There are many perceptual disorders but first we must cover what a perceptual disorder actually is. Perceptual disorders are cognitive disorders characterised by impaired ability to perceive objects through sense organs as a result of the brain or eye being damaged. In this essay I will compare and contrast a variety of perceptual disorders and provide insight as to how they are caused by deficits.
The first disorder that will be mentioned is Agnosia and the two types of Agnosia; Apperceptive Agnosia and Associative Agnosia. Agnosia in general is a failure of recognition which is not attributed to a sensory deficit. There is a visual specific Agnosia which interferes with visual stimuli recognition, in particular inability to recognise objects from visual information. As prior mentioned there are two forms one being, Apperceptive Agnosia. This is the inability to recognise objects and have impaired ability to draw objects. The second type of Agnosia is associative Agnosia, this is the inability to make meaningful associations between objects that are visually presented. While they can copy unlike Apperceptive they can recognise these drawings. In Associative damage is usually located in borders between optical and temporal lobes in both hemispheres but it can be limited to one. Damage in Apperceptive which not always in a fixed place usually has high correlation of damage caused to the occipital lobes usually in the left hemisphere which causes these recognition problems.
Lissauer (1890) made an important distinction between Apperceptive and Associative Agnosia. He found that Apperceptive recognition can occur without acuity or other sensory functions whereas associative cannot. Ettlinger (1956) can follow on with his research sh...
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...ioned that Blindsight may be a direct result of a scotoma it has also been noted that it is generally caused by lesions to their striate cortex or their primary visual cortex.
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The symptoms of a right-hemisphere stroke are very much similar like the symptoms Mr. Fix-it is experiencing. For example, both suggest that functions on the left side of the body are completely neglected; therefore, the left visual section of the body does not respond effectively to stimuli due to the neglect. Damage to the right occipital lobe is very likely. The patient may have experienced some damage to areas 18 and 19 of the occipital lobe. “Damage to these association areas resulted in the patient’s failure to recognize items even when they have been seen before”, such as Mr. Fix-it’s deficiency to recognize geometric shapes (Carlson, 2010). Moreover, the patient could have also experience damage in the frontal lobe, specifically on area 8, in which it could have r...
The ultimate goal for a system of visual perception is representing visual scenes. It is generally assumed that this requires an initial ‘break-down’ of complex visual stimuli into some kind of “discrete subunits” (De Valois & De Valois, 1980, p.316) which can then be passed on and further processed by the brain. The task thus arises of identifying these subunits as well as the means by which the visual system interprets and processes sensory input. An approach to visual scene analysis that prevailed for many years was that of individual cortical cells being ‘feature detectors’ with particular response-criteria. Though not self-proclaimed, Hubel and Wiesel’s theory of a hierarchical visual system employs a form of such feature detectors. I will here discuss: the origins of the feature detection theory; Hubel and Wiesel’s hierarchical theory of visual perception; criticism of the hierarchical nature of the theory; an alternative theory of receptive-field cells as spatial frequency detectors; and the possibility of reconciling these two theories with reference to parallel processing.
Understanding of Children with Congenital Profound Visual Impairment." British Journal of Developmental Psychology, 22.1 (2004): 1-17.
Hemineglect does not just present itself visually, but also through other senses such as motor neglect, auditory neglect, representational neglect and also personal neglect (Plummer, Morris, & Dunai, 2003). Hemineglect is not a result of sensory disorder. It is not uncommon to receive left hemisphere lesions or trauma and gain hemisphere remission. It does seem however that it is easier to treat and rehabilitate patients to a full recovery if this damage has occurred, compared to right hemisphere damage. Hemineglect is present when there is damage to the dorsal/ visual pathway in the brain which leads from the occipital lobe of the brain to the parietal lobe.
Classical theories demonstrating the inattentional blindness paradigm are (1) the perceptual load, (2) inattentional amnesia and (3) expectation.
Visual agnosia is a neurological disorder characterized by the inability to recognize familiar objects (Farah, 1990). Object recognition is the ability to place an object in a category of meaning. Most cases of visual agnosia are brought about through cerebral vascular accidents or traumatic brain injury typically inhibiting sufficient amounts of oxygen from reaching vital body tissues (Zoltan, 1996). There are a vast array of impaired abilities and deficits associated with individuals diagnosed with visual agnosia. These impairments vary considerably from individual to individual (Farah, 1990). Some patients cannot recognize pictures of things such as trees and birds, despite being able to describe such objects or recognize them through other senses such as sound and touch. Other patients demonstrate an inability to recognize faces of friends and family members (Goodale, 1995). The functional impairments experienced as a r...
[19]Tranel, D., Damasio, H., Damasio, A.R., 1995. Double dissociation between overt and covert recognition. Journal of Cognitive Neuroscience 7, 425–432.
