The term brain fitness reflects a hypothesis that cognitive abilities can be maintained or improved by exercising the brain, in analogy to the way physical fitness is improved by exercising the body. Although there is strong evidence that aspects of brain structure remain plastic throughout life, and that high levels of mental activity are associated with reduced risks of age-related dementia, scientific support for the concept of "brain fitness" is limited. The term is virtually never used in the scientific literature, but is commonly used in the context of self-help books and commercial products. It first came into play in the 1980s, and appeared in the titles of self-help books in 1989 and 1990.
Brain fitness is the capacity of a person to meet the various cognitive demands of life. It is evident in an ability to assimilate information, comprehend relationships, and develop reasonable conclusions and plans. Brain fitness can be developed by formal education, being actively mentally engaged in life, continuing to learn, and exercises designed to challenge cognitive skills. Healthy lifestyle habits including mental stimulation, physical exercise, good nutrition, stress management, and sleep can improve brain fitness. On the other hand, chronic stress, anxiety, depression, aging, air pollution, decreasing estrogen, excess oxytocin, and prolonged cortisol can decrease brain fitness as well as general health.
As of 2010, there was insufficient evidence to recommend any method of preventing age-related memory deficits or Alzheimers.
Neurogenesis is the creation of new neurons. The more active a particular brain cell is, the more connections it develops with its neighboring neurons through a process called dendritic sprouting. A single neuron can have up to thirty thousand such connections, creating a dense web of interconnected activity throughout the brain. Each neuron can then be stimulated directly through experience (real or imagined) or indirectly through these connections from its neighbors, which saves the cell from cell death.
Physical exercise boosts the brain-s rate of neurogenesis throughout life, while mental exercise increases the rate at which those new brain cells survive and make functional connections into existing neural networks. Both physical exercise and the challenge from mental exercise increase the secretion of nerve growth factor, which helps neurons grow and stay healthy.
Brain fitness is purported to be positively influenced through mental and physical exercises that increase levels neurotrophins. Neurotrophins are a small class of proteins that are vital in neuronal development and function. In development, neurotrophins act to protect and warrant the survival of an adequate number of neurons. The survival of ample neurons is vital to ensure that they are match for target innervations. Neurotrophins also assist cell fate decisions, innervations patterns, the development of axons, dendrite pruning, etc. Neurotrophins are also important for regulating neural function and neuronal survival. Neurons are affected most predominantly by neurotrophins; however, they are important for many parts of the body in addition to the nervous system. Neurotrophins are crucial for the survival of neurons in the peripheral nervous system (PNS) as well as neurons in the central nervous system (CNS). The four most common neurotrophins are Nerve Growth Factor (NGF), Brain Derived Neurotrophic Factor (BDNF), Neurotrophic Factor-3 (NT-3), and Neurotrophic Factor-4/5 (NT-4/5). In order to understand how neurotrophins affects brain fitness, it is important to understand how they work.
Nerve growth factor (NGF) was the first neurotrophin to be discovered and is the most famous. The effects of NGF are present in a multitude of tissues through human development as well as adulthood. NGF is associated with immunity, stress reaction, nerve maintenance and neurodegenerative diseases. NGF is known have a predominant effect on the sympathetic ganglion cells and dorsal root ganglion cells with free nerve endings and the cholinergic neurons of the basal nucleus. Sympathetic ganglion cells are masses of neuronal cell bodies in the sympathetic branch of the visceral (autonomic) nervous system. Dorsal root ganglion are masses of neuronal cell bodies in the posterior portion of the spinal cord where sensory information is processed. Cholinergic neurons are profuse in parts of the brainstem, the base of the forebrain, and the basal ganglia. They are thought to play a role in regulating the general level of activity of CNS neurons, especially during the different phases of wakefulness and sleep and also during learning. Therefore, it can be purported that increased secretion of NGF can stimulate the sympathetic nervous system, the sensory portion of the spinal cord, parts of the brainstem, the base of the forebrain, and the basal ganglia. Perhaps the roles of these individual structures can be facilitated or preserved with increased NGF.
