D’Orazio, S. J. (2016). “Assessing the Impact of Adverse Childhood Experiences on Brain Development.” Inquiries Journal, 8(07). Retrieved from http://www.inquiriesjournal.com/a?id=1429
Assessing the Impact of Adverse Childhood Experiences on Brain Development
2016, VOL. 8 NO. 07
In this paper, I review the course of brain development during childhood and adolescence and examine how early adverse experiences affect structural changes in the neural correlates of higher-order cognitive abilities. I also discuss the therapeutic potential for early intervention to mitigate problematic developmental outcomes. Finally, I provide a brief summary of the major conclusions made from this body of evidence.
Meeting the developmental needs of children lays the groundwork for lifelong physical and mental health. Changes in brain connectivity and network topology occur during infancy and continue throughout childhood and adolescence. It is well established that postnatal brain development is characterized by a substantial increase in the number of synapses.16
This overabundance of synapses within the brain fosters maximal adaptation to the environment, and during development, neurons or synapses that receive only minimal stimulation wither away.16 Following synapse proliferation, the pruning of less active synapses reduces the number of connections between neurons and increases the efficiency of neuronal transmission. Myelination is another process involved in brain development, and it functionally supports increased neuronal conduction, speed, and communication.
Sensitive periods in brain development mark critical points in which a particular neural network has a higher plasticity and is more open to environmental fine-tuning.16 These distinct periods occur throughout the brain in a region-specific and time-dependent manner. Adverse experiences early in life occur at a developmental point in which the brain has heightened sensitivity to environmental input. These experiences can critically disrupt structural properties of brain development and change circuitries involved in higher-order cognitive processes.
The following sections detail how early-life exposure to adverse experiences alters normative development of brain network architecture and higher-order cognitive abilities, as well as the potential for therapeutic intervention to reduce the risk of problematic outcomes.
The Development of Brain Network Architecture
Evidence across a number of studies indicates that changes in brain connectivity throughout childhood and adolescence reflect regional differences in maturation.5,10 These findings suggest a sequential model for fiber tract development in which the strengthening of connections between modality-specific regions occurs early on in childhood, followed by the forming of connections from modality-specific regions to association regions, while the strengthening of synapses between frontal and parietal association cortices is characteristic during adolescence.10
The largest age-related changes occur in the association fibers within the frontal and parietal lobes, as well as between them. These association areas of the brain contribute to higher-order cognitive abilities in humans.10 The frontal lobe consists of the primary motor, premotor, and prefrontal regions. Distinct cytoarchitectonic characteristics are used to divide prefrontal regions into dorsolateral, orbital, and medial regions.
Findings have shown that adolescence marks a period in which the prefrontal cortex (PFC) forms continued connections with limbic areas.10 The PFC exhibits top-down control over limbic regions and governs the regulation of emotions. Thus, exposure to adverse experiences during this period in brain development may elicit problems in emotion regulation. The PFC is the last brain region to complete myelination, and its extended sensitivity to environmental experience is advantageous for tailoring neurobiology to environmental surroundings.10However, in the absence of an optimal environment or when the early environment elicits maladaptive adaptations, this sensitivity poses challenges for the brain to reach its full genetic potential.
Therefore, the extent to which early-life stressors shape prefrontal development is an important public health concern. This review examines two different forms of abnormal caregiving that children can experience – psychosocially-deprived institutional rearing and maltreatment within family settings. Exposure to either of these experiences at periods when the brain is highly sensitive to environmental input increases risk for a wide span of developmental difficulties across both cognitive and emotional domains, underpinning problematic outcomes.
Consequences of Psychosocial Deprivation on Brain Structure
Access to stable caregivers throughout early childhood and adolescence is critical for ongoing brain and behavioral development. Caregivers must provide an environment that is nurturing, loving, and stimulating to provide input that guides development of the neural circuitry which underlies higher-order cognitive, social, and emotional capabilities in humans. There has been an increased effort to understand the consequences of adverse rearing experiences on the structural properties of brain development.
This particular form of adversity focuses on experiences that compromise the relationship between child and parent. Institutional rearing provides a useful model for examining the effects of early life neglect on brain structure, and evidence suggests structural alterations in the brain development of adopted children.
