|
tazzygirl -> RE: 20 weeks abortion bill passes the HOR (6/19/2013 10:34:38 AM)
|
Before I believe a physician who himself says its his "belief" that a fetus feels pain based upon the response of pre-term infants response to surgery, SOME need to read the following.
Lets look at a more scientific explanation....
The neurobiology of the fetus: anatomical pathways
Notwithstanding limitations, it is useful to view the pain system as an alarm system. Viewed in this way, a noxious stimulus is an event that activates free nerve endings in the skin, similar to pushing an alarm button. The electric cable from the button to the alarm is similar to the connection between the nerve endings and the brain. The brain is the alarm that rings out pain. Whether the fetus can respond to a noxious stimulus with pain can thus be decided in part by determining when the alarm system is completely developed.
Free nerve endings, the “alarm buttons,” begin to develop at about seven weeks' gestation; projections from the spinal cord, the major “cable” to the brain, can reach the thalamus (the lower alarm) at seven weeks' gestation. An intact spinothalamic projection might be viewed as the minimal necessary anatomical architecture to support pain processing, putting the lower limit for the experience of pain at seven weeks' gestation.
At this time, however, the nervous system has yet to fully mature. No laminar structure is evident in the thalamus or cortex, a defining feature of maturity. The external wall of the brain is about 1 mm thick and consists of an inner and outer layer with no cortical plate. The neuronal cell density of the outer layer is much higher than that of a newborn infant or adult and at seven weeks' gestation has yet to receive any thalamic projections. Without thalamic projections, these neuronal cells cannot process noxious information from the periphery.periphery.
The first projections from the thalamus to cortex (the higher alarm) appear at 12-16 weeks' gestation. By this stage the brain's outer layer has split into an outer cortical rim, with a subplate developing below. The thalamic projections that develop from 12-16 weeks penetrate the subplate. Within the subplate, cortical afferents establish prolonged synaptic contacts before entering the cortical plate. The subplate is a “waiting compartment,” required for mature connections in the cortex. The major afferent fibres (thalamocortical, basal forebrain, and corticocortical) can wait in the subplate for several weeks, before they penetrate and form synapses within the cortical plate from 23-25 weeks' gestation. Subsequent dissolution of the subplate occurs through prolonged growth and maturation of associative connections in the human cerebral cortex.
Spinothalamic projections into the subplate may provide the minimal necessary anatomy for pain experience,The following popper user interface control may not be accessible. Tab to the next button to revert the control to an accessible version.Destroy user interface control8 but this view does not account for the transient nature of the subplate and its apparent role in the maturation of functional cortical connections. A lack of functional neuronal activity within the subplate calls into question the pain experience of a fetus before the penetration of spinothalamic fibres into the cortical plate.
Current theories of pain consider an intact cortical system to be both necessary and sufficient for pain experience. In support are functional imaging studies showing that activation within a network of cortical regions correlate with reported pain experience. Furthermore, cortical activation can generate the experience of pain even in the absence of actual noxious stimulation. These observations suggest thalamic projections into the cortical plate are the minimal necessary anatomy for pain experience. These projections are complete at 23 weeks' gestation. The period 23-25 weeks' gestation is also the time at which the peripheral free nerve endings and their projection sites within the spinal cord reach full maturity. By 26 weeks' gestation the characteristic layers of the thalamus and cortex are visible, with obvious similarities to the adult brain, and it has recently been shown that noxious stimulation can evoke haemodynamic changes in the somatosensory cortex of premature babies from a gestational age of 25 weeks. Although the system is clearly immature and much development is still to occur (fig 1), good evidence exists that the biological system necessary for pain is intact and functional from around 26 weeks' gestation.
............
Without consciousness there can be nociception but there cannot be pain. Thus to understand how pain experience becomes possible it is necessary to understand the origin and developmental course of conscious experience. It is reasonable to assume that conscious function can only emerge if the necessary neural circuitry to carry out that function is fully developed and functional.The following popper user interface control may not be accessible.
