Less than fifteen years ago, it was a known fact that the neural connections in the adult brain were hard-wired and the specific neurons in each brain area were only for that region’s form and function. Neuroscientists also believed that brain injury resulted in permanent loss of function because new neurons could not be created. In 1990, President George H. Bush, observing that “a new era of discovery is dawning in brain research” proclaimed the decade beginning January 1, 1990 as the Decade of the Brain.
Plasticity is an essential organizational feature of human brain function. Historically, the brain was thought to be hardwired following a critical period in development. This brain plasticity underlies normal development and maturation, skill learning and memory, recovery from injury, as well as the consequences of sensory deprivation or environmental enrichment. The brains of infants and children are known to be plastic, undergoing spurts of neuronal development in response to stimulus exposure during critical periods (Mundkur, 2005).
This development consists of the genesis of neurons, increased connectivity between neurons and the routing of new synaptic connections between previously unrelated neurons. There is an incredible increase in synapses occurs during the first year of life. The functional architecture of the brain is created through the development of these synapses. By the time a child is three years old, a baby’s brain has formed about 1,000 trillion connections about twice as many as adults have. Near age eleven, a child’s brain begins eliminating the extra connections in a process calling “pruning”.
However, it is now known that neuroplasticity occurs with many variations, in many forms, and in many contexts. The discovery of the growth of new neural tissue in the adult human hippocampus, a brain region responsible for memory (Eriksson et al. , 1998), led the widely accepted concept of the hardwired brain to be renounced. The ability of the adult brain to grow new neurons, once scoffed at, is now accepted as a reality. This determination complemented earlier data from primate studies demonstrating that sensory xperience and learning new behaviors triggers neuron growth in the somatosensory and motor cortices, areas of the brain subserving tactile perception and limb movement (Jenkins, Merzenich, Ochs, Allard, & Guic-Robles, 1990; Nudo, Milliken, Jenkins, & Merzenich, 1996). Subsequent to the discovery of neurogenesis in the adult human brain, neuroscience has enthusiastically pursued additional investigation of these findings, aided by advances in brain imaging techniques such as functional magnetic-resonance imaging (fMRI) and diffusion tensor imaging (DTI) .
The growth of neurons in the brains of adults repeatedly exposed to a variety of experiences has been well documented. Taxi drivers develop the areas of their brains involved in spatial relationships by memorizing the streets and avenues of the cities in which they work (Maguire et al. , 2000). Violinists evidence neural growth in the portion of their somatosensory cortex devoted to their fingering hand through hours of musical practice (Elbert, Pantev, Wienbruch, Rockstroh, & Taub, 1995), as do people who juggle. (Draganski et al. , 2004).
Additionally, mental practice promotes neuroplasticity: neurogenesis occurs in the motor cortex just by imagining playing the piano (Pascual-Leone, Amedi, Fregni, & Merabet, 2005). While the underlying mechanisms are different, neuroplasticity research suggests that challenging learning experiences can lead to the development of brain tissue just as exercise stimulates muscle development. Studies have shown that mental practice has successfully used on stroke patients, who visualize motor movements through mental imagery, complementing other cognitive-based treatments.
It has been suggested that patients should be taught to mentally visualize and practice an activity complementary to other conventional treatments in order to improve motor functions, especially arm movement (NICE Guidelines, 2008; Johansson, B. B. , 2011). When seeking rehabilitation of fine motor skills, the repetition of the activities of daily living (such as styling your hair, picking up and putting down a coin) that require fine motor skills as opposed to gross motor skills, mental practice can also have a positive effect on post-stroke ehabilitation. The concept is to produce new neural pathways in order to compensate for the damaged pathways, and these exercises can help promote neuroplasticity in post-stroke patients (Johansson, B. B. , 2011; NICE Guidelines, 2008). For rehabilitation of gross motor movements, the recommended therapies are different. For example, with arm movement, studies have shown that it is more beneficial to conduct bimanual exercises as opposed to only exercising the affected arm (Bracewell, R. M. , 2003; Johansson, B.
