Intrinsic functional connectivity strength of SuperAgers in the default mode and salience networks: Insights from ADNI.

There exists a group of older individuals who appear to be resistant to age-related memory decline. These "SuperAgers" have been shown to demonstrate preservation of cortical thickness and functional connectivity strength across the cortex which positively correlates with memory performance. Over the last decade, roughly 30 articles have been published regarding SuperAgers; however, to our knowledge, no replications of these studies have been published. The current study sought to conceptually replicate Zhang and colleagues' (2020) findings that SuperAgers demonstrate stronger intrinsic functional connectivity within the default mode (DMN) and salience networks (SN), and that connectivity strength within these networks correlates with memory performance. We identified 20 SuperAgers and 20 matched Normal Agers in the control cohort of the Alzheimer's Disease Neuroimaging Initiative (ADNI) database. We compared the functional connectivity strength of the DMN and SN between these groups, and used the Rey Auditory Verbal Learning Test (RAVLT) to evaluate correlations between functional connectivity and memory performance. Our results did not replicate Zhang and colleagues' (2020) results, as we found negligible differences between SuperAgers and Normal Agers in the DMN and SN, and no significant correlations between functional connectivity and memory performance after accounting for multiple comparisons. More replications are needed to confirm existing work. In addition, more research with larger SuperAger samples and more consistent definitions of SuperAging is needed, so that we can better understand this remarkable group of older adults.

Pain feedback interferes with reward positivity production.

The reinforcement learning (RL) theory of the reward positivity (RewP) proposes that RewP indexes a reward prediction error (RPE) signal processed in the anterior cingulate cortex (ACC). According to this theory, RewP is an event-related potential (ERP) that is more positive-going for feedback stimuli that predict better-than-expected outcomes (positive feedback) than for feedback stimuli that predict worse-than-expected outcomes (negative feedback). Despite strong evidence for this hypothesis, findings have been equivocal for tasks involving painful outcomes. We hypothesized that the RewP is modulated by high-level task goals such that outcomes that are congruent with the goals elicit positive RPEs even if their immediate consequences are negative. Accordingly, changes in high-level task goals should modulate RewP amplitude for tasks that involve seeking pain compared to tasks that involve avoiding pain. We recorded the electroencephalogram from participants who were instructed to navigate a virtual T-Maze to find reward-predictive feedback in a reward condition and pain-predictive feedback in a pain condition. We expected more positive-going ERPs to reward feedback in the reward condition and more positive-going ERPs to pain feedback in the pain condition. Despite behavioral results indicating that participants complied with task instructions, contrary to our predictions, we did not find a RewP to pain feedback. We suggest that pain feedback interfered with the effect of high-level task goals on RewP amplitude, which is indicative of conflict at different levels of task hierarchy.

Effects of increasing lipopolysaccharide concentrations on in vitro developmental competence of ovine oocytes.

Although a considerable number of studies have investigated the effects of lipopolysaccharide (LPS) on the reproductive performance of dairy cows, the response of ovine oocytes to LPS during their in vitro maturation and development is not well defined yet. Ewe's ovaries were obtained from a slaughterhouse, the oocytes were collected and matured in the presence of increasing concentrations (0, 0.01, 0.1, 1 and 10 µg/mL) of LPS in order to evaluate the meiotic maturation by measuring the proportion of oocytes reaching the MII stage. The concentration of intracellular glutathione (GSH) was measured in oocytes following maturation in vitro. In addition, concentrations of selected metabolites including glucose, pyruvate, lactate and glutamine were quantified in the medium following maturation. A number of treated matured oocytes along with the control group were subsequently fertilized using frozen semen and assessed for the rate of cleavage and for the proportion reaching the blastocyst stage. The number of oocytes in MII stage was significantly reduced in response to the increasing concentrations of LPS (77.83%, 70.64%, 68.86%, 66.32%, respectively, in case of 0.01, 0.1, 1 and 10 µg/mL LPS when compared to the control group, 76.34%; P<0.05). There were no differences neither in the intracellular concentration of GSH in the oocytes nor in case of the metabolites in the maturation medium. Although the rate of cleaved oocytes was not affected by increasing levels of LPS, the blastocyst rate was reduced in a dose dependent manner (36.69%, 34.21%, 30.35%, 17.27% and 14.03% for the control, 0.01, 0.1, 1 and 10 µg/mL LPS, respectively (P<0.05). These results demonstrate that the developmental competence of ovine oocytes may be affected detrimentally by LPS and such deleterious effects could be related to the maturation process.

Reward positivity: Reward prediction error or salience prediction error?

The reward positivity is a component of the human ERP elicited by feedback stimuli in trial-and-error learning and guessing tasks. A prominent theory holds that the reward positivity reflects a reward prediction error signal that is sensitive to outcome valence, being larger for unexpected positive events relative to unexpected negative events (Holroyd & Coles, 2002). Although the theory has found substantial empirical support, most of these studies have utilized either monetary or performance feedback to test the hypothesis. However, in apparent contradiction to the theory, a recent study found that unexpected physical punishments also elicit the reward positivity (Talmi, Atkinson, & El-Deredy, 2013). The authors of this report argued that the reward positivity reflects a salience prediction error rather than a reward prediction error. To investigate this finding further, in the present study participants navigated a virtual T maze and received feedback on each trial under two conditions. In a reward condition, the feedback indicated that they would either receive a monetary reward or not and in a punishment condition the feedback indicated that they would receive a small shock or not. We found that the feedback stimuli elicited a typical reward positivity in the reward condition and an apparently delayed reward positivity in the punishment condition. Importantly, this signal was more positive to the stimuli that predicted the omission of a possible punishment relative to stimuli that predicted a forthcoming punishment, which is inconsistent with the salience hypothesis.