The structural development of limbic circuitry occurs relatively early and rapidly in the course of human brain development, which may make these regions more susceptible to early adverse experiences. The subcortical brain structures that have been the particular focus in most studies are the amygdala and hippocampus. Smaller4 and larger8 amygdala volumes observed in institutionally reared children have made it difficult to label the pattern of amygdala growth following adversity. There have since been several influential factors considered to potentially contribute to these seemingly discrepant findings across studies. One obvious explanation is that different techniques used to estimate volume are not equivalent and will not provide consistent measurements.8
When smaller amygdala volumes were observed in children reared in an orphanage, automated segmentation was the method used to provide volumetric estimates.8 In contrast, the use of the hand tracing method in another study documented larger amygdala volumes in children that were reared in an institution.4 Other studies have shown an association between the magnitude of volumetric change and the amount of time spent in the institutional environment.8 Some evidence has indicated that the degree of volumetric decrease is functionally related to the cumulative life stressors an individual faces.4 The majority of studies involving adopted children have not shown any hippocampal volume changes relative to healthy controls.4,8
The PFC in humans exhibits a prolonged period of structural development.16 Volumetric reductions were observed in certain PFC regions, including superior, middle, and inferior frontal gyri, orbital frontal cortex, and anterior cingulate cortex.5 Both earlier adopted children and their later adopted counterparts showed reductions in cortical surface area, but only later adopted children had reduced cortical thickness, suggesting that prefrontal volumetric decreases in the early adopted group are due primarily to observed decreases in cortical surface area but not thickness.5
Currently, the neurobiological mechanism underlying these changes in prefrontal thickness, surface area, and volume is unknown.5 Chronic behavioral stress has been modeled in adult rats and exhibited decreases in length, number of branches, spine volume, and total number of apical dendrites in medial PFC.17 Atypical structural brain development is a potential biological marker that predicts behavioral responses in foster children and may explain why particular cognitive and social-emotional problems emerge during PFC-related tasks.
Consequences of Psychosocial Deprivation on Brain Function
The impact of institutional rearing on brain function has not been studied as extensively as it has been in regard to brain architecture. Nevertheless, the majority of evidence indicates that institutional rearing experiences have lasting effects on functional brain development.
The amygdala plays an important role in the detection of emotional information and supports fear and emotional learning.16 Relative to controls, foster children exhibited increased levels of amygdala activity in response to fearful faces, but no difference between the groups was observed for neutral faces.7 Increased amygdala activation was associated with the length of time reared in an institution.7 This heightened activity in the amygdala co-occurs with an increased vigilance to emotionally salient stimuli.7 Given the mixed evidence on the functional relationship between institutional rearing and volumetric changes in the amygdala, it is worth mentioning that numerous studies have given credence to the idea that longer durations of institutional care correspond to more substantial emotional difficulties.7,18
Cognitive control is defined as the ability to carry information that is currently representative of goals as well as a design to achieve such goals. In one study that used an inhibitory control task to compare brain activation in foster children to that in normal children, the bilateral inferior frontal gyrus and right anterior cingulate cortex exhibited higher levels of activation during no go trials relative to go trials.14 This difference in the patterns of brain activation between groups suggests that institutional rearing experiences impacted the neural correlates of inhibitory cognitive control. Damage to right inferior frontal regions compromises performance on the no go task, which indicates the importance of these regions in response inhibition.15
It is well documented that post-institutionalized children commonly have difficulties with social relationships and that social competence varies inversely with amygdala reactivity to fearful faces.20
Structural Consequences of Maltreatment
Children exposed to conditions involving abuse or neglect are faced with atypical caregiving at periods in development when the brain is markedly more sensitive to input from the environment. Childhood maltreatment is a broad dimension that encompasses physical, emotional, and sexual abuse, as well as any kind of physical or emotional neglect. Conditions involving abuse expose children to increased levels of traumatic input, whereas conditions of neglect are missing critical developmental experiences.
The limbic system supports a wide variety of functions and so continued efforts to better understand how maltreatment impacts the developmental outcomes of the amygdala and hippocampus have been particularly important. Early exposure to abuse and neglect have been linked to greater rates of pediatric posttraumatic stress disorder (PTSD).19 In a previous study, the use of anatomical imaging showed that more pronounced differences in the brain structures of youth with maltreatment-related PTSD were associated with an earlier age of onset, length of abuse duration, and increased PTSD symptoms relative to non-maltreated youth.1
Maltreated youth without PTSD exhibited larger amygdala and hippocampal volumes relative to youth with PTSD and non-maltreated controls.2 This observation is consistent with previous findings in which maltreated PTSD youth had no significant differences in amygdala and hippocampal volumes compared to non-maltreated controls.1 Substantial psychopathology for internalizing disorders and externalizing problems was observed in pediatric patients with maltreatment-related PTSD.2
Smaller posterior cerebral and cerebellar grey matter volumes were observed in maltreated PTSD youth relative to maltreated youth without PTSD and non-maltreated controls.2 The neurobiological substrate by which volumetric decreases in posterior cortex and cerebellar grey matter may be influenced by an association between trauma mechanisms and an oversensitivity to PTSD symptoms that drives comorbidity.19
These posterior cortical regions support face recognition, language, and object recognition, and diffuse projections to frontal and parietal cortices and subcortical structures are involved in visuospatial imagery, retrieval of episodic memories, and self-processing operations.2 It has been discussed that grey matter deficits in these regions have the potential to mitigate the formation of lucid memories about the traumatic experiences, driving the impaired processing of traumatic cues and the inability to abrogate PTSD symptoms.2
Functional Consequences of Maltreatment
In one study that used the fMRI technique, increased activation of the anterior insula (AI) and amygdala was observed in response to angry faces but not sad faces in children who were previously exposed to family violence.6 Furthermore, the family violence group showed heightened activity in the right amygdala and bilaterally in the AI when angry faces but not sad faces were presented with neutral faces.6 The greater activation of the right amygdala but not the left amygdala corroborates the theory that emotional perception and expression are lateralized to the right hemisphere.
