Alzheimer’s Disease And Visual Clutter

senior-coupleSuppose you were at a football game where the home team spectators were wearing red hats, but your sister was wearing a yellow one because nobody told her that today was red hat day. Could you pick her out of the crowd? Kind of easy, right? Now, suppose one of her friends gave your sister the extra red hat she carried in her tote bag.  Finding her in the crowd would be more of a challenge, eh? What is it that causes the confusion? Is it the hat or that your sister tends to look like everyone else? How sorry do you feel for the guy who comes to work wearing one maroon and one brown sock because he is retinal rod-deficient and has a hard time distinguishing shades (despite that he has another pair just like this one)? Under some circumstances, recognition can be a challenge, particularly when crowding of images occurs, as in both the stadium and the sock drawer. Such is the trial of the Alzheimer’s or the mildly demented patient, only it happens more often.

Those with Alzheimer’s disease may be unable to recognize once-familiar faces and objects because of infirm perceptions or the incapacity to recall from memory. The face is important to social interaction. Its perceptions are complexed by the myriad facial expressions and shapes that need to be analyzed and interpreted. Additionally, context affects recognition. Although you’ve seen a colleague in the office day after day for years, you may suddenly forget his name when seeing him, after your or his retirement, in a venue that is unfamiliar to both of you, such as a shopping mall in a distant city.  Face perception involves more than one area of the brain, with some areas being more important than others. One of these is called the medial temporal lobe, a kind of garage that houses the memory “toolbox,” most notably the hippocampus, the part that is critical to memory formation. In here sits the perihinal cortex, which receives data from the sense organs. It favors visual perception and memory while the rest of the hippocampus processes spatial and temporal relationships (Murray, 2007) (Buckley, 2005).

Damage to, or interference with, the perihinal cortex or its immediate surroundings can hamper the availability of semantic (long-term factual) memory and the formation of new memories from recent perceptions. The capacity to attach meaning to new percepts is compromised, and memories are not completely formed. Because faces share common features, ambiguity of interpretation can occur and recognition becomes an uncertain proposition. Recognition of faces may also be tied to events. Reliving the past, using episodic memory, may be able to jar recall, but not always and not always with the same reliability. Impairment of episodic memory is the hallmark of Alzheimer’s disease, but in some circles is viewed more as the inability to encode and store information than an inability to retrieve it (Traykov, 2007).

Because perception and memory are linked, it is possible that one affects the other.  Your mentally challenged aunt may fail to recognize you not only because she forgot who you are, but also because she can’t clearly perceive the distinct combination of facial features that make you, you. But this is more apt to happen in a crowd of other, competing, faces than if you walk into her room by yourself. It’s been determined that minimizing the degree of perceptual interference can improve facial/object perception by eliminating features that are visually similar. Low interference conditions, where perceptually dissimilar objects occupy proximal space, present less visual clutter, often resulting in improved cognitive performance (Newsome, 2012). The less feature ambiguity, the more meaningful the perceptual representation (Barense, 2010). This means that a person with a square facial feature would be more easily recognizable than if he had a rounded feature, like everybody else. Thus, if the whole family comes to visit your demented aunt, it can be supposed that entering the room one at a time, allowing her to react and to respond to one face at a time, may be more positive an encounter  that entering en masse. Object or facial recognition in clutter may also depend on whether or not the original perception occurred in visual clutter, which purportedly has an effect on later discrimination. Meeting a person for the first time while in a large group, compared to meeting him in a twosome or threesome, will have an effect on the recognition of that person at a later time, whether alone or not. Unless special attention is paid to new perceptions, memory lapses should not be a surprise.  Visual clutter demands competitive selection, and reducing clutter could help not only the cognitively impaired with everyday tasks, but also the inattentive, distracted or disinterested people around us.

Everyone sometimes has trouble recognizing faces, and it’s even more common for people to forget names. There is a name for face “blindness.” It’s prosopagnosia. One of the complaints of sufferers is that they can’t follow the plot of a TV serial because they don’t recognize the characters they saw on the previous show. Most cases involve brain damage, including that from trauma, stroke or the degeneration of AD. In these instances, face recognition was normal at one time. Of course, this can cause serious social problems, but it is downright frightening when people cannot recognize themselves in a mirror.

References

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