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At birth there are only rudimentary acts of communication symptoms 5th week of pregnancy buy generic asacol on-line, such as crying treatment genital herpes order asacol 800mg with visa, whereas by the third year children have the sophistication and competence to symptoms gallbladder problems cheap asacol 800mg without prescription use language. This chapter will consider two major topics: joint attention and language acquisition. Rather than providing a detailed review of the process of communicative development, the purpose of this chapter is to present arguments about the need to look beyond the form of communicative behavior to try to understand the important aspects of knowledge and representation which allow infants to be involved in communicative processes. Origins and Development: Procedures and Assumptions Communication is usually regarded as involving the transmission of information. The communication of information can be considered to occur without the intention to affect others, as when a newborn baby cries. However, this chapter will concentrate on communicative behavior that appears to involve some form of Many thanks to Suzanne Zeedyk and Gavin Bremner for their comments on an earlier version of this chapter. One of the main arguments put forward in this chapter is that when considering development, it is useful to distinguish between procedures and assumptions. I will use the term "procedure" to refer to either behaviors directed toward some specific objective that we can observe. Consequently, there is usually little in the way of disagreement among investigators about whether a procedure is present or absent. In contrast, "assumptions" involve knowledge or perspectives about the world, and the presence of assumptions has to be inferred from the organization of behavior and/ or information processing. As a result, procedures are influenced by the assumptions that infants have about their world. It should be apparent that there is likely to be much more debate amongst investigators about the presence and nature of assumptions. Thus, pointing at an object or monitoring the gaze of another person can be thought of as procedures. Such procedures are largely automatic and do not usually involve conscious control beyond deciding whether to point, or whether to continue to monitor the gaze of the person. As children develop, procedures usually become more skilled, efficient, and effective (see Bruner, 1977). Procedures might also occur in parallel, such as when infants smile and wave their arms in excitement at greeting someone. Infants have a number of primitive procedures to help them manage social interaction, for example smiling, vocalizing, expressing pleasure, turning away, and crying. It is worth commenting that much of the recent research on communication during infancy has concentrated on procedures associated with the processing of information rather than on the communicative acts of infants. Part of the reason for this is that there are relatively few conventional gestures, apart from pointing, to study (but see Bruner, 1975; Lock, 1980), and that the coding of less conventional movements is extremely difficult. It could be objected that the monitoring of gaze of another person or working out what is the referent of a word are aspects of information processing. However, these aspects of information processing are in a sense complementary to producing an act of communication such as pointing; communication involves both producing communicative acts and decoding the communicative acts of others. In both cases, infants 286 David Messer can become more skilled, effective, and efficient as they become older and more experienced. For example, Hollich, Hirsh-Pasek, and Golinkoff (2000) have shown the way that infants between 12 and 18 months greatly expand their ability to make a link between a word and an object. Older infants are much better at identifying relevant objects because they are much better at understanding the format of social interaction and the perspective of other people. These infants are able to divorce themselves from the attractiveness of objects to become able to relate to objects in which an adult is interested. Nor does it seem that this is the result of a major cognitive reorganization; much more likely is that it is a gradual change in efficiency and effectiveness. As already mentioned, the term assumptions will be used to refer to the knowledge or perspectives that guide procedures. However, I will argue that investigators interested in social and communicative development have paid less attention to assumptions and, as a result, we still have a partly fragmented picture of the organizational processes that are responsible for behavior. Furthermore, although I will be discussing procedures and assumptions about the communication of information, the perspective also could be applied to socioemotional aspects of communication. In addition, it is worth stressing that assumptions can most clearly be identified from evidence that various behaviors across different situations show evidence of the same principles being employed.
