Cognitive Plasticity in Neurologic Disorders

Book Preface

Plasticity refers to the property of a material to undergo alterations. Of all human organs,the brain is the most plastic, and it is continually undergoing alterations. The brain senses and perceives; it learns, stores, and manipulates knowledge; and, based on goals and drives, it plans and executes mental and physical actions. The brain is most plastic during youth, but it is the mature and aging brain that is more likely to be injured by disorders such as vascular, autoimmune, infectious, metabolic, endocrine, deficiency, neoplastic, and degenerative diseases, while head trauma can affect the brain at any age. These diseases often induce neurobehavioral disorders with serious disability.

Some people with these injuries and diseases spontaneously recover. This recovery may be related to several factors. For example, the injured neuronal networks, which initially were not functioning, may recover, or other areas that can perform the functions of the injured portion of the brain may substitute for the injured areas. With acute injury to a portion of the brain, uninjured but connected areas may become inhibited and dysfunctional. Von Monakow called this phenomenon “diaschisis.” With time, this inhibition may remit, and functionally impaired networks may perform normally. Since the human brain is plastic, after an injury there may be remyelination, dendritic and axonal sprouting, and an increase of dendritic spines with the formation of new synaptic connections in uninjured areas of the brain, as well as alterations in neurotransmitter and neuromodulator systems. These changes may allow recovery of function. This “spontaneous” improvement of function shortly after an acute brain injury usually abates after several months, and many patients remained disabled. Thus, clinicians must determine how they can best enhance plasticity and improve the functional capacity of patients with neurobehavioral deficits. In addition to advising patients to discontinue medications that may impair neuroplasticity and treating patients with medications and procedures (e.g., transcranial magnetic stimulation and transcranial direct current stimulation) that can enhance plasticity, clinicians may also have patients engage in activities that will allow them to relearn the cognitive skills they have lost. In addition, clinicians may help patients develop compensatory neurobehavioral procedures, including prosthetic devices that can reduce these patients’ disability.

In this book, experts discuss many of the diseases and disorders that induce neurobehavioral deficits; however, rather than just focusing on the familiar signs, symptoms, and the pathophysiology of these diseases and disorders, emphasis is placed on describing the neuroplastic responses and cognitive mechanisms of reorganization related to both spontaneous recovery and successful intervention. There are many disorders in which both spontaneous recovery and intervention fail, and these suffering patients remain disabled. The reasons for these failures, as well as the future research that is needed to develop successful interventions, are also discussed in this important book. A particularly interesting feature of this book is its examination of neurobehavioral plasticity from a number of different perspectives: specific neurologic diseases (e.g., stroke, epilepsy), particular neurobehavioral conditions (e.g., aphasia, amnesia), and emerging technologies. The chapter authors focus on the dynamic changes that occur over time in each condition or with specific clinical interventions. The volume as a whole offers interesting and innovative insights at the level of neural networks. The book makes clear that an emphasis on dynamic change in neural networks is increasingly relevant to behavioral neurology and cognitive neurorehabilitation, and will yield great progress in these fields. The editors are to be commended for putting together a fine team of experts and creating a book that focuses on broadly applicable principles related to cognitive and behavioral plasticity, one that will be of much interest to a wide readership, including both clinicians and scientists.

Kenneth M. Heilman, MD
Department of Neurology, the University of Florida College of Medicine,
and the Malcom Randall Veteran’s Affairs Hospital,
Gainesville, Florida