Neuroscience [neurobiology]

Neuroscience (or neurobiology) is the study of the nervous system, including anatomy, physiology and emergent proprieties. It is a field to which belong anatomy, molecular biology, mathematics, medicine, pharmacology, physiology, physics, engineering and psychology. The term neuroscience is a neologism coined by the American neurophysiologist Francis O. Schmitt. He argued that if we wanted to obtain a total understanding of the complexity of brain and mental functioning, all barriers between different scientific disciplines had to be removed, combining their resources. The first research group created was called Neurosciences Research Program, and was made up of scientists from different backgrounds.

According to neuroscience, mental representations are patterns of neural activity and inference, or deductive reasoning, is the application of these patterns to different situations in order to address and resolve them.

Neuroscience investigates the development, maturation, and maintenance of the nervous system, its anatomy, its functioning, the connections that exist between different brain areas, and manifest behaviors. Neuroscience seeks to understand not only how the nervous system works under healthy conditions, but also, when it is not functioning properly. Deficient brain functioning is shown through the presence of developmental, psychiatric, and neurological disorders. The purpose of neuroscience is also to carry out empirical studies in order to prevent the occurrence of various deficits and to treat them through a series of rehabilitative tasks developed ad hoc.

The main branches of neuroscience

DTI sagittal fibers
Visualization of a DTI measurement of a human brain. Depicted are reconstructed fiber tracts that run through the mid-sagittal plane. Especially prominent are the U-shaped fibers that connect the two hemispheres through the corpus callosum (the fibers come out of the image plane and consequently bend towards the top) and the fiber tracts that descend toward the spine (blue, within the image plane).[Image credits]

The scientific discipline of neuroscience is a diverse and multidisciplinary field, which as we have already seen includes biology, psychological sciences, neurology, anatomy, physiology, etc.. Within this vast multidisciplinary landscape it is possible to identify some main branches, which are often related and interdependent. For example, the most relevant are the following:

  • Cellular neuroscience – study of neurons at a cellular level.
  • Cognitive neuroscience – study of biological substrates underlying cognition, with a focus on the neural substrates of mental processes.
  • Computational neuroscience – study of the information processing functions of the nervous system, and the use of digital computers to study the nervous system.
  • Developmental neuroscience – study of the cellular basis of brain development and addresses the underlying mechanisms.
  • Molecular neuroscience – studies the biology of the nervous system with molecular biology, molecular genetics, protein chemistry and related methodologies.
  • Neuroanatomy – study of the anatomy of nervous tissue and neural structures of the nervous system.
  • Neuroendocrinology – studies the interaction between the nervous system and the endocrine system, that is how the brain regulates the hormonal activity in the body.
  • Neuroethology – study of animal behavior and its underlying mechanistic control by the nervous system.
  • Neuroimmunology – study of the nervous system, and immunology, the study of the immune system.
  • Neuropharmacology – study of how drugs affect cellular function in the nervous system.
  • Neurophysiology – study of the function (as opposed to structure) of the nervous system.
  • Neuropsychology – studies the structure and function of the brain related to psychological processes and behaviors. The term is used most frequently with reference to studies of the effects of brain damage in humans and animals.
  • Systems neuroscience – studies the function of neural circuits and systems. It is an umbrella term, encompassing a number of areas of study concerned with how nerve cells behave when connected together to form neural networks.

History of neuroscience

The study of the nervous system and the brain in its functions has a long history. Galen, a physician in Ancient Rome, is one of the first to place the mind in the brain and is the first to observe that there can be mental dysfunction as a result of brain damage.

The scientific study of the brain was born in the late 1800s following the invention of the microscope and the development of a staining procedure by Camillo Golgi. Through a particular staining method, Golgi discovered the reticular structure of the brain: the brain is made up of networks, and networks are made up of distinct cells, the neurons. We owe to the Spanish physician Santiago Ramon y Cajal (1852-1934) the first conceptualization of a model of the neuron. According to this model, the neuron is a cell body (soma) from which the dendrites expand on one side and the axon on the other. The connection between the different neurons would give rise to neural networks. These neuroscientific studies earned Golgi and Ramon y Cajal the Nobel Prize for medicine in 1906.

The first to identify the subdivision of the brain into functional areas was Franz Joseph Gall, father of phrenology; at the time of phrenology it was believed that specific conformations of the skull were associated with certain personality characteristics of individuals (a concept not confirmed by current neuroscience).

