Children's memory distortions following social contact with a co-witness: Disentangling social and cognitive mechanisms

This study examined whether recalling an event with a co-witness influences children's recall. Individual 3-5-year-olds (n = 48) watched a film with a co-witness. Unbeknown to participants, the co-witness was watching an alternative version of the film. Afterwards both the co-witness and the participant answered questions about the film together (public recall), and the degree to which children conformed to the co-witness's alternative version of events was measured. Subsequently participants were questioned again individually (private recall). Children also completed false belief and inhibitory control tasks. By separating errors made in public and private, the results indicated that both social conformity (32% of errors) and memory distortion (68% of errors) played a role in co-witness influence. Inhibitory control predicted the likelihood of retracting errors in private, but only for children who failed (r=.66) rather than passed false belief tasks (r=-.10). The results suggest that children with a theory of mind conform in the company of the co-witness to avoid social embarrassment, while those a poor theory of mind conform on the basis of an inability to inhibit the co-witness's response. The findings contribute to our understanding of the motivations responsible for co-witness conformity across early childhood.     

How are Strouhal number, drag, and efficiency adjusted in high level underwater monofin-swimming?

Strouhal number (St) corresponds to a wake parameter based on the tail kinematics of swimming animals according to St=A.f/U, where f is the stroke frequency, A is the fin-beat peak-to-peak amplitude, and U is the forward speed. St number is a trade-off between amplitude and frequency that generates a forward velocity. This parameter may therefore be affected by swimming technique, which can be evaluated through active drag (AD) and Froude efficiency (eta(F)). The aim of our study was therefore to (1) investigate the range of AD and eta(F) values for high level monofin-swimmers, (2) explore the range of St numbers, and (3) examine to what extent this latter non-dimensional parameter may affect AD and eta(F). To this end, experiments have been conducted on 12 international level monofin-swimmers. St number, eta(F) (calculated according to the elongated-body theory), and AD (computed with velocity perturbation method) were calculated at the same time for an underwater fin-swimming trial, at maximal speed. Lowest values of St numbers (St=0.34) corresponded to fin-swimmers with highest velocities (R=-.77, p<.05), highest efficiencies (R=-.86, p<.001), and lowest active drag (R=.91, p<.001). On the one hand, AD was increased with vertical motion of the fin (R=.84, p<.001), which increased cross-sectional area (R=.78, p<.05). On the other hand, efficiencies showed a tendency to peak at eta(F)=0.82 in a narrow range of St numbers close to 0.4. This St range corresponded to the upper limit of the 0.25-0.4 range usually claimed for maximum efficiency of marine and flying animals. Such results suggest that increasing efficiency and reducing drag improves performance per se (regardless how these parameters are related with St number).     

The multiple neural networks of familiarity: A meta-analysis of functional imaging studies

Recent research has demonstrated the critical role of the feeling of familiarity in recognition memory. Various neuroimaging paradigms have been developed to identify the brain regions that sustain the processing of familiarity; however, there is still considerable controversy about the functional significance of each brain region implicated in familiarity-based retrieval. Here, we focused on the differences between paradigms that assess familiarity, with or without the encoding phase. We used the activation likelihood estimation (ALE) algorithm to conduct a whole-brain meta-analysis of neuroimaging studies that involved a familiarity task. Sixty-nine studies, performed in healthy subjects to determine the specific functions of the identified regions in familiarity processing, were finally selected. Distinct subanalyses were performed according to the experimental procedures used in the original studies. The ALE clusters that were highlighted revealed common activations for paradigms with and without encoding in the prefrontal cortex and in the parietal cortex. Additionally, supplementary activations related to specific familiarity (i.e., without the encoding phase) were observed in the limbic system (i.e., the amygdala, hippocampus, cingulate cortex, and insula) and in the associative sensory areas. The differences in the reported findings for different procedures are possibly due to differences in the concept of familiarity. To aid the exploration of the neural correlates of familiarity in future studies, the strengths and weaknesses of these experimental procedures are critically discussed.     

Default-mode network functional connectivity in aphasia: Therapy-induced neuroplasticity

Previous research on participants with aphasia has mainly been based on standard functional neuroimaging analysis. Recent studies have shown that functional connectivity analysis can detect compensatory activity, not revealed by standard analysis. Little is known, however, about the default-mode network in aphasia. In the current study, we studied changes in the default-mode network in subjects with aphasia who underwent semantic feature analysis therapy. We studied nine participants with chronic aphasia and compared them to 10 control participants. For the first time, we identified the default-mode network using spatial independent component analysis, in participants with aphasia. Intensive therapy improved integration in the posterior areas of the default-mode network concurrent with language improvement. Correlations between integration and improvement did not reach significance, but the trend suggests that pre-therapy integration of the default-mode network may predict therapy outcomes. Functional connectivity allows a better understanding of the impact of semantic feature analysis in aphasia.