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Acinetopsia or motion blindness, life in frames

Acinetopsia or motion blindness, life in frames

The term acinetopsia or akinetopsia It comes from the Greek words akinesia (absence of movement) and opsis (see). It was introduced shortly before 1991 by the British neurobiologist Semir Zeki to name a selective deficit of the ability to perceive movement.

Acinetopsia is also known as motion blindness, and it is a neuropsychological disorder in which a patient cannot perceive movement in their visual field, despite being able to see stationary objects without problem. There are different degrees of acinetopsia: from seeing the movement as a film reel to the inability to discriminate any type of movement. There is currently no effective treatment or cure for acinetopsia.

Types, signs and symptoms of movement blindness

Acinetopsia can be separated into two categories according to severity of the symptom and the amount that blindness affects the patient.

Fine or discrete acinetopsia

In these cases the movement is perceived as a film reel or a multiple exposure photograph. This is the most common type of acinetopsia and many patients consider this type of strobe vision a huge nuisance. This acinetopsia often occurs with residual images that are left in each frame of the movement.

The pathophysiology of this type of acinetopsia is not known, but the hypothesis that it is due to inappropriate activation of physiological movement suppression mechanisms which are normally used to maintain visual stability during eye movements (e.g. saccadic suppression).

Macroscopic acinetopsia

Thick acinetopsia is an extremely rare disorder. Patients have deep movement blindness and huge problems to carry out the activities of daily life. Instead of seeing the vision as a film reel, these patients they have trouble perceiving the movement as a whole. Most of what is known about this extremely rare condition was learned through the case study of a patient, LM. He described that pouring a cup of tea or coffee was difficult "because the liquid seemed to be frozen, like a glacier." She did not know when to stop pouring, because she could not perceive the movement of liquid li increasing from it in the cup. LM and other patients have also expressed having trouble following the conversations, because lip movements and changing facial expressions were lost. LM stated that she felt insecure when more than two people walked around the room: "people were suddenly here or there but had not seen them move." The movement is deduced by comparing the change in the position of an object or person. LM and others affected have described that crossing the street and driving cars is almost impossible. LM to deal with these problems, trained his hearing to be able to estimate the distance of moving objects.

Causes

The causes of acinetopsia can be: the interruption of the cortical area that is in the central area of ​​the temporal lobe, may appear as a side effect to certain antidepressant drugs, can also be caused by a cerebral infarction or by certain cranial surgeries. In some cases, acinetopsia may disappear when antidepressant treatment ceases or by brain surgery.

A change in the structure of the brain (usually lesions) is capable of alter the psychological process of understanding sensory information, in this case visual information. Alteration only visual movement is possible due to the anatomical separation of visual movement processing from other functions. Like acinetopsia, color perception can also be selectively altered as in the case of achromatopsia (also called monochromatism), which is a congenital and non-progressive disease that consists of an abnormality of vision as a result of which only white, black, gray and all its colors are perceived.

There is an inability to see movement despite normal spatial acuity. Other intact functions include the perception of visual space and the visual identification of shapes, objects and faces. In addition to simple perception, acinetopsia also alter visomotor tasks, such as reaching objects and catching objects. When performing tasks, feedback from the movement itself seems to be important.

Brain injuries

Acinetopsia can be a deficit acquired by lesions on the back side of the visual cortex (area V5). These types of lesions most often cause macroscopic acinetopsia. The neurons of the medium temporal cortex respond to mobile stimuli and therefore is the area of ​​motion processing of the cerebral cortex. In the aforementioned case of LM, for example, the brain injury was bilateral and symmetrical, and at the same time small enough not to affect other visual functions. It has been reported that some unilateral lesions also affect movement perception. Acinetopsia through lesions is rare, since damage to occipital lobe It generally alters more than one visual function.

Antidepressants

Acinetopsia can be triggered with high doses of certain antidepressants and vision returns to normal once the dose is reduced.

It may interest you: What are psychoactive drugs? Types and function

Hallucinogens

The usual consumption of hallucinogenic drugs it can also cause a serious perception disorder and even movement blindness, although the least severe, fine acinetopsia.

The aura of migraine

Migraine is a severe headache It usually affects one side or part of it and is often accompanied by nausea and vomiting. It can present very varied symptoms. The most frequent are neurological, gastrointestinal and sensitive.

The aura it is a phenomenon mainly of visual origin, although not exclusively, that appears a few hours or minutes before the attack. It is like a warning of the imminent arrival of pain. They are transient and variable duration episodes, which usually last between four and 60 minutes. It seems to be due to small contractions of the vessels before dilation in response. During these contractions, the blood supply to some areas of the brain decreases temporarily; but it is enough for the characteristic signs of this state to appear. Is that decreased irrigation resulting in the appearance of: visual symptoms, such as dots, flashes, rays, fractional images or mosaic, decreased visual field ... these are the most frequent signs of aura and acinetopsia.

Transcranial magnetic stimulation

Fine or discrete acinetopsia can be induced selectively and temporarily by transcranial magnetic stimulation (EMT) of the V5 area of ​​the visual cortex in healthy subjects. It is carried out on a surface of 1 cm² of the head, which corresponds in position to the area V5.

Alzheimer disease

In addition to memory problems, Alzheimer's patients They may suffer varying degrees of acinetopsia. This could contribute to its marked disorientation. While Pelak and Hoyt have registered an Alzheimer's case, not enough research has been done on the subject.

References

Zihl, J., Cramon, D., Mai, N. (1983). Selective alteration of movement vision after bilateral brain damage. Brain, 106, 313-340.

Zeki, S. (1991). Acinetopsiacerebral (visual motion blindness). Brain, 114, 811-824.

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