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Primitive reflexes are reflex actions originating in the central nervous system that are exhibited by normal infants, but not neurologically intact adults, in response to particular stimuli. These reflexes are absent due to the development of the frontal lobes as a child transitions normally into child development.〔(【引用サイトリンク】 Primitive & Postural Reflexes )〕 These primitive reflexes are also called infantile, infant or newborn reflexes. Older children and adults with atypical neurology (e.g., people with cerebral palsy) may retain these reflexes and primitive reflexes may reappear in adults. Reappearance may be attributed to certain neurological conditions including, but not limited to, dementia (especially in a rare set of diseases called frontotemporal degenerations), traumatic lesions, and strokes. An individual with cerebral palsy and typical intelligence can learn to suppress these reflexes, but the reflex might resurface under certain conditions (i.e., during extreme startle reaction). Reflexes may also be limited to those areas affected by the atypical neurology, (i.e., individuals with cerebral palsy that only affects their legs retaining the Babinski reflex but having normal speech); for those individuals with hemiplegia, the reflex may be seen in the foot on the affected side only. Primitive reflexes are primarily tested with suspected brain injury for the purpose of assessing frontal lobe functioning. If they are not being suppressed properly they are called frontal release signs. Atypical primitive reflexes are also being researched as potential early warning signs of autistic spectrum disorders. Primitive reflexes are mediated by extrapyramidal functions, many of which are already present at birth. They are lost as the pyramidal tracts gain functionality with progressive myelination. They may reappear in adults or children with loss of function of the pyramidal system due to a variety of reasons. However with the advent of ''Amiel Tison method of neurological assessment'', the importance of assessment of such reflexes in paediatric population has come down.〔Amiel-Tison C, Grenier A. Neurological Assessment during first year of life. New York. Oxford University Press, 1986; 46-94.〕 ==Adaptive value of reflexes== Reflexes vary in utility. Some reflexes hold a survival value (e.g., the rooting reflex, which helps a breastfed infant find the mother's nipple). Babies display the rooting reflex only when they are hungry and touched by another person, not when they touch themselves. There are a few reflexes that likely assisted in the survival of babies during human evolutionary past (e.g., the Moro reflex). Other reflexes such as sucking and grabbing help establish gratifying interaction between parents and infants. They can encourage a parent to respond with love and affection, and to feed their child more competently. In addition, it helps parents to comfort their infant while allowing the baby to control distress and the amount of stimulation they receive.〔Berk, Laura E.. Child Development. 8th. USA: Pearson, 2009.〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「primitive reflexes」の詳細全文を読む スポンサード リンク
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