The occipital lobe is the posterior part of the cerebral cortex. In this brain area, visual information is processed. This lobe can be further divided into several parts. The posterior part is known as the primary visual cortex, or striate cortex. Other visual areas are also located in the occipital cortex. You can think of V2, V3, V4, and V5, which together with V1 form the dorsal and ventral pathway of visual processes.
Some people are blind from birth, but these people still have an occipital lobe that can be used. In this case, the area does not become active during visual stimuli, but when performing other tasks. An example of this is touch. Blind people read by sliding their fingers over Braille letters. A study using an fMRI scanner showed that the occipital lobe becomes active during Braille reading in blind people. This activity was not found in normally sighted people reading Braille. The finding was also confirmed by a study where TMS was applied to the occipital lobe. Blind people could no longer read Braille because of the magnetic disturbance, whereas in sighted people there was no effect of the disturbance.
Another study produced approximately the same results, but in a verbal task. In this task, all subjects were told a noun, after which they had to name a verb that matched it (for example, people are told the word "apple," and have to respond with "peel" or "eat"). Blind people were not only faster at performing this task, but again, their occipital lobe became active during the task. In sighted people, this area did not become active during the task.
The above studies show that the function of the occipital lobe can change. These changes occur when there is no longer visual input from the lateral geniculate nucleus of the thalamus. The neurons then make connections to other brain regions, such as the parietal and temporal lobes.
Author: Myrthe Princen (translated by Melanie Smekal)
Image: Marcel Loeffen
This lobe is featured in the following brain matters articles:
A first encounter with the brain