The role of intrinsic excitability in the evolution of memory: Significance in memory allocation, consolidation, and updating.

Memory is a dynamic process that is continuously regulated by both synaptic and intrinsic neural mechanisms. While numerous studies have shown that synaptic plasticity is important in various types and phases of learning and memory, neuronal intrinsic excitability has received relatively less attention, especially regarding the dynamic nature of memory. In this review, we present evidence demonstrating the importance of intrinsic excitability in memory allocation, consolidation, and updating. We also consider the intricate interaction between intrinsic excitability and synaptic plasticity in shaping memory, supporting both memory stability and flexibility.

Association of maternal exposure to Superstorm Sandy and maternal cannabis use with development of psychopathology among offspring: the Stress in Pregnancy Study.

BACKGROUND: Early-life adverse experiences can elevate the magnitude of the risk of developmental psychopathology, but the potential synergistic effects of multiple factors have not been well studied. AIMS: To determine whether prenatal exposures to maternal stress (Superstorm Sandy) and maternal cannabis use synergistically alter the risk of developmental psychopathology. METHOD: The study included 163 children (53.4% girls), longitudinally tracked (ages 2-5 years) in relation to the effects of two early-life adverse exposures (Superstorm Sandy and maternal cannabis use). Offspring were grouped by exposure status (neither, only maternal cannabis use, only Superstorm Sandy or both). DSM-IV disorders for offspring were derived from structured clinical interviews; caregiver-reported ratings of family stress and social support were also assessed. RESULTS: A total of 40.5% had been exposed to Superstorm Sandy and 24.5% to maternal cannabis use. Offspring exposed to both (n = 13, 8.0%), relative to those exposed to neither, had a 31-fold increased risk of disruptive behavioural disorders (DBDs) and a seven-fold increased risk of anxiety disorders. The synergy index demonstrated that offspring with two exposures had synergistic elevation in risk of DBDs (synergy index, 2.06, P = 0.03) and anxiety disorders (synergy index, 2.60, P = 0.004), compared with the sum of single risks. Offspring with two exposures had the highest parenting stress and lowest social support. CONCLUSIONS: Our findings are consistent with the double-hit model suggesting that offspring with multiple early-life adverse exposures (Superstorm Sandy and maternal cannabis use) have synergistically increased risks of mental health problems. Given the increasing frequency of major natural disasters and cannabis use, especially among women under stress, these findings have significant public health implications.

Dynamic and heterogeneous neural ensembles contribute to a memory engram.

In the century since the notion of the 'engram' was first introduced to describe the physical manifestation of memory, new technologies for identifying cellular activity have enabled us to deepen our understanding of the possible physical substrate of memory. A number of studies have shown that memories are stored in a sparse population of neurons known as a neural ensemble or engram cells. While earlier investigations highlighted that the stability of neural ensembles underlies a memory representation, recent studies have found that neural ensembles are more dynamic and fluid than previously understood. Additionally, a number of studies have begun to dissect the cellular and molecular diversity of functionally distinct subpopulations of cells contained within an engram. We propose that ensemble fluidity and compositional heterogeneity support memory flexibility and functional diversity.