This book provides a comprehensive synthesis of 30 years of research on the effects of perinatal brain injury on human brain development. Authors are distinguished scientists in the field of cognitive science and human development. It is now known that it is the complex interaction of genetic and environmental factors that underlies the development of the human brain. The concept of neural plasticity is discussed and refers to “the capacity of the developing brain to adapt to current demands and circumstances, whether that involves epigenetic modulation of gene expression, the responsiveness of axons to guidance molecules, neuronal competition for trophic factors at synaptic junctions, adjustments of neural networks to variations in input, or the reorganization of neural systems in the wake of injury or insult.”
Animal studies demonstrate the range and limits of plasticity in the developing animal brain. This book discusses some of these animal studies and further illustrates the idea of “critical and sensitive periods” for brain development. The term “critical period” refers to the specific times of postnatal development when specific environmental signals or experience is absolutely essential for certain “experience-dependent” neurobehavioral milestones to manifest. Conversely, the term “sensitive period” acknowledges “experience-expectant” periods of development in which variations in the organism's environment or experiences cause alternative patterns of neural organization, which conveys more flexibility in the process. Research shows that rearing conditions have significant effects, such that animals raised in enriched environments have more dendrites per neuron, larger and more complex neurovascular systems, and increased neural support cells compared to animals raised in unfavorable conditions.
This book begins with an overview of basic brain development and the effect of perinatal lesions (PL) on the developing brain using both animal models and studies on effects of timing, etiology, and mechanisms of perinatal stroke.
The next section of the book summarizes research on the effects of perinatal injury on various domains of behavior and development. This research consistently illustrates the role of plasticity in the development of cognitive, linguistic, motor, sensory, and affective functions in affected children. The degree of plasticity and adaptation is different across these different domains. For example, obvious motor and sensory deficits are typical after early third trimester periventricular injury and late third trimester stroke, whereas cognitive deficits after these events are more subtle. Motor and sensory systems show limited capacity for reorganization when compared to cognitive systems, which have adaptable and more widely distributed networks. Lexical semantic associations typically use both hemispheres during early neurodevelopment, and it is only in late adolescence that this function lateralizes to the left hemisphere. Although there is initial language delay in children with PL, by mid school age, these children perform in the low normal range. Complex language skills in children with PL are more sensitive to variation in input when compared with those of typically developing children, highlighting the need for early and continued intervention. The mean IQ level of children with PL seems to be in the low normal range (IQ 80–90). Academic difficulties are common in children with PL, possibly reflecting their lower cognitive level. This may also be related to behavioral problems that have been found to be elevated in children with PL. Reading comprehension is generally affected more than the other academic domains. There are also potential behavioral implications for children with perinatal stroke particularly as they reach school age.
The final section of this book offers a guide for clinicians based on neurodevelopmental research. Pediatric clinicians need to be aware of how PL could affect their patients in order to provide prognostic information and guidance regarding effective interventions. Clinicians need to emphasize the role of enriched environments and early intervention. As the child reaches school age, educators should consider the need for classroom modifications given issues with reading comprehension and somewhat lower cognitive skills, including impact on executive function. Understanding and addressing the child's needs will improve his/her success in school, at home, and in other areas of his/her life.