'The risks of playing it safe': a prospective longitudinal study of response to reward in the adolescent offspring of depressed parents

BACKGROUND Alterations in reward processing may represent an early vulnerability factor for the development of depressive disorder. Depression in adults is associated with reward hyposensitivity and diminished reward seeking may also be a feature of depression in children and adolescents. We examined the role of reward responding in predicting depressive symptoms, functional impairment and new-onset depressive disorder over time in the adolescent offspring of depressed parents. In addition, we examined group differences in reward responding between currently depressed adolescents, psychiatric and healthy controls, and also cross-sectional associations between reward responding and measures of positive social/environmental functioning. Method We conducted a 1-year longitudinal study of adolescents at familial risk for depression (n = 197; age range 10-18 years). Reward responding and self-reported social/environmental functioning were assessed at baseline. Clinical interviews determined diagnostic status at baseline and at follow-up. Reports of depressive symptoms and functional impairment were also obtained. RESULTS Low reward seeking predicted depressive symptoms and new-onset depressive disorder at the 1-year follow-up in individuals free from depressive disorder at baseline, independently of baseline depressive symptoms. Reduced reward seeking also predicted functional impairment. Adolescents with current depressive disorder were less reward seeking (i.e. bet less at favourable odds) than adolescents free from psychopathology and those with externalizing disorders. Reward seeking showed positive associations with social and environmental functioning (extra-curricular activities, humour, friendships) and was negatively associated with anhedonia. There were no group differences in impulsivity, decision making or psychomotor slowing. CONCLUSIONS Reward seeking predicts depression severity and onset in adolescents at elevated risk of depression. Adaptive reward responses may be amenable to change through modification of existing preventive psychological interventions

Time-To-Degree And Credits-To-Degree Of Baccalaureate Degree Graduates

The purpose of this study was to a;sess two measures of accountability (i.e., time- to-degree (TTD) and credits-to-degree (CTD)). A total of 800 University of Wisconsin- Stout (UW-Stout) graduates, 200 from each graduating class from 1990 to 1993 were surveyed to determine the obstacles to four year degree completion and to determine why they completed excess credits beyond what was required to complete a degree program. Four hundred and twelve graduates returned the survey. Data were obtained from student transcripts and from the Bursar’s Office for only those graduates who returned the survey. The data were segmented in order to answer questions relating to validity, credits-to- degree, gender and success, major and degree program, academic preparedness, learning, and cost. The two measures of accountability were evaluated against the following predictors: cost of the degree (dollar amount), GPA, self-rating, post baccalaureate salary, post B.A./B.S. degree or education, parental education, and the student’s rating of post B.A./B.S. success. A significant negative correlation was obtained between overall GPA and TTD. TTD appears to be a better indicator of educational achievement using the criterion of overall GPA. The TTD measure of accountability appears to be a better indicator than CTD using the criteria of cost of the degree. Overall 65% of UW-Stout’s graduates who participated in this study remained in their initially selected majors. Graduates who switched majors were found to have higher TTD and CTD. Women appeared better prepared to succeed in courses at UW-Stout. Men withdrew from more courses, repeated more courses, and averaged slightly more semesters than women. UW-Stout graduates earned more credits than were required for a degree program. The top three reasons for completing more credits than required was: “other”(e.g., difficulty getting required courses and courses were not offered), changed major, and took additional courses that would benefit their career opportunities. The top three reasons indicated for taking longer to complete a degree program were: academic, institutional efficiency, and personal. Within the academic factor, the top four influences on extending TTD were: a) intemship/cooperative educational experience, b) decided to take fewer credits per semester, c) repeated courses, and d) keep GPA high

Endogenous Wnt signalling in human embryonic stem cells generates an equilibrium of distinct lineage-specified progenitors.

The pluripotent nature of human embryonic stem cells (hESCs) makes them convenient for deriving therapeutically relevant cells. Here we show using Wnt reporter hESC lines that the cells are heterogeneous with respect to endogenous Wnt signalling activity. Moreover, the level of Wnt signalling activity in individual cells correlates with differences in clonogenic potential and lineage-specific differentiation propensity. The addition of Wnt protein or, conversely, a small-molecule Wnt inhibitor (IWP2) reduces heterogeneity, allowing stable expansion of Wnt(high) or Wnt(low) hESC populations, respectively. On differentiation, the Wnt(high) hESCs predominantly form endodermal and cardiac cells, whereas the Wnt(low) hESCs generate primarily neuroectodermal cells. Thus, heterogeneity with respect to endogenous Wnt signalling underlies much of the inefficiency in directing hESCs towards specific cell types. The relatively uniform differentiation potential of the Wnt(high) and Wnt(low) hESCs leads to faster and more efficient derivation of targeted cell types from these populations

Aging in the Relaxor Ferroelectric PMN/PT

The relaxor ferroelectric (PbMn$_{1/3}$Nb$_{2/3}$O$_3$)$_{1-x}$(PbTiO$_3$)$_{x}$, $x=0.1$, (PMN/PT(90/10)) is found to exhibit several regimes of complicated aging behavior. Just below the susceptibility peak there is a regime exhibiting rejuvenation but little memory. At lower temperature, there is a regime with mainly cumulative aging, expected for simple domain-growth. At still lower temperature, there is a regime with both rejuvenation and memory, reminiscent of spin glasses. PMN/PT (88/12) is also found to exhibit some of these aging regimes. This qualitative aging behavior is reminiscent of that seen in reentrant ferromagnets, which exhibit a crossover from a domain-growth ferromagnetic regime into a reentrant spin glass regime at lower temperatures. These striking parallels suggest a picture of competition in PMN/PT (90/10) between ferroelectric correlations formed in the domain-growth regime with glassy correlations formed in the spin glass regime. PMN/PT (90/10) is also found to exhibit frequency-aging time scaling of the time-dependent part of the out-of-phase susceptibility for temperatures 260 K and below. The stability of aging effects to thermal cycles and field perturbations is also reported.Comment: 8 pages RevTeX4, 11 figures; submitted to Phys. Rev.

Are there compact heavy four-quark bound states?

We present an exact method to study four-quark systems based on the hyperspherical harmonics formalism. We apply it to several physical systems of interest containing two heavy and two light quarks using different quark-quark potentials. Our conclusions mark the boundaries for the possible existence of compact, non-molecular, four-quark bound states. While $QQ\bar n \bar n$ states may be stable in nature, the stability of $Q\bar Qn \bar n$ states would imply the existence of quark correlations not taken into account by simple quark dynamical modelsComment: 10 pages, 1 figure. Accepted for publication in Phys. Rev.