Minggu, 01 Juli 2018

Sponsored Links

Infantile Amnesia: A Critical Period of Learning to Learn and ...
src: www.jneurosci.org

In developmental psychology and developmental biology, critical period is the stage of maturation in the life span of organisms in which the nervous system is very sensitive to certain environmental stimuli. If, for some reason, the organism does not receive the right stimulus during this "critical period" to learn certain skills or traits, it may be difficult, ultimately less successful, or even impossible, to develop some functionality later on. The indispensable functions for the survival of organisms, such as vision, are highly likely to develop during this critical period. "Critical Period" also relates to the ability to get one's first language. Researchers found that people who passed a "critical period" would not get their first language fluently.

Some researchers distinguish between 'critical' and 'sensitive' periods - defining the 'sensitive' period as a longer period, after which learning is possible. Other researchers consider this the same phenomenon.

For example, the critical period for the development of binocular vision of the human child is estimated to be between three and eight months, with sensitivity to damage extending to at least three years. Further critical periods have been identified for the development of hearing and vestibular systems.

Confirming the existence of a critical period for a given ability requires evidence that there is a point after the associated behavior no longer correlates with age, and the ability remains at the same level. Some experimental studies into the critical period have involved extracting animal stimuli at various stages of development, while other studies have looked at children who have lost certain experiences due to illness (such as temporary blindness), or social isolation (such as wild children). Many studies that investigate critical periods for language acquisition focus on deaf children who hear parents.


Video Critical period



Linguistics

First language acquisition

The critical period hypothesis (CPH) states that the first few years of life represent the time in which language develops easily and after that (sometimes between the age of 5 and puberty) language acquisition is much more difficult and ultimately less successful. The hypothesis that language was acquired during the critical period was first proposed by neurologists Wilder Penfield and Lamar Roberts in 1959 and popularized by linguist Eric H. Lenneberg in 1967. Lenneberg argues for a hypothesis based on evidence that children who suffered brain injury early in life developing language skills that are much better than adults with similar injuries.

Dr. Maria Montessori was one of the previous educators who brought attention to this phenomenon and called it the "Sensitive Period", which is one of the pillars of his educational philosophy.

The two most famous cases of children who failed to get language after a critical period were Genie and the wild child of Victor of Aveyron. However, the tragic circumstances of these cases and the moral and ethical impossibility of replicating them make it difficult to draw conclusions about them. Children may have cognitive defects since infancy, or their inability to develop language may be due to their neglect and abuse.

Many later researchers have developed CPH, especially Elissa Newport and Rachel Mayberry. Studies conducted by these researchers show that individuals who are very deaf who are not exposed to sign language because the children never achieve full proficiency, even after 30 years of daily use. While the effect is most intimate for individuals who do not receive sign language input until after the age of 12, even deaf people who start sign language study at age 5 are significantly less current than the signatories of genuine deafness (whose exposure to sign language begins at birth). Early language exposure also affects the ability to learn a second language later on: individuals who are very deaf with early language exposure achieve a comparable level of proficiency in a second language to hear individuals with early language exposure. Conversely, deaf people without early language exposure do much worse.

Steven Pinker discusses CPH in his book, The Language Instinct. According to Pinker, language should be viewed as a concept rather than a particular language because sound, grammar, meaning, vocabulary, and social norms play an important role in the acquisition of language. Physiological changes in the brain are also a possible cause for the critical period term for language acquisition. Because language acquisition is essential during this phase, parent-baby attachment is essential for the baby's social development. A baby learns to trust and feel secure with parents, but there are cases where a baby may live in an orphanage where he does not receive the same attachment as their caregiver. Research shows that infants who are unable to develop this attachment have great difficulty in maintaining close relationships, and have maladaptive behavior with adopted parents.

Other evidence comes from neuropsychology where it is known that adults far beyond the critical period are more likely to suffer from a permanent language disorder than brain damage than children, believed to be the resilience of young neural reorganization.

Secondary language acquisition

This theory is often extended to a critical period for the acquisition of a second language (SLA), which has influenced researchers in the field on both sides of the spectrum, supporting and not supporting CPH, to explore. However, the nature of this phenomenon has been one of the most debated issues in the field of psycholinguistics and cognitive science in general for decades.

