Peterson and Martin R. Sawhill Of course the fact the synaptogenesis occurs and sensitive periods exist, does not tell us why evolution settled on these mechanisms. To address this question N2N, as do most other discussions of synaptogenesis in brain development, appeals to a distinction made by William Greenough and his colleagues. The first type Greenough called experience-expectant synapse change: the over-production of synapses early in life, followed by their selective elimination, allows an organism to adjust or tune its neural circuits to its species-specific environment.
Neural systems have evolved to expect certain types of stimuli in the environment, such as patterned visual stimuli, that re-enforce some neural connections and eliminate others.
The three curves in Figure 1 show periods during development when experience-expectant synaptic change is likely to occur. It is generally accepted that the experiences needed to affect this neural fine-tuning are ubiquitous in all normal human environments. The second type of synaptic change Greenough called experience-dependent synapse formation, the type of change Nelson showed at the top of Figure 1. Experience-dependent change occurs throughout the lifespan. Unlike experience-expectant change, which involves pruning synapses, experience-dependent change involves growth of new synapses.
Experience-dependent change allows individuals to encode and learn from information that occurs in their own personal, social, and cultural environments.
It is the mechanism that enables us to learn throughout life. In its chapter on the developing brain, N2N provides a reasonably measured presentation of the neuroscientific research that might be relevant to framing improved early childhood and education policies. It cautions that most of what we know about brain development is based on animal studies and that these studies may not be immediately translatable to humans. It acknowledges that interpreting data on synaptic densities in humans is difficult or even inappropriate when considering development of cognition, language, emotion and social behavior.
The chapter states that a few, not all, aspects of brain development require particular experiences at particular times; that sensitive or critical periods in human development are largely unexplored; that the experiences needed for normal brain development are ubiquitous; and that the brain remains open to modification by experience throughout the lifespan.
Nonetheless N2N expresses a view that early experiences are particularly important in brain development and that they determine the course of future development and learning. Ongoing neurogenesis in the hippocampus does not appear in the figure.
More interestingly, neither does the occurrence of life-long experience-dependent synapse formation. The texts explaining Figure 2 also differ from that found in N2N. I will focus on the discussions of Figure 2 emanating from the Harvard Center, because these are the most influential and widely cited.
John T. Bruer President Emeritus - James S. McDonnell Foundation. The other two factors, also related to synaptic blooming and pruning, are i the highly active molecular environment and cellular mechanisms present during synapse formation and elimination, and ii the finding that neural circuits are more flexible before a particular pattern of connections has been shaped and fully activated. All of the scientific work cited in support of these three explanatory factors is research on sensory systems in animals.
What differentiates the working paper from N2N is the lack of any qualifications about the generalizability of the neuroscience it cites. There are no cautions about the advisability of generalizing from animal studies to humans, no acknowledgement that most of the work cited is on sensory systems, and no mention of experience-dependent brain plasticity over the life span.
For example, caution about generalizing from animals to humans in areas of social, emotional and cognitive development give way to claims that there are sensitive periods for social cues, where these claims are supported by citing research on imprinting in chicks and rearing of rat pups. Common sense tells us that the learning and behavior problems of young children can be fixed more easily and at less cost than those of adolescents and young adults.
Shortly after Figure 1 appeared in N2N , Nelson himself, along with Ross Thompson from the University of Nebraska, published an article containing their version of Figure 1. Thompson and Nelson present a critical review of the neuroscience and offer advice to scientists and professional organizations on how to assure accurate and timely coverage of scientific findings in the media.
In their paper, they describe Figure 1 as portraying major events in brain development. Their version contains all the items shown in Figure 1, but it also depicts important prenatal events, such as neural tube formation and cell migration, as well as myelination that occur from two months prenatally until 10 years of age.
Thompson and Nelson present their critical review of developmental synaptogenesis in an early section of their paper. They reprise the standard presentation of synaptic overproduction and pruning, citing the human work of Huttenlocher and the monkey work of Rakic.
However, they caution that while this process no doubt occurs in human development, it is not clear how extensively it occurs, in which brain regions it occurs, and at which times in development it occurs. There were relatively few specimens available for some age ranges and not every brain region was studied.
Furthermore, they caution, synaptic density counts do not tell us whether the synapses counted are due to a genetic program or to experience.
Thompson and Nelson grant that the blooming and pruning phenomenon generalizes to human brain development, at least to the sensory systems. Still others learn to recognise the different meanings of the sounds they make when they cry. Can you imagine how rewarding it is for a non-verbal child and a receptive parent, when they can communicate with each other?
All across America each year, children start kindergarten unprepared to learn. In some states, the vast majority of kindergarten Join our growing number of parents with access to the best early education resources. Early Education. Windows of Opportunity in your Child's Life April 07, Previous The Myth of Developmental Lag in Reading April 06, "The longer you wait to get help for a child with reading difficulties, the harder it will be for that child to catch up.
Join the newsletter Join our growing number of parents with access to the best early education resources. We never send spam. Anyone can be an artist. Creating artistic environments that nurture creativity, self-expression, cultural awareness AND support development at any age is feasible. No doubt, you've created art before Maria Montessori developed a child-centered educati One of the questions we get asked all the time is about the differences between Montessori schools and traditional education.
I discuss this question in the introduction to my new, soon-to-be-publishe Did you know that you can earn your masters degree while you earn Age of Montessori teacher certification?
When winter weather is getting you down, consider these fun activities to keep your spirits up. As you will see from the pictures, these activities bring genuine engagement, concentration and great jo It happens in the fullness of life, when w Movement At birth, your child has limited control of movement, but rapidly gains in areas of both gross and fine motor control.
Emotional Control Your child experiences a sensitive period for learning about relationships, communication, and emotional control from birth to approximately age two and a half.
Need for Order Starting at around six months old, your child begins to develop a need for order. Interest in Small Objects Between one- and four-years old, your child is experiencing a sensitive period for interest in small objects. To talk is in the nature of man.
More Blog Posts. Montessori for Early Childhood Homeschool Families Thousands of families all over the nation are opting out of traditional public schools. Normalization in the Montessori Classroom Normalization is the term Maria Normalization is the term Maria Montessori used for the process of internalizing multiple skills through coordination and organization.
Spring is in the Air - Activities for Children at Home Despite the challenges we all face, spring is here and it is beautiful! Your kid is biologically prepared to learn. It has more synapses gaps between nerve fibers that make your child more sensitive to learning , and the density of the synapses remain high throughout the first 10 years of life. The effect of these experiences lasts for the rest of his life.
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