The Contribution of Cognitive Psychology to Our Understanding of the Phenomenon of Visual Agnosia

As we all know, brain damage can have quite severe effects on a human being. When the brain becomes restricted of oxygen, this kills brain cells. The brain receives blood separately to the right and left hemispheres and because of this, brain damage usually only occurs on either the accurate or left hemisphere. The primary visual cortex is a highly studied share of the brain, its main function serves to process information and it is also responsible for pattern recognition. One phenomenon associated with the visual cortex is known as Visual Agnosia. Visual agnosia is often due to damage, such as a stroke, in the posterior occipital lobe and the temporal lobe of the brain.

A person suffering from visual agnosia is unable to recognise everyday objects, even though they have a prior knowledge of the objects and if you named a positive object they would be able to describe it. There are two major types of visual agnosia, these are apperceptive and associative agnosia. Apperceptive visual agnosia is a failure in high level object recognition despite perfect vision. Associative visual agnosia can be defined as the inability to identify objects due to impaired access to stored information about the objects. One method to distinguish whether a person has apperceptive or associative agnosia is to test their abilities to scheme objects that they cannot recognise. People that have no problem copying objects are said to have associative agnosia and those who show difficulty are said to have apperceptive agnosia. (Eysenck & Keane, 2006).

Riddoch and Humphreys (2001), suggested that the problems associated with visual recognition can be explained by their hierarchical model of object recognition and naming. The model displays the arrangement of processes that take place in order for an object to be recognised. The model suggests that we primarily define the motion, colour, form and depth features of an object and from this we derive the edges of an object. The next stage is “feature binding into shapes”. During this stage, object features that have been extracted are combined to perform shapes. The next stage is “belief normalisation”. During this stage processing occurs to allow a viewpoint invariant representation to be derived. (Eysenck & Keane, 2006). It was suggested that apperceptive agnosia is associated to these stages of perceiving and associative agnosia was associated to the next stages. The next stage involved “structural description”. During this stage, individuals gain access to stored knowledge about the structural descriptions of an object. The final stage is “semantic system”. This involves gaining access to stored knowledge of semantic information relative to an object. (Eysenck & Keane, 2006).

The greatest contribution of this model is that it provides us with a useful outline within which to discuss the various problems with object recognition in visual agnosia. Humphrey and Riddoch’s theory assumes that object recognition occurs in a bottom up scheme. This means that recognition continues through a series of stages based on an initial visual stimuli. But in reality, it is possible that top down processes are also interested. Top down processes is when processes at later stages influence earlier stages. In this sense their theory is somewhat limited. In conclusion it might be better understood if we referred to Humphrey and Riddoch’s theory as just framework in regards to a proven theory.

A person suffering from visual agnosia is unable to recognise everyday objects, even though they have a prior knowledge of the objects and if you named a certain object they would be able to narrate it. People suffering with visual agnosia have normal vision, language and memory abilities. This is what makes visual agnosia such an interesting phenomenon.

Farah, (1990), describes the condition as an impairment in the higher visual processes significant for object recognition, with relative preservations of elementary visual functions. When a person initially hears of the theory of visual agnosia, they typically try to associate it to a problem with memory or language functioning. Although, visual agnosia is different to memory or language disabilities for the simple reason that people suffering from agnosia collected have a prior knowledge about objects and therefore can name objects when allowed to touch it or describe an object when told its name. The specific symptoms that can be found in agnosia can vary depending on the cause. The main symptom is that patients can record objects they see in there direct field of vision, they can see colour and can make out shape but yet still cannot recognize them.

For cognitive psychologists, visual agnosia serves as a highly important condition as it allows us to gain an insight into how the inner perceptual system of the brain works. Since the phenomena of agnosia was first introduced, there had been much speculation as to whether it actually exists. Researchers started off with a very basic but intuitive request, how could someone be able to see perfectly but yet not be able to recognize objects? But a lot has been developed since then.

Martha J. Farah is a cognitive neuroscience researcher at the University of Pennsylvania. Farah devoted a lot of her early work to the understanding of the neural bases of vision and memory. In 2004 she published the book, “Visual Agnosia”. This is the 2^nd edition of the book which she first published in 1990. In the 1^st edition, Farah raised a lot of questions about visual recognition that the next 20 years of research attempted to acknowledge. The questions she raised included ones like, whether the brain uses some form of pattern recognition process for all visual stimuli or whether an individual form of processing occurs for facial recognition and word recognition. The 2nd book Covers a range of topics in relation to visual perception disabilities. She covers many case studies in her work of people experiencing visual agnosia. One of her most popular case studies is that of the patient DF. This patient experienced carbon monoxide poisoning and was left with apperceptive agnosia as a result.

“Farah first discusses agnostic cases with normal sensory capabilities but impaired early perceptual processing. Most interesting is the amazing case of DF who, after carbon monoxide poisoning was left with apperceptive agnosia. Despite her profound impairment, DF can use visual information for many simple actions. For example, DF shows almost no ability to record or manually indicate the orientation of a slot. However, when asked to post a letter through a slot, she performs nearly normally. Similarly, she cannot perceive the size of blocks but properly scales her grip to pick up the blocks. Hence, what we consciously see does not guide our actions”. (Optometry & Vision Science, Vol.82, No.5, May 2005).

