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Early relationships as regulators of infant physiology and behavior. Acta Pzdiatr 1994; (Suppl 397):9-18. Stockholm. ISSN 0803-5326In recent years, animal research has revealed a network of simple behavioral and biological processes that underlie the psychological constructs we use to define early social relationships. Hidden within the observable interactions of parent and offspring are sensorimotor, thermal and nutrient-based events which have unexpected and widespread regulatory effects on infant behavior and physiology. The complex pattern of responses resulting from early separation in infant rats can be traced to the abrupt withdrawal of a number of discrete, independent regulatory processes which had been acting on individual components of the infant's physiology and behavior. These regulatory processes also appear to mediate long-term shaping effects exerted by early relationships, for example, on the vulnerability of the adult rat to hypertension and stress ulcer. In human development, early regulatory interactions may provide a bridge between biological and psychological processes in the development of our earliest mental representations. 0 Attachment, development, parent-injant intermcrion, psychobiology, separation M A Hojer,

Two-week-old rats were found to emit very little ultrasound in their cage except during arrivals and departures of the mother, when average peak rates of approximately 1 ultrasonic pulse/rat/min were detected. However, when all pups except one were removed from the home cage, the remaining isolated pup emitted ultrasound at a mean rate of 12 pulses/min for at least 30 min. When young rats of this age were placed alone in an unfamiliar test area, the ultrasound pulse rate was approximately 25/min, whereas groups of 4 littermates in the same situation emitted only occasional ultrasonic pulses. If an isolated pup in the novel environment was allowed access to a single anesthetized littermate or mother this also significantly reduced the rate of ultrasound emission, whereas a warm clay model did not.

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New laboratory research has revealed a network of simple behavioral, physiological, and neural processes that underlie the psychological constructs of attachment theory. It has become apparent that the unique features of early infant attachment reflect certain unique features of early infant sensory and motor integration, learning, communication, and motivation, as well as the regulation of biobehavioral systems by the mother-infant interaction. In this article, I will use this new knowledge to answer three major questions that have remained unsettled in our understanding of early human attachment: What creates an attachment bond? Why is early maternal separation stressful? How can early relationships have lasting effects? I will discuss the implications of these new answers for human infants and for the development of mental processes. Attachment remains useful as a concept that, like hunger, describes the operation of subprocesses that work together within the frame of a vital biological function.The word attachment has assumed new meanings as it has spread from literature to psychology, and most recently to biology. These changes have spanned the half century since the Second World War, when the vast numbers of displaced and orphaned children made the importance of a child's early tie to its mother evident to all. As different groups within psychology used the concept, there developed champions and detractors of one or another formulation. I think that a crucial change came when concept of attachment as a unique motivational system was gradually found to be incapable of generating testable hypotheses that could explain several puzzling observations. Developmental psychobiology researchers focused instead on simpler processes at work within the interactions between infant and parent-such as orientation, nursing, early learning, thermoregulation, and sensorimotor-system development. There was a period between the early 1970s and late 1980s when attachment was seldom used by developmental psychobiologists. In the last decade, however, the word has found a new usefulness as a general descriptive term for the processes that maintain and regulate sustained social relationships, much the same way that appetite refers to a cluster of behavioral and physiological processes that regulate food intake.The concept of attachment provides a good example of how a psychological construct can be analyzed at the level of the component processes that underlie it. This approach does not attempt to reduce psychological questions to the most basic units of biological organization. Rather, the focus is on the processes of behavioral and physiological regulation that closely underlie psychological constructs, providing a much-needed link between psychology and the cellular/molecular mechanisms of brain function. New knowledge at the level of behavior and integrative physiology promises to deepen our understanding of psychological constructs rather than eliminate the need for them.In order to illustrate this point, I will describe how...

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This study describes the development of anxiety and motor activation in mice lacking the serotonin (5HT) 1B receptor and in wild type controls and characterizes their early mother-infant interactions. In the isolation-induced ultrasonic vocalization paradigm, 5HT1B knockout pups vocalized less and were hyperactive, rearing, jumping, and rolling more often than wild type pups. One week postpartum, 5HT1B knockout mothers spent 20% more of their time outside the nest and were also hyperactive, rearing and climbing to the edge of the cage more often than the wild type mothers. There were no genotype effects on pup retrieval. Knockout adults were less anxious in the elevated plus-maze, defecated less, and head-dipped more, although none of the standard measures of anxiety (time and entries in the open arms) were different. 5HT1B knockout mice of both sexes were hyperactive during both the light and the dark phases of the 24-hr cycle. Thus, 5HT1B knockout mice show reduced anxiety and are hyperactive throughout their life.