Barr – sensory pathways

That’s a huge question. But one of the ways we can think about that is to understand the different sensory pathways, each of which has a biological substrate underneath it. So for example, if a mother is holding an infant, there are a number of sensory pathways that are activated. One is the touch pathway, of course, and that generates a whole series of central neurological stimuli that activate certain neurotransmitters in the central nervous system which then become functional in terms of how the mother responds to the infant and so on in a continuing circle. Similarly, it helps regulate temperature of the infant, and that’s critical, especially when the infants are very, very young, but even later. And thirdly, there’s the en face position we talk about where the mothers and the infants are looking at each other. That generates the pathway of sight and vision and a variety of pieces, if you want to put it that way, of information that flows through that pathway. And the fourth one, which we are more excited about all the time because of the new research, is the smell pathway, which is very, very important for many other animals, in fact absolutely critical.  

In humans it’s not quite so important because we have the other pathways we’ve been talking about but the smell pathway has been very interesting in terms of infants identifying their mothers and beginning to have appropriate interactions around important functions like feeding right from the first minutes after birth.  

So all of these pathways have a biological substrate through which these sensory inputs are being transmitted. They affect the mother and the mother’s response to the infant and in the infant they affect the response of the infant to whatever else is going on in the dyad. A particularly nice example of that in our own work is the issue about how the mother and the infant together, as opposed to the infant being separated from these biological pathways, can handle the stress of early pain. And the paradigm that we use for that is the kind of pain experiences that every normal infant in our society has which includes what we call the PKU heel stick for phenylketonuria, where we take a sample of blood at birth to see whether or not that particular genetic disease is present in the infant or the infant’s at risk for it, and in the process of studying that we can study whether or not the infant’s response to this pain experience is the same or different if the infant is being held by the mother or separate from the mother, at the same time. That is, not at the same time but separate from the mother during the time that procedure is being performed.  

And it depends, interestingly, on which pathway you measure to understand what the effect is. And they’re not all the same; it’s not like everything goes up or everything goes down. But it’s a very interesting complex of responses depending on the system that you’re looking at. But when the mother is in contact with the infant and all of these sensory pathways are being activated, all of the neurotransmitters that are in the brain that need to be used in order for these sensory experiences to be experienced, that the infant’s response to the pain experience is reduced significantly, in most measures on the order of 50 percent or more. So it turns out to be a very powerful, if we can put it this way, analgesic. Although it’s not a pill that the infant’s taking but it has similar effects and indeed stronger effects than most of the analgesics that we can give, that we  
can give to infants. So we consider this a nice demonstration of the power of these early regulators when the infant and the mother are together.