Conditioned pain modulation (CPM) is a promising psychophysical biomarker of central pain mechanisms because it significantly discriminates patients with chronic pain from healthy controls. Nevertheless, it is unclear in what extent CPM assessed experimentally is correlated with clinical manifestations of pain. To assess the concurrent validity of CPM, we performed a systematic review of the literature reporting correlations between CPM responses and pain intensity, disability, duration, and area in patients with different chronic pain conditions. We included 32 studies that altogether encompassed data from 1958 patients and provided 62 correlations. The majority of the results (69%) reported nonsignificant correlations between CPM efficiency and clinical manifestations of pain, whereas the remaining results showed a correlation between CPM reduction and worse clinical symptoms of pain. The modality of stimulation, the type of pain, and the stimulation site appear to be critical variables that influenced the pattern of results. Given that most of the studies were conducted with highly heterogeneous methodologies and unclear risk of bias, the findings highlight the need for future studies using standardized measures of clinical and experimental pain before considering CPM as a valid biomarker of pain. We discuss some guidelines to overcome the constraints in this promising line of research.

Background: Emotion identification is a fundamental component of social cognition. Although it is well established that a general cognitive decline occurs with advancing age, the effects of age on emotion identification is still unclear. A meta-analysis by Ruffman and colleagues (2008) explored this issue, but much research has been published since then, reporting inconsistent findings. Methods: To examine age differences in the identification of facial expressions of emotion, we conducted a meta-analysis of 24 empirical studies (N = 1,033 older adults, N = 1,135 younger adults) published after 2008. Additionally, a meta-regression analysis was conducted to identify potential moderators. Results: Results show that older adults less accurately identify facial expressions of anger, sadness, fear, surprise, and happiness compared to younger adults, strengthening the results obtained by Ruffman et al. (2008). However, meta-regression analyses indicate that effect sizes are moderated by sample characteristics and stimulus features. Importantly, the estimated effect size for the identification of fear and disgust increased for larger differences in the number of years of formal education between the two groups. Discussion: We discuss several factors that might explain the age-related differences in emotion identification and suggest how brain changes may account for the observed pattern. Furthermore, moderator effects are interpreted and discussed.

Adult mammalian brains continuously generate new neurons, a phenomenon called neurogenesis. Both environmental stimuli and endogenous factors are important regulators of neurogenesis. Sleep has an important role in normal brain physiology and its disturbance causes very stressful conditions, which disrupt normal brain physiology. Recently, an influence of sleep in adult neurogenesis has been established, mainly based on sleep deprivation studies. This review provides an overview on how rhythms and sleep cycles regulate hippocampal and subventricular zone neurogenesis, discussing some potential underlying mechanisms. In addition, our review highlights some interacting points between sleep and neurogenesis in brain function, such as learning, memory and mood states, and provides some insights on the effects of antidepressants and hypnotic drugs on neurogenesis.