But this is not to treatment vertigo asacol 800 mg free shipping deny the role of another action system in the process: exploration of objects via eye movements medicine keri hilson lyrics order 800 mg asacol overnight delivery. The oculomotor system is largely functional at birth and matures rapidly (Johnson treatment zenkers diverticulum order asacol from india, 2001a), and even neonates scan the environment in a systematic fashion, attending more, for example, to edges than to homogeneous regions of visual space (Haith, 1980; Slater, 1995). There are important developments between 2 and 4 months in the extent of scanning some kinds of stimuli, such as displays of partly occluded objects: younger infants scan less "efficiently," tending to fixate specific parts of the display rather than all the visible surfaces (Johnson 196 Scott P. It remains unknown, however, how scanning patterns contribute to unity perception directly. It could be, for example, that infants learn about unity by frequent alternating fixations of the visible regions of partly occluded objects. Learning and experience Learning about occlusion and perceptual filling-in might be a deductive process: repeated exposure to many instances of objects becoming occluded and reemerging, and subsequent identification of partly occluded objects as continuous, via an associative process. Occlusion and disocclusion are ubiquitous: all sighted observers, including young infants, are exposed to multiple instances of such events routinely in the normal visual environment, and young infants are remarkably adept at rapid associative learning. Recently, Denis Mareschal and I asked whether associative learning may be a viable mechanism by which an observer could learn to perceive object unity (Mareschal & Johnson, 2002). We created several connectionist models that were presented with input representing moving objects and an occluder, and subsequently tested the models for their response to a partly occluded object. During training, the models were exposed to events in which a complete object was seen to become occluded and then emerge again, so that the model received information for the identity of views of a single object. The models were successful at responding to a partly occluded object as being continuous, despite the occlusion, providing evidence for the possibility that a similar associative process might be at work in human infants in building object representations from multiple exposures of objects. A second demonstration of learning from experience was completed recently in my laboratory. We reasoned that perception of the ball as persistent despite occlusion, and perception of the trajectory as continuous, would be evinced by a pattern of consistent anticipations. First, 4-month-olds were expected to exhibit fewer anticipations than would 6-month-olds, because of earlier evidence of marked changes in perception of trajectory continuity across this age range (Johnson, Bremner et al. Second, 4-month-olds were expected to benefit from a short time of exposure to an unoccluded trajectory event, as reflected in a greater proportion of anticipations when subsequently viewing the partly occluded trajectory. Six-month-olds, in contrast, were expected to receive no special benefit from this kind of experience, because the older infants are already capable of perceiving trajectory continuity (Johnson, Bremner et al. Infants in the younger age group produced far fewer anticipations than did the older infants when viewing the partly occluded trajectory displays. When first presented with events in which the ball moved on an unoccluded trajectory (the "training" condition), however, the number of anticipatory eye movements made by 4-month-olds was roughly equivalent to the number made by the 6-month-olds who had viewed the partly occluded trajectories only. The 6-month-olds in the enrichment condition, however, did not produce more anticipations than did the 6-montholds who had seen only the partly occluded trajectories. This may indicate that 6-month-olds are immune to the potential effects of experience in enhancing performance on this task, because they come to the task with the ability to form object concepts. Neurophysiological development A complete account of cortical development is beyond the scope of this chapter, of course, and excellent recent reviews are available. For the sake of the present discussion of developmental origins of object concepts, it is worth highlighting some of what is known about cortical mechanisms of perceptual filling-in, and how such mechanisms might develop in infancy (see Johnson, in press, for further consideration of these possibilities). Perception of edge connectedness across a spatial gap may be accomplished with relatively low- and mid-level mechanisms. First, long-range cell-to-cell interactions in early visual areas connect neural circuits coding for common edge orientations may reach sufficient maturity within several months after birth to support unity perception under some circumstances (cf. Second, there are improvements in firing patterns of cell assemblies across the brain by reduction of neural "noise" (Singer, 1995; Skoczenski & Norcia, 1998). Perception of object persistence under occlusion may be accomplished by somewhat higher-level mechanisms. These behaviors include anticipatory eye movements in young infants, and reaching behaviors in older infants. This progression toward appropriate search in the context of complex hiding tasks is consistent with a view positing age-related strengthening of neural representations, such that with development, stronger representations support success at enacting appropriate behaviors across a wide range of situations involving occlusion (Munakata, 2001).