Children exposed to maltreatment often exhibit deficits in executive functioning. Several studies have employed electrophysiological approaches to assess any functional alterations during cognitive tasks resulting from maltreatment. Interestingly, tasks that rely on medial temporal areas and those that rely on frontal cortex have a more pronounced decrement in performance.3
In one study focusing on the impact of socioeconomic status (SES) on brain function, evidence supported that SES is significantly associated with neurocognitive development.3The most extreme SES disparities were observed in language and memory ability, followed by working memory ability, and then trended more weakly towards varying levels of ability for cognitive control.3 Despite being a sociological construct, SES encompasses an extremely broad domain of physical and psychosocial factors that will ultimately shape brain development.
One study expanded upon the current body of research by examining the impact of developmental timing of maltreatment on higher-order functioning and showed increased deficits in performance on both inhibitory control and working memory tasks in maltreated youth compared to controls.21 Furthermore, it provided evidence that children who were either maltreated as infants or have a history of maltreatment performed more poorly than children without a chronic history of maltreatment.21 This adds credence to the idea that exposure to maltreating environments during infancy induces structural and functional deviations. The protracted stress of chronic maltreatment during infancy further potentiates these deficits.21
Well-timed interventions are particularly important for young children who are most vulnerable to early physiological disruptions that alter normal structural and functional brain development. There is substantial evidence supporting Trauma-Focused Cognitive-Behavioral Therapy as an effective treatment to reduce symptoms of PTSD and depression, as well as behavioral difficulties in children who have experienced sexual abuse, domestic violence, or other childhood traumas.11 Evidence of decreased behavioral problems in foster children in response to treatment with parent-child interaction therapy (PCIT) has been documented across several studies.12,13
The primary insight gained from experimental evidence is that early exposure to adversity disrupts normative brain development. Findings across studies have indicated that deficits in developmental structure and function are further instantiated by cumulative exposures to adverse rearing experiences.21 Time-dependent and region-specific sensitive periods drive the protracted course of brain development.10 There is strong evidence that well-timed therapeutic intervention can abrogate changes in developmental trajectories.11,12,13
Promising new initiatives to change the current face of primary health care make this an exciting time to be involved in research that is currently at the interface between science and medicine. As the present body of knowledge on brain development expands, so will the capacity to effectively contribute towards the resolve of this public health concern.
- De Bellis, M. D., M. S. Keshavan, H. Shifflett, S. Iyengar, S. R. Beers, J. Hall, and G. Moritz. “Brain Structures in Pediatric Maltreatment-Related Posttraumatic Stress Disorder: A Sociodemographically Matched Study.” Biological Psychiatry 52.11 (2002): 1066-078. Elsevier. Web. 10 Mar. 2016.
- De Bellis, Michael D., Stephen R. Hooper, Steven D. Chen, James M. Provenzale, Brian D. Boyd, Christopher E. Glessner, James R. MacFall, Martha E. Payne, Robert Rybczynski, and Donald P. Woolley. “Posterior Structural Brain Volumes Differ in Maltreated Youth with and without Chronic Posttraumatic Stress Disorder.” Development and Psychopathology 27 (2015): 1555-576. Web. 13 Mar. 2016.
- Farah, Martha J., David M. Shera, Jessica H. Savage, Laura Betancourt, Joan M. Giannetta, Nancy L. Brodsky, Elsa K. Malmud, and Hallam Hurt. “Childhood Poverty: Specific Associations with Neurocognitive Development.” Brain Research 1110.1 (2006): 166-74. Elsevier. Web. 1 Mar. 2016.
- Hanson, Jamie L., Brendon M. Nacewicz, Matthew J. Sutterer, Amelia A. Cayo, Stacey M. Schaefer, Karen D. Rudolph, Elizabeth A. Shirtcliff, Seth D. Pollak, and Richard J. Davidson. “Behavioral Problems after Early Life Stress: Contributions of the Hippocampus and Amygdala.” Biological Psychiatry 77 (2014): 314-23. Web. 13 Mar. 2016.