It was later Paul Broca to begin to associate specific brain areas, not so much personality characteristics as some psychological functions such as language, associated with the so-called Broca’s area. Carl Wernicke brought forward in an even more specific way the theory of specialization of specific brain structures in the understanding and production of language.

At the beginning of the 20th century the German neurologist Broadmann developed the so-called Broadmann cytoarchitectonic map, a map of specific cerebral cortical areas that are activated during the execution of specific tasks and specific psychological functions. Even today in neuroscience is used and cited the Broadmann cytoarchitectonic map.

To date, in the contemporary scientific scene there are several organizations and associations related to neuroscience in order to provide a link between the various researchers and professionals in this disciplinary area. As early as the 1960s, the International Brain Research Organization, the International Society for Neurochemistry, the European Brain and Behaviour Society and the Society for Neuroscience were founded in 1969.

Neuroscience and neuroimaging techniques

Neuroscientists very often perform controlled experiments, through neuroimaging techniques, funizonal Magnetic Resonance Imaging (fMRI), Positron Emission Tomography (PET), MagnetoEncephalography (MEG), Transcranial Magnetic Stimulation (TMS), etc., which allow to record neural activity and, consequently, to identify the regions of the brain involved in the performance of a range of activities. In this way, functional maps of particular areas of the brain imputed to the performance of specific tasks are obtained.

Functional Magnetic Resonance Imaging (fMRI) is a recently introduced technique to study in detail the brain activity. It was born in the nineties by Thulborn and Ogawa, who realized the importance of blood oxygenation over time (BOLD signal, Blood Oxygenation Level Dependent), to acquire images related to a particular brain area. The BOLD effect had been studied by L. Pauling, who had linked it to structural brain images to make them more informative from a functional point of view. Functional MRI, therefore, allows to localize brain activity by exploiting hemodynamic changes. This method of investigation is based on the change of the MRI signal, to which is associated the hemodynamic and metabolic response in a region where there is a neuronal activation induced by internal or external stimuli. The fMRI, is closely linked to experimental and research contexts to identify, both in normal and in pathological subjects, the areas of the brain activated during stimulation tasks. In this way you get activation maps (functional) that allow you to illustrate which brain areas subtend specific cognitive functions.

Clearly, the tasks performed by a subject in fMRI are specific to a function performed by a particular area. The fMRI works in relation to changes in magnetization that occur between oxygen-poor and oxygen-rich blood flow, having as a basis from which to acquire anatomical MRI images of the subject, which allow you to reconstruct the entire basic brain structure. When an increase in brain activity is generated in an area, it determines a greater blood flow in that area with a consequent local increase in the amount of oxygen. Consequently, blood flow will also increase because a greater amount of oxygenated hemoglobin is needed. In activated areas, therefore, the increase in the concentration of oxyhemoglobin indicates an increase in electrical activity in the brain.

The fMRI does not produce direct images of what is happening in the brain, because these images are an indirect effect, resulting from the hemodynamic response, of neuronal activity. They are, in essence, statistical distribution maps, derived from average effects, of the activation of an area in the performance of a specific task.

PET and SPECT (single photon emission computed tomography), are widely used in clinical practice especially in neurology, since they allow a detailed analysis of the metabolic activity of the central nervous system, and consequently an accurate early diagnosis of many important diseases. Unlike X-ray, CT and structural MRI, instruments that return purely anatomical images of morphological alterations on the analyzed cellular district, PET provides functional information, that is, it determines which areas of the body metabolize more of a tracer, a substance that allows to detect more accurately an area that works more than others. In some respects, PET is similar to functional MRI, but the information provided is more detailed and accurate.

Transcranial magnetic stimulation, or TMS, is a non-invasive technique of electromagnetic stimulation, induced current, of the brain and nervous system in general. It allows to study the functioning of circuits and neuronal connections within the brain, causing a transient micro lesion that inhibits the functioning of the area under investigation. Transcranial magnetic stimulation involves the deep but non-invasive and painless stimulation of the brain, in order to obtain responses in relation to the stimulated brain area and to modify its excitability and plasticity.

Transcranial magnetic stimulation is widely used for research purposes, but recently benefits have been observed in the clinical setting, where it is used to treat psychiatric and neurological disorders such as depression, hallucinations, Parkinson’s disease. The use of transcranial magnetic stimulation has been approved by the Food and Drug Administration (FDA) for use in the treatment of migraine headaches. While, the use of repeated TMS (rTMS) is permitted in the treatment of depression resistant to other treatments, both therapeutic and pharmacological.

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