Neural Plasticity and Cognitive Development is the story of three decades of research on the course and outcome of neurobehavioral development following perinatal brain injury. It is a journey through the theoretical and methodological shifts that have occurred since the 1980's, as imaging technology has enabled the direct linkage between structure and function in living, developing children. The book was co-authored by a team of researchers whose long-standing collaborative study of children with perinatal brain injury renders them uniquely poised to chronicle this journey. Their collaboration, combined with their backgrounds in cognitive psychology, pediatric neurology, developmental psychology, and linguistics gives the text a rich, collective flavor. Ultimately, insights gleaned from their interdisciplinary studies are melded together into a modern perspective on the neural underpinnings of behavior.
Lesion studies provide a useful means by which to study neurobehavioral development, as progress through this dynamic process by children with perinatal brain injury can be charted against that of typically developing children. In Neural Plasticity and Cognitive Development, every aspect of development is considered, including basics such as sensory, motor, and visuospatial, as well as higher-order functions, like executive control and language. The authors synthesize many decades of research on each of these aspects of development in order to provide a holistic picture from which useful insights emerge. For example, sensory and motor functions are often worse-affected than cognitive functions, suggesting that their phylogenetically older and more unimodal nature render them less modifiable by the brain's post-lesion neuroplastic efforts.
Nonetheless, the developing brain is capable of stunning post-lesion plasticity. Indeed, Neural Plasticity and Cognitive Development beautifully illustrates that, in the face of perinatal injury, development prevails and function emerges. A theme that runs throughout the book is that neural development is characterized by “dynamic, interactive, and progressive change.” What this means for the developing brain is that perinatal damage (in contrast to similar damage incurred in adulthood) does not just create a lesion that the brain must circumvent. It also disrupts the brain's developmental trajectory, resulting in “alternative patterns of brain organization” within the finished product. These alternative patterns of organization result in alternative patterns of impairment compared with similar lesions acquired in adulthood. One of the most intriguing examples of this is the fact that children with left hemisphere perinatal injury do not have aphasia, whereas adults with lesions similar in size and location typically do. The authors thoroughly address this phenomenon, synthesizing decades of research that makes it clear that the developing brain is far from modular. That is, compared with the adult brain, developing telencephalic regions are relatively undifferentiated, perhaps enabling them to adapt more fully to the disruption wrought by early injury.
Collectively, the authors have many decades of experience and insight to impart. Based on this, they make it clear that within the field of post-lesion development, knowledge and understanding of outcomes has increased dramatically over the years, in part due to advances in neuroimaging technology. In the early stages of the authors' collaboration, such technology was nascent, making it difficult to test new, emerging ideas about neural development after brain injury. Modern neuroimaging methods enable the size, type, and site of injury to be determined in living, developing children, providing researchers with insight into the role of the lesioned tissue, as well as how the developing brain circumvents damage in order to permit function.
Clinical neuropsychologists will find this book a useful resource. The authors thoroughly cover a vast temporal range of studies, converging the thoughts and findings of researchers from as far back as Broca with those published very recently. Within a given topic, every effort has been made to synthesize large numbers of studies, often with conflicting findings, and fit them into a global perspective on neurobehavioral development. Moreover, the book is chock-full of cautionary notes to clinicians, which could only have been obtained with the benefit of career-long attention to the dynamic process of neurobehavioral development. For example, the necessity of assessing IQ at multiple time points post-lesion is highlighted. There are conflicting findings concerning the IQ of children with perinatal brain injury, which may in large part result from the fact that IQ deficits appear minimal if children are assessed only early after damage. More significant impairments frequently emerge if testing continues throughout development, thus providing a more complete picture of maturing function, as well as providing insight into the developmental trajectory of relevant brain regions.
Neurodevelopment is a dynamic process. Indeed, this is precisely what the totality of research on perinatally brain-injured children shows us and what Neural Plasticity and Cognitive Development makes so abundantly clear. The authors' thorough coverage of every aspect of development provides a framework for the presentation of an overarching perspective on brain development made possible by decades of research on functional outcome in children with perinatal brain injury. Ultimately, while theories of neural development abound, the study of perinatally brain-injured children provides a means by which to judge them and provides an invaluable framework to guide future research.