Of course, older learners of the second language rarely achieve the original eloquence shown by younger students, though often run faster than children in the early stages. This is generally accepted as evidence supporting CPH. Combining the idea, "younger is better" by Penfield, David Singleton (1995) states that in learning a second language there are many exceptions, noting that five percent of adult bilinguals master a second language even though they begin to learn it when they are okay. into adulthood - long after the critical period may have ended. The critical period hypothesis states that the acquisition of the first language must occur before the cerebral lateralization is completed, around the age of puberty. One prediction of this hypothesis is that the acquisition of a second language is relatively fast, successful, and qualitatively similar to the first language only if it occurs before puberty. To understand a better understanding of SLAs, it is important to consider linguistic, cognitive, and social factors rather than age alone, as they are all important for language acquisition.

Over the years, many researchers have tried to find evidence in favor of or against a critical period for the acquisition of a second language. Many have found evidence that young people acquire language more easily than adults, but there are also special cases of adults acquiring a second language. with such native capabilities. Thus it is difficult for researchers to separate the correlation from cause and effect.

In 1989, Jacqueline S. Johnson and Elissa L. Newport found support for the claim that a second language was more readily obtained before puberty, or more specifically before the age of seven. They tested a second language of English learners who arrived in the United States at various ages ranging from three to thirty-nine, and they found that there was a decrease in grammatical accuracy after the age of seven. Johnson and Newport link this claim with a decline in the ability to learn language with age. Critical period opponents argue that the differences in language abilities found by Johnson and Newport can be due to the various types of inputs received by children and adults; children receive reduced input while adults receive more complex structures.

Additional evidence of a rigorous critical period is also found in the work of Pallier et al. (2003) who found that children who were adopted to France from Korea were able to become indigenous as in their performance from France even after a critical period for phonology. Their experiments can represent a special case where subjects must lose their first language to get the second one more perfectly.

There is also some debate about how one can judge the genuine quality of the speech participants and what it really means to be an almost identical foreign speaker. White et al. found that it was possible for non-native speakers of the language to be indigenous as in some aspects, but those aspects were influenced by their first language.

Maps Critical period



Vision

In mammals, the neurons in the brain that process vision actually develop after birth based on signals from the eye. An important experiment by David H. Hubel and Torsten Wiesel (1963) suggests that a one-eyed cat sewn from birth to three months of age (monocular deprivation) only develops a complete vision of the open eye. They show that columns in the primary visual cortex receive input from the other eye take over an area that normally receives input from a deficient eye. In general, the electrophysiological analysis of axons and neurons in the geniculate lateral nucleus suggests that the visual receptive field properties are comparable to that of adult cats. However, the captured cortex layer has fewer activities and fewer isolated responses. Kittens have small, small ocular dominated columns (part of the brain processing the vision) connected to the closed eye, and large, abnormal columns connected to the open eye. Since the time of critical period has passed, it is impossible for kittens to change and develop vision in the closed eyes. This is not the case in adult cats even when one eye is sewn for a year because they have developed their vision during a critical period. Further experiments on monkeys found similar results.

In a follow-up experiment, Hubel and Wiesel (1963) explored the cortical response present in kittens after binocular deprivation; they find it difficult to find the active cells in the cortex, and the responses they get are either slow-moving or rapidly exhausting. Furthermore, the responding cells are selected for edges and bars with different orientation preferences. Nevertheless, these kittens developed a normal binocularity. Hubel and Wiesel first describe a mechanism, known as selectivity orientation, in the mammalian visual cortex. The tuning orientation, a model derived from their model, is a concept in which the field of receptive neurons in LGN stimulates simple cortical cells and is arranged in rows. This model is important because it is able to describe the critical period for the proper development of normal ocular domination columns in the geniculate lateral nucleus, and thus be able to explain the effects of monocular deprivation during this critical period. The critical period for cats is about three months and for monkeys, about six months.

In similar experiments, Antonini and Stryker (1993) examined the observable anatomical changes after monocular deprivation. They compared the long-term (4- to 7-week) long-term (4-7 day) long-term (4-7 day) axonic arbor sequestered axillary arbor during the critical period established by Hubel and Wiesel (1993). They found that in the long run, monocular deprivation leads to reduced branching at the tip of the neuron, while the amount of afferent allocated to the tooth that is not tooth increases. Even in the short term, Antonini and Stryker (1993) found that geniculocortical neurons were also affected. This supports the concept of a critical period for the development of the right nerve for vision in the cortex.

In humans, some babies are born blind in one or both eyes, for example, because of cataracts. Even when their vision is restored later by treatment, their vision will not function in the normal way as for a person who has binocular vision from birth or undergoes surgery to restore vision soon after birth. Therefore, it is important to treat babies born blind soon if their condition can be treated.

Expression of Lynx1 protein has been associated with the normal end of the critical period for synaptic plasticity in the visual system.