- Hodel, Amanda S., Ruskin H. Hunt, Raquel A. Cowell, Sara E. Van Den Heuvel, Megan R. Gunnar, and Kathleen M. Thomas. “Duration of Early Adversity and Structural Brain Development in Post-Institutionalized Adolescents.” NeuroImage 105 (2015): 112-19. Elsevier. Web. 12 Mar. 2016.
- McCrory, Eamon J., Stephane A. De Brito, Catherine L. Sebastian, Andrea Mechelli, Geoffrey Bird, Phillip A. Kelly, and Essi Viding. “Heightened Neural Reactivity to Threat in Child Victims of Family Violence.” Current Biology 21.23 (2011): 947-48. Elsevier. Web. 13 Mar. 2016.
- Tottenham, N., T. A. Hare, A. Millner, J.D. Zevin, and B. J. Casey. “Elevated Amygdala Response to Faces following Early Deprivation.” Developmental Science 14.2 (2011): 190-204. Web. 13 Mar. 2016.
- Tottenham, Nim, and Margaret A. Sheridan. “A Review of Adversity, The Amygdala and the Hippocampus: A Consideration of Developmental Timing.” Frontiers in Human Neuroscience 3 (2010): 1-18. PMC. Web. 10 Mar. 2016.
- White, Michael G., Ryan Bogdan, Patrick M. Fisher, Karen Munoz, Douglas E. Williamson, and Ahmad R. Hariri. “FKBP5 and Emotional Neglect Interact to Predict Individual Differences in Amygdala Reactivity.” Genes, Brain, and Behavior 11.7 (2012): 869-78. PMC. Web. 5 Mar. 2016.
- Wieranga, Lara M., Martjin P. Van Den Heuvel, Sarai Van Dijk, Yvonne Rijks, Marcel A. De Reus, and Sarah Durston. “The Development of Brain Network Architecture.” Human Brain Mapping 37 (2016): 717-29. Print.
- “Trauma-Focused Cognitive Behavioral Therapy for Children Affected by Sexual Abuse or Trauma.” Child Welfare. Child Welfare Information Gateway, Aug. 2012. Web. 25 Mar. 2016.
- Timmer, Susan, Anthony Urquiza, and Nancy Zebell. “Challenging Foster Caregiver-Maltreated Child Relationships: The Effectiveness of Parent-Child Interaction Therapy.” Children and Youth Services Review 28 (2006): 1-19. Elsevier. Web. 2 Apr. 2016.
- McNeil, Cheryl, Amy Herschell, Robin Gurwitch, and Laurie Clemens-Mowrer. “Training Foster Parents in Parent-Child Interaction Therapy.” Education and Treatment of Children 28.2 (2005): 182-96. JSTOR. Web. 2 Apr. 2016.
- Bruce, Jacqueline, Philip Fisher, Alice Graham, William Moore, III, Shannon Peake, and Anne Mannering. “Patterns of Brain Activation in Foster Children and Nonmaltreated Children during an Inhibitory Control Task.” Development and Psychopathology 25 (2013): 931-41. Cambridge University Press. Web. 2 Apr. 2016.
- Aron, A. R., P. C. Fletcher, E. T. Bullmore, B. J. Sahakian, and T. W. Robbins. “Stop-Signal Inhibition Disrupted by Damage to Right Inferior Frontal Gyrus in Humans.” Nature Neuroscience 6 (2003): 115-16. NCBI. Web. 2 Apr. 2016.
- Banich, Marie T., and Rebecca J. Compton. Cognitive Neuroscience. 3rd ed. Belmont, CA: Wadsworth, Cengage Learning, 2011. Print.
- Cook, S. C., and C. L. Wellman. “Chronic Stress Alters Dendritic Morphology in Rat Medial Prefrontal Cortex.” Journal of Neurobiology. 60.2 (2004): 236-48. NCBI. Web. 2 Apr. 2016.
- Tottenham, Nim, et al. “Prolonged Institutional Rearing is Associated with Atypically Larger Amygdala Volume and Difficulties in Emotion Regulation.” Developmental Science 13.1 (2010): 46. PMC. Web. 3 Apr. 2016.
- DeBellis, M. D., and A. Zisk. “The Biological Effects of Childhood Trauma.” Child and Adolescent Psychiatric Clinics of North America: Disaster and Trauma 23.2 (2014): 185-222. NIH. Web. 2 Apr. 2016.
- Hodges, Jill, and Barbara Tizard. “Social and Family Relationships of Ex-Institutional Adolescents.” Journal of Child Psychology and Psychiatry 30.1 (1989): 77-97. Wiley. Web. 3 Apr. 2016.
- Cowell, Raquel, Dante Cicchetti, Fred Rogosch, and Sheree Toth. “Childhood Maltreatment and its Effect on Neurocognitive Functioning: Timing and Chronicity Matter.” Development and Psychopathology 27 (2015): 521-33. Cambridge University Press. Web. 2 Apr. 2016.