The human brain is capable of perceiving and interpreting information or stimuli received through the sense organs (i.e., eyes, ears, nose, mouth, and skin) (Weiten, 1998). This ability to perceive and interpret stimulus allows the human being to make meaningful sense of the world and environment around them. However, even as the human being is able to perceive and interpret stimuli information through all sense organs, stimuli is most often or primarily interpreted using the visual (eyes) and auditory (ears) sense organs (Anderson, 2009). However, for the purpose of this paper, the visual information process will be examined. Conditions that impair the visual information process will be analyzed, in addition to, an examination of the current trends in research that are advancing the understanding of research of visual information processing. Understanding Sensation and Perception
To understand better how the brain processes visual information, an understanding of, and a clear differentiation between sensation and perception is required. Before stimuli can be perceived or interpreted, it must first be sensed through the sense. Therefore, sensation is the stimulation of sense organs (i.e., eyes, ears, nose, mouth, and skin) and involves the absorption of energy, such as light and sound waves through the sensory organs, (Weiten, 1998). Perception refers to psychological processes in which the immediate organization and interpretation of sensations are involved (Riegler & Riegler, 2008) and “involves organizing and translating sensory input into something meaningful,” (Weiten, 1998, p. 123). The Visual Processing System
People rely heavily on their sense of sight; it allows them to establish a keen sense of what in their environment is trustworthy, (Weiten, 1998). Consequently, sight is depended upon almost more than any other sense organ. As primates, human beings use as much as 50% of their brains to process visual information (Anderson, 2009). Because people primarily have an enormous dependency on sight, let us consider the functions of the eyes and how we are able to perceive and interpret information using the eyes.
The eyes serve two distinct purposes: “…they channel light through to the neural tissue that receives it, called the retina, and they house that tissue,” (Weiten, 1998, 9. 129). The eyes, a living ocular instrument, generates images of the visual world by allowing light to pass through the lens and vitreous humor to fall on the “light-sensitive retina lining the inside back surface of the eye,” (Weiten, 1998, p.129). The retina houses the light-sensitive molecules called the photoreceptor cells, which undergo structural changes when exposed to light (Anderson, 2009). A photochemical process converts light (which is scattered slightly in passing through the vitreous humor) into neural energy.
According to Anderson (2009), there are two types of photoreceptors present within the eye: cones and rods. Cones, are responsible for producing acuity and high resolution and is involved in color vision. Rods, require less light to trigger a responsiveness in the rods and produce poorer resolution, which consequently makes the rods responsible for the less acute, black and white vision experienced at night (Anderson, 2009). Cons are concentrated in a minimal area of the retina called the fovea. When the eye focuses on an object, the eyes move to allow the object to fall on the fovea. The fovea, then allows for the maximization of high resolution of the cones in perceiving the object and the detection of fine details (Anderson, 2009).
Anderson (2009) asserts that the receptor cells synapse onto bipolar cell which synapse onto ganglion cells. The ganglion cells axons leave the eye and form what is known as the optic nerve which leads to the brain. There are approximately 800,000 cells is the optic nerve of each eye and each cell encodes information from a lesser region of the retina (Anderson, 2009).
The neural pathways from the eyes to the brain consist of the optic nerves from both eyes meeting at the optic chiasma, and the nerves from the inside of the retina crossing over to go to the opposite side of the brain. The nerves from the outer part of the retina continue to the same side of the brain as the eye so that the right half of both eyes are connected to the right brain (Anderson, 2009). Therefore, the left side of the visual field falls on the right half of each eye. Accordingly, information concerning the left part of the visual field goes to the right side of the brain.
Fibers from the ganglion cells, once inside the brain, synapse onto cells in various parts of the subcortical structures located below the cortex: the lateral geniculate nucleus and the superior colliculus (Anderson, 2009). The lateral geniculate nucleus perceived detains and recognizes objects and the superior colliculus is involved in located objects in space (Anderson, 2009). Both structures are connected to the primary visual cortex which is the first cortical area to receive visual input. The ganglion cells then encode the visual fields by means of the on-off and off-on cells which “…generally fire at some spontaneous rate even when the eyes are not receiving light,” (Anderson, 2009, p. 37). The on-off cells are cells for which light father from the center elicits no change from the spontaneous firing rate with neither an increase nor decrease. The off-on cells are cells for which “…light at the center deceases the spontaneous rate of firing, and light in the surrounding areas increase that rate,” (Anderson, 2009, p. 37).
When damage to certain regions of the brain occurs, conditions may develop where one is able to register visual information but incapable to distinguish anything (Anderson, 2009). Consequently, difficulties with visual impairments can include an inability within the brain to interpret and or process visual information (Anderson, 2009). Thus, visual perception impairments or disorders typically refer to the inability to make sense of information received through sight (the eyes) (Weiten, 1998). One such visual perception disorder is visual agnosia.
Visual agnosia refers to the “…inability to recognize objects that results neither from general intellectual loss nor from a loss of basic sensory abilities,” (Anderson, 2009, p. 32). There are generally two types of visual agnosia: apperceptive agnosia and associative agnosia. Apperceptive agnosia is the inability to recognize or draw simple shapes as they are shown or represented. Associative agnosia is the ability to recognize and copy drawings of simple and complex shapes. However, person with associative agnosia are unable to recognize the complex objects (Anderson, 2009).
Visual agnosia can drastically affect one’s ability to learn. For example, a child with visual agnosia may find it difficult to recognize letters and numbers, thereby making it difficult to learn to read and perform other tasks imperative for retaining information learned. To compensate for the damage caused by visual agnosia one might increase other senses to replace or compensate for the damaged or impaired visual sense. For example, the impaired visual sense can be compensated for by using auditory and touch sensation to make sense of information that cannot be interpreted visually.
Another type of visual impairment is prosopagnosia. This impairment involves a damage to the temporal lobe. Persons with this impairment have selective difficulties recognizing faces (Anderson, 2009). Studies show that people are better equipped to recognize faces when the face is presented in the upright orientation than they are at recognizing other objects (Anderson, 2009). Studies also so that when faces are upside down there is a dramatic decrease in the ability to recognize the face.
According to Psychology Today (2013) “Acquired prosopagnosia can kick in after a brain injury or stroke, whereas developmental prosopagnosia appears early and seems to have genetic roots.” Also called face blindness, there is no cure for prosopagnosia. Consequently, those with this visual impairment must learn to recognize and recall other features about a person to readily identify the person (e. g., the color of the hair, the tone of their voice, body mannerisms, and height) (Psychology Today, 2013). Current Trends in Visual Information Processing Research
Current developments in the visual information processing research is centered on a lesser degree of prosopagnosia in persons with Autism Spectrum Disorder (ASD). According to Behrmann, Thomas, and Humphreys (2006), recent behavioral and neuroimaging studies have documented an impairment in face recognition in individuals with autism. While it is still relatively unknown what causes the face processing difficulty in persons with autism, some theories suggest that the difficulty derives from a pervasive problem in social interaction and or motivation. However, other theories suggest that the difficult with face processing is not entirely social in nature and that a visual perceptual impairment might also contribute to the difficulty. Conclusion
This paper has shown the unique shown the complexities of the visual information processing system. Detailing the sequential processing of stimuli information as it flows through the visual sense to cognitive processes, the visual information process uses the functions of the eyes to effectively generate visual images by allowing light to pass through the eye to transmit visual sensory information to the brain or perception and interpretation. Damage to the brain can damage the visual processing system causing a varied number of impairments that can make perceiving and interpreting stimuli received through the visual extremely difficult.
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