Sally A. Marik and Charles D. Gilbert
The cerebral cortex is a learning engine. The ability to encode information about sensory experience or practiced movements is a universal property of all cortical areas. This capacity, known as cortical plasticity, is seen in experience dependent changes in the functional properties of cortical neurons and in the alteration of cortical circuits. Certain properties are mutable only during a short period in postnatal life, which is known as the critical period, while others retain the ability to change throughout life. The same changes associated with assimilating normal experiences can be implemented for functional recovery following lesions of the central nervous system.
Maya Opendak and Regina Sullivan
Traumatic experiences can be challenging at any age, but recent evidence has highlighted the trauma experienced from an attachment figure as particularly detrimental. Fear, or threat, conditioning is a major experimental paradigm that has uncovered the neurobiology of trauma processing. This controlled paradigm has enabled us to understand the changing neurobiology of trauma processing as well as the developmental importance of caregiver presence during trauma. Maternal presence buffers the infant during brief trauma exposure, although repeated trauma in her presence programs the enduring trauma effects on the neurobiology of cognition and emotion. We review the data on innate and learned fear responses across development and describe the interaction between trauma and attachment in early life when threatening cues are processed by the attachment circuitry, rather than fear circuitry, within the brain. This approach can provide insight into age-specific treatments and interventions following infant trauma in the presence of a caregiver.
Bruce S. McEwen and Conor Liston
The hippocampus has provided a gateway for understanding of how stress, as well as sex hormones, affect cognitive process and has revealed adaptive plasticity in neuronal structure and function throughout the brain and also contributes to damage. This involves direct and indirect epigenomic transcriptional regulation, as well as rapid, non-genomic signaling pathways initiated by membrane-bound glucocorticoid and mineralocorticoid receptors. Downstream of glucocorticoids, multiple mediators—including secreted factors as well as intracellular processes—play critical roles in driving stress-induced remodeling of dendritic arborization and postsynaptic dendritic spines. To understand how these processes act to maintain synaptic homeostasis; prevent permanent, excitotoxic damage; and adaptively regulate learning and decision making, and how we might go about intervening to promote resilience in stress-related neuropsychiatric conditions, new technologies for visualizing and manipulating dendritic spine remodeling and neuronal activity in specific neural circuits are being used to establish causal mechanisms and define new therapeutic strategies.
Bernard Kripkee and Robert C. Froemke
Plasticity of inhibitory synapses keeps inhibition in balance and in register with excitation when changes occur in excitatory synapses. Inhibition has many functions to perform, and there are many kinds of inhibitory neurons to perform various computations and regulate network activity. Different forms of long-term changes in inhibitory synapses have been demonstrated that depend on neural activity. Inhibitory plasticity appears to be partly responsible for the specificity of the inhibitory connections needed to carry out some inhibitory functions. The evolving story of cortical inhibitory plasticity shows that different types of inhibitory interneurons play different roles in a variety of inhibitory functions, that several types of inhibitory plasticity have been attested, and that different forms of plasticity can be expected to have different effects on the organization and specificity of inhibitory connections.
Elizabeth A.D. Hammock
Oxytocin plays well-known roles in modulating social behavior in mammals. Oxytocin function depends on the brain circuitry it modulates, which is determined by the cell-type specific expression of the oxytocin receptor and the network integration of those cells. This review describes emerging evidence for the neural network mechanisms of oxytocin in behavioral plasticity in adults and development. A role for oxytocin in modulating excitatory/inhibitory balance and improving signal:noise processing is an emerging mechanism of function. This emerging literature calls for developmental studies of oxytocin modulation of signal:noise processing in socially naïve circuits. In this review, current oxytocin research findings are placed within the coordinate system of the Uncanny Valley Hypothesis as a model to better understand the role of oxytocin in experience-dependent development and adulthood, to translate research results among diverse mammalian species, and to generate testable predictions for future research.