Sensory Processing Disorder is a condition that exists when sensory signals don’t get controlled into proper responses. It prevents part of the brain from receiving information to understand everything correctly. Sensory processing is the way our nervous system receives messages from the senses and turns them into appropriate motor and behavioral responses. An individual with sensory processing disorder finds it complicated to process and operates from receiving information. Sensory Process Disorder develops when the child is in the womb and stays with the person throughout their life. Sensory Processing Disorder creates difficulty in interaction with others, daily routines, socially, behaviorally, emotionally and could have effects on
In this lab we apply the technique known as a two point discrimination test. This test will allow us to determine which regions of the skin are best able to discriminate between two simultaneous sensory impulses. According to (Haggard et al. 2007), tactile discrimination depends on the size of the receptive fields located on the somatosensory neurons. However receptive fields for other types of sensations are located elsewhere. For vision we find that the receptive fields are located inside the visual cortex, and for hearing we find receptive fields in the auditory cortex. The ability for the body to discriminate two points depends on how well that area of the body is innervated with neurons; and thus conferring to the size of the receptive fields (Haggard et al. 2007). It is important to note that the size of the receptive field generally decreases in correlation to higher innervations. As was seen in the retinal receptive fields, the peripheries of tissue had contained larger receptive fields (Hartline, 1940). In our test we hypothesized that the finger region will be able to discriminate better than the forearm. This means that they will be much more innervated with neurons than the forearm, and likewise contain smaller receptive fields. This also means that convergence is closer to a 1:1 ratio, and is less the case the farther from the fingers we go. We also think that the amount of convergence is varied with each individual. We will test to see if two people will have different interpretations of these results.
Amblyopia is a condition in which visual acuity in one eye is greatly reduced. It is caused by lack of stimulation or disuse during visual development (Rose, 1998). Because the eye is not fully developed at birth (Jarvis, 1992, as cited in Rose, 1998), infants need stimulation to complete the visual neural pathway. When one or both eyes are inhibited, for example due to misalignment of one eye (strabismus) or a large difference in refractive power between two eyes (anisometropia), the neural pathway for the inhibited eye develops abnormally, or does not develop at all. At approximately six years of age eye development is complete (Stager, 1990, as cited in Rose, 1998). Before visual development is complete amblyopia can be treated. If it is caught and treated at an early age, normal vision can be preserved (Rose, 1998).
Broadbent’s (1958) filter theory of attention proposes that there is a filter device between sensory identification and short-term memory. This filter is used as a buffer that allows an individual to manage several different forms of simultaneous stimuli where one stimulus is processed in the filter whilst the second stimulus is kept in the buffer to be processed at a later time (Broadbent, 1958). The extent to which this theory of attention can provide an effective explanation of how we attend to objects is questionable due to the fact that Broadbent’s filter theory is designed to explain auditory attention as opposed to visual attention. In this sense, Broadbent’s filter theory cannot explain how we attend to objects and thus provides no useful information for such attention. An object was making a sound co...
Perception is defined as the process of organizing, interpreting, and selectively extracting sensory information . Visual perception is left to the individual person to make up their own mind. Perceptual organisation occurs when one groups the basic elements of the sensory world into the coherant objects that one perceives. Perception is therefore a process through which the brain makes sense of incoming stimuli.
Each one of us lives in our own unique world of perception. As individuals, we may experience life in an entirely different way through our senses and life experiences. Therefore, perception can be tricky since it is very personal to each one of us. According to the Merriam-Webster online dictionary, perception has three meanings; (1) “the way you think about or understand someone or something,” (2) “the ability to understand or notice something easily,” and, (3) “the way that you notice or understand something using one of your senses” (2014, para. 1). C.S. Lewis said, “What you see and what you hear depends a great deal on where you are standing. It also depends on what sort of person you are” (n.d., para. 11). In other words,
The patient is a 43 year-old female insurance sale agent who came to the clinic for annual eye examination. She complained from symptoms of ocular irritation and burning when she wakes up in the morning. She felt ocular dryness in the afternoon and the eyes look red. She has also noted different height of her eyelids when putting make-up on. She denied significant problems with driving, TV watching, computer use or reading. She also denied flashes, floaters or diplopia. The patient was myopia with no prior eye surgeries, previous history of eye trauma, amblyopia or strabismus. She did not use any medication. The past ocular family history was negative. Social history was negative, too.
Perception is defined as the awareness of the world through the use of the five senses, but the concept of perception is often used to isolate one person’s point of view, so how reliable can perception be if no one person’s is exactly the same? The word perception itself is riddled with different, well, perceptions of its meaning. When some hear the word, they might automatically think of it as something innately flawed, that can easily be fooled by illusions, while others may think of its usefulness when avoiding scalding a hand on a hot stove. I am here to agree with both and to argue that perception is something necessary and helpful, and something that should be scrutinized for its flaws. By looking at perception as a way of knowing in the context of memory and human sciences, it can be concluded that perception can contribute to the acquisition of knowledge by constructing a foundation on which incoming stimuli from the environment are able to be quickly interpreted and acted upon, but perception can also hinder the acquisition of knowledge by wrongly interpreting those stimuli, causing inappropriate reactions.