Neural Plasticity in Rehabilitation and Psychotherapy

It is only a short period of time since one of the most basic convictions about the brain, postulated by the Spanish neuroanatomist, Santiago Ramon y Cajal, became undermined by new and opposing discoveries. In 1928, Ramon y Cajal postulated that the neural setup of the human brain would be fixed and unable to change beyond the end of maturation of the brain around the age of 22–24 years. What structure or function of the human brain is not shaped until that time point by an individual’s interaction with her/his physical and social environments and through learning and adaptation would not be changeable any more during the succeeding years of life. The only accepted reason for change was damage of the brain by traumatization and/or inflammation or by changes in genetic functioning. This view of the human brain has changed considerably since the early 1970s and has been replaced by a myriad of experimental evidence demonstrating that the brain’s structure and functions are open to change throughout the whole lifetime.

The terms coined for this form of modification are “neuroplasticity” and “reorganization.” Although there is currently no generally accepted definition of neuroplasticity and reorganization, most contemporary scientists in this field would agree that neuroplasticity refers to a property at all levels of the human brain, that is, from molecules to larger cortical neural networks, to adapt its structures and functions to environmental pressures, experiences, and challenges, including brain damage (Johansson, 2011; Merzenich, Van Vleet, & Nahum, 2014). In addition, neural reorganization refers to the capacity of the brain to extend and/or change the control of behavior, cognition, and emotion by enlarging the neural networks involved through learning-induced response coordination (Merzenich et al., 2014). Other options represent optimization and economizing the activity of neural networks or the transference of the control of behavior and cognition to other structures that formerly did not control these actions (Merzenich, 2013). The latter was often addressed as rewiring the brain.

Three forms of neuroplasticity and reorganization can further be distinguished by: (a) developmental or maturational plasticity, where changes of brain structures and functions occur as a function of natural development and maturation; (b) adaptive neuroplasticity, where plasticity is induced in the course of adaptation to new environmental conditions, by learning and by skill formation, and (c) restorative neuroplasticity, where plasticity and reorganization occur as a consequence of trauma, inflammation, or epigenetic reprogramming (Will, Dalrymple-Alford, Wolff, & Cassel, 2008).

Following the conviction of the Nobel laureate Eric Kandel (1979, 2008) that any positive outcome of therapy and rehabilitative measure will only occur when the interventions significantly change the underlying neural structures and/or functions of the brain, the present topical issue of the Zeitschrift für Psychologie focuses on structural and functional plasticity of the brain as a result of behavioral and cognitive training and training of emotion regulation in several areas of therapy and rehabilitation.

The first article by Thomas Straube (2016) presents recent findings and developments of neuroplasticity in the psychotherapy of anxiety disorders. He summarizes current evidence that cognitive and behavioral interventions have demonstrated massive cortical plasticity of structures and functions that are considered central in the generation and individual expression of anxiety, like the amygdala, the anterior cerebral cortex (ACC), the insula, and the bed nucleus of the stria terminalis. He also presents a number of methodological issues in the use of functional brain imaging techniques that are critical in order to obtain valid experimental results in this field.

Thomas Weiss (2016) comprehensively summarizes current evidence for neural plasticity and cortical reorganization in subjects suffering from chronic pain in the next paper. In contrast to traditional views that postulated changes of peripheral neural systems being central causes of chronicity, he shows that cortical neuroplasticity and reorganization of neural networks in the somatosensory cortex, motor cortex, limbic and cognitive functional structures mainly account for the chronification of pain, and that these structures are also relevant targets for successful interventions in the behavioral and cognitive treatment of pain.

Eckart Altenmüller’s and Christos Ioannou’s paper (Altenmüller & Ioannou, 2016) specifies some negative sides of neuroplasticity, namely that neuroplasticity is not always beneficial but can lead to massive impairments of motor functions. Too intensive behavioral training of musicians in order to master their instruments might induce a serious condition known as musician’s dystonia and related disorders. Altenmüller and Ioannou elegantly show that in most cases such developments are consequences of training-induced maladaptive processes of plasticity in cortical and subcortical networks.

The paper by Wolfgang Miltner (2016) summarizes a number of processes that demonstrate the enormous plasticity and reorganization capacity of the human brain following brain lesion and highlights a series of behavioral and neuroscientific studies that indicate that successful intensive behavioral rehabilitation is paralleled by plastic changes of brain structures and by cortical reorganization. He shows that the amount of such plastic changes is obviously significantly determining the overall outcome of rehabilitation.

In the final review article, Klingner, Brodoehl, Volk, Guntinas-Lichius, and Witte (2016) explore the plasticity which is induced in the brain when it experiences a pronounced disturbance of the expected body responses: within the face, a lesion of the seventh nerve causes a motor paralysis with intact sensory input which is conveyed through the fifth cranial nerve. As a consequence, the intact brain orders a motor command, which is not executed, resulting in a mismatch between perceived and expected sensory information. This mismatch requires a major adaptive plasticity of the brain, which was studied in detail by this group.

Turning to the original articles, firstly Wolfgang Miltner, Heike Bauder, and Edward Taub (2016) present an example how neuroplasticity can be addressed by means of electroencephalographic measures known as Bereitschaftspotential (BP) that normally precede that execution of voluntary movements of, for example, fingers, hands, and legs. This technique was applied in a group of patients with chronic stroke who were given constraint-induced movement therapy (CIMT) over an intensive 2-week course of treatment. The intervention resulted in a large improvement in use of the more affected upper extremity in the laboratory and in the real-world environment. The evaluation of BP showed that the treatment produced marked changes in cortical activity that correlated with the significant rehabilitative effects. The results are consistent with the rehabilitation treatment having produced a use-dependent cortical reorganization and demonstrate where the physiological data interdigitates with and provides additional credibility to the clinical data.

Brodoehl, Klingner, Schaller, and Witte (2016) explore, in the second original article, the adaptation which the brain performs upon eye closure: with closure of the eyes the brain fundamentally alters the processing of afferent information, from a visually dominated multisensory mode to a monosensory mode. This plasticity is independent of the visual information and takes place in complete darkness, indicating that this switch of processing modes is caused by state-dependent, inherent brain plasticity. Based on these observations one can assume that the ability to cause functional reorganizations can be substantially modified by optimized conditions for such learning processes.

In their opinion piece, Otto Witte and Malgorzata Kossut (2016) emphasize the impact of inflammatory factors on brain plasticity: following a stroke or in the aging brain, the inflammatory system is activated and impairs brain plasticity. The analysis of these processes opens a window for therapeutic interventions that may be employed to enhance the efficacy of behavioral and other rehabilitative procedures.