Secretion of brain derived neurotrophic factor (BDNF) is stimulated by cortical neurons, and is essential for permanence of striatal neurons in the brain. Both patients with Alzheimer's and with Huntington disease exhibit reduced levels of BDNF. Striatal neurons are the nerve cells that make up the stratium. The stratium is an inclusive term for several structures of the midbrain. The stratium is the major point of entry for receiving input from most or all cortical areas and analyzing inhibitory outputs to the various parts of the midbrain. Therefore, it may be deduced that secretion of BDNF can have an influence on many parts of the cerebral cortex and coincidentally the functions of the areas influenced.
Spiral ganglion neurons are particularly sensitive to neurotrophic factor-3 (NT-3). The spiral ganglion neurons contain the cell bodies of the auditory primary afferent fibers. The central process of these cells collect at the base of the cochlea to form the cochlear division of the eight nerve These afferent fibers carry auditory impulses toward the central nervous system. Therefore, it may be reasoned that healthy levels of NT-3 can preserve the function of these cells that are crucial for processing auditory information in the brain.
An article entitled "Neurotrophin 4/5 is a trophic factor for mammalian facial motor neurons" summarizes a study that was conducted on the researchers- findings in 1993. The research suggests that NT-4/5 prevents injuries that cause death of facial motor neurons in neonatal rats. Additionally, there is functional receptor for NT-4/5 in facial motor neurons that can be serviceable thought embryonic development and even postnatal life. Thus, both NT-4/5and brain-derived neurotrophic factor (BDNF) may be physiological survival factors for facial motor neurons and may serve as restorative means for motor neuron disease.
Not all brain activity exercises the brain in the same way.
A significant issue in brain fitness work has been establishing that brain training exercises have impacts on brain function that exist outside the context of the training task.
Other studies, however, have looked at changes in tests of everyday function that occur after brain-based training. In a review of these studies, the following significant effects were noted. Improvements on speed of processing training tests were related to improvements in the Timed Instrumental Activities of Daily Living test (TIADL). Evidence of ceiling effects were also noted, indicating that subjects who were further below normal at the beginning of training had the largest expected gains. Further, the effect sizes may be related to customizing the training difficulty to the performance level of the trainee. Subjects trained with one training strategy, the Useful Field of View test (UFOV), showed significant improvements in an on-the-road driving test designed to evaluate driver response during potential dangerous situations. Specifically, subjects trained with UFOV made fewer dangerous maneuvers after training. In another study, the researchers have found that action video game experience is shown to improve trainees- probabilistic inference. These results were established both in visual and auditory tasks, indicating generalization across modalities. In a study performed with Air force flight cadets it has been shown that training addressing attention control processes yielded significant transfer of skills from the training environment to actual flight.
Lately, brain training games have been actively marketed as a "magic bullet" for Alzheimer's and Dementia. While there are few studies showing effectiveness of brain training for older adults, it has to be noted that many brain training games are purely commercial and have no scientific footing. To address growing public concerns with regard to aggressive online marketing of brain games to older population, a group of neuroscientists published a letter warning general public that there is a lack of research showing effectiveness of brain games in elderly. Authors of this letter suggest that many popular computerized training programs are not very effective and some other interventions, such intense physical exercise, may have greater benefits. With regard to research studies supporting benefits of brain training games for older adults, there is a strong evidence that participants only gain in the trained task and that there is limited transfer of skills to the real life activities.
Another recent market for Brain Training services is children who are not meeting academic expectations in school. Student's performance on standardized norm-reference tests of cognitive abilities (e.g., Woodcock-Johnson Test of Cognitive Ability - IV) serve as a guide to determine which cognitive processes are relative strengths and weaknesses. For a description of these processes see Cattell-Horn-Carroll theory. A pre-training test provides both data on proposed weaknesses in need of training and a baseline measurement to compare performance on post-training administrations of the test. The assumption is that identifying and training a weaker cognitive process will result in generalizable improvements to academic performance. Cognitive training takes an analogue form of the skill performed on the test, and predictably does improve performance on that discrete skill in post-test measures. There is currently no evidence that this improvement in these discrete, trained skills, generalizes to better performance on higher order, more complex intellectual or academic skills.
Several commercial and academic programs have arisen to provide brain training services.