Acinetopsia (motion blindness): types and symptoms

When we observe the environment, our eyes perform a large number of movements to capture each and every one of the details and movements that compose it. Next, our brain composes a harmonious picture of everything around us, including moving objects and people.

Our eyesight works like a video camera that makes thousands of frames of what surrounds it, while our brain projects the "film" in our mind. However, what happens when this function is impaired? In these cases, acinetopsia appears, a disorder in which the person has difficulty perceiving movement.

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What is acinetopsia?

Acinetopsia, also known under the terms akinetopsia or motion blindness, consists of a disorder of a neurological nature and that affects the sense of sight. Specifically, acinetopsia causes, in those who suffer from it, an inability to perceive movement through sight.

This condition, first described around 1991 by the British-born neurologist Semir Zeki,

makes the affected person unable to perceive movement. The patient cannot see the movement of his own body, like that of other people or objects.

However, acinetopsia is not an “all or nothing” condition. This condition can be of varying severity. From the mildest, in which the person perceives the movement as if it were a sequence of images or a film in which the frames pass in slow motion; even the most serious, in which the patient experiences a total inability to perceive movement.

In this disorder, the person can only perceive other subjects, objects or himself in a specific place and suddenly in another. Or at most, he perceives a kind of blurred trail behind the moving object.

Although all other sensory functions and abilities remain intact, people with acinetopsia also have their visual-motor skills impaired. Since they do not perceive their own movements well, tasks such as walking and moving, or reaching objects can be really complicated.

Types of acinetopsia and symptoms

As mentioned above, acinetopsia can present in different degrees of condition. These degrees constitute the different typologies of this disorder, which vary both in the severity of the symptoms and in the level of blindness it causes in the person.

There are two different types of acinetopsia. They are as follows.

1. Fine or discrete acinetopsia

This first type of acinetopsia, known as fine or discrete, is the one that presents the mildest symptoms and, therefore, less disabling for the person. Although equally, people who suffer from it report experiencing enormous discomfort.

In slight acinetopsia, the person senses movement as if viewing a reel in which the frames pass at a much slower speed. Another example would be a multiple exposure photograph, in which the person can perceive the wake of movement of both objects and people, including the patient himself.

At the moment, it is not known what abnormality in the functioning of the body causes this disorder. However, experts point to the idea that abnormal functioning in the mechanisms that we allow to maintain visual stability in eye movements can cause this type of acinetopsia.

2. Macroscopic acinetopsia

Also known as thick acinetopsia, this type of movement blindness is extremely rare and very low incidence among the population.

In contrast to fine acinetopsia, on the macroscopic view, the person is completely unable to perceive movement in its entirety. This means that the person can only see a static world in which for a moment the object or the person is in one place and at the moment in a different one.

The few people who suffer from it, tend to have numerous problems performing their daily tasks normally. Daily activities such as having a conversation are highly complicated since the patient is unable to perceive changes in the movement of facial expressions. Likewise, daily routines, like crossing the street, become very dangerous; since it is not possible to perceive the movement of the cars.

In order to compensate for these difficulties, people with acinetopsia train their hearing. In this way, through the sense of listening they can, for example, calculate the distance of objects that are in motion.

What are the causes?

The origin of acinetopsia is an abnormal functioning or interruption of activity in the area of ​​the cortex that is located in the central area of ​​the temporal lobe. Structural alterations in this area of ​​the brain can transform the processes of understanding sensory information. In the case of this strange disorder, it is the processes that deal with visual information that are compromised.

There are several reasons why this brain region can be affected. From brain injuries, to the consumption of certain antidepressants or hallucinogens, or some diseases such as Alzheimer's disease.

1. Brain injuries

One of the causes of this disorder may be an injury to the posterior area of ​​the visual cortexAlthough it is really complicated, since an injury of this type is capable of generating many more sensory deficits.

• Related article: "Visual cortex of the brain: structure, parts and pathways"

2. Antidepressant medication

Administration of very high doses of some antidepressants it can cause visual problems such as acinetopsia. However, this tends to disappear when the treatment is removed or the dose is readjusted.

3. Hallucinogenic substances

A habitual or recurrent use of certain hallucinogenic substances can cause sensory disturbances of all kinds, including the less severe version of acinetopsia, acinetopsia fina.

4. Migraine aura

The aura is a visual phenomenon that accompanies migraine headaches. This tends to appear moments before the onset of pain and is manifested by visual symptoms such as spots in space, flashes or fine acinetopsia.

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5. Alzheimer disease

Although they do not appear very frequently, acinetopsia, present in different degrees, can accompany alterations in memory in patients with Alzheimer's.

Is there a treatment?

At the moment, there are no pre-established guidelines for the treatment of acinetopsia. In the cases in which this is caused by the administration of psychotropic drugs, the interruption of its consumption should eliminate the symptoms of this disorder.

Nevertheless, brain surgery, although risky, is an option to try to eliminate acinetopsia in those cases in which an underlying brain injury.