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.
To test these hypotheses, we first collected a two point discriminator containing a variety of distances for two points. The point distances on the discriminator included values of.25 millimeters being the smallest, ...
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...7 millimeters was guessed incorrectly, thus indicating the lack of sharpness subject 1 possessed in this area of the body. Next we proceeded with subject 2, under very similar conditions. Subject 2 was tested with more pressure points than subject 1 to proceed to more detailed results. Beginning with the finger, subject 2 guessed 7 out of 8 pressure points correctly. This result shows a very good acuity to his tactile system around the fingers, as stated by (Bruce et al. 1980). Next we proceeded with his forearm, in methods similar to subject 1 but with more pokes. In this test subject 2 only guessed 2 out of 7 of the points correctly, indicating a sharp decrease in acuity in these areas. Lastly we applied the moving two point discrimination test on a third subject. We started at the palm and he felt the two points only by the time we moved 3 mm towards the finger.
Sullivan, G. D., Georgeson, M. A., & Oatley, K. (1972). Channels for spatial frequency selection and detection of single bars by the human visual system. Vision Research, 12, 383-94.
The first, which he refers to as the “weak view” (5), is that we simply perceive with different sense modalities (e.g. touch, taste, vision, etc.). But, this view appears inadequate in the face of physiological and experiential evidence. O’Callaghan points out that neurological pathways activate in unison, and that our perception appears to us as one continuous experience, rather than subdivided into individual experiences of each different sense. (6) O’Callaghan admits that the senses often outwardly appear to be unimodal, experience does not seem broken up into different senses but appears continuous. He then goes on to support this claim with evidence from psychological
The hand is also becoming more advanced with a system discussed in the January 1998 issue of Tech Directions. This system, know as Sabolich's Sense of Feel System, uses a cuff attached to the remaining portion of the limb. Over time a user is able to recognize exactly how much pressure they are using. This system differs form earlier ones in which judgement was based simply on sight, which is not very accurate.
The merging of certain senses points to a crossing of signals in the brain. Although the theory is an old one, it has come to the forefront of the scientific researcher's minds, with increased focus on the topic.
Let’s say that there is a mechanical sense. If someone touched your hand, your somatosensory system will detect various stimuli by your skin’s sensory receptors. The sensory information is then conveyed to the central nervous system by afferent neurons. The neuron’s dendrites will pass that information to the cell body, and on to its axon. From there it is passed onto the spinal cord or the brainstem. The neuron's ascending axons will cross to the opposite side either in the spinal cord or in the brainstem. The axons then terminates in the thalamus, and on into the Brodmann Area of the parietal lobe of the brain to process.
Touch---travels through spinal cord---into medulla---left side functions of the body is controlled by the right side of the brain and the right side of the body is controlled by the left side of the brain.
These patterns occur only with intense stimulation. Because strong and mild stimuli of the same sense modality produce different patterns of neural activity, being hit hard feels painful, but being caressed does not. It suggested that all cutaneous qualities are produced by spatial and temporal patterns of nerve impulses rather than by separate, modality specific transmission routes. Gate control theory of pain states that stimulation by non-noxious input is able to nullify pain.
Weber, in his study of the senses, experimented with muscular sensations and cutaneous senses by way of the two-point threshold and the just noticeable difference. His research revealed that there could not be a direct connection between our perception of a physical stimulus and the stimulus itself.
The purpose of this experiment is to determine which body areas are well represented with touch receptors. For lab 1 (tactile localization), a student’s hypothesis was; If the marker is dotted on a palm, then this will be the most accurate tactile localization. The palm showed this characteristic partially but is not true. Based on the experiment, the palm was more accurate than half of the other locations. With the fingertip averaging 4 mm, back of the hand with 5.7 mm, the neck with 9.7 mm, then the palm of the hand with 11.4 mm and three other locations with greater average distances. So the hypothesis was incorrect, the correct hypothesis would be; “If the marker is dotted on the fingertip, then this will be the most accurate tactile localization.”
One of the more recent studies done on extra sensory perception was conducted by Daryl B...
Fisher discriminants group images of the same space and separates images of different classes (Delac, Grgic, 2006). Images are projected from N2 dimensional space to C dimensional space that are projected onto a single line. Depending on the direction of the line, the points can either be mixed together, or separated (Batagelj, 2006).
If one was required to put a definition on analytical discrimination, what would it mean? In the article “Discrimination is a virtue,” author Robert Keith Miller discusses the word “discrimination” and its true meanings, stating it as just knowing a difference. So if the question were asked once again, would it be possible to discriminate the appeals used in analytical analysis? Miller presents us stories and examples to point out a “lost” definition of a word often overheard, but never studied. His use of appeals sides with logos, discriminates against ethos, and makes anti-pathos a reality. His writing appeals to the mind, leaving much to ponder, though these thoughts may be lost in the whirlwind of ink ideas thrown into a paperback debate.
Interestingly, the same type of brain arousal takes place whether people actually do finger tapping or only imagine it. What surprised Sutton most, however, was the detection of remarkably similar activity in much larger networks spanning areas of the cortex dealing with both input from the senses and output signals to the muscles. "Patterns of activity in small, more primitive areas of the brain are recapitulated in larger, more advanced parts," Sutton says. "This means that nature did not have to develop new rules of operation for different levels of the brain from small clusters of cells to large systems."
The distance where by a search scanner can discover something different first from its surroundings but not yet identify it.