The major branches of modern neuroscience

Branches of neuroscience can be broadly categorized in the following disciplines (neuroscientists usually cover several branches at the same time):

  • Affective neuroscience – in most cases, research is carried out on laboratory animals and looks at how neurons behave in relation to emotions.
  • Behavioral neuroscience – the study of the biological bases of behavior. Looking at how the brain affects behavior.
  • Cellular neuroscience – the study of neurons, including their form and physiological properties at cellular level.
  • Clinical neuroscience – looks at the disorders of the nervous system, while psychiatry, for example, looks at the disorders of the mind.
  • Cognitive neuroscience – the study of higher cognitive functions that exist in humans, and their underlying neural basis. Cognitive neuroscience draws from linguistics, psychology, and cognitive science. Cognitive neuroscientists can take two broad directions: behavioral/experimental or computational/modeling, the aim being to understand the nature of cognition from a neural point of view.
  • Computational neuroscience – attempting to understand how brains compute, using computers to simulate and model brain functions, and applying techniques from mathematics, physics, and other computational fields to study brain function.
  • Cultural neuroscience – looks at how beliefs, practices, and cultural values are shaped by and shape the brain, minds, and genes over different periods.
  • Developmental neuroscience – looks at how the nervous system develops on a cellular basis; what underlying mechanisms exist in neural development.
  • Molecular neuroscience – the study of the role of individual molecules in the nervous system.
  • Neuroengineering – using engineering techniques to better understand, replace, repair, or improve neural systems.
  • Neuroimaging – a branch of medical imaging that concentrates on the brain. Neuroimaging is used to diagnose disease and assess the health of the brain. It can also be useful in the study of the brain, how it works, and how different activities affect the brain.
  • Neuroinformatics – integrates data across all areas of neuroscience, to help understand the brain and treat diseases. Neuroinformatics involves acquiring data, sharing, publishing, and storing information, analysis, modeling, and simulation.
  • Neurolinguistics – studying what neural mechanisms in the brain control the acquisition, comprehension, and utterance of language.
  • Neurophysiology – looks at the relationship of the brain and its functions, and the sum of the body’s parts and how they interrelate. The study of how the nervous system functions, typically using physiological techniques, such as stimulation with electrodes, light-sensitive channels, or ion- or voltage-sensitive dyes.
  • Paleoneurology – the study of ancient brains using fossils.
  • Social neuroscience – this is an interdisciplinary field dedicated to understanding how biological systems implement social processes and behavior. Social neuroscience gathers biological concepts and methods to inform and refine theories of social behavior. It uses social and behavioral concepts and data to refine neural organization and function theories.
  • Systems neuroscience – follows the pathways of data flow within the CNS (central nervous system) and tries to define the kinds of processing going on there. It uses that information to explain behavioral functions.

Read more at www.medicalnewstoday.com

Neuroplasticity (source Britannica)

Neuroplasticity (source Britannica)

Neuroplasticity, capacity of neurons and neural networks in the brain to change their connections and behaviour in response to new information, sensory stimulation, development, damage, or dysfunction. Although neural networks also exhibit modularity and carry out specific functions, they retain the capacity to deviate from their usual functions and to reorganize themselves. In fact, for many years, it was considered dogma in the neurosciences that certain functions were hard-wired in specific, localized regions of the brain and that any incidents of brain change or recovery were mere exceptions to the rule. However, since the 1970s and ’80s, neuroplasticity has gained wide acceptance throughout the scientific community as a complex, multifaceted, fundamental property of the brain.

Rapid change or reorganization of the brain’s cellular or neural networks can take place in many different forms and under many different circumstances. Developmental plasticity occurs when neurons in the young brain rapidly sprout branches and form synapses. Then, as the brain begins to process sensory information, some of these synapses strengthen and others weaken. Eventually, some unused synapses are eliminated completely, a process known as synaptic pruning, which leaves behind efficient networks of neural connections. Other forms of neuroplasticity operate by much the same mechanism but under different circumstances and sometimes only to a limited extent. These circumstances include changes in the body, such as the loss of a limb or sense organ, that subsequently alter the balance of sensory activity received by the brain. In addition, neuroplasticity is employed by the brain during the reinforcement of sensory information through experience, such as in learning and memory, and following actual physical damage to the brain (e.g., caused by stroke), when the brain attempts to compensate for lost activity.

Today it is apparent that the same brain mechanisms—adjustments in the strength or the number of synapses between neurons—operate in all these situations. Sometimes this happens naturally, which can result in positive or negative reorganization, but other times behavioral techniques or brain-machine interfaces can be used to harness the power of neuroplasticity for therapeutic purposes. In some cases, such as stroke recovery, natural adult neurogenesis can also play a role. As a result, neurogenesis has spurred an interest in stem cell research, which could lead to an enhancement of neurogenesis in adults who suffer from stroke, Alzheimer disease, Parkinson disease, or depression.

