Neurophysics

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Neurophysics (or neurobiophysics) is the branch of biophysics dealing with the development and use of physical methods to gain information about the nervous system. Neurophysics is an interdisciplinary science using physics and combining it with other neurosciences to better understand neural processes. The methods used include the techniques of experimental biophysics and other physical measurements such as EEG [1] mostly to study electrical, mechanical or fluidic properties, as well as theoretical and computational approaches. [2] The term "neurophysics" is a portmanteau of "neuron" and "physics".

Contents

Among other examples, the theorisation of ectopic action potentials in neurons using a Kramers-Moyal expansion [3] and the description of physical phenomena measured during an EEG using a dipole approximation [1] use neurophysics to better understand neural activity.

Another quite distinct theoretical approach considers neurons as having Ising model energies of interaction and explores the physical consequences of this for various Cayley tree topologies and large neural networks. In 1981, the exact solution for the closed Cayley tree (with loops) was derived by Peter Barth for an arbitrary branching ratio [4] and found to exhibit an unusual phase transition behavior [5] in its local-apex and long-range site-site correlations, suggesting that the emergence of structurally-determined and connectivity-influenced cooperative phenomena may play a significant role in large neural networks.

Recording techniques

Old techniques to record brain activity using physical phenomena are already widespread in research and medicine. Electroencephalography (EEG) uses electrophysiology to measure electrical activity within the brain. This technique, with which Hans Berger first recorded brain electrical activity on a human in 1924, [6] is non-invasive and uses electrodes placed on the scalp of the patient to record brain activity. Based on the same principle, electrocorticography (ECoG) requires a craniotomy to record electrical activity directly on the cerebral cortex.

In the recent decades, physicists have come up with technologies and devices to image the brain and its activity. The Functional Magnetic Resonance Imaging (fMRI) technique, discovered by Seiji Ogawa in 1990, [7] reveals blood flow changes inside the brain. Based on the existing medical imaging technique Magnetic Resonance Imaging (MRI) and on the link between the neural activity and the cerebral blood flow, this tool enables scientists to study brain activities when they are trigerred by a controlled stimulation. Another technique, the Two Photons Microscopy (2P), invented by Winfried Denk (for which he has been awarded the Brain Prize in 2015 [8] ), John H. Strickler and Watt W. Webb in 1990 at Cornell University, [9] uses fluorescent proteins and dyes to image brain cells. This technique combines the two-photon absorption, first theorized by Maria Goeppert-Mayer in 1931, with lasers. Today, this technique is widely used in research and often coupled with genetic engineering to study the behavior of a specific type of neuron.

Theories of consciousness

Consciousness is still an unknown mechanism and theorists have yet to come up with physical hypotheses explaining its mechanisms. Some theories rely on the idea that consciousness could be explained by the disturbances in the cerebral electromagnetic field generated by the action potentials triggered during brain activity. [10] These theories are called electromagnetic theories of consciousness. Another group of hypotheses suggest that consciousness cannot be explained by classical dynamics but with quantum mechanics and its phenomena. These hypotheses are grouped into the idea of quantum mind and were first introduced by Eugene Wigner.

Neurophysics institutes

Awards

Among the list of prizes that reward neurophysicists for their contribution to neurology and related fields, the most notable one is the Brain Prize, whose last laureates are Adrian Bird and Huda Zoghbi for "their groundbreaking work to map and understand epigenetic regulation of the brain and for identifying the gene that causes Rett syndrome". [11] The other most relevant prizes that can be awarded to a neurophysicist are: the NAS Award in the Neurosciences, the Kavli Prize and to some extent the Nobel Prize in Physiology or Medicine. It can be noted that a Nobel Prize was awarded to scientists that developed techniques which contributed widely to a better understanding of the nervous system, such as Neher and Sakmann in 1991 for the patch clamp, and also to Lauterbur and Mansfield for their work on Magnetic resonance imaging (MRI) in 2003.

See also

Books

Related Research Articles

<span class="mw-page-title-main">Neuroscience</span> Scientific study of the nervous system

Neuroscience is the scientific study of the nervous system, its functions and disorders. It is a multidisciplinary science that combines physiology, anatomy, molecular biology, developmental biology, cytology, psychology, physics, computer science, chemistry, medicine, statistics, and mathematical modeling to understand the fundamental and emergent properties of neurons, glia and neural circuits. The understanding of the biological basis of learning, memory, behavior, perception, and consciousness has been described by Eric Kandel as the "epic challenge" of the biological sciences.