Blindness after a period of darkness | Proceedings of the Royal ...
src: rspb.royalsocietypublishing.org


Imprinting

In psychology, printing is the kind of quick learning whatever happens in a particular stage of life. While this rapid learning does not depend on the outcome of behavior, it also establishes it and can influence behavioral responses to different stimuli. Konrad Lorenz is renowned for his classic studies of gracious inclusion in gray swans. From 1935 to 1938, he surrendered himself to a group of newly hatched hoops and recorded how he was immediately accepted, followed, and called as if he were the one who laid them himself. As the first moving object they encountered, Lorenz studied the phenomenon in how quickly the swan was able to form irreversible bonds. Through his work he shows that this only develops during a brief "critical period", which is about a few hours after hatching. Lorenz also discovered the long-term effects of his studies, and that is a shift in the sexual imagery of species as a result of printing in the adoptive mother of the second species. For certain species, when raised by the latter, they develop and maintain printed preferences and approach the second species raised rather than self-selected, if given a choice.

Imprinting serves as a distinguishing factor between the mother's own and other mother figures. Mother and baby both identify each other, this is a moment of strong bond for humans. It provides a kind of model or guide to adult behavior in addition to other factors such as nurturing, infant protection, guidance, and food. The printing process, Lorenz also found, brings a sense of familiarity for young animals. When strong bonds are formed at an early stage, it creates a sense of security and comfort for the subject and actually encourages the printing behavior.

Pheromones play a key role in the printing process, they trigger a biochemical response in the receiver, leading to a confirmed identification in another individual. If direct contact between the mother and the baby is not maintained during the critical printing period, then the mother goose may deny the baby because she is unfamiliar with her new scent. If that happens, then the baby's life will be in danger unless it is claimed by the surrogate mother and if it fails to imprint, it will trigger psychological trauma, which may lead to awkward social behavior later on. In relation to humans, newborns during this critical period identify with the scent of the mother and others because the aroma is one of the most advanced senses at the stage of life. Newborns use this pheromone identification to look for people who are identified with, in times of distress, hunger, and discomfort as a survival skill. Conclusions can be made for newborns based on the Lorenz study. When implanted in their mother, newborns look to them for food, safety, and comfort. Newborns are one of the most powerless babies to be known, and with very little they can do by themselves the most they can do is form the bonds of people they can rely on to provide basic needs. Imprinting is an important factor of the critical period as it facilitates the ability of newborns to form bonds with others, from infancy to adulthood.

Critical periods in development - “nature” vs. “nurture” - Part 2 ...
src: slideplayer.com


Audit processing

Many studies have supported the correlation between the types of auditory stimuli that exist in the postnatal environment and the development of topographical and structural development of the auditory system.

The first report in the critical period comes from deaf children and animals that receive cochlear implants to restore hearing. At approximately the same time, both electroencephalographic studies by Sharma, Dorman and Spahr and in-vivo investigations of cortical plasticity in deaf cats by Kral and colleagues showed that adaptation to cochlear implants was subject to early and develop- ment sensitive periods.. The closure of a sensitive period may involve many processes which in its combination make it difficult to reopen this behavior. Understanding the mechanism behind the critical period has consequences for medical therapy for hearing loss. M. Merzenich and colleagues point out that during the initial critical period, exposure to noise can affect the auditory cortical frequency organization.

Recent studies have examined the possibility of a critical period for thalamocortical connectivity in the auditory system. For example, Zhou and Merzenich (2008) studied the effects of noise on progression in the primary auditory cortex in mice. In their study, mice exposed to pulsed voices over a critical period and effects on cortical processing were measured. Mice exposed to pulsed sounds during critical periods have cortical neurons that are less able to respond to recurrent stimuli; the initial auditory environment disrupts the normal organizational structure during development.

In a related study, Barkat, Polley and Hensch (2011) looked at how exposure to different sound frequencies affects the development of the tonotape map in the primary auditory cortex and the medical ventral geniculate body. In this experiment, rats were kept either in normal environments or in the presence of 7 kHz tones during the early postnatal days. They found that mice exposed to abnormal hearing environments during the critical period P11-P15 had atypical toto-atypical maps in the primary auditory cortex. These studies support the idea that certain sound exposures in critical periods can influence the development of the tonotypes map and the response properties of neurons. Critical periods are important for brain development for the function of connectivity patterns. In general, the initial auditory environment affects the structural development and specificity of the response of the primary auditory cortex.

