The where pathway is important for identifying locations of different objects and is also called the dorsal pathway. The where pathway also processes the movements of hands and one's own body. Damage to this part of the visual cortex can lead to ataxia.
The where pathway is important for recognizing where objects are in space. This information can be used to perform movements that bring the body to the object. For example, when you want to grab a glass of water from the table, it is important to know how far away the glass is from you. Otherwise, you might knock the glass over, or not extend your arm far enough. The where pathway is therefore also important for detecting movements.
In the literature, there is a very clear distinction between the ventral (what) and the dorsal (where) pathways. This idea was first written down and coined in 1982, by two researchers named Ungerleider and Mishkin. However, more recent studies have shown that this separation may not be as simple as Ungerleider and Mishkin thought. It turns out that the two pathways are highly interconnected and exchange a lot of information. This is why some of today's researchers think that there is only one visual pathway, rather than two.
Damage to the dorsal pathway can lead to optic ataxia. This is a condition in which people have difficulty grasping a visual object. This is caused by a deteriorated view of the environment, but also because the movements of the arm cannot be properly perceived. As a result, the patient does not properly know that his arm is already at the object. Ataxia also occurs with damage to other parts of the brain, such as the cerebellum. This area is responsible for the fine coordination of movements. Here, damage has the same effect as not being able to properly perceive one's own movements.
Author: Myrthe Princen (translated by Melanie Smekal)