Fig. 1.

A ventral view of the human brain showing the early visual pathway. Normally, light enters the system through the optics of the eyes, and is focused on the retina where photons are converted to neural activity. From the retina, this activity flows down the optic nerves and through the chiasm, along the optic tract to the lateral geniculate nucleus of the thalamus (LGN). The chiasm serves to sort fibers from the two eyes such that signals are combined by visual hemifield (both right hemifields go to the left LGN, and vice-versa). From the LGN, signals then flow through the optic radiation to the primary visual cortex (V1), and on to the higher visual areas