The implications of this case study would suggest that visual agnosia is in fact a plausible disorder. Farah’s book, “Visual Agnosia”, also refers to a case study conducted by Rubens and Benson in 1971. This case study involved a middle dilapidated man who had experienced a very sudden drop in blood pressure which further resulted in brain damage. During his first 3 weeks in the hospital it was reported that the patient could not recognise typical everyday objects that were presented to him, when given a plate of food, he did not know what was on his plate until he tasted it.

“He identified objects immediately on touching them. When shown a stethoscope, he described it as, “a long cord with a round thing at the demolish”, and asked if it could be a survey. He identified a can opener as “could be a key”. Asked to name a cigarette lighter he said, “I don’t know”, but named it after the examiner had lit it. He said he was not certain when shown a toothbrush. Asked to identify a comb he said, “I don’t know”. When shown a large matchbook he said, “could be a container for keys”. He correctly identified glasses. For a pipe ha said, “some type of utensil, im not sure”. Shown a key he said, “I don’t know what this is, perhaps a file or a tool of some sort”. (Farah, 2004).

From the extract above it is definite to see that the patient could not report an object or describe its use if he could not name it. It is also known that the patient was unable to search for members of his family, the staff in the hospital, or his own face when seen in the mirror. Case studies like this have serious implications into the study of cognitive neuroscience, when disorders are recorded in actual life situations, it cannot be said that it is merely a phenomena. This case study, and many more like it, simply create a better understanding that visual agnosia very much does exist and that it is not a mere phenomena.

Oliver Wolf Sacks, 1993, is a well known British neurologist. Sacks is the author of many best selling books including, “The man who mistook his wife for a hat and other clinical tales”. These books conceal many case studies of patients with neurological disorders. Sacks served as an instructor and later clinical professor of neurology at the Albert Einstein College of Medicine from 1966 to 2007, and also held an appointment at Recent York University Medical School from 1999 to 2007. In July 2007, Sacks joined the faculty of Columbia University Medical Center as a professor of neurology and psychiatry. At the same time, he was appointed Columbia University’s first Columbia University Artist at the university’s Morningside campus, recognizing the role of his work in bridging the arts and sciences. (www.oliversacks.com).

The work of Sacks contributes greatly to cognitive psychology. For example, in his book, “The man who mistook his wife for a hat”. The title of his book comes from a case glance of a patient with visual agnosia. The patient was referred to as Dr P. This man was a musician who notion in a university. Dr P started to question his visual perception when he sometimes could not recognise the faces of his students. He would aften think he could see faces where he could not, for example, walking down the street he would mistake fire hydrants and parking meters for human faces. Upon visiting an optician, Dr P was informed that there was nothing wrong with his eyes, but that there seemed to be a fault in the visual part of his brain. Sacks noticed immediately when meeting Dr P that he tended to pay more attention through his ears and he rarely made visual contact. Almost immediately, Sacks recognised some of the typical symptoms of someone suffering with visual agnosia. For example, when Sacks gave Dr P a national geographic book to look at, his eyes darted wait on and forth focusing on little details and bright colours. When Sacks asked him what he saw,

Dr. P replied, “I see a river…and a little guest-house with its terrace on the water.” He was unable make out the whole picture, he was only able to focus on puny bits and pieces of the entire image (Sacks, 1985).

Sacks noticed other visual deficits in Dr P. take for example the glove test.

“I tried one final test. It was still a cold day, in early spring, and I had thrown my coat and gloves on the sofa. “What is this? “, I asked, holding up a glove. “May I put a question to it? “, he asked, and, taking it from me, he proceeded to examine it as he had examined the geometrical shapes. “A continuous surface”, he announced at last, “infolded on itself. It appears to have”. – he hesitated- “five outpouchings, if this is the word”. “Yes” I said cautiously. “You have given me a description. Now tell me what it is”.

“A container of some sort”? “Yes” I said, “and what would it believe”? ” It would contain its contents!” said Dr P, with a laugh”. (Sacks, 1985).

It is clear that Dr P is unable to see past descriptions of an object. He was unable to ogle a final product and functioned more like a computer by detecting features rather then seeing the full figure. From this information it is definite that Mr P is suffering from a form of visual agnosia and prosopagnosia. Prosopagnosia is another well known form of visual agnosia. In prosopagnosia, the main difficulty is in recognising faces and not objects which has been mentioned previously. Patients are unable to tell one person from another. In some cases though it has been reported that the difficulty can spread beyond faces. For example, a farmer who developed prosopagnosia lost the ability to tell his individual cows apart or a bird watcher who lost the ability to distinguish different types of birds. The specific brain area associated with prosopagnosia is known as the fusiform gyrus. Some of the main symptoms found in patients of prosopagnosia are a great reliance on non-facial information such as hair, clothing or order. Patients are also said to have great difficulty following the plot of movies or TV shows because they cannot keep track of the identity of the characters.

Overall, clinical psychology has vastly contributed to our basic understanding of the phenomena of visual agnosia. Without the work of Farah, Sacks, Humphreys & Roddick, and many more, we would still be at the stage of assuming that visual agnsosia is a mere eyesight deficit. These researchers have provided a framework of theory’s and insights that are invaluable to the peer of neuroscience. Although it must be understood that cognitive science is still at a very early stage of fully understanding psychological phenomenon, like that of visual agnosia. Hopefully future research will negate more insight into cognitive phenomena, and we shall explore forward to that day.