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The majority of oral cancers involve the tongue symptoms 7 order discount asacol online, oropharynx chi royal treatment asacol 400 mg without a prescription, and floor of the mouth symptoms underactive thyroid purchase asacol online from canada. Individuals who have had a previous cancer are at high risk of developing a second oropharyngeal cancer. Etiology and risk Factors the incidence of oral cancer is age related, which may reflect time for the accumulation of genetic changes and duration of exposure to initiators and promoters (these include chemical and physical irritants, viruses, hormonal effects), cellular aging, and decreased immunologic surveillance with aging. NutritioNal Factors Tobacco and alcohol are acknowledged risk factors for oral and oropharyngeal cancer. Tobacco smoke contains carbon monoxide, thiocyanate, hydrogen cyanide, nicotine, and metabolites of these constituents. Epidemiologic studies have shown that up to 80% of oral cancer patients were smokers. Smoking has declined in North America, particularly in adults; approximately 30% of adults smoke. This trend may be emerging worldwide but is not seen in teenagers and young adults. The incidence of oral squamous cell cancer varies worldwide and may be explained partly by differences in the use of tobacco products. In parts of Asia where the use of tobacco, betel nuts, or lime to form a quid is widespread (eg, India, Taiwan), the incidence of oral cancer is high and more commonly involves the buccal mucosa. The use of smokeless tobacco products (chewing tobacco and snuff) is of increasing concern due to the increase in their use and to their use at a young age. However, it has been suggested that smokers may use mouthwash more frequently; thus, the correlation between regular use of high-alcohol mouthwash and oral cancer may be confounded by alcohol and tobacco use. In lip cancer, sun exposure, fair skin and a tendency to burn, pipe smoking, and alcohol are identified risk factors. There is no epidemiologic evidence of an association between fluoride and osteosarcoma or other malignant disease in humans. There is an ongoing debate about whether oral lichen planus is a premalignant lesion or a disorder. The assessment of molecular change may become the primary means of diagnosis and may guide management. Cytokine growth factors, angiogenesis, cell adhesion molecules, immune function, and homeostatic regulation of surrounding normal cells also play a role. Proto-oncogenes may coding for growth factors, growth factor receptors, protein kinases, signal transducers, nuclear phosphoproteins, and transcription factors. Chromosomes are numbered (1 to 23), and the arms of each chromosome are divided by the centromere into a short arm (designated P) and a long arm (designated Q). Molecular markers are likely to become important clinical markers in diagnosis and staging and in treatment planning. Later changes are seen on chromosomes 13 and 17, which are associated with progression to malignancy. Syndecans are a family of heparan sulfate proteoglycan receptors that are thought to participate in both cell-to-cell and cell-to-matrix adhesion. The interaction of viruses with other carcinogens and oncogenes may be an important mechanism of disease. Other cell surface changes include a loss of cytoplasmic membrane binding of lectins, which has been shown to correlate to the degree of cellular atypia. Alterations in cell-bound immunoglobulins and circulating immunocomplexes are detectable, but the importance of these changes is unclear. Intracellular enzymes are altered or lost, commensurate with the degree of cellular dysplasia. The development of malignant disease in immunosuppressed patients indicates the importance of an intact immune response (see above). Mononuclear cell infiltration correlates with prognosis, and more aggressive disease is associated with limited inflammatory response.
