Depression is characterized by disturbed sleep and eating, a variety of other, nonspecific somatic symptoms, and significant somatic comorbidities. Why there is such close association between cognitive and somatic dysfunction in depression is nonetheless poorly understood. An explosion of research in the area of interoception—the perception and interpretation of bodily signals—over the last decade nonetheless holds promise for illuminating what have until now been obscure links between the social, cognitive-affective, and somatic features of depression. This paper reviews rapidly accumulating evidence that both somatic signaling and interoception are frequently altered in depression. This includes comparative studies showing vagus-mediated effects on depression-like behaviors in rodent models as well as studies in humans indicating both dysfunction in the neural substrates for interoception (e.g., vagus, insula, anterior cingulate cortex) and reduced sensitivity to bodily stimuli in depression. An integrative framework for organizing and interpreting this evidence is put forward which incorporates (a) multiple potential pathways to interoceptive dysfunction; (b) interaction with individual, gender, and cultural differences in interoception; and (c) a developmental psychobiological systems perspective, emphasizing likely differential susceptibility to somatic and interoceptive dysfunction across the lifespan. Combined with current theory and evidence, it is suggested that core symptoms of depression (e.g., anhedonia, social deficits) may be products of disturbed interoceptive-exteroceptive integration. More research is nonetheless needed to fully elucidate the relationship between mind, body, and social context in depression.

The traditional approach to the study of thermoregulation in young animals focuses on the regulatory capacities of individuals, which, for multiparous species, risks ignoring critical aspects of the early developmental niche. Here, we examined the ontogeny of regulatory behavior in C57BL/6 mice, employing simultaneous behavioral, thermographic, and acoustic measures of groups and individual pups. Litters of mice were placed in a chamber on Postnatal Day (PND) 2, 4, or 8, in which the ambient temperature (Ta) gradually cycled (over 50 min) from warm (36.5°C) to cool (20°C) and back (to 36.5°C). Litters of all three ages displayed “group regulatory behavior,” whereby group size varied with changes in Ta. This coupling, moreover, improved with age. Infrared thermography was used to monitor skin temperature of pups’ interscapular (TIS) and rump (Trump) areas, and to estimate brown adipose tissue (BAT) thermogenesis (TIS − Trump) in PND4 and PND8 individuals and huddles. Huddling was found to significantly reduce heat loss in pups subject to thermal challenge as groups, compared to pups challenged as individuals. Additionally, females were found to display significantly warmer TIS and Trump values than male huddlemates. Huddling did not have a consistent effect on emissions of ultrasonic vocalizations, which were generally correlated with ambient temperature and BAT activation. Our results indicate that simultaneous measures of behavioral and physiological response to cooling may prove useful for a variety of applications, including the phenotyping of social dysfunction.

Brown adipose tissue (BAT) is a thermogenic effector abundant in most mammalian infants. For multiparous species such as rats and mice, the interscapular BAT deposit provides both an emergency “thermal blanket” and a target for nestmates seeking warmth, thereby increasing the cohesiveness of huddling groups. Sex differences in BAT regulation and thermogenesis have been documented in a number of species, including mice (Mus musculus)–with females generally exhibiting relative upregulation of BAT. It is nonetheless unknown whether this difference affects the behavioral dynamics occurring within huddles of infant rodents. We investigated sex differences in BAT thermogenesis and its relation to contact while huddling in eight-day-old C57BL/6 mouse pups using infrared thermography, scoring of contact, and causal modeling of the relation between interscapular temperature relative to other pups in the huddle (TIS rel) and contacts while huddling. We found that females were warmer than their male siblings during cold challenge, under conditions both in which pups were isolated and in which pups could actively huddle in groups of six (3 male, 3 female). This difference garnered females significantly more contacts from other pups than males during cold-induced huddling. Granger analyses revealed a significant negative feedback relationship between contacts with males and TIS rel for females, and positive feedback between contacts with females and TIS rel for males, indicating that male pups drained heat from female siblings while huddling. Significant sex assortment nonetheless occurred, such that females made more contacts with other females than expected by chance, apparently outcompeting males for access to each other. These results provide further evidence of enhanced BAT thermogenesis in female mice. Slight differences in BAT can significantly structure the behavioral dynamics occurring in huddles, resulting in differences in the quantity and quality of contacts obtained by the individuals therein, creating sex differences in behavioral interactions beginning in early infancy.

