Saturday, July 6, 2019

A balanced review of the literature & evaluation of the data indicate that adult neurogenesis in human brain is improbable; the focus of research should be the preservation of neurons, not replacement

A balanced evaluation of the evidence for adult neurogenesis in humans: implication for neuropsychiatric disorders. Alvaro Duque, Reynold Spector. Brain Structure and Function, July 5 2019.

Abstract: There is a widespread belief that neurogenesis exists in adult human brain, especially in the dentate gyrus, and it is to be maintained and, if possible, augmented with different stimuli including exercise and certain drugs. Here, we examine the evidence for adult human neurogenesis and note important limitations of the methodologies used to study it. A balanced review of the literature and evaluation of the data indicate that adult neurogenesis in human brain is improbable. In fact, in several high-quality recent studies in adult human brain, unlike in adult brains of other species, neurogenesis was not detectable. These findings suggest that the human brain requires a permanent set of neurons to maintain acquired knowledge for decades, which is essential for complex high cognitive functions unique to humans. Thus, stimulation and/or injection of neural stem cells into human brains may not only disrupt brain homeostatic systems, but also disturb normal neuronal circuits. We propose that the focus of research should be the preservation of brain neurons by prevention of damage, not replacement.

Keywords: Adult neurogenesis Neural stem cells Memory Bromodeoxyuridine Homeostasis Neuronal protection DNA repair/methylation

Rolf Degen summarizing: People who were made feel morally superior actually acted more morally - but only in public, not in private, exposing our penchant for moral hypocrisy

Self-enhancement in moral hypocrisy: Moral superiority and moral identity are about better appearances. Mengchen Dong, Jan-Willem van Prooijen, Paul A. M. van Lange. PLOS, July 5, 2019.

Abstract: People often consider themselves as more moral than average others (i.e., moral superiority) and present themselves as more moral than they actually are (i.e., moral hypocrisy). We examined whether feelings of moral superiority—as a manifestation of self-enhancement motives—motivates people’s hypocritical behavior, that is, their discrepant moral performances in public versus private settings. In three studies (total N = 1,151), participants distributed two tasks (one favorable and one unfavorable) between themselves and an anonymous partner, with the option of using an ostensibly fair randomizer (e.g., a self-prepared coin). We found that when experiencing feelings of moral superiority (vs. non-superiority), people, especially those who highly identified with moral values (Studies 1 and 2), were less likely to directly give themselves the favorable task, but they were not less likely to cheat in private after using the randomizer (Studies 1 to 3). Both self-enhancement motives and moral identity have implications for hypocritical behavior, by motivating public moral appearances but not private moral integrity.