Music capabilities

The absolute pitch manifests itself almost always before adolescence and rarely if ever among the first individuals exposed to music after mid-childhood, suggesting that a musical exposure or a similar phenomenon ( eg , tonal) until mid-childhood is a necessary condition for its development or refinement. Studies requiring musicians and non-musicians to sing or sing popular popular songs that have a definitive recording (and hence are sung in a standard key) show that - average - participants sing in semitones of a standard key but that is beyond a small subset of participants with absolute pitch there is wide variation ("bell curve" which reflects the level of approach to broad and flat standard keys). {{{1}}} This result shows that almost all humans have innate intelligence for the recognition of absolute tones - though other factors can increase or limit the level of talent. Also, the result of his association with the chronological observations mentioned earlier suggests that early to mid-childhood exposure to an environment whose interpretation depends on pitch is a "trigger" of development for any intelligence possessed by an individual.

Conceptual Business Illustration Words Critical Period Stock ...
src: image.shutterstock.com


Sports

In physical exercise, humans need several years of practice before reaching the highest level of competition. Until now, there is not a single professional soccer or basketball player who can play in the best leagues after starting to practice at the age of 20. The same goes for mental sports like chess, where no player gets to the top 100 after starting to practice at age 20. In general, to reach the highest level in sports, the sooner a person starts to practice, the best.

The Critical Period for Language Acquisition: Evidence from Second ...
src: images.slideplayer.com


Vestibular System

In our vestibular system, neurons do not develop at neuronal birth and mature during critical periods of the first 2-3 weeks postpartum. Therefore, maturation disorders during this period may cause changes in normal balance and movement through space. Animals with abnormal vestibular development tend to have irregular motor skills. Studies have consistently shown that animals with genetic vestibular deficiency during this critical period have altered the vestibular phenotype, most likely as a result of lack of inadequate input from the semicircular canals and dopaminergic disorders. In addition, exposure to abnormal vestibular stimuli during critical periods is associated with irregular motor development. Children with vestibular hypofunction receptors often delay motor development. The results of studies conducted on ferrets and rats reinforced the notion that the vestibular system is essential for motor development during the early neonatal period. If a vestibular receptor is present during the first six months to a year when the baby is learning to sit and stand, then the child can develop motor control and balance normally.

Vestibulo-ocular reflex (VOR) is a reflex eye movement that stabilizes the image on the retina during head movement. It produces eye movement in the opposite direction of the head movement, thus preserving the image in the center of the visual field. Studies on fish and amphibians reveal a sensitivity in their VOR. They launched space flights for 9-10, some by developing VOR and others with developed reflexes. Fish with reflexes develop developing a bend upward on their tails. Gravity is changed resulting in a shift in orientation. Those who are mature with reflexes are not sensitive to microgravity exposure.

Critical Period Hypothesis (VideoScribe) - YouTube
src: i.ytimg.com


Memory

Recent studies also support the possibility of a critical period for the development of neurons that mediate memory processing. Experimental evidence supports the idea that young neurons in adult dentate gyrus have a critical period (about 1-3 weeks after neuronal birth) in which they are an integral part of memory formation. Although the precise reasoning behind these observations is uncertain, studies show that the functional properties of neurons at this age make them most appropriate for this purpose; these neurons: (1) Stay hyperactive during memory formation; (2) more excited; and (3) More easily depolarized due to the GABAergic effect. It is also possible that hyperplasticity makes the neurons more useful in memory formation. If these young neurons have more flexibility than adult neurons in the same context, they can be more influential in smaller amounts. The role of these neurons in adult dentate gyrus in memory processing is supported by the fact that behavioral experiments have shown that the intact dentate gyrus is an integral part of memory formation of the hippocampus. It is thought that the dentate gyrus acts as a relay station for information relating to memory storage. The possibility of a critical period may change the way we look at memory processing because it will ultimately mean that the existing collection of neurons is constantly replenished as new neurons replace old neurons. If a critical period does exist, this might mean that: (1) The diverse population of neurons representing events occurring immediately after each other can relate those events temporally in the formation and processing of memory; OR (2) These different populations of neurons can distinguish between similar events, regardless of temporal position; OR (3) Separate populations may mediate the formation of new memories when the same event is common.

Critical periods in development - “nature” vs. “nurture” - ppt ...
src: slideplayer.com


See also

  • Cusp Behavior
  • Child development
  • Hypothesis of critical period
  • Developmental psychology
  • Soft intelligence
  • Universal grammar

The Critical Period for Language Acquisition: Evidence from Second ...
src: images.slideplayer.com


External links

  • Bibliography of papers at a critical period in the acquisition of a second language

Critical periods in development - “nature” vs. “nurture” - ppt ...
src: slideplayer.com


References

Source of the article : Wikipedia

Comments
0 Comments