Studies examining the effects of stimulus contingency on filial imprinting have produced inconsistent findings. In the current study, day-old bobwhite chicks (Colinus virginianus) received individual 5-min sessions in which they were provided contingent, noncontingent, or vicarious exposure to a variant of a bobwhite maternal assembly call. Chicks given contingent exposure to the call showed a significant preference for the familiar call 24 hr following exposure and significantly greater preferences than chicks given noncontingent exposure. Chicks given vicarious exposure to recordings of another chick interacting with the maternal call showed significant deviations from chance responding; however, the direction of chick preference (toward the familiar or unfamiliar) depended on the particular call used. These results indicate that both direct and indirect (vicarious) exposure to stimulus contingency can enhance the acquisition of auditory preferences in precocial avian hatchlings. Precocial avian hatchlings thus likely play a more active role in directing their own perceptual and behavioral development than has typically been thought. Keywordsfilial imprinting; contingency; interactive stimulation; vicarious learning; Northern bobwhite Social interaction and contingency are known to have potent influences on learning across a wide range of organisms and contexts. Grey parrots (Psittacus erithacus), for example, have been shown to learn the proper use of referential labels only when provided interactive sessions with live tutors (e.g., Pepperberg, 1994Pepperberg, , 1998. Human infants have also been found to produce more sophisticated vocalizations when their mothers respond to their babbling in a contingent manner (Goldstein, King, & West, 2003). In contrast to such findings, filial imprinting has traditionally been viewed as a special type of learning that occurs largely independent of contingent interaction or overt reinforcement (e.g., Lorenz, 1935Lorenz, , 1937.A number of studies have directly examined the effects of stimulus contingency on the behavior of precocial hatchlings, the majority of which have focused on whether imprinting stimuli are capable of functioning as reinforcers. Such studies have demonstrated that precocial avian neonates will indeed work to be exposed to such stimuli (e.g., Bateson & Reese, 1968;Campbell & Pickleman, 1961;Eacker & Meyer, 1967;Gaioni, Hoffman, DePaulo, & Stratton, 1978;Hoffman, Schiff, Adams, & Searle, 1966;Meyer, 1968;Peterson, 1960). Relatively few studies, on the other hand, have examined the effects of contingency on the formation of filial preferences. Some of these studies have reported enhanced acquisition of filial preferences under conditions of stimulus contingency (e.g., Bateson & Reese, 1969;Evans, 1991;Johnson, Bolhuis, & Horn, 1985; ten Cate, 1989b), whereas others have found little or no difference in the level of filial preference between chicks provided with contingent versus noncontingent exposure to stimuli (Bolhuis & Johnson, 1988; ten Cate...

Many precocial birds show a robust preference for the maternal call of their own species before and after hatching. This differential responsiveness to species-specific auditory stimuli by embryos and neonates has been the subject of study for more than four decades, but much remains unknown about the dynamics of this ability. Gottlieb [Gottlieb [1971]. Development of species identification in birds: An enquiry into the prenatal determinants of perception. Chicago/London: University of Chicago Press.] demonstrated that prenatal exposure to embryonic vocalizations serves to canalize the formation of species-specific preferences in ducklings. Apart from this, little is known about the features of the developmental system that serve to canalize such species-typical preferences, on the one hand, and generate novel behavioral phenotypes, on the other. In the current study, we show that briefly exposing bobwhite quail embryos to a heterospecific Japanese quail (JQ) maternal call significantly enhanced their acquisition of a preference for that call when chicks were provided with subsequent postnatal exposure to the same call. This was true whether postnatal exposure involved playback of the maternal call contingent upon chick contact vocalizations or yoked, non-contingent exposure to the call. Chicks that received both passive prenatal and contingent postnatal exposure to the JQ maternal call redirected their species-typical auditory preference, showing a significant preference for JQ call over the call of their own species. In contrast, chicks receiving only prenatal or only postnatal exposure to the JQ call did not show this redirection of their auditory preference. Our results indicate that prenatal sensory stimulation can significantly bias postnatal responsiveness to social stimuli, thereby altering the course of early learning and memory.