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Form perception is the recognition of objects in the environment. We originally perceive an object on our retina as a 2D image . The Retinal image can vary for the same object in terms of the context with which it is viewed, the apparent size of the object, the angle from which it is viewed, how illuminated it is, as well as where it resides in our field of vision  . It is remarkable that despite the fact that each instance of observing the same object leads to a unique retinal response pattern, the visual processing that takes place in our brain is capable of recognizing these experiences as analogous in a way that allows for invariant object recognition  . Through visual processing in the temporal, parietal and occipital lobe these retinal images are converted into a 3D image . Visual processing occurs in a hierarchy with the lowest levels recognizing lines and contours, and slightly higher levels performing tasks such as completing boundaries and recognizing contour combinations. The highest levels integrate the perceived information to recognize an entire object . Essentially object recognition is the ability to assign labels to objects that allow us to categorize and identify them, in a way that distinguishes one object from another. It is important to recognize that during visual processing information is not created, but rather reformatted in a way that draws out the most detailed information of the stimulus. Our ability to recognize objects evolved to allow us to find food, avoid predators, and to communicate with written language; our ability to perform all of these tasks efficiently and accurately has been key to our survival .
• Perceptual Grouping
• Surface Perception
• Object Perception
• Figure-Ground Perception
Since it is not fully understood how the brain completes the process of object recognition, there are currently a couple theories as to what actually happens. One theory proposes that as a stimulus progresses along the visual processing pathway each area has increasing processing power . It is thought that this is necessary in order to complete the increasingly complex tasks involved in object recognition. This theory is analogous to a factory assembly line in which each successive worker completes the next task, with each task requiring more and more specialization or training . Another theory suggests that there is some interaction between the different levels of hierarchy in visual processing, with certain areas of the brain getting feedback from others . This mechanism is believed to be necessary to deal with degraded images that require the brain to make inferences, such as when edges and boundaries are not clear . This would be analogous to the structure in the army in which foot soldiers make observations, report them to their superiors, who then receive orders themselves and pass them back to the foot soldiers to be carried out. These orders help the foot soldiers who can then make better observations, with the cycle repeating until the processing is complete . Although these theories could be equally valid, a majority of the experts believe that no new information needs to be presented in order to properly recognize an object, even when the image is degraded . Therefore, the first theory is more widely supported.
In order to recognize an object our eyes must have a properly functioning lens, photoreceptors, retina, and an undamaged optic nerve . Disorders of the lens that prevent proper object recognition include: cataracts, myopia, and hyperopia. It is also possible for there to be damage to the optic nerve, in the form of glaucoma . First light travels through the lens, hits the retina, activates the appropriate photoreceptors, depending on available light, which convert the light into an electrical signal that then travels along the optic nerve to the lateral geniculate nucleus of the thalamus and then to the primary visual cortex. It is in the primary visual cortex where the adult brain processes information such as lines, orientation and color. These inputs are then integrated in the occipito-temporal cortex where a representation of the object as a whole is created . Visual information then continues to be processed in the posterior parietal cortex, also known as the dorsal stream, where the representation of an objects shape is formed using motion-based cues   . This portion of the brain is primarily tasked with identifying where an object is located . It is believed that simultaneously information is being processed in the anterior temporal cortex, also known as the ventral stream, where object recognition, identification and naming are primarily thought to take place  . When we are in the process of recognizing an object both the dorsal and ventral streams are active, but the ventral stream, and therefore shape cues, seem to be more important in discriminating between and recognizing objects . There only seems to be a significant contribution to object recognition by the dorsal stream when two objects we are trying to discriminate between have very similar shapes and the images are degraded . It is estimated that we are capable of categorizing an object in 150 ms, completing the recognition in 200 ms, and able to behaviorally react to the object recognition within 350 ms . It is the observed latency in activation of different parts of the brain that supports the idea of hierarchal processing of visual stimuli, with object representations progressing from simple to increasingly complex  .
