Suppression weakens unwanted memories via a sustained reduction of neural reactivation.

Aversive events sometimes turn into intrusive memories. However, prior evidence indicates that such memories can be controlled via a mechanism of retrieval suppression. Here, we test the hypothesis that suppression exerts a sustained influence on memories by deteriorating their neural representations. This deterioration, in turn, would hinder their subsequent reactivation and thus impoverish the vividness with which they can be recalled. In an fMRI study, participants repeatedly suppressed memories of aversive scenes. As predicted, this process rendered the memories less vivid. Using a pattern classifier, we observed that suppression diminished the neural reactivation of scene information both globally across the brain and locally in the parahippocampal cortices. Moreover, the decline in vividness was associated with reduced reinstatement of unique memory representations in right parahippocampal cortex. These results support the hypothesis that suppression weakens memories by causing a sustained reduction in the potential to reactivate their neural representations.

Neural Correlates of Successful Memory Encoding in Kindergarten and Early Elementary School Children: Longitudinal Trends and Effects of Schooling.

From age 5 to 7, there are remarkable improvements in children's cognitive abilities ("5-7 shift"). In many countries, including Germany, formal schooling begins in this age range. It is, thus, unclear to what extent exposure to formal schooling contributes to the "5-7 shift." In this longitudinal study, we investigated if schooling acts as a catalyst of maturation. We tested 5-year-old children who were born close to the official cutoff date for school entry and who were still attending a play-oriented kindergarten. One year later, the children were tested again. Some of the children had experienced their first year of schooling whereas the others had remained in kindergarten. Using 2 functional magnetic resonance imaging tasks that assessed episodic memory formation (i.e., subsequent memory effect), we found that children relied strongly on the medial temporal lobe (MTL) at both time points but not on the prefrontal cortex (PFC). In contrast, older children and adults typically show subsequent memory effects in both MTL and PFC. Both children groups improved in their memory performance, but there were no longitudinal changes nor group differences in neural activation. We conclude that successful memory formation in this age group relies more heavily on the MTL than in older age groups.

The oral 13C-bicarbonate technique for determination of energy expenditure in dogs: dietary and environmental factors affecting the respiratory quotient and 13C recovery factor.

The oral 13C-bicarbonate technique (o13CBT) can be used for short-term measurements of CO2 production (RCO2) and energy expenditure (EEx). The method relies on appropriate estimates for the respiratory quotient (RQ) and recovery factor (RF) of 13C. Four Retriever dogs were included in four experiments to validate the o13CBT against indirect calorimetry (IC), and determine RQ and RF; Expt. 1: feeding different protein:fat:carbohydrate ratios [in % of metabolisable energy]: 25:33:42 in a maintenance (Mnt.) diet; 38:26:36 in a high-protein high-fibre (HFibre) diet and 27:56:17 in a high-fat (HFat) diet, simultaneously with start of measurements (T0); Expt. 2: the Mnt. diet at T0 or 4 h postprandial (T4); Expt. 3: T4 at different ambient temperatures, 22°C and 15°C; Expt. 4: T4 after 1 h physical activity. The RCO2 and EEx were determined from the respiration chamber measurements made simultaneously with IC and the o13CBT (o13CBTonline), and in Expts. 1 and 2, also on two consecutive days using o13CBT with collection of breath into breath bags (o13CBTbreathbags). The RQ values obtained at T0 reflected dietary compositions, with the highest least square mean (LSM) of 0.954  for the Mnt. diet, 0.905 for the HFibre and 0.877 for the HFat diet (p < 0.05). An increased interval between meal and measurement period decreased RQ significantly (p < 0.05) in Expt. 2, LSM being 0.954 at T0 and 0.909 at T4. Ambient temperature (Expt. 3) and physical activity (Expt. 4) did not influence postprandial RQ. The RF values were not significantly affected by diet (Expt. 1). Measurements starting at T0 (Expt. 2) resulted in higher (p < 0.05) RF values than at T4 (LSM = 0.971 and 0.836, respectively). The ambient temperatures (Expt. 3) did not influence postprandial RF. However, when dogs were physically active prior to measurements (Expt. 4), RF values (LSM = 1.019) were higher (p < 0.05) than when resting only (LSM = 0.836). Calculations based on RQ and RF determined in each experiment resulted in RCO2 and EEx values which were not different regardless of method used, except for Expt. 1 where EEx-values [kJ · kg BW-0.75 · d-1] were higher (p < 0.05) when measured with o13CBTbreathbags (460) than by IC (421) and o13CBTonline (420). Provided accurate RQ and RF values, the o13CBTbreathbags can be used as an independent and minimally invasive research tool to determine EEx in dogs under carefully standardised conditions.

Memory suppression and its deficiency in psychological disorders: A focused meta-analysis.

It is still debated whether suppressing the retrieval of unwanted memories causes forgetting and whether this constitutes a beneficial mechanism. To shed light on these 2 questions, we scrutinize the evidence for such suppression-induced forgetting (SIF) and examine whether it is deficient in psychological disorders characterized by intrusive thoughts. Specifically, we performed a focused meta-analysis of studies that have used the think/no-think procedure to test SIF in individuals either affected by psychological disorders or exhibiting high scores on related traits. Overall, across 96 effects from 25 studies, we found that avoiding retrieval leads to significant forgetting in healthy individuals, with a small to moderate effect size (0.28, 95% CI [0.14, 0.43]). Importantly, this effect was indeed larger than for more anxious (-0.21, 95% CI [-0.41, -0.02]) or depressed individuals (0.05, 95% CI [-0.19, 0.29])-though estimates for the healthy may be inflated by publication bias. In contrast, individuals with a stronger repressive coping style showed greater SIF (0.42, 95% CI [0.32, 0.52]). Furthermore, moderator analyses revealed that SIF varied with the exact suppression mechanism that participants were instructed to engage. For healthy individuals, the effect sizes were considerably larger when instructions induced specific mechanisms of direct retrieval suppression or thought substitution than when they were unspecific. These results suggest that intact suppression-induced forgetting is a hallmark of psychological well-being, and that inducing more specific suppression mechanisms fosters voluntary forgetting. (PsycInfo Database Record (c) 2021 APA, all rights reserved).