- An infant is extraordinarily sensitive to its mother's behavior.
- Baby rats nursed by their intoxicated mothers exhibit greater overall distress and aversion to alcohol.
- The infants' distress and aversion seem dependent on maternal reaction to alcohol.
- Alcohol's effects on maternal behavior may have long-lasting consequences for the infant.
It's no secret that a baby's survival, under normal circumstances, is dependent on the mother's behavior. Nourishment, appropriate body temperature, protection from harm - these are the basics. Yet researchers are also beginning to determine, as shown in a study in the April issue of Alcoholism: Clinical & Experimental Research, that a mother's behavior, altered by alcohol, can have powerful and enduring effects on her infant's subsequent memories.
"Infants are exquisitely sensitive to maternal behavior," said Norman E. Spear, distinguished professor of psychology at Binghamton University and one of the study's lead authors, "that's their entire context. If the mother's behavior deviates just a little bit from the norm, the infants notice and it's not a pleasant experience for them."
"Specific memories may be generated in relation to alcohol," added Juan Carlos Molina, co-author, professor of psychology at the University of Cordoba, and senior research scientist at the Instituto de Investigacion Medica Mercedes y Martín Ferreyra in Argentina.
In the study, baby rats were nursed by intoxicated mother rats. When compared with baby rats that nursed from alcohol-free mothers, the alcohol-exposed pups later demonstrated higher ultrasonic vocalizations (a traditional distress signal), greater motor activity during isolation (which is what rats do when they're disturbed), and aversion to a texture (sandpaper) that had been matched through smell with alcohol. Spear believes that the mother's alcohol-altered behavior, rather than the pup's reaction to the alcohol itself, is what caused their distress and related behavior.
"The effects of the alcohol on the mother's behavior are very subtle," he explained, "but enough to make the experience aversive for the rat pup. There are some aspects of maternal behavior that are poorer in mother rats that have had alcohol. For example, retrieval behavior -- when a mother retrieves a baby rat that has wandered away from the nest -- is inhibited by alcohol. Another effect of alcohol on the mother is a decrease in body temperature; it may be a drop of only one and a half degrees centigrade, but the pups may detect the difference in warmth."
"The animal model and the human literature are telling a similar story," said Julie A. Mennella, biopsychologist at Monell Chemical Senses Center. "Memories are not only formed as a result of early sensory experiences with alcohol in the context of the mother, but they're also retained for a considerable time span. This study is telling us that the presence of alcohol odor is capable of supporting some type of conditioning, such as aversion, when it's paired with a new stimulus, such as sandpaper."
Mennella said that Spear and Molina's study is part of a growing body of research that speaks to the relevance of early learning. "Other research has shown that elementary-school-aged children of alcoholics were more likely to report more negative experiences about alcohol than children from non-alcoholic homes," she said. "Some of the early learning about alcohol appears to be based on sensory experience and the context in which alcohol is experienced." Indeed, Mennella believes this study speaks to the power of odor associations.
"Odors are often thought to provide us with the best memory cues," she said. "Some of our oldest and most emotionally laden memories are associated with odors. Odors take us to our past." Mennella described a study conducted at her institution in which children were asked to complete a difficult task in a room that was scented with a particular odor. None of the children completed the difficult task. Shortly afterwards, the children were divided into three groups, all were given the same simple task to complete, but each were placed in three different rooms with different odors. The group of children located in the room scented with the same odor as the room of the preceding difficult task performed worse that the other two groups. Mennella said that exposing rat pups to a sandpaper texture and children to a difficult task could both be classified as "arousing, emotionally salient" situations.
"Associative learning in the context of these very emotionally salient conditions," said Mennella, "is a really powerful mechanism by which odors acquire personal significance." In other words, the emotional context in which children, or infants, experience an odor can influence their subsequent behaviors, likes and dislikes, and conditioning to alcohol.
A related area of study is what Mennella calls the "folklore" of alcohol consumption by lactating women. This refers to beliefs, brought to America by various immigrant groups, that alcohol consumption might increase milk production, facilitate milk release, relax the mother, increase the infant's milk intake, and/or help the baby sleep. Yet apart from possibly helping the mother relax, said Mennella, "there's no scientific evidence that supports the folklore, in fact, it's the opposite."
"Some doctors today still recommend drinking before nursing," observed Spear, "but there is still so much that is unknown about when and how much may be acceptable. In addition, there are a lot more days during a human infant's nursing period (up to two or three years) than a baby rat's (21 days). Perhaps there is a cumulative effect."
Molina is cautious about encouraging direct extrapolations from animal studies to the human domain. "The most important contribution about our study," he said, "is simply to indicate that breastfeeding potentially represents a source of generating alcohol-related memories." He nonetheless noted that cumulative studies "certainly emphasize the need to avoid alcohol exposure during prenatal, neonatal and early postnatal periods of development."
As Spear said, "the bottom line is that we still don't know what the long-term detrimental effects of drinking while nursing may be."
Co-authors of the Alcoholism: Clinical & Experimental Research paper included: Marta Yanina Pepino of the Instituto de Investigacion Medica M.M. Ferreyra, Cordoba, Argentina; and Johnmarc Johnson (now deceased) of the Department of Psychology, Binghamton University. The study was funded in part by the National Institute on Alcohol Abuse and Alcoholism and the Agencia Nacional de Promoción Científica y Tecnológica, Consejo Nacional de Investigaciones Científicas y Tecnológicas.
Add'l Contact: Juan Carlos Molina, Ph.D.
54-351-468-1465 X108 (Argentina)
Instituto de Investigacion Medica M.M. Ferreyra