<span class="mw-page-title-main">Cognitive neuroscience</span> Scientific field

Cognitive neuroscience is the scientific field that is concerned with the study of the biological processes and aspects that underlie cognition, with a specific focus on the neural connections in the brain which are involved in mental processes. It addresses the questions of how cognitive activities are affected or controlled by neural circuits in the brain. Cognitive neuroscience is a branch of both neuroscience and psychology, overlapping with disciplines such as behavioral neuroscience, cognitive psychology, physiological psychology and affective neuroscience. Cognitive neuroscience relies upon theories in cognitive science coupled with evidence from neurobiology, and computational modeling.

<span class="mw-page-title-main">Functional magnetic resonance imaging</span> MRI procedure that measures brain activity by detecting associated changes in blood flow

Functional magnetic resonance imaging or functional MRI (fMRI) measures brain activity by detecting changes associated with blood flow. This technique relies on the fact that cerebral blood flow and neuronal activation are coupled. When an area of the brain is in use, blood flow to that region also increases.

The following outline is provided as an overview of and topical guide to neuroscience:

Rehabilitation of sensory and cognitive function typically involves methods for retraining neural pathways or training new neural pathways to regain or improve neurocognitive functioning that have been diminished by disease or trauma. The main objective outcome for rehabilitation is to assist in regaining physical abilities and improving performance. Three common neuropsychological problems treatable with rehabilitation are attention deficit/hyperactivity disorder (ADHD), concussion, and spinal cord injury. Rehabilitation research and practices are a fertile area for clinical neuropsychologists, rehabilitation psychologists, and others.

<span class="mw-page-title-main">Functional neuroimaging</span>

Functional neuroimaging is the use of neuroimaging technology to measure an aspect of brain function, often with a view to understanding the relationship between activity in certain brain areas and specific mental functions. It is primarily used as a research tool in cognitive neuroscience, cognitive psychology, neuropsychology, and social neuroscience.

<span class="mw-page-title-main">Behavioral neuroscience</span> Field of study

Behavioral neuroscience, also known as biological psychology, biopsychology, or psychobiology, is the application of the principles of biology to the study of physiological, genetic, and developmental mechanisms of behavior in humans and other animals.

Brainwave entrainment, also referred to as brainwave synchronization or neural entrainment, refers to the observation that brainwaves will naturally synchronize to the rhythm of periodic external stimuli, such as flickering lights, speech, music, or tactile stimuli.

Neural engineering is a discipline within biomedical engineering that uses engineering techniques to understand, repair, replace, or enhance neural systems. Neural engineers are uniquely qualified to solve design problems at the interface of living neural tissue and non-living constructs.

<span class="mw-page-title-main">Neural oscillation</span> Brainwaves, repetitive patterns of neural activity in the central nervous system

Neural oscillations, or brainwaves, are rhythmic or repetitive patterns of neural activity in the central nervous system. Neural tissue can generate oscillatory activity in many ways, driven either by mechanisms within individual neurons or by interactions between neurons. In individual neurons, oscillations can appear either as oscillations in membrane potential or as rhythmic patterns of action potentials, which then produce oscillatory activation of post-synaptic neurons. At the level of neural ensembles, synchronized activity of large numbers of neurons can give rise to macroscopic oscillations, which can be observed in an electroencephalogram. Oscillatory activity in groups of neurons generally arises from feedback connections between the neurons that result in the synchronization of their firing patterns. The interaction between neurons can give rise to oscillations at a different frequency than the firing frequency of individual neurons. A well-known example of macroscopic neural oscillations is alpha activity.

<span class="mw-page-title-main">Neuroimaging</span> Set of techniques to measure and visualize aspects of the nervous system

Neuroimaging is the use of quantitative (computational) techniques to study the structure and function of the central nervous system, developed as an objective way of scientifically studying the healthy human brain in a non-invasive manner. Increasingly it is also being used for quantitative research studies of brain disease and psychiatric illness. Neuroimaging is highly multidisciplinary involving neuroscience, computer science, psychology and statistics, and is not a medical specialty. Neuroimaging is sometimes confused with neuroradiology.

Sensory neuroscience is a subfield of neuroscience which explores the anatomy and physiology of neurons that are part of sensory systems such as vision, hearing, and olfaction. Neurons in sensory regions of the brain respond to stimuli by firing one or more nerve impulses following stimulus presentation. How is information about the outside world encoded by the rate, timing, and pattern of action potentials? This so-called neural code is currently poorly understood and sensory neuroscience plays an important role in the attempt to decipher it. Looking at early sensory processing is advantageous since brain regions that are "higher up" contain neurons which encode more abstract representations. However, the hope is that there are unifying principles which govern how the brain encodes and processes information. Studying sensory systems is an important stepping stone in our understanding of brain function in general.

