Critical vs Sensitive Periods in Child Brain Development

[00:00:00][Music] this is nni bites big learnings a podcast where fellow healthc Care Professionals Converse about the latest on nutrition science we are joined by the chairs and speakers of nni and wnsc workshop 102 as they share practical insights on the impact of proper nutrition that contribute in the optimal growth of children well hello and welcome to our podcast nni I bites big learnings my name is Andrew Apprentice I'm professor of international nutrition at the London School of hygiene and tropical medicine and it's my huge pleasure today to welcome Professor akmad suan to our podcast and he's going to tell us a quite a complicated story about critical and sensitive periods in child development and how how we disting is these Dr s is Professor of child development at elanga University in suraya here in Indonesia and among his many esteemed positions he heads the division of growth and development in the faculty of medicine uh at uh the University of elanga and suoma general academic hospital he's a member of the international Pediatric Association working group on schoolage children and sits on the Council of the international Society for developmental origins of health and disease so Professor it's a special pleasure to welcome you uh in your own country to and to talk about this uh topic of uh Child Development yeah Professor Andrew of course I feel very honored to be invited and to do this podcast with you today my name is uh hamatan I'm professor of child development at faculty of medicine aanga University in sh bya Indonesia here as a pediatrician consultant in the field of growth development of infant and children my lines of uh research are mostly uh regarding early detection of Developmental disorder uh brain development in early age long-term growth and development outcome of highrisk infant and the impact of early intervention on typical or atypical development fantastic and the paper you presented um was in the 102nd neste nutrition institute's Workshop here in barley uh and the the overall title of the workshop was growing strong harnessing the power of nutrition for child health and your talk you know set Central to that and we could have no one better to tell us about this very important period of uh development now you concentrated our attention on the child's developing brain yeah you know that's the most wondrous organ that is really the essence of human development isn't it I mean this is what sets us apart from other species yes our big brain yeah um and before we get to the issues around how the brain learns things we could start I thought by talking to us through about the complex process of how the brain develops in the fetus yeah uh you know the development of the brain is a very uh complex and long lasting process I just focus on the timing of ontogenic event of Talen healon neuronal proliferation and migration especially of uh occur during the first half of gestation the second half of gestation is the period of existence of the functionally important thran structure called sulet and the major period of Cal cell proliferation and program cell death this intrauterine whatever and axon and Dage sprin and C formation blooming during the last trimester of gestation and the first postnatal year major part of mization occurs also during the first year afterward many developmental processes such as my initiation signup formation and signup elimination continues through all childhood and Adolescent every evident is emerging that the peak of sign up elimination occurs between poverty and onset of a de hold I think a neurotransmitter system are present from early fetal life onward and their pre and perinal development is characterized by period of transure of expression you so let me may I interrupt you let me get this right yeah because with most organ systems the cells form and divide and then stay there yeah but with the brain something different is going on yeah many of the gal cells the neurones they form yeah and then many of those are killed off again can you talk me through that in a bit more detail it's kind of hard to get your head do you mean uh why that happens uh pruning process the pruning yes yeah the pruning process yeah the pruning process just uh principally if we a pruning process in the healthy brain is the not a pathological process this is a physiological right yeah this is a apoptosis a program cell de this is programming so so why is that done then the brain is trying to is it trying to set up this network of connectivity yes and sometimes it creates bits that aren't needed and that then have to be taken away again in order not to clog the whole thing up is that right it just uh uh simply if you uh never use this a circuit uh they will uh printing itself with the uh something called like apoptosis yeah apoptosis intentional cell death yes yeah okay that's a for for healthy uh brain processes they need it okay so so if a neuron isn't used it's redundant yes then it dies yeah okay and then all the active ones are left and that leaves space for the cont unic this only uh happen in early okay all right so let's move on so you said that a lot of this occurs in the second trimester in the second half of gestation the third second and third trimesters then the baby's born yes suddenly it's exposed to all these stimula I mean I'm sure in utro it can hear things it can hear its mother's heartbeat and things but suddenly it's born yeah and the Big Wide World Is there it's smelling things it's hearing things it's feeling things it's tasting things um tell us what happens then yeah after child is born there are only three processes in the child Brint that are very active and also only in the first years after birth including Aon and dendroid uh sprouting mhm signup formation and mization the two main keys of uh determinant in this case a fullfill of early nutrition and early experience from the their environment which absolutely this thing cannot and should not should not be separated the brain cups network will only form If the child get sensory experience from the outside which is what known as a stimulation stimulation s formation occurs most actively when the child is still young with the different speed of various areas of the brain but uh we must know the peak of signup formation in a child brain occurs before the child is 2 years this is a princip of uh the first Thousand Days Of Life yeah and when a child reaches of the age of six the brain volume has reached uh until 95% compared with the the ad brain yeah the adult brain practically the combination of early nutrition and ear Le stimulation this will form 95% of the child brain architecture with the function of determinant whether the child can have basic development abilities that include cross M language and uh Speech socialization and so on so from these four basic abilities in the early age children form the the main abilities and the next uh age namely intelligent and emotion and also Behavior and and ultimately what we capture in the