ͉ V1 development

Unravelling the development of the visual cortex: implications for plasticity and repair

“…For example, damage to the primary visual cortex (V1) in an adult leads to blindness through production of a scotoma; however, during infancy the magnitude of the deficits can be greatly attenuated and there is significant sparing of vision. This phenomenon has been observed in both humans (Lambert et al 1987;Kiper et al 2002;Filan et al 2006;Werth, 2006;Muckli et al 2009) and non-human primates (Rodman et al 1993;Moore et al 1995Moore et al , 1996. Interestingly, damage to the occipital region of the neocortex, which includes V1, is a common occurrence as a result of a stroke, neurotrauma, disease or hypoxia in perinates.…”

“…A. Bourne Rakic, 1999), and would probably have a role in the increased plasticity observed. Muckli et al (2009) reported on a single case study of a 10-year-old girl (AH) who lacked her entire right hemisphere and most of her right eye (microphthalmus) from birth but remarkably had close to normal vision in both hemifields. In subject AH it was demonstrated that, despite the complete loss of her right hemisphere, the patient's remaining hemisphere has not only developed maps of the contralateral visual hemifield but, surprisingly, also maps of the ipsilateral visual hemifield.…”

Altered organization of the visual cortex in FHONDA syndrome

“…Consequently, the left visual hemifield is represented on the right hemisphere and vice versa. In patients with congenital malformations of the optic chiasm there can be reduced crossing of nasal axons, as reported for achiasma and hemihydranencephaly (Apkarian et al, 1994;Victor et al, 2000;Muckli et al, 2009;Hoffmann et al, 2012;Fracasso et al, 2016), or additional crossing from the temporal axons, as evident for albinism. In fact, the latter has been regarded to be pathognomonic, i.e.…”

Large-scale remapping of visual cortex is absent in adult humans with macular degeneration

“…Abnormal visual development can modify these retinotopic maps [2][3][4][5] . Under circumstances where individuals acquire early visual experience in the presence of a lesion to the center of the retina, reorganization of the visual representation occurs 6 .…”