B. , 2011). Bimanual exercises have also been shown to have a direct effect on promoting cortical neural plasticity in various ways: ‘(a) motor cortex disinhibition that allows increased use of the spared pathways of the damaged hemisphere, (b) increased recruitment of the ipsilateral pathways from the contralesional or contralateral hemisphere to supplement the damaged crossed corticospinal pathways, and (c) upregulation of descending premotorneuron commands onto propriospinal neurons’ (Cauraugh J. H. Summers J. J. , 2005, abstract). Research on the study of meditation has found significant evidence of mental training leading to neuroplastic modifications in brain activity. A study by Lutz, et al. , found marked alterations in the synchronization of neurons as an effect of long-term training in Buddhist loving-kindness meditation, a practice which is thought by some practitioners to promote a state of unconditional compassion and benevolence (Lutz, Greischar, Rawlings, Ricard, & Davidson, 2004).
The synchronization of brain activity found in some of the practitioners sampled, whose experience ranged between 10,000 and 50,000 hours spent in meditation, was higher than any previously reported in the literature. Such increased neural synchrony was observed not only during the meditative state, but also when not meditating, suggesting that long-term mental practice can induce lasting, trait-level changes possibly mediated by structural modifications to the brain (Begley, 2006). A study by Slagter et al. 2007) compared attentional performance of a group of experienced meditators participating in a three month mindfulness meditation retreat to that of a novice control group who received a 1-hour meditation class and were asked to meditate 20 minutes daily for one week.
Relative to controls, experienced meditators evidenced significant improvements in attentional performance that correlated with alterations in brain activity. This cognitive enhancement was maintained three months after formal meditation practice, suggesting mental training can stimulate neuroplastic changes in the adult human brain (Slagter et al. 2007). The research of Lutz and Slagter did not examine structural brain changes. Subsequent MRI studies comparing the brains of experienced meditators vs. control subjects matched by sex, age, race, and education found that years of meditation experience correlated with increased cortical thickness in brain areas where visceral attention (e. g. right anterior insula) and self-awareness (e. g. left superior temporal gyrus) have been localized (Holzel et al. , 2008; Lazar et al. , 2005). These empirical investigations of meditation suggest that mental training may stimulate structural brain changes.
There is also research being conducted on the whether neuroplasticity could offer a natural recovery option from mental illness. Cognitive-Behavioral Therapy (CBT) has been demonstrated to induce functional changes in brain activation. One example, a brain imaging study found that persons with obsessive-compulsive disorder who were treated with a mindfulness-oriented form of cognitive-behavioral therapy (CBT) exhibited functional changes in the orbital frontal cortex and striatum, two brain structures found to be overactive in OCD (Schwartz & Begley, 2002).
There are several other studies researching the effects of neuroplasticity on depression, PTSD and other mental illnesses. There is compelling evidence from longitudinal studies that measured changes in brain anatomy across separate time points as a function of musical practice. Hyde and others (2009) found that 6-year-old children showed structural brain changes in regions such as the precentral gyrus, the corpus callosum, and the Heschl gyrus after receiving musical training for 15 months. These brain changes correlated with performance on various auditory and motor tasks.
The findings indicate that plasticity can occur in brain regions that control sensory functions important for playing a musical instrument. The malleability of the developing brain implies that interventions that target multisensory regions can facilitate plasticity in children and be used to treat certain developmental disorders. The effects of intensive training on the aging adult brain have been investigated by several studies. For example, Sluming and others (2002) reported that practicing musicians have greater gray matter volume in the left inferior frontal gyrus compared to that of matched non-musicians.
For the non-musicians, significant age-related reductions in total brain volumes, specifically in regions such as the dorsolateral prefrontal cortex and the left inferior frontal gyrus were not observed in musicians. It can be inferred that musicians may be less susceptible to age-related degenerations in the brain, presumably as a result of their daily musical activities To improve a patient’s brain function and take advantage of any neuroplasticity, Jeffrey A. Kleim, Ph. D. , and Theresa A. Jones, Ph. D. , suggest that we follow these 10 key principles: Use it or lose it.
If you do not drive specific brain functions, functional loss will occur. Use it and improve it. Therapy that drives cortical function enhances that particular function. Specificity. The therapy you choose determines the resultant plasticity and function. Repetition matters. Plasticity that results in functional change requires repetition. Intensity matters. Induction of plasticity requires the appropriate amount of intensity. Time matters. Different forms of plasticity take place at different times during therapy. Salience matters. It has to be important to the individual.
Age matters. Plasticity is easier in a younger brain, but is also possible in an adult brain. Transference. Neuroplasticity, and the change in function that results from one therapy, can augment the attainment of similar behaviors. Interference. Plasticity in response to one experience can interfere with the acquisition of other behaviors.
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