Karen, 

Motor learning is a complex process, even when supported by the primitive survival reflexes, and thus my response is not a short one (with my apologies).  

The following studies have long been cited in the text, Breastfeeding and Human Lactation, in a table comparing breastfeeding and bottle-feeding in full-term infants.  This chapter was originally written by Jan Riordan, and since her retirement, Riordan's comparison table has been maintained in Chapter 3 by Catherine Watson Jenna and Karen Wambach.  Please see Table 3-4 on page 104 in the current (5th) edition by Wambach and Riordan.  

IBCLCs often cite items from this comparison chart in discussing the greater oro-facial development in breastfed populations, yet there are many more insights to be found in this comparison table.  

I utilize a cognitive science point of view to further discuss these comparisons, with particular emphasis on kinesiology, the study of human movement, motor learning, and motor control.  In regard to the infant's motor learning toward motor control for milk-feeding skills, a number of items listed in this table are differences in feeding movements, while other items are differences in physiologic responses to these feeding movements.  

You may find the studies that cite the differences in physiologic responses specific to breastfeeding and bottle-feeding methods to be particularly helpful for your NICU discussions in regard to breastfeeding as the far greater physiologic feeding method.  For example:  

- At breast, inspiration is prolonged, while expiration is shortened.
- In contrast, inspiration is shortened, while expiration is prolonged, and greater ventilator disruption has been observed during bottle-feeds [presumably due to the constant, rapid gravity flow during bottle-feeding]. 
Mathew OP.  Regulation of breathing patterns during feeding:  Role of suck, swallow, and nutrients.  In: Mathew OP, Sant’Ambrogio G (Eds.), Respiratory Function of the Upper Airway.  New York: Marcel Dekker Inc., 1988:535-560.   

- Episodes of cyanosis in preterm infants have been observed during bottle-feeding.
- Hypoxemia in preterm and full-term infants has been observed during bottled feeds.
- Occasional periods of prolonged airway closure (obstructed breaths) have been observed during bottle-feeding in all preterm and full-term infants studied.
Koenig JS, Davies AM, Thach BT.  Coordination of breathing, sucking, and swallowing during bottle feedings in human infants.  Journal of Applied Physiology 1990;69(5):1623-1629.

- No apneic episodes were observed while breastfeeding.
- Two apneic episodes were observed while bottle-feeding with a breath pause greater than 20 seconds.
Chen CH, Wang TM, Chang HM, Chi CS.  The effect of breast- and bottle-feeding on oxygen saturation and body temperature in preterm infants.  Journal of Human Lactation 2000;16:21-27.    

- Higher oxygen saturation levels have been observed during breastfeeding.
- Lower oxygen saturation levels have been observed during bottle-feeding.
- Very low birth weight infants had a lower incidence of oxygen saturation levels below 90% while breastfeeding.
- VLBW infants had a higher incidence of oxygen saturation levels dropping below 90% while bottle-feeding.
- Extremely low birthweight infants were observed to have higher oxygen saturation rates while breastfeeding. 
- ELBW infants were observed to have lower oxygen saturation rates while bottle-feeding.  
Bier JAB, Ferguson A, Anderson L, Solomon E, Voltas C, Oh W, Vohr BR.  Breast-feeding of very low birth weight infants.  Journal of Pediatrics 1993;123:773-778. 
Bier JB, Ferguson A, Morales Y, Liebling M, Oh W, Vohr B.  Breastfeeding infants who were extremely low birth weight.  Pediatrics 1997;100:e3.    
Chen CH, Wang TM, Chang HM, Chi CS.  The effect of breast- and bottle-feeding on oxygen saturation and body temperature in preterm infants.  Journal of Human Lactation 2000;16:21-27. 
Goldfield EC, Richardson MJ, Lee KG, Margetts S.  Coordination of sucking, swallowing, and breathing and oxygen saturation during early infant breast-feeding and bottle-feeding.  Pediatric Research 2006;60(4):450-455.    
Hammerman C, Kaplan M.  Oxygen saturation during and after feeding in healthy term babies.  Biology of the Neonate 1995;67(2):94-99. 

Preterm infants' sequential transcutaneous oxygen pressure (tcPO2) have been observed to be significantly higher while breastfeeding, as compared to significantly lower tcPO2 among preterm infants during bottled feeds.  
Meier P.  Bottle- and breast-feeding: effects on transcutaneous oxygen pressure and temperature in preterm infants.  Nursing Research 1988;37:36-41.

No episodes of abnormally low heart rates have been observed in infants while breastfeeding, while a number of infants in each of the following three studies experienced bradycardia during bottled feeds.
Infant body temperatures were also found to be higher while breastfeeding, and significantly lower during bottled feeds.
Mathew OP.  Regulation of breathing patterns during feeding:  Role of suck, swallow, and nutrients.  In: Mathew OP, Sant’Ambrogio G (Eds.), Respiratory Function of the Upper Airway.  New York: Marcel Dekker Inc., 1988:535-560.  
Hammerman C, Kaplan M.  Oxygen saturation during and after feeding in healthy term babies.  Biology of the Neonate 1995;67(2):94-99.  
Meier P, Anderson GC.  Responses of small preterm infants to bottle- and breast-feeding.  MCN (American Journal of Maternal and Child Nursing) 1987;12:97-105.   
 
A teaching point that may be helpful for your NICU colleagues in relating to what infants experience:  
Differences in physiologic responses to feeding and drinking movements are similarly seen in older infants, children, and adults, to wit: Cardiac and respiratory rates are faster during and shortly after the very thirsty person rapidly drinks a large glass of water (drinking a large volume quickly is more work for the body) as compared to the same individual’s lower cardiac and respiratory rates while slowly sipping a cup of tea (drinking a small volume slowly is less work for the body).  