It is also necessary to assume that conscious function can only emerge if the proper psychological content and environment has been provided. Before infants can think about objects or events, or experience sensations and emotion, the contents of thought must have an independent existence in their mind. This is something that is achieved through continued brain development in conjunction with discoveries made in action and in patterns of mutual adjustment and interactions with a caregiver. The development of representational memory, which allows infants to respond and to learn from stored information rather than respond to material directly available, may be considered a building block of conscious development. Representational memory begins to emerge as the frontal cortex develops between two and four months of age, supported by developments in the hippocampus that facilitate the formation, storage, and retrieval of memories.w5 From this point tagging in memory is possible, or labelling as “something,” all the objects, emotions, and sensations that appear or are felt. When a primary caregiver points to a spot on the body and asks “does that hurt?” he or she is providing content and enabling an internal discrimination and with it experience. This type of interaction provides content and symbols that allow infants to locate and anchor emotions and sensations. It is in this way that infants can arrive at a particular state of being within their own mind. Although pain experience is individual, it is created by a process that extends beyond the individual.
This is likely to strike anyone as strange because it is simply not how we intuitively believe pain to be. Because pain is so automatic and personal we perceive it to be natural and private. But because we are able to experience pain as such a personal event does not mean that we individually acquired the ability to experience pain in the first place. Nor does it mean that the psychological mechanisms by which we experience pain arose within our own brains by some individualistic process such as neuronal maturation
This is not to deny that neonates and fetuses have the neural apparatus to discriminate information; clearly, fetuses and neonates do not respond to tactile stimuli in the same way as they do to auditory stimuli, for example. Indeed, this discriminatory processing is the raw material for a primary caregiver's assessments of his or her infant's need and for the interactions and behavioural adjustments that occur in the forthcoming months. Innate neural and behavioural discrimination are part of the material for developing experiential discrimination, but experiential discrimination is yet to develop and relies critically on interactions with a primary caregiver. For fetuses and newborn infants, these interactions have yet to occur.
By this line of reasoning fetuses cannot be held to experience pain. Not only has the biological development not yet occurred to support pain experience, but the environment after birth, so necessary to the development of pain experience, is also yet to occur.
..........
The medical goals of survival and long term normal development of fetuses should not influence medical decisions when a woman seeks an abortion. Under these circumstances, the question of analgesia or anaesthesia in fetuses can be more directly tackled by examining the possibility of pain in fetuses and the consequences of any pain relief for fetuses on the health and wellbeing of the pregnant woman. The case against fetal pain, as documented here, indicates that a mandate to provide pain relief before abortion is not supported by what is known about the neurodevelopment of systems that support pain. Proposals to directly inject fetuses with fentanyl or to provide pain relief through increased administration of fentanyl or diazepams to pregnant women, which increase risks to the women and costs to the health provider, undermine the interests of the women and are unnecessary for fetuses, who have not yet reached a developmental stage that would support the conscious experience of pain.
Summary points
The neuroanatomical system for pain can be considered complete by 26 weeks' gestation
A developed neuroanatomical system is necessary but not sufficient for pain experience
Pain experience requires development of the brain but also requires development of the mind to accommodate the subjectivity of pain
Development of the mind occurs outside the womb through the actions of the infant and mutual adjustment with primary caregivers
The absence of pain in the fetus does not resolve the morality of abortion but does argue against legal and clinical efforts to prevent such pain during an abortion
Conclusion
The neural circuitry for pain in fetuses is immature. More importantly, the developmental processes necessary for the mindful experience of pain are not yet developed. An absence of pain in the fetus does not resolve the question of whether abortion is morally acceptable or should be legal. Nevertheless, proposals to inform women seeking abortions of the potential for pain in fetuses are not supported by evidence. Legal or clinical mandates for interventions to prevent such pain are scientifically unsound and may expose women to inappropriate interventions, risks, and distress. Avoiding a discussion of fetal pain with women requesting abortions is not misguided paternalism but a sound policy based on good evidence that fetuses cannot experience pain.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1440624/
BMJ. 2006 April 15; 332(7546):
|
|
|
|
