Co-induction of long-term potentiation and long-term depression at a central synapse in the leech

Most studies of long-term potentiation (LTP) have focused on potentiation induced by the activation of postsynaptic NMDA receptors (NMDARs). However, it is now apparent that NMDAR-dependent signaling processes are not the only form of LTP operating in the brain [Malenka, R. C., & Bear, M. F. (2004). LTP and LTD: An embarrassment of riches. Neuron, 44, 5–21]. Previously, we have observed that LTP in leech central synapses made by the touch mechanosensory neurons onto the S interneuron was NMDAR-independent [Burrell, B. D., & Sahley, C. L. (2004). Multiple forms of long-term potentiation and long-term depression converge on a single interneuron in the leech CNS. Journal of Neuroscience, 24, 4011–4019]. Here we examine the cellular mechanisms mediating T-to-S (T → S) LTP and find that its induction requires activation of metabotropic glutamate receptors (mGluRs), voltage-dependent Ca²⁺ channels (VDCCs) and protein kinase C (PKC). Surprisingly, whenever LTP was pharmacologically inhibited, long-term depression (LTD) was observed at the tetanized synapse, indicating that LTP and LTD were activated at the same time in the same synaptic pathway. This co-induction of LTP and LTD likely plays an important role in activity-dependent regulation of synaptic transmission.     

Book reviews

International Journal for Philosophy of Religion -     

Resolving arguments accurately

This empirical investigation examined how ordinary language users resolved disagreements over the solutions to categorical syllogisms. Forty-six participants completed puzzles in logic. After completing the puzzles, participants were then randomly paired into 23 to compare their answers and to resolve 159 disagreements. Results indicate that the most frequently used strategies for resolving disagreements centered on: (a) arguing over the merits of the position (47% of the time) and (b) appealing to past solutions as a means of addressing current disputes (28% of the time). In addition, the data revealed that the most frequently used strategy (arguing the merits of the positions) was no more effective than random choice (52% increase in correct solutions) while the strategy of appealing to past solutions significantly aided dyads in reaching correct solutions (70% increase in correct solutions).     

Recent Scholarship on Aquinas

Books reviewed in this article:
John Bowlin, Contingency and Fortune in Aquinas's Ethics
John I. Jenkins, C.S.C., Knowledge and Faith in Thomas Aquinas
John Milbank and Catherine Pickstock, Truth in Aquinas     

Body mass index,inflammatory biomarkers and neurocognitive impairment in HIV-infected persons

To determine the relationships among body mass index (BMI), and HIV-associated neurocognitive impairment and the potential mediating effects of inflammatory cytokines. Among the HIV-infected individuals (N = 90) included in this study, obesity was associated with slower processing speed (β = ?.229, standard error (SE) = 2.15, p = .033), compared to participants with a normal BMI, after controlling for psychosocial and HIV clinical factors. Serum concentrations of the interleukin-16 (IL-16) cytokine were significantly associated with slowed processing speed (β = ?.235, SE = 1.62, p = .033) but did not mediate the relationship between obesity and processing speed These findings suggest that obesity may contribute to cognitive processing speed deficits in HIV-infected adults. Elevated concentrations of IL-16 are also associated with slowing, though the results suggest that obesity and IL-16 may exert independent effects.     

Maternal Relationship Insecurity and Depressive Symptoms as Moderators of Home Visiting Impacts on Child Outcomes

The purpose of this study was to determine the extent to which maternal relationship insecurity and severe depressive symptoms moderate home visiting impacts on developmental and behavioral outcomes in 2-year old children. In an experimental trial of the Healthy Families Alaska home visiting program, families (N = 249) were randomly assigned to home visiting (n = 126) or community services as usual (n = 123). Maternal severe depressive symptoms (CES-D ≥ 24) and relationship insecurity were measured using the Center for Epidemiologic Studies Depression Scale and the Attachment Style Questionnaire at baseline. Child cognitive and psychomotor development and behavior problems were measured with the Bayley Scales of Infant Development and the Child Behavior Checklist at follow-up. The results revealed that home visiting significantly impacted three outcomes—child cognitive development, internalizing behavior, and externalizing behavior. Home visiting impacts were limited to subgroups defined by maternal depressive symptoms and relationship insecurity. Home visiting improved cognitive development (B = 6.02, p < .03), and decreased internalizing behavior (B = ?3.83, p = .02) and externalizing behavior problems (B = ?3.74, p = .03) in children of mothers with either severe depressive symptoms or high levels of discomfort with trust at baseline, but not both. Family engagement in home visiting seems to play a role in mediating these moderating effects. These findings reflect the importance of screening for maternal relationship insecurity and depressive symptoms to distinguish family subgroups likely to benefit from home visiting from those for whom an enhanced service model might be needed.