phrase human capital yes their ability to have a good life their ability to earn a living yeah to raise a family Etc which is so important now this of course is a conference about nutrition and we have a separate talk and podcast with um Dr Sarah Sarah yeah who is going to tell us more about the importance of nutrition in the growing brain yeah but I'd like to return to your um the point you've just made which is that nutrition and stimul need to go hand in hand you cannot and should not have one without the other yes um but also now get back to what I think initially I found very confusing and what I think listeners will find confusing which is could you explain to us the difference between a critical period yeah and a sensitive period yeah this this thing is very tricky because it's like similar but exactly it's not the same between critical and sensitive period understanding the concept of critical and sensitive period of child development is uh constantly changing along with technological advances in the study of the human brain you know because the concept of critical period of Child Development cannot be separated from the uh processing of maturation of the child GRE development itself in the context of time the critical period is a certain part of the sensitive Peri period this is the concept of time M if the sensitive period is a representation of a time when the experience received by the child from exposure to the surrounding environment have a significant influence of the development of the child brain then the critical period is representation of the time when the development of the child brain that has formed at the time can no longer be changed when the period has ended MH mhm so uh there are uh two uh principally uh concept comparing the sensitive period and critical period uh in term of plasticity critical period narrow time Windows of the plasticity driven by nutrition and also environmental input and if I'm not mistaken it has a sort of sharp beginning and a sharp end it ends begins and ends abruptly yes abruptly okay yeah yeah this that is critical period and closer of the critical period is AI through molecular breaks molecular processes so once those molecular processes have switched there's no going back and allow for uh uh that's constraint plasticity and allow for permanent structural consolidation of a one of a few possible connectivity pattern that is permanently there no no point to it yeah uh in the other hand sensitive period is a brad time uh critical period is a neural time and sensitive period is Broad time Windows of gradually changes in plasticity driven by nutrition and also environmental input also sensitive period are not close by molecular constraint and can be further reopen by changing the firan situation so the consolidation of uh one of the broad range of possible pattern of contivity is reversible okay and remain a functionally dynamic so so so that's so important in terms of teaching parents through healthc Care Professionals that yeah um the window of s the critical window of development the physiology has finished its process but you can still the brain can still be sensitive to external stimulation and learning yeah uh so the uh weing is the concept of critical ancest period is a manifestation of maturation of child brain development uh right now evident clearly demonstrated that critical aspect of brain architecture begin to be SI by nutrition experience before and soon afterward yeah so critical period is subset of sensitive period of which the effect of nutrition and experience on performance are irreversible that's a critical period current study exploring this possibility that timely nutritional and stimulation intervention during this critical period and and so I mean perhaps we should be careful about bringing a third term in here but you mentioned it in your lecture which is critical Windows yes and so if I'm not mistaken a critical window which um occurs with other organs development of the pancreas or the liver or whatever but in terms of the brain we're discussing now the um critical period This is a concept you quoted my great friend Pat Bateson from Cambridge who did many studies in in monkeys and primates many years ago so tell us tell us how the window of opportunity this terminology fits with critical and sensitive periods is that just a big term that captures critical and sensitive Windows uh for me myself window opportunity window of opportunity just only a popular metaphor okay that describe uh uh yeah just describe the sensitive period itself okay yeah so we're not we're not wrong to just go to the short hand of critical windows but it's a bit um perhaps naive it's much more complicated than that is that that's your message yeah yeah okay well um Professor San thank you so much for helping us to understand the important distinction between critical and sensitive periods in a child's growth and development it's been a huge honor to talk to you and to learn from you and um a long time since we last met so I hope it won't be so long into the future thank you very much Andrew it's been a pleasure now let me try and end by summarizing your key messages we learned I think that a critical period represents a window in time where there's a a heightened plasticity by plasticity we mean um adaptability in brain development um when it's especially sensitive to environmental inputs be they positive good nutrition for example or be they negative maybe irradiation in the womb or something um and these critical periods the thing about critical periods is that they have a defined ending which is achieved as you told us by molecular changes now sensitive period on the other hand are periods of gradual change in plasticity shaped by environmental inputs especially nutrition and you made the important point that nutrition needs to go hand in hand with stimulation of the baby of the infant and of the child and a sensitive period is not closed by molecular events and although so so it means that later gains in brain function uh can be achieved although they're more difficult outside the sensitive period and the periods of Greater sensitivity in human development are as a fetus and young infant which is why we as nutritionists are constantly emphasizing huge importance of the first thousand days this magical number which is the 270 days of pregnancy added to the 730 days of the first two years of life and if we can apply optimal nourishment to the child's brain in this early life period that child will reap the fruits of our intervention and our investment for the rest of their lives is that a good summary yes very nice thank you all based on what you told us yeah yeah so dear listeners thank you very much forist listening to our podcast and we hope that you'll subscribe through the nni 365 app to ensure that you don't miss any future offerings and that concludes today's episode thank you for joining us for this special episode from nni and wnsc workshop 102 we hope you enjoyed and learned from this quick discussion fellow experts till the next episode