Neuroplasticity in Humans

Abstract

Neuroplasticity describes the ability of human and animal brains to reorganize themselves continuously throughout the lifespan. In addition to the genetic information that is accumulated during evolution to secure the survival of an organism, neuroplasticity serves as a mechanism to cope successfully with ongoing changes of environmental conditions that are not specified by genetic constraints. While prima facie, huge plastic capacities appear desirable, brains require substantial stability to maintain proper functioning. Therefore, neuroplasticity constitutes a trade-off between modifiability and stability.

The present chapter, focused on human neuroplasticity, has two parts: first, rules and basic characteristics of neuroplastic changes are introduced; the second part recapitulates milestones and very recent developments and illustrates the current status of neuroplasticity research in humans. Major factors that modify brains and, by that perception, behavior and cognition, are development and aging as well as changes following brain injuries. Other sources imposing plastic changes come from constraints arising under everyday life conditions. Examples are particularities of occupation including life style and prolonged episodes of heavy schedule of sensory stimulation as exemplarily present in blind Braille readers or musicians. While it takes several 10,000 hours of intense practicing to develop musical skills found in professional musicians, short periods of only a few minutes of practicing can induce neuroplastic changes leading to significant gains in perception and behavior. Accordingly, neuroplasticity is not a unitary process, but numerous mechanisms enable the emergence of different forms of plasticity. The recent development of non-invasive imaging techniques allows you study the impact of neuroplasticity in human brains. This approach confirmed previous findings from animal studies and demonstrated that any possible aspect of brain processing and functioning is altered by plastic reorganization. Large reorganizational changes correlate with large perceptual and behavioral gains and vice versa, indicating that interindividual differences of the outcome of plastic changes have a neural substrate in the amount of plastic capabilities. During the last years, a new and fascinating discipline evolved, where neuroscientists successfully design stimulation conditions based on neuroplasticity mechanisms that do not rely on the conventional modification of use, training, and practicing. By targeting defined brain regions, either through sensory or through direct stimulation of the brain from the outside, plasticity can be induced without any explicit task training. Furthermore, the long-held view that external events are required to drive neuroplasticity has been challenged by observations where the induction of plastic changes is possible by mere mental events without the presence of physical stimuli. From a practical side, understanding the conditions that either facilitate or impede the emergence of neuroplastic changes is a prerequisite for a large scale application of neuroplasticity principles in education as well as in intervention and rehabilitation. However, as neuroplasticity is a rather novel discipline, our current knowledge must necessarily be limited, with many facets of brain changes been overseen due to inappropriate technologies and concepts. Extrapolating from our current knowledge, neuroplasticity will almost certainly offer unimaginable ways of interfering with brains leading to implications unforeseen.