suggest that early maltreatment alters emotional responses and behaviors in adulthood while supporting learned preferences that are necessary for attachment to abusive caregivers (Moriceau and Sullivan, 2006; Roth and Sullivan, 2005; Sevelinges, Moriceau, et al., 2007). Additional evidence for sensitive periods in humans comes from studies reporting that prenatal but not postnatal exposure to tobacco smoke increases the risk of attention disorders in school-age children (Braun, Kahn, et al., 2006). The neural bases for the effects of early experience on higher-order neurodevelopmental outcomes in humans and in animal models are thus far largely unknown.

NEURAL SYSTEMS

Developmental processes early in brain development establish fundamental brain structure and circuitry. To achieve the complex functions of the brain, signaling circuits that serve similar functions are grouped and integrated in networks both within the cortex and between the cortex and other regions of the brain. These neural systems subserve complex processes, such as learning and memory, attachment, social relatedness, and self-regulatory control. These behaviors underlie the cognitive and social competence that is an essential part of healthy emotional and behavioral development, and deficits in these systems play a role in many MEB disorders.

Learning and Memory

Multiple systems for learning and memory exist in the brain. Working memory, for example, is the “scratch pad” where information is retained for conscious manipulation (D’Esposito, 2007). Declarative memory, in contrast, is the conscious recall of facts, prior experiences, and semantic knowledge that is rapidly acquired and then consolidated for storage as long-term memory (Kandel, 2001; Purves, Augustine, et al., 2000). The hippocampus, working within networks with cortical regions, is important for remembering spatial and temporal relationships and for associative learning processes. It is centrally important for conscious learning and memory, contributing significantly to overall intellectual capacity (Amat, Bansal, et al., 2008; Atallah, Frank, and O’Reilly, 2004; Eichenbaum, 2000; Moser and Moser, 1998). A form of memory that often stands in starkest contrast to declarative memory is the incremental learning and memory of motor skills, procedures, and habits, which collectively is termed “procedural,” “habit,” or “stimulus-response” (S-R) learning. S-R learning relies on a neural system that is distinct anatomically and functionally from the hippocampus-based declarative memory system and includes the striatum, a portion of the basal ganglia deep within the brain (Packard and Knowlton, 2002). Changes in activity of dopaminergic neurons within the striatum



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