In my opinion, any infant who is bottle-fed, regardless of milk type, should be bottle-fed in a paced manner versus the rapid and constant gravity flow when bottles are positioned at a more vertical angle, simply as a more compassionate approach to the infant who is learning not just the oral grasp and effective sucking, but who is also learning how to coordinate suck and swallow with breathing.  Having said this, please know that I wholly support the Ten Steps to Successful Breastfeeding.  In a recent MoreThanReflexes webinar discussion, I was delighted to hear Katinka Musavaya of Harare, Zimbabwe state that in Zimbabwean hospitals, infants are breastfed and/or cup-fed, and bottles are not used in hospitals there due to the various risks of bottle-feeding.  Katinka has given me permission to share that information here.  

The above comparisons in physiologic responses to breastfeeding movements and bottle-feeding movements reflect the differences in their respective feeding movements.  For greater insight, I recommend viewing these differences through the lens of the cognitive sciences in regard to the cognitive demands of task switching, and the well-known switch costs of decreased speed and accuracy for the task.       

One important aspect of breastfeeding versus bottle-feeding movements not listed in the Watson Genna & Wambach (Riordan) chart is the reflexive lunge toward the nipple-areolar complex, as compared to bottle-feeding, in which the bottle is moved toward the infant, rather than the infant being moved toward the bottle.  The latter technique would involve an unnecessary workload for the parent or other caregiver(s), and thus the beginning of that feeding technique has long been reversed for the bottle-feeding parent or other caregiver's greater ease.  This reflects Thorndike’s learning precept of the Law of Least Effort.  

When a breastfed infant has been bottle-fed and subsequently returns to the breast, difficulties with the infant's oral grasp of nipple-areolar complex are frequently observed, particularly but not only during learning.  These difficulties include a measurable inhibition of the infant's reflexive lunge toward the breast, termed the inhibition of return (IOR), the delay in responding to the previously cued (or orienting) stimulus.   The IOR is measured as at least 300 to 500 ms, and as clinicians in the field of infant feeding, we often observe far greater IORs than 300 to 500ms.  So yes, inhibition, as well as inhibition of return, is highly significant during the task switching that is often expected of breastfed infants re: bottle-feeding and back to the breast, but formal study awaits in this area of infant feeding among human infants.  

We would never expect NICU or Peds or well-baby nursery nurses to recommend switching to a different style of artificial nipple for bottle-feeding infants when bottle-feedings have been going well with a particular style of artificial nipple.  When a departing nurse is giving report to an oncoming nurse during shift change, the departing nurse may report that Baby Smith "is doing better" with a particular style of artificial nipple.  The oncoming nurse intuitively understands that the specific artificial nipple described by the departing nurse is the bottle nipple that should be used during the upcoming shift, in order for the infant to continue building motor memory toward motor control for the oral grasp as well as effective suckling for adequate milk transfer, while learning how to coordinate suck and swallow with breathing.  

Other movement differences listed in the Wambach and Riordan text (Table 3-4, page 104) include: 
- extended wide oral gape at the breast, versus less oral extension to grasp the artificial teat
- at breast, the tongue moves in a wavelike, rolling, peristaltic manner from the front of the tongue toward the back
- during bottled feeds, the baby's tongue moves in an upward and forward thrust against the end of the teat, moving in a piston-like manner, presumably for controlling the rapid gravity-flow of milk through the artificial nipple
- extension excursion of the mandible during breastfeeding, versus minimal action of the mandible needed if bottle-feeding
- greater range of contraction of the masseter, buccinator, and temporalis muscles during breastfeeds, versus lesser activity of the masseter, buccinator, and temporalis muscles during bottled feeds

From a cognitive science point of view, task-switching between the two methods is often challenging to infants, particularly but not only during early skill acquisition when motor memories are particularly fragile.  Task switching is considered costly even among elite performers.  Consider the professional musician who is rehearsing for a job audition on the clarinet.  Those rehearsals will never take place on an oboe when the job audition is for a clarinet position.  If such foolish rehearsal did occur, switch costs of decreased speed and accuracy would be expected when the musician would return to the clarinet for the audition.  There are many differences between the oral grasp of a clarinet and the oral grasp of an oboe, even though those instruments may appear very similar to the non-musician.  

This fragility of early motor memories is seen elsewhere, such as learning a new computer password or a new telephone number, where there must be enough repetition of practice in order to build robust memory for that information.  That information is encoded in the brain in overlapping, multi-sensory fashion:  visual, tactile, motor, and perhaps also auditory memory if we happen to state the numbers aloud as we are learning their sequence (sequential learning).  The sequential motor learning in breastfeeding is far different than the sequential learning for bottle-feeding skills, beginning with the reflexive lunge toward the breast and its frequent inhibition that often follows the infant's learning experience with an artificial nipple.     

Task switching is cognitively demanding across the lifespan.  Furthermore, the younger we are, the greater the limitations in our cognitive flexibility for task switching.  

Task switching, cognitive flexibility, and inhibition are all heavily studied in the cognitive sciences.  Today's PubMed search using the term "task-switching" yields 1,391 results, but when using the term "task switching" without the hyphen, note that the results are nearly three-fold at 3,032.  

Today's PubMed search using the term "cognitive inhibition" yields 12,266 results.  

Today's PubMed search using the term "inhibition of return" yields 2,767 results.

With best regards,

Debbie

Debra Swank, RN BSN IBCLC
MoreThanReflexes Education
Ocala, Florida USA
http://www.MoreThanReflexes.org

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