Apologies and a new challenge
First i would like to apologise for not having posted a challenge since April. I have been very involved with finishing some research so my nose hasnt been near a computer! Now my research is finished and I would like to share the article I presented recently...
The Impact of Neurology on Infant Sleep Patterns by Kate Byrne
It seems that infant sleep, in our Western world, is the yardstick that we appear to judge ourselves as a parents and our children as good, bad, fussy, hungry and many other positive and negative labels. Friends, family and anyone we know ask if our baby is good and if they sleep. One seems to equal the other good=sleep. No wonder that we become fixated about sleep, when everyone around is appears to be focussing on it.
Sleep is linked in our minds with hunger, need, independence, self soothing and routine. I wonder how our modern perception of infant sleep came about. Surely the late Dr Truby King had a huge influence on scheduling babys sleep and feeding patterns and although he decreased infant mortality in New Zealand in the early 1900s, his focus was on hygiene and with little understanding of anthropology, neurology and good old mother nature.
How many people look upon 10-12 hours of night sleep as the ultimate goal of parenting? Forums and books dedicated to various methods of getting a baby to sleep in a particular way, The Baby Whisperer, Gina Ford and Ferber to mention a few. Many of these methods rely on a shut down or survival mechanism that is in built that when a babys cortisol levels go above a certain threshold they shut down to ensure survival. This mechanism is blueprinted into our infants brain since time started, more noise would attract predators so shutting down in a high stress situation would ensure better odds for survival.
There is a theory that light sleep helps the brain develop because the brain doesn't rest during REM sleep. In fact, blood flow to the brain nearly doubles during this time. During REM sleep the body increases its manufacture of certain nerve proteins, DHEA (dehydroepiandrosterone), is necessary for duplication of DNA in all tissues, melatonin, acts with DHEA.
The brain uses a large amount that measurable levels of DHEA decline; the body is also using the same mechanism for growth at this time in the competition for DHEA. The J. of Endocrinology 1991; 128: 8 reports the following: "(1) After birth and until the third month of neonatal life, low levels of MLT are secreted by the pineal gland without any pronounced diurnal rhythm. (2) From about the third month of life, there is a pronounced diurnal variation in MLT secretion by the pineal and circulating MLT levels are high, particularly at night. (3) After the first year or two of life, as children age, there is a profound reduction in the circulating levels of MLT, particularly at night."
Infants respond readily to holding. That is, frequent holding and attention which appears to stimulate prolactin and, therefore, DHEA production.
Learning is also thought to occur during REM, storing what is beneficial to the individual and discarding what is not. Some sleep researchers believe that REM sleeps acts to auto-stimulate the developing brain, providing beneficial imagery that promotes mental development. During the light sleep stage, the higher centres of the brain keep operating, yet during deep sleep these higher brain centres shut off and the baby functions on her lower brain centres. It is possible that during this stage of rapid brain growth the brain needs to continue functioning during sleep in order to develop. It is interesting to note that premature babies spend even more of their sleep time (approximately 90 percent) in REM sleep, perhaps to accelerate their brain growth.
Neonates show no evidence of circadian variations in sleep or waking states; it begins to emerge by about 5-6 weeks of age. In addition, the consolidation of sleep-waking states and their synchronization with a 24-hour day appear to be independent processes. Recent findings further support the notion that episodes of sleep and wakefulness are regulated independently, and suggest that their developmental changes can be attributed in part to increasing forebrain influences (Blumberg et al., 2005).
Sleep and brain development
A key factor in the maturing of central sensory pathways is stimulus-induced neuronal activity (Hubel and Wiesel, 1979). Depriving kittens of normal visual experience during the critical period for visual development permanently alters the physiologic response of the brain to visual stimulation. During this developmental period, synaptic connectivity in the cortex exhibits a high level of plasticity as synapses are formed and retracted, a process strongly driven by sensory activity. Brain plasticity, therefore, refers to the ability of the brain to persistently change its structure and function according to genetic information in response to environmental changes or to comply with the interaction between these two factors (Chen and Tonegawa, 1997). By facilitating brain plasticity, sleep would allow the organism to adapt its behaviour to the circumstances. (Maquet et al., 2003).
In the first weeks after birth the babys brain has brief periods of waking in which to interact and learn in the adult sense of the word. The gradual reduction in REM sleep amount with advancing age is offset by an increase in how long our babies are awake. Whilst awake, the baby absorbs all it sees. Transient periods of alertness can be induced or prolonged by changes in position, sound or sight. However, the essential changes in alertness that occur at 2 months of age are "the infant's ability to construct its own context of wakefulness by initiating goal-directed actions and inventing new combinations among coordinated movements" (Wolff, 1984). The timing for these changes coincides with major transitions in various aspects of the infant's neural and sensory ability, understanding and development.
We are also born with more than 70 primary reflexes, such as sucking, grasping and rooting, have been identified as naturally developing in babies before birth and persist for up to one year. They play a crucial role in the survival of newborns. During the first year of life the primary reflexes are naturally inhibited and transformed into secondary reflexes, which are important for coordination and balance.
These change the structure of our infants brain as they develop skills in place of their primary reflexes, for example for our baby to crawl they have to Lose the Tonic Labyrinthine Reflex (TLR) and the Symmetrical Tonic Neck Reflex (STNR). The TLR is active during the birth process, where the baby retracts or pushes back its head, flexes or folds in its arms and extends or straightens its legs. If the baby is in a posterior presentation (face up) before birth the head will push into the mother's spine causing great pain. This reflex can be felt in the newborn by simply pushing on the back of the head. The baby will immediately resist and push backwards. At around 3 months the TLR enables the baby to lie on its front and lift up its head. It must be inhibited or switched off, however, before the baby can come up into a crawling position at around 8-9 months. If the TLR is still present at this stage the baby is not able to support its weight by straightening its arms and bringing its knees beneath its body.
The transition up into a crawling position is assisted by the emergence of the STNR which enables extension of the arms and flexion of the legs at the same time. However, the STNR has to be 'switched off' before the baby can crawl forward as this involves a combination of flexion and extension - e.g. in a cross-pattern crawl the right arm and left leg flex while the left arm and right leg extend.
Crawling is a major developmental milestone. It represents the transition from fetal/infant movement, which is dominated by primary reflexes, to movement which allows the young child to explore its surroundings independently. At around 12 months, the baby, who began life in the fluid environment of the womb, may be ready to take its first tentative steps on 'dry land'.
Remember that at least 70 reflexes have to be replaces or suppressed within the first year or so of life, this is a time of rapid brain growth for our infants and due to this Sleep patterns during periods of rapid brain growth are affected, connectivity and synaptic plasticity suggest a role for sleep in brain development. The evidence indicates that sleep states may be important for neuronal development, although the contribution of each state is likely to be different. In addition, the possible importance role of the succession of NREM sleep and REM sleep has recently been emphasized. Finally, since both sleep states also appear to promote processes dependent on synaptic remodelling, such as learning and memory (Maquet et al., 2003; Walker and Stickgold, 2006; Yoo et al., 2007; Stickgold and Walker 2007), they might influence periods of heightened synaptic plasticity and development in the maturing brain.