Motion blindness

Motion blindness is a neurological condition caused by brain damage (e.g. from a stroke). Visual perception is intact in other ways and a person with motion blindness is therefore able to perceive color and form, for example, as accurately as a normally sighted person. However, they are unable to see motion and instead are only able to gauge movement in frames rather than as a fluid process. In a particular example the subject's stroke caused lesions to the middle temporal area (area MT or V5) in both sides of the brain, just above the ear. This condition makes it difficult to do simple things such as cross the street, or pour a cup of coffee.[1] [2] It has been suggested that the ability to see motion is crucial for survival.[3] This condition has been associated with Alzheimer's disease. It is possible that Alzheimer's patients lose their bearings and become lost not due to a memory problem, but perhaps as a result of this condition. It may therefore be that a person's failing ability to detect motion accurately could give doctors a way to detect Alzheimer's disease in its earliest stages.

Akinetopsia

Akinetopsia is a very rare neuropsychological disorder, it means disorder between the nervous system and other mental functions, in this case between the brain and perception. In this disorder the person affected by it cannot perceive motion.

Imagine the effects of a strobe light and how you do not seem to detect motion, but rather see a series of still images. However, there is more to akinetopsia than simply perceiving a series of changing, but static images without motion. Recall pictures of city lights taken while in a moving car at night. The lights have a sort of comet trail behind them. For people with this disorder, the comet trail of images is present as well. The movement of an arm can appear as several, fuzzy arms trailing after the original one. Only when they and the world around them is perfectly still do they see images normally. However, when things are moving there is a trail of repetitive images, such as one dog appearing several times in a trail after itself, which catch up to the original image when that object is standing still.

Akinetopsia is caused by a lesion in area V5 of the extrastriate cortex. It can also be caused as a side effect of certain antidepressant drugs, or due to damage by a stroke or certain brain surgeries. In some cases akinetopsia can be treated by brain surgery or discontinuation of antidepressants.