Integrative neuroscience is the study of neuroscience that works to unify functional organization data to better understand complex structures and behaviors. The relationship between structure and function, and how the regions and functions connect to each other. Different parts of the brain carrying out different tasks, interconnecting to come together allowing complex behavior. Integrative neuroscience works to fill gaps in knowledge that can largely be accomplished with data sharing, to create understanding of systems, currently being applied to simulation neuroscience: Computer Modeling of the brain that integrates functional groups together.

Evoked activity is brain activity that is the result of a task, sensory input or motor output. It is opposed to spontaneous brain activity during the absence of any explicit task.

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Robert Turner is a British neuroscientist, physicist, and social anthropologist. He has been a director and professor at the Max Planck Institute for Human Cognitive and Brain Sciences in Leipzig, Germany, and is an internationally recognized expert in brain physics and magnetic resonance imaging (MRI). Coils inside every MRI scanner owe their shape to his ideas.

<span class="mw-page-title-main">Brain activity and meditation</span>

Meditation and its effect on brain activity and the central nervous system became a focus of collaborative research in neuroscience, psychology and neurobiology during the latter half of the 20th century. Research on meditation sought to define and characterize various practices. The effects of meditation on the brain can be broken up into two categories: state changes and trait changes, respectively alterations in brain activities during the act of meditating and changes that are the outcome of long-term practice.

<span class="mw-page-title-main">Consciousness after death</span> Common metaphysical theme in society and culture

Consciousness after death is a common theme in society and culture, and the belief in some form of life after death is a feature of many religions. However, scientific research has established that the physiological functioning of the brain, the cessation of which defines brain death, is closely connected to mental states.

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The following outline is provided as an overview of and topical guide to brain mapping:

References

  1. 1 2 Nunez, Michael; Nunez, Paul; Srinivasan, Ramesh (2016-01-01), Electroencephalography (EEG): neurophysics, experimental methods, and signal processing, pp. 175–197, ISBN   9781482220971 , retrieved 2018-06-30
  2. ↑ "Process Philosophy". The Stanford Encyclopedia of Philosophy. Metaphysics Research Lab, Stanford University. 2022.
  3. ↑ Frank, T. D. (2007-01-08). "Kramers–Moyal expansion for stochastic differential equations with single and multiple delays: Applications to financial physics and neurophysics". Physics Letters A. 360 (4): 552–562. Bibcode:2007PhLA..360..552F. doi:10.1016/j.physleta.2006.08.062. ISSN   0375-9601.
  4. ↑ Barth, Peter F. (1981). "Cooperativity and the Transition Behavior of Large Neural Nets". Master of Science Thesis. Burlington: University of Vermont: 1–118.
  5. ↑ Krizan, J.E.; Barth, P.F.; Glasser, M.L. (1983). "Exact Phase Transitions for the Ising Model on the Closed Cayley Tree". Physica. 119A. North-Holland Publishing Co.: 230–242. doi:10.1016/0378-4371(83)90157-7.
  6. ↑ Haas, L (2003). "Hans Berger (1873–1941), Richard Caton (1842–1926), and electroencephalography". Journal of Neurology, Neurosurgery, and Psychiatry. 74 (1): 9. doi:10.1136/jnnp.74.1.9. ISSN   0022-3050. PMC   1738204 . PMID   12486257.
  7. ↑ Ogawa, S.; Lee, T. M.; Nayak, A. S.; Glynn, P. (1990). "Oxygenation-sensitive contrast in magnetic resonance image of rodent brain at high magnetic fields". Magnetic Resonance in Medicine. 14 (1): 68–78. doi:10.1002/mrm.1910140108. ISSN   0740-3194. PMID   2161986. S2CID   12379024.
  8. ↑ "Nokia Bell Labs: Neurophysics Research". www.bell-labs.com. Retrieved 2020-11-16.
  9. ↑ Denk, W.; Strickler, J.; Webb, W. (1990). "Two-photon laser scanning fluorescence microscopy". Science. 248 (4951): 73–76. Bibcode:1990Sci...248...73D. doi:10.1126/SCIENCE.2321027. PMID   2321027. S2CID   18431535.
  10. ↑ McFadden, J. (2013-01-01). "The