Hi. Good to see you all with another interesting topic. This time I have come up with a disorder which I got inspired from a series “Undateables.” As we are in 21st century facing n number of diseases with minimum percentage of recovering rate. There are lot more unknown diseases which haven’t came into notice by all. Facial blindness is one among them.
What is facial blindness?
The term facial blindness is derived from a Greek word, called as Prosopagnosia (prosopon means face and agnosia means non-knowledge). It is a kind of disease where the individual will lack the ability to recognize the familiar faces, there own face at times. But they can identify the object discrimination and other visual items. They have strong intellectual functioning (such as learning, reasoning, problem solving and good IQ).
This disorder occurs mainly due to acute brain damage or from birth defect. The widespread range is measured to be 2.5 percent.
How is brain related to face blindness?
Usually temporal lobe (considered as one of the major lobes of cerebral cortex, which is located near the ear level in the skull. It helps in creating and recollecting long term memories/ consciousness.) of the brain plays main role in identifying faces. The order from the lobe reaches the gyrus called as fusiform gyrus. This gyrus becomes active while we are looking into faces and helps us to recognize them.
The gyrus helps individual in recognizing the faces in depth more than the other objects differentiation. But if the individual is affected with face blindness, their ability to identify faces becomes equal to the way they identify random objects (lack of temporal lobes and gyrus functions). As for the study, fusiform gyrus in the right hemisphere of the human brain plays vital role in facial recognition comparable to the left. Still solution left unclear whether the fusiform gyrus take part only in face identification or it plays major role in highly trained visual stimuli. This blindness is most common in adults.
Types of facial blindness:
Apperceptive agnosia occurs due to lack of face perception system. Damage of
occipital (mainly responsible for vision)-temporal lobe of the brain regions results in
agnosia. In this case, the individual completely loses the ability to identify faces, shapes
or differentiate them by seeing through the pictures.
They were not able to spot both the new or familiar faces. They also have struggle in understand people facial emotions. People also have difficulty in redraw the drawing/ rewrite the text or numbers by looking into it. They can differentiate people through clothing, hair color, hair style, skin color, voice, and perfume. This illness occurs due to damage of fusiform gyrus.
Associative agnosia is due to damage of right anterior temporal regions of human brain and parahippocampal gyrus (outer layer of the cerebrum and plays important role in memory coding and retrieval). Unlike apperceptive, here the individual can redraw pictures or rewrite the text though they couldn’t recognize what they drew or write.
Here the affected person has stable semantic knowledge (portion of long-term memory especially concepts, ideas which are not related to personal experience). The person can recall colors, sounds of letters pronouncing, capitals of various countries, and other basic facts that happens over a lifetime.
Even the person can find differences between the photos shared, age, male or female. They lack in recalling the opponent name, occupation, and when they met them for the last time. The patient can distinguish 6% of living things and 90% of non-living things.
Developmental agnosia (DP) also called as congenital prosopagnosia (CP). This agnosia is no way related to brain damage. An individual affected with this illness can never recognize faces lifelong right from the birth.
As per the study, short fall of DP have been diagnosed by EEG (Electroencephalography is the method used to record the electrical activity of the brain using electrodes placed over the scalp) and fMRI (Functional magnetic resonance imaging helps in measuring brain activity by detecting changes in blood flow) scan.
The root cause of this blindness is due to genetic factors. The survey has been taken to check whether this blindness is hereditary disorder. They randomly picked 689 students from different families and recognized around 50 percent of the student from different families are affected by this illness.
In 2005, Ingo Kennerknecht study proved that CP occurs due to genetic disorder and can be shared to the next generation right from their birth. This disease is also called as autosomal dominant inheritance (either father or mother is affected will eventually carry over to the kids.)
Prosopagnosia is also associated with other disorders in the nearby brain areas are:
Hemianopsia: kind of vision loss, where the individual has half visual field (black areas in half of the eye either left or right). This disorder is caused by stroke, brain tumor, and trauma.
Achromatopsia: hereditary disorder can be characterized by absence of color vision, decreased vision, light sensitivity, and nystagmus (involuntary movement of the eye from side to sided, up/down, or a circle leads to blur vision). Main cause is absence of functioning of photoreceptors (cells that respond to light) in retina.
Topographical disorientation: here the individual lack the familiarity of environment. For example, they couldn’t recollect the places, routes, location which they travel on regular basis. Have difficulty in finding the landmark. This disorder is mainly due to focal damage of the brain (when the people get head strikes in windshield during vehicle accident affects the brain tissue which is visible to naked eye).
History and difficulties:
The first document of facial blindness was released during 19th century which includes the case studies of Hughlings Jackson (English neurologist who is well known for his research Epilepsy (abnormal functioning of brain)) and Charcot (French neurologist and professor of anatomical pathology, he is well known for hypnosis and hysteria psychology).
The term Prosopagnosia was first used in 1947 by German neurologist Joachim Bodamer. He investigated 24-year-old man who lost his ability to recognize his family, relatives, friend, his own face after the head injury (bullet wound to the head). However, he tried identifying them by sensory modalities (interchangeably with sense: touch, light, smell, voice).
In 1985, a book titled “The Man Who Mistook His Wife for a Hat” was written by Dr. P Oliver Sacks. Oliver himself has difficulty in identifying his wife, where he recognizes his wife by her voice. Other relatives were spotted by specific characteristics of them like big mouth, wide eyes, and so on. Oliver haven’t known about his illness much of his lifetime.
As this disorder is crucial to identify, each of them undergoes various symptoms. Facial blindness involves multiple stages with different impairments/damages.
A test was carried out between group of people. Each of them is provided with a picture of dog in a piece of paper. At level one, everyone identifies it without any error. At level two, the same image was given by reciprocating it. Most of the individual suffered to recognize them. The result finalized as, the person affected with blindness can identify the parts of the human face (nose, mouth, eyes, ears) easily but has difficulty in spotting them as a complete face.
Children with this illness, faces lot of issues in making friends; watching dramas, even to spot the familiar person outside the house. They only make friends with more specific characteristics. So that they can distinguish them easily. They prefer watching cartoons because characters appear here has common dress code, voice, and personality to differentiate among other casting.
There is no widely accepted treatment for this disorder. One commonly used test to diagnose blindness is recognize faces of famous person. This test is not considered to be standardized test.
Test to diagnose blindness:
Benton Facial Recognition Test (BFRT): it is used for clinical and research purpose. Here the male and female faces are used. Those faces are closely cropped so that no clothing or hair of the face are visible. Person with illness are advised to undergo this test. This test is applicable to diagnose the patients with apperceptive prosopagnosia.
Cambridge Face Memory Test (CFMT): this test was developed by Duchaine and Nakayama to better diagnose people with prosopagnosia. Here the individual is provided with three images with six different target faces. Later they are presented with many three-image series where one contains target face and two distractors. Comparing to BFRT, this test was highly recommended to identify the person with illness.
20-item Prosopagnosia Index (PI20): this test is freely available and self-validated questionnaire. This can be used along computer-based face recognition test to spot the illness. Comparing to BFRT and CFMT, this test is more effective in identifying the illness.
This blog gives an idea about face blindness in detail. Stay safe and calm! Happy learning:)
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