Neuroblasts produced in the hippocampal dentate gyrus synapse with existing neurons in the cerebral cortex, taking the place of older neurons in the neural circuitry. So instead of creating additional synapses, neuroblasts replace and weed out less-fit neurons, which then die. Activity-dependent neuroplasticity is what happens as existing neurons form new synapses and create new circuits based on how we choose to use our brains; this is learning.
If you practice the tango every day, the neural pathways involved in controlling your dance moves will continually get stronger and more efficient. The secret to using activity-dependent neuroplasticity in your favor is to learn your new skill and then practice, practice, practice. Neurologists in Germany did brain scans of people as they learned to juggle and compared them with controls.
The scans clearly showed how brain areas involved in processing and storing complex visual motion increased in size over three months as the volunteers learned to juggle. Then three months later, after discontinuing the juggling practice, these brain areas had decreased in size, losing about half of the gray matter they had gained by juggling.
Similar cortical reorganization occurs in people and animals who have lost limbs due to amputation. After amputation, people and animals adapt by increasing use of their intact limbs; for example, someone who has lost their right hand will start using their left hand much more than they used to.
Parts of the motor and somatosensory cortices that control and sense the intact body parts adapt to increased use by growing in size, while the parts that control and sense the lost limb decrease in size or sometimes move into nearby brain areas due to lack of use. Now scientists are finding that if you stimulate a certain area of the brain, it causes neurons to migrate toward that area; this is activity-dependent neural migration.
In , researchers in South Korea showed how hippocampal neurons migrate toward a site of electrical stimulation. Neurons communicate with each other via electrical signals called action potentials and chemical signals called neurotransmitters. Similar results have been found using cortical neurons. Are you ready to make the most of your neuroplasticity and neurogenesis? First, you need to stop doing things that inhibit neurogenesis.
Then you need to start doing things—or keep doing them! Finally, you need to stimulate neuroplasticity and neurogenesis in the brain areas where you want them to occur, by doing the activities you want to get better at.
Four of the lifestyle factors that inhibit neurogenesis the most are are stress, alcohol consumption, sleep deprivation, and diet. Chronic stress decreases neurogenesis in the hippocampus, and also lowers the chances that the new neurons that do get produced will survive. Neuroinflammation the inflammatory response of the immune system when it occurs in the brain that results from stress also likely prevents the production of new neurons. And sadly, stress experienced in childhood can inhibit neurogenesis in adulthood.
Constant stimulation and worrying about the future is not good for brain health—we need to slow down and relax our minds in the same way we rest our bodies.
Regular alcohol consumption reduces the size of the hippocampus to a degree proportional to the amount that people drink. The same is true for overall brain atrophy; researchers found that brain volume decreases in proportion to alcohol consumed, and the effect is measurable even in light and moderate drinkers in comparison to non-drinkers.
Luckily, it seems that the effects can be reversed. While heavy alcohol consumption inhibits neurogenesis, subsequent abstinence allows neurogenesis to return to relatively normal levels in a short period of time. Both sleep deprivation and sleep fragmentation disrupted sleep inhibit neurogenesis in the hippocampus.
Even a single day of sleep deprivation reduces the rate at which new neural cells are produced. Not to worry— normal rates of neurogenesis can be recovered within about two weeks after adequate sleep is resumed. Researchers have found a number of dietary factors that prevent the production of new neurons. Being deficient in vitamin A and vitamin B can also inhibit neurogenesis. And pay attention to the texture of your food: eating a diet of soft foods decreases neurogenesis , while eating solid foods that require more chewing increases production of new neurons.
Exercise is one of the best ways to increase neurogenesis, largely because it boosts production of brain-derived neurotrophic factor BDNF. BDNF is a protein that acts like Miracle-Gro for brain cells: it stimulates the growth of neuroblasts, helps them survive, and encourages the formation of new synapses. The positive effects of exercise are enhanced by environmental enrichment EE , which can include being in new, stimulating surroundings or going outdoors.
Sustained aerobic exercise like running increases neurogenesis, while resistance exercise has not been shown to have the same effect. John Ratey, the author of Spark: The Revolutionary New Science of Exercise and the Brain , recommends doing both aerobic exercise and activities that demand focus and coordination, like martial arts, dance, rock climbing, and yoga, in order to fully stimulate your brain.
Learning improves the chances that neuroblasts will survive, mature, and integrate into neural circuitry. Damage to this part of the brain will impair movement of the right arm. In other words, neuroplasticity is not synonymous with the brain being infinitely malleable.
In a study of Caenorhabditis elegans , a type of nematode used as a model organism in research , it was found that losing the sense of touch enhanced the sense of smell. This suggests that losing one sense rewires others. As in the developing infant, the key to developing new connections is environmental enrichment that relies on sensory visual, auditory, tactile, smell and motor stimuli.
The more sensory and motor stimulation a person receives, the more likely they will be to recover from brain trauma. For example, some of the types of sensory stimulation used to treat stroke patients includes training in virtual environments, music therapy and mentally practising physical movements. The basic structure of the brain is established before birth by your genes.
But its continued development relies heavily on a process called developmental plasticity, where developmental processes change neurons and synaptic connections. In the immature brain this includes making or losing synapses, the migration of neurons through the developing brain or by the rerouting and sprouting of neurons. There are very few places in the mature brain where new neurons are formed. The exceptions are the dentate gyrus of the hippocampus an area involved in memory and emotions and the sub-ventricular zone of the lateral ventricle , where new neurons are generated and then migrate through to the olfactory bulb an area involved in processing the sense of smell.
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