Imagine that, on any given day, we get up in the morning, open the fridge, take the milk to make a coffee and pour it in the cup. When we have the amount of milk we want, we stop throwing. Up to here everything normal. Now we change the situation. We start pouring milk, but nothing falls. We continue to pour more, but we still do not see the milk fall … until, suddenly, the cup is overflowing and there is milk everywhere. How is it possible? What has happened? Welcome to the acinetopsia.
Acinetopsia is the inability to perceive objects in movement. It is a visual agnosia. As described by Arnedo, Bembibre and Triviño (2012), a visual agnosia is “an alteration in the visual recognition of objects (or of specific characteristics of the stimulus such as color or movement), with the preservation of other visual abilities, such as acuteness , the tracking or the differentiation between figure-bottom, and of the other superior functions “.
People with acinetopsia see the world in frames. For this reason, they have great difficulty in carrying out such simple activities as crossing a street. When you see the world in frames, you are not able to see a car moving. They see it here, and then there; this means that, in the best of cases, they can intuit the transition (speed). Therefore, lacking the perception of movement and not knowing at what point a car is at any given moment, they can easily be run over.
In the example of the cup, the trick is to introduce a finger on the edge and, in this way, notice through touch when the cup is full. However, in other tasks it is not so easy. Driving, for example, is an activity that is vetoed by people with acinetopsia. Also mention that if we know someone with this type of agnosia, it is advisable not to throw anything at him to take it on the fly: the most likely thing is to hit him in the face or body. Better give it to him in his hand.
People with akinetopsia lack the ability to unite images in a fluid way.
Types of acinetopsia
Fine or discrete
It is the most widespread type of acinetopsia. The movement is perceived as an exhibition of continuous photographs (very often of refreshment, so that the person could reconstruct the movement quite accurately). In the example of the cup, instead of going from seeing it empty to full, you would see how it fills up through static images. Therefore, this type of acinetopsia is not so disabling, but it is annoying.
It is the type of acinetopsia with less incidence, but the most severe. Blindness to movement is total. The patients affected by this pathology go from seeing the image of a car in the distance to seeing it near them. They lose the information of the movement between one image and another. Therefore, they are unable to predict the movement of an object external to them. They may even become witnesses of “strange apparitions”.
Imagine that a person with macroscopic acinetopsia is in his room, and someone discreetly enters it. It is very possible that the subject with this pathology is, suddenly, with someone in front. Because of this their lives are very limited.
Where is the problem?
The visual information circulates forward (feedforward), that is, from the retina to the thalamus and from here to the occipital cortex. As it moves away from the receiver, this information acquires greater computational complexity. Now, this information is also processed backwards (feedback).
This process backwards, as pointed out by Javier Cudeiro (2008), of the University of A Coruña, “is established by the connections back through which a certain area can influence (or modulate) the activity of previous areas of the visual system “
“Our sense of sight is like a video camera, it captures a large number of images that when reproduced at a continuous speed generates a sense of continuity and movement. In patients with acinetopsia there is no such sensation and only see the images separately. “
Cudeiro affirms that this is a very important finding and for this he points out the temporary middle crust as an example. This area seems to be key to the perception of movement and its direction. Thus, the lesions of the temporal middle cortex or electrical microstimulation have allowed to verify the appearance of severe deficits such as akinetopsia.
Álvarez and Masjuan (2015) state that “akinetopsia occurs after bilateral occipitoparietal lesions (there are described cases of unilateral lesion), usually of ischemic or traumatic cause”.
Without a doubt, we are talking about agnosia in the middle of the research phase: we still have a lot of data to know. Even so, each advance is highly relevant due to the valuable contribution that can be made to improve the quality of life of patients. Some patients whose life is altered in their day to day.
Álvarez and Masjuan point out that “these patients have the sensation that objects jump instead of having a continuous and fluid movement, appearing and disappearing in different positions”. What should it be like to be on the skin of someone with this agnosia for a day?
These authors also point out that the fact of perceiving their surroundings thus causes them great difficulty in knowing if an object moves away or approaches. How to know then if a car is near or far? How to move around a world in constant movement?