Types Of Cortical Neuroplasticity

Developmental plasticity occurs most profoundly in the first few years of life as neurons grow very rapidly and send out multiple branches, ultimately forming too many connections. In fact, at birth, each neuron in the cerebral cortex (the highly convoluted outer layer of the cerebrum) has about 2,500 synapses. By the time an infant is two or three years old, the number of synapses is approximately 15,000 per neuron. This amount is about twice that of the average adult brain. The connections that are not reinforced by sensory stimulation eventually weaken, and the connections that are reinforced become stronger. Eventually, efficient pathways of neural connections are carved out. Throughout the life of a human or other mammal, these neural connections are fine-tuned through the organism’s interaction with its surroundings. During early childhood, which is known as a critical period of development, the nervous system must receive certain sensory inputs in order to develop properly. Once such a critical period ends, there is a precipitous drop in the number of connections that are maintained, and the ones that do remain are the ones that have been strengthened by the appropriate sensory experiences. This massive “pruning back” of excess synapses often occurs during adolescence.

American neuroscientist Jordan Grafman has identified four other types of neuroplasticity, known as homologous area adaptation, compensatory masquerade, cross-modal reassignment, and map expansion.

Map expansion

Map expansion, the fourth type of neuroplasticity, entails the flexibility of local brain regions that are dedicated to performing one type of function or storing a particular form of information. The arrangement of these local regions in the cerebral cortex is referred to as a “map.” When one function is carried out frequently enough through repeated behaviour or stimulus, the region of the cortical map dedicated to this function grows and shrinks as an individual “exercises” this function. This phenomenon usually takes place during the learning and practicing of a skill such as playing a musical instrument. Specifically, the region grows as the individual gains implicit familiarity with the skill and then shrinks to baseline once the learning becomes explicit. (Implicit learning is the passive acquisition of knowledge through exposure to information, whereas explicit learning is the active acquisition of knowledge gained by consciously seeking out information.) But as one continues to develop the skill over repeated practice, the region retains the initial enlargement.

Read more at   www.britannica.com

Dopamine controls formation of new brain cells –  Karolinska Institutet

Dopamine controls formation of new brain cells –  Karolinska Institutet

A study of the salamander brain has led researchers at Karolinska Institutet to discover a hitherto unknown function of the neurotransmitter dopamine. In an article published in the prestigious scientific journal Cell Stem Cell they show how in acting as a kind of switch for stem cells, dopamine controls the formation of new neurons in the adult brain. Their findings may one day contribute to new treatments for neurodegenerative diseases, such as Parkinson’s.

The study was conducted using salamanders which unlike mammals recover fully from a Parkinson’s-like condition within a four week period. Parkinson’s disease is a neurodegenerative disease characterised by the death of dopamine-producing cells in the mid-brain. As the salamander re-builds all lost dopamine-producing neurons, the researchers examined how the salamnder brain detects the absence of these cells. This question is a fundamental one since it has not been known what causes the new formation of nerve cells and why the process ceases when the correct number have been made.

What they found out was that the salamander’s stem cells are automatically activated when the dopamine concentration drops as a result of the death of dopamine-producing neurons, meaning that the neurotransmitter acts as a constant handbrake on stem cell activity.

“The medicine often given to Parkinson’s patients is L-dopa, which is converted into dopamine in the brain,” says Dr András Simon, who led the study at the Department of Cell and Molecular Biology. “When the salamanders were treated with L-dopa, the production of new dopamine-producing neurons was almost completely inhibited and the animals were unable to recover. However, the converse also applies. If dopamine signalling is blocked, new neurons are born unnecessarily.”

As in mammals, the formation of neurons in the salamander mid-brain is virtually non-existent under normal circumstances. Therefore by studying the salamander, scientists can understand how the production of new nerve cells can be resumed once it has stopped, and how it can be stopped when no more neurons are needed. It is precisely in this regulation that dopamine seems to play a vital part. Many observations also suggest that similar mechanisms are active in other animal species too. Further comparative studies can shed light on how neurotransmitters control stem cells in the brain, knowledge that is of potential use in the development of therapies for neurodegenerative diseases.

“One way of trying to repair the brain in the future is to stimulate the stem cells that exist there,” says Dr Simon. “This is one of the perspectives from which our study is interesting and further work ought to be done on whether L-dopa, which is currently used in the treatment of Parkinson’s, could prevent such a process in other species, including humans. Another perspective is how medicines that block dopamine signalling and that are used for other diseases, such as psychoses, affect stem cell dynamics in the brain.”
The salamander is a tailed member of the frog family most known for its ability to regenerate lost body parts, such entire limbs.

Publication
Dopamine controls neurogenesis in the adult salamander midbrain in homeostasis and during regeneration of dopamine neurons.
Berg D, Kirkham M, Wang H, Frisén J, Simon A
Cell Stem Cell 2011 Apr;8(4):426-33

Source: Karolinska Institutet