By 5 months of age infants like adults are capable of using line junction information to perceive 3D images, including depth and shape . However, there are differences between younger infants and adults in the ability to use motion and color cues to discriminate between two objects . The identification of differences between the infant and adult brain make it clear that there is either functional reorganization of the infant’s cortex or simply age related differences in which the brain completes the process of object recognition . Functional reorganization seems very likely since there is a marked increase in synaptic growth and axon myelination observed early in the life of the infant . Although the infant brain is not identical to the adult brain it is similar in that it has areas of specialization and that a hierarchy of processing exists .
In infants motion processing is the earliest visual processing capability to develop, and assists them with maintaining their balance and allows them to avoid objects coming towards them . It has been demonstrated that by 4.5 months of age infants are able to distinguish between two objects based on contours and shapes, but that they still cannot interpret color differences . In these younger infants activation is mainly seen in the parietal cortex, indicating that they are very dependent on motional cues . The next step is the development of the ability to process colors, which develops slower in females than males, however by the time the child is 11.5 months old they are able to recognize that the same object in another color is different . These older infants mainly show activation in the temporal cortex, providing evidence that they are using the ventral stream, indicating they are more dependent on cues from shape than they are on motional cues . This shift is very similar to what is seen in the adult brain  . The greatest changes in an infant’s ability to recognize objects occurs between the ages of 3 months and 11 months, however, changes do continue to occur after this time, with the child’s visual acuity increasing .
When there is dysfunction in the perception of objects, people can have trouble distinguishing differences in sizes and shapes of objects and also have difficulty reading words. It is also possible to develop problems in recognizing faces, also known as prosopagnosia .As we get older or suffer traumatic brain injury, certain abilities can be lost . It is also possible for object recognition to be impaired because of disorders such as epilepsy .
Injury and Illness
Potential injuries to the brain include but are not limited to stroke, oxygen deprivation, blunt force trauma, and surgical injuries. When patients have lesions on their brain that develop as a result of injury or illness, such as multiple sclerosis or epilepsy, it is possible that they may have impaired object recognition which can manifest in the form of many different agnosias . Similar deficits have also been observed adults that have suffered blunt force trauma, strokes, severe carbon monoxide poisoning as well as in adults that have surgical damage following removal of tumors . Deficits have also been observed in children with types of epilepsy that do not lead to the formation of lesions . It is believed that in these cases the seizures cause a functional disruption that is capable of interfering with the processing of objects . Regions that specifically lead to deficits in object recognition when a lesion is present include the right lateral fusiform gyrus and the ventrolateral or ventromedial occipito-temporal cortex  . These structures have all been identified as being crucial to the processing of shape and contour information, which is the basis for object recognition . Although people with damage to these structures are not able to properly recognize objects, they are still capable of discerning the movement of objects . Only lesions in the parietal lobe have been associated with deficits in identifying the location of an object . Although there is strong evidence to support that damage to the above mentioned areas leads to deficits in object recognition it is important to note that brain damage, regardless of the cause, is typically extensive and present on both halves of the brain, complicating the identification of key structures . Although most damage cannot be undone, there is evidence of reorganization in the unaffected areas of the affected hemisphere, making it possible for patients to regain some function .
Our brain evolved the capacity to recognize objects found in nature in order to survive. This capacity is the reason we are so good at reading since we have developed a written language that mimics the shapes of objects found in nature. Since our written languages, whether they be Russian or English, have been developed to be object-like, any deficit that prevents efficient recognition of objects will also affect our ability to read . These learning disabilities fall into the category of nonverbal learning disorders.
The most obvious causes of visual dysfunction in the older population are defects of the eyes such as cataracts that make it more difficult to develop the necessary retinal image. As we get older we are also not able to process stimuli as efficiently, hindering our ability to identify objects. More specifically, recognizing the most basic visual components of an object takes a lot longer. Since the time it takes to recognize the object-parts is expanded, the recognition of the object itself is also delayed . Recognition of partially blocked objects also slows down as we age In order to recognize an object that is partially obscured we need to make perceptual inferences based on the contours and borders that we can see. This is something that most young adults are able to do easily, but it is something that slows down with age . In general, there is a decrease in the processing capabilities of the central nervous system, which delays the very complex process of form perception .
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