Summary paragraph Adult pair bonding involves dramatic changes in the perception and valuation of another individual1. One key change is that partners come to reliably activate the brain's reward system2-6, though the precise neural mechanisms by which partners become rewarding during sociosexual interactions leading to a bond remain unclear. Using a prairie vole model of social bonding7, we show how a functional circuit from medial prefrontal cortex (mPFC) to nucleus accumbens (NAcc) is dynamically modulated to enhance females' affiliative behavior towards a partner. Individual variation in the strength of this functional connectivity, particularly after the first mating encounter, predicts how quickly animals begin affiliative huddling with their partner. Rhythmically activating this circuit in a social context without mating biases later preference towards a partner, indicating that this circuit's activity is not just correlated with how quickly animals become affiliative but causally accelerates it. These results provide the first dynamic view of corticostriatal activity during bond formation, revealing how social interactions can recruit brain reward systems to drive changes in affiliative behavior.

Power reflectance measurements are significantly different for ears that pass newborn hearing screening and ears that refer with middle-ear transient conditions. At age 1 month, about 90% of ears that referred at birth passed an auditory brainstem response hearing evaluation; within these ears the power reflectance at 1 month did not differ between the ear that initially referred at birth and the ear that passed the hearing screening at birth for frequencies above 700 Hz. This study also proposes a preliminary set of criteria for determining when reflectance measures on young babies are corrupted by acoustic leaks, probes against the ear canal, or other measurement problems. Specifically proposed are "data selection criteria" that depend on the power reflectance, impedance magnitude, and impedance angle. Additional data collected in the future are needed to improve and test these proposed criteria.

The existence of sex-based differences in tendon and ligament injury rates has led investigators to test the hypothesis that sex plays a significant role in modulating tendon and ligament composition and material properties. To date, no studies have attempted to characterize how such differences develop during the course of normal tissue maturation and growth. Thus, the primary aim of the present study was to use a murine model to test the hypothesis that sex-based differences in the normal age-related development of tendon composition and material properties exist by assessing these parameters in the Achilles and tail tendons from 4-, 6-, 9-, 12-, and 15-week-old male and female C57Bl/6J mice. Despite significantly lower levels of total collagen content in females subsequent to sexual maturity (p < 0.0001), as well as a significant effect of sex on glycosaminoglycan content (p < 0.0001), Achilles tendon elastic modulus was not compromised in females. Female Achilles tendons did exhibit a significantly higher failure strain (p ¼ 0.0201) and strain energy density (p ¼ 0.0004) than did males, as well as a trend toward higher ultimate strength (p ¼ 0.0556). In contrast to the high load-bearing environment of the Achilles tendon site, sex did not have a statistically significant effect on any compositional or material property in the low load-bearing tendon fascicles of the tail. These data support recent studies by others, which suggest that male and female tendons have a differential adaptational response to their local mechanical loading environment. Keywords: tendon; sex; mouse; material properties; compositionThe existence of sex-based differences in tendon and ligament injury rates is well established, although the precise nature of this sex-bias appears to be dependent on anatomical location. [1][2][3][4][5] In the anterior cruciate ligament (ACL) of the knee, for example, the incidence of noncontact injury is roughly four to six times greater for women than men. 1-3 The prevailing theories used to explain the higher ACL injury rate among women include anatomical differences, 6-10 neuromuscular differences, 11-14 and hormonal effects on the metabolism of the tissue 15-18 that could potentially result in inferior material properties, thereby rendering the ligament more susceptible to failure. In contrast to the ACL, injury rates for the Achilles tendon are roughly four times greater in men than women, 4,5,[19][20][21] with the primary theory put forward being the differential participation of men and women in certain sports. 5 Despite the notably higher incidence of Achilles tendon rupture in males, no studies to date have examined whether there are sex-based differences in the material properties of the Achilles tendon. Further, among the studies that have investigated possible sexbased differences in the material properties of other tendons and ligaments, 9,10,22 none has attempted to examine how such differences develop during the course of normal tissue maturation and growth. The primary aim of t...