As infants become more independently mobile during the first year symptoms jaw pain proven 400 mg asacol, they begin to treatment for vertigo best purchase asacol explore the relationship between their body orientations and the spatial layout of the environment symptoms bladder infection buy discount asacol on-line. According to a detailed longitudinal study by Adolph (1997), as infants move forward across the floor, they pause, pat the floor, and rock back and forth over their wrists. Using the hand to pat the floor is probably a means for testing the suitability of a surface ahead for locomotion. Indeed, studies on the visual cliff show that some crawling infants will reorient the body to extend forward the longest appendage, a leg, rather than the arm, to test a surface to be crossed (Campos, Bertenthal, & Kermoian, 1992). The use of the hands for exploratory purposes in the development of postural control has also been demonstrated in a paradigm developed by Barela, Jeka, and Clark (1999). They found that prior to walking, infants used greater force in touching the cube, indicating that they were using it for support. However, once infants began to walk, hand contact preceded body sway, and was used prospectively to modulate sway before it occurred. The muscles and tendinous elements exhibit the additional properties of elasticity and damping. Based upon consideration of these constraints, Holt (1998) has developed a force-driven hybrid pendulum-spring model of the preferred gait patterns of adults. Understanding how force production is Infant Action: A Dynamical Systems Perspective 23 related to the dynamics of walking is crucial not only for healthy adults but also for adults and children with cerebral palsy. The model addresses two well-documented findings for walking: (1) there is a preferred combination of stride frequency and length (a speed) at which energy expenditure per unit distance is minimized at approximately 0. A dynamical systems perspective predicts that the nervous system does not choose frequency or stride length; they are emergent properties of a linear oscillator operating in its resonant mode. To test this prediction, Holt, Hamill, and Andres (1990) experimentally increased inertial load by adding ankle weights during walking. If frequency is driven by the dynamics, then it should change according to the resonant period for the new inertial condition. We just saw that the fundamental property of a nonlinear oscillator, such as a mass attached to a spring, is that it requires a minimal amount of force to sustain oscillation of a mass when driven at its natural frequency. When a driver forces a mass-spring system, a peak occurs in the amplitude response near its natural frequency. At this peak, the system is said to "resonate" to the driver, and so this is called a resonance peak. On the basis of this work with adults, Goldfield, Kay, and Warren (1993) conducted longitudinal observations of infants learning the dynamics of a mass-spring system: their own body suspended in a harness with feet touching the floor from a spring of known stiffness and damping. Videotape recordings were made in the home once each week over a period of several weeks, as the infants learned to bounce. It was further hypothesized that over longitudinal observations, infants were searching frequencystiffness space to find the resonant frequency. The resonant frequency depends upon the stiffness of both the spring and the legs, so in order to achieve maximum amplitude, the infant should match leg stiffness to spring stiffness. There was also an increase in amplitude over sessions, consistent with the hypothesis of exploration of a resonance peak, observed when a system is driven at its resonant frequency. More recently, Foo, Goldfield, Kay, and Warren (2001) examined what infants learned during this task by experimentally manipulating the system parameters of mass and spring stiffness once infants had already achieved their peak bout length while bouncing in the jumper. The major question was whether infants learned particular parameter settings per se, or learned the dynamics of the task, which would allow them to quickly adapt their leg stiffness and kicking frequency to new conditions. Both the mass and spring manipulations were effective in changing the bouncing frequency. Moreover, at their first opportunity under each of the experimental conditions, infants began to bounce, indicating that they were exploring the dynamics of their actions rather than learning a particular parameter setting. Conclusion the foregoing account of a dynamical systems approach to infant motor development highlights the processes of self-organization and selection by which new behaviors emerge. Its promise as a unique approach lies in the methods by which new questions about motor development can be addressed. By developing mathematical models and computer simulations that attempt to capture neural, biomechanical, and environmental contributions to the emergence of new behaviors, the approach will continue to be useful for addressing the complexities of motor behavior. Its greatest challenge remains in providing ways to understand the relation between action and the domains that have traditionally Infant Action: A Dynamical Systems Perspective 25 been treated as separate human capabilities, namely, cognition, language, and social discourse. The use of somatosensory information during the acquisition of independent upright stance. Development of postural control of gravity forces in children during the first 5 years of walking.