Neural plasticity is conceived as the ability of the brain to reorganize neural pathways that are based on new experiences encountered throughout the course of life span development (Huttenlocher, Reference Huttenlocher2002). Neural plasticity can occur at multiple levels, including molecular changes, cellular alterations, shaping of neuronal structures and interconnections, and reorganization of functions (Cicchetti & Curtis, Reference Cicchetti, Curtis, Cicchetti and Cohen2006; Kolb, Reference Kolb1995; Nelson, Reference Nelson1999; Stiles, Reference Stiles2008; Whitten, Reference Whitten2013). These observable changes in the neural substrate may be translated into changes observable at the behavioral level.
Mechanisms of plasticity are integral to the very anatomical structures of cortical tissue and cause brain development to be an extended malleable process (Cicchetti & Tucker, Reference Cicchetti and Tucker1994a). These mechanisms of plasticity cause the brain's anatomical differentiation to be dependent on stimulation from the environment (Cicchetti & Tucker, 1984a). Thus, environmental experiences are considered to be critical to the differentiation of brain tissue (Black, Jones, Nelson, & Greenough, Reference Black, Jones, Nelson, Greenough, Alessi, Coyle, Harrison and Eth1998; Greenough, Black, & Wallace, Reference Greenough, Black and Wallace1987). Sensitive periods are conceived as times during development when experience exerts a very strong influence on the brain and on behavior (Knudsen, Reference Knudsen2004). It is during sensitive periods when experience is thought to instruct neural circuits to process or represent information in ways that are adaptive for the individual (Knudsen, Reference Knudsen2004).
Advances in the study of neural plasticity and sensitive periods could be utilized as a model for hypothesizing about the genetic and biological underpinnings of psychopathology and resilience (Cicchetti & Curtis, Reference Cicchetti, Curtis, Cicchetti and Cohen2006; Knudsen, Reference Knudsen2004). Presently it is not known whether the difficulties displayed by individuals who have experienced significant adversity are irreversible or whether there are particular sensitive periods when it is more likely that neural and behavioral plasticity will occur (Cicchetti & Blender, Reference Cicchetti and Blender2006). Moreover, it is not known whether some neural or behavioral systems may be more plastic than other neural or behavioral systems. Furthermore, it is not yet known whether particular neural or behavioral systems may be more refractory to change or have a more time-limited sensitive window when neural plasticity can occur.
Slightly over 20 years ago, Don Tucker and I coedited a Special Issue of Development and Psychopathology devoted to the topic of “Neural Plasticity, Sensitive Periods, and Psychopathology” (Cicchetti & Tucker, Reference Cicchetti and Tucker1994b). This topic is revisited in this current Special Issue. Prior to the publication of the Cicchetti and Tucker Special Issue, the vast majority of the articles published in Development and Psychopathology were psychosocial in nature. The papers that appeared in the Cicchetti and Tucker Special Issue were multilevel and helped to usher in the multiple levels of analysis approach and the interdisciplinary focus that are now principles inherent to a developmental psychopathology perspective (Cicchetti & Dawson, Reference Cicchetti and Dawson2002; Cicchetti & Natsuaki, Reference Cicchetti and Natsuaki2014; Cicchetti & Toth, Reference Cicchetti and Toth2009).
In the interim 20 years, research on neural plasticity and sensitive periods/developmental timing has burgeoned (Knudsen, Reference Knudsen2004; Kolb, Reference Kolb1995). The theoretical and empirical papers in this Special Issue are exemplars of the growth of theorizing and research on sensitive periods and neural plasticity. As knowledge in these areas continues to grow, findings can be translated into the design and implementation of interventions that are developmentally appropriate and that can contribute to reducing psychopathology and to promoting resilience.