Early brain development begins shortly after conception. First, the developing tissues begin to fold, the central fluid-filled cavity thickens. The forebrain begins to develop around 3 months and the spinal cord around 7 weeks. The first stage of brain development is proliferation and migration, the brain begins to produce new cells and neurons. In fact, many more neurons present until adulthood are produced, the cells divide in two, the stem cells remain in place and continue to divide. , newly formed neurons and glial cells move to their new location in the nervous system. Secondly, differentiation occurs, this is the formation of axons and dendrites which give neurons their distinct shape from other cells, the axon usually grows first and once it has reached the target length, dendrites are formed. Third, myelination, glial cells produce a fatty sheath that covers axons called myelin, this speeds up transmission between neurons, the fatty sheath continually grows over decades as connections are strengthened through learning and l In my experience, myelin first covers the axons of the spinal cord and later. in the hindbrain. Finally, there is synaptogenesis, or the formation of synapses, a process that occurs continually throughout life as we learn additional information, synapses that are not useful. No new neurons are produced after birth. Say no to plagiarism. Get a tailor-made essay on “Why violent video games should not be banned”?Get original essay Axon orientation refers to the process by which the axon knows where its place is in the brain. A study of how this happens came from Weiss, 1924, who attached an extra leg to a salamander, after a while the extra leg began to move in sync with the others. This is proof that axons can find their own way through the nervous system. Speary, 1943, conducted experiments on newts in which he cut the optic nerve to see if it would reconnect to the same areas, and it did. However, when the eye rotated 180 degrees, the axons grew again to connect in exactly the same place, causing the newt to see the world upside down. Speary concluded that axons follow a chemical gradient to find where to go. During child development, neurons engage in neuronal competition, in which some neurons survive while others are eliminated. Useful axons are provided with neurotrophin, a growth factor released by muscles that promotes axon rebirth and growth. Axons that are not useful, and therefore not exposed to NGF, undergo aptosis, a pre-programmed “suicide” for neurons, whereby the neuron destroys itself. After maturity, the apoptotic mechanism of neurons becomes dormant. Evidence for apoptosis comes from Jiang et al, 2009. Jiang and colleagues reported that the visual cortex is thicker in people blind at birth than in people who become blind later, because synapses cannot use visual experience to classify which ones are useful and which ones. are not, so pruning does not occur and the same number of synapses remains throughout development. People who become blind as adults have a thinner visual cortex, their early visual experience allowed for pruning andirrelevant synapses were destroyed. The brain is the fastest developing organ in humans. At birth it weighs around 350 grams but will weigh around 1000 grams in the first year, the adult brain weighs between 1200 and 1400 grams, highlighting the importance of the first year of life for synaptic development. Yet the brain will continue to develop throughout an individual's life, through a process called fine-tuning. Axons and dendrites continue to change their structure throughout life, they gain new spines as we learn new information and strengthen connections through information processing, they also lose spines if they do not are more relevant, meaning the brain can continually reorganize itself to become more efficient. Enriched environments in the brain will often result in a thicker cortex, this is due to the formation of a greater number of dendritic branches. Maguire et al, 2000, found that taxi drivers had increased GM in their hippocampus due to their extensive knowledge of the roads. People who learn to play stringed instruments such as the guitar have a different organization in M1 motor neurons to respond to this skill. Language learning also produces an increase in GM volume; however, this reorganization of the brain differs depending on the age at which language is acquired. Children who grew up in bilingual households show different brain activation during sentence production than people who learn new languages ​​as adults (Kim et al, 1997). The later the second language is acquired, the less effect it has on the density of GMOs (Mechelli et al, 2004). However, there is a critical period of language learning (Lenneberg 1967); a lack of early exposure to language can lead to permanent impairment. This is also the case for deaf children: if they are not taught sign language from a young age, it is much more difficult for them to learn it as adults. Additionally, cochlear implants are most effective if installed within the first two years of life. , suggesting a critical period for the brain in reorganizing the auditory and linguistic cortices. The brain can also reorganize its structures to compensate for deficiencies; Sadato et al, 1996, found that blind subjects show activation of the primary and secondary visual cortices during tactile discrimination tasks (braille). Brain reorganization and plasticity also mean that in some cases of damaged areas of the brain, survivors may show subtle or significant behavioral recovery. Diaschisis refers to the process by which, following brain injury, surviving areas increase or reorganize their activity to avoid a decrease in activity caused by damage to other parts of the brain. Neuronal supersensitivity also occurs, this is where postsynaptic regions deprived of input develop increased sensitivity to the neurotransmitter they are receiving to compensate for the lack of chemical release. Sensitivity to denervation implies that axons exhibit increased sensitivity to NT after destruction of incoming axons, or disuse supersensitivity, whereby nerves become more sensitive to NT after inactivity of an incoming axon. Destroyed cell bodies cannot be replaced, but damaged axons will regrow under certain conditions. Under certain circumstances, in peripheral NS, axons can follow the myelin sheath to their target andgradually regrow, although sometimes they can reattach incorrectly after damage, this is called axon sprouting, undamaged axons will attach to vacant receptors. Brain lateralization, the process by which different structures become specialized for certain functions, can also be reorganized after damage. An example of lateralization is the specialty of the left and right hemispheres for different functions, each hemisphere is connected to the contralateral side of the body and communicates through the corpus callosum via electrical impulses. The right hemisphere is known to be dominant for recognizing emotions and understanding complex visual patterns, while the left hemisphere is specialized for language. This contralateral specialty is represented in split-brain patients. When a shape is projected to the left hemisphere, patients report seeing a circle. However, if projected to the right hemisphere they report seeing nothing, it is because the right hemisphere can no longer communicate with the left hemisphere to use language abilities - we can. I don't verbalize what we see. Patients who are shown the key word will only see the word ring, because it is processed by the left hemisphere, and will only write the word ring when the right hand is commanded by the motor cortex of the hemisphere. LEFT. However, if he reaches for an object with his left hand, whether it is the key or the ring, he will search for a key, this is because the left hand is controlled by the right hemisphere which sees the key word. The corpus callosum develops during adolescence, so evidence of limited connections between the two hemispheres comes from young children who can sometimes behave like split-brain patients. Gallin et al, 1979, asked three- and five-year-old children to judge whether fabrics were different or the same, and they could only do so if they touched each fabric with the same hand, suggesting a lack of communication between the hemispheres. This can be implemented in treatments to help people recover after a stroke. Nelles et al, 2001, used a PET scanner to study plasticity after hemiparetic stroke and found that patients who did not receive the treatment only activated the IPC after treatment. Patients showed activation of the IPC, premotor cortex, and contralateral sensorimotor cortex, showing that rehabilitation and physiotherapy can induce reorganization of brain function in motor systems. Sensory neurons can also reorganize themselves, so a hand amputated from the face will begin to produce more sensory neurons to compensate, patients without hands sometimes experience a "phantom limb" when the face receives sensory stimuli, the motor cortex will think it is involves working the hand, whereas it is about the face (Pons et al, 1991). However, the problem with these studies on split-brain patients is that it is not a common phenomenon. Normally, split-brain patients have other defects in their brain, such as uncontrolled seizures or some sort of developmental disorder. Instead, the WADA test was developed to study lateralization in normal individuals. Before brain surgery, a barbiturate is injected into one of the internal carotid arteries, a drug is then injected into one hemisphere at a time to stop the function of that hemisphere, this allows the effectiveness of the opposite hemisphere to be assessed , in a way that it induces “split brain” syndrome in healthy subjects. There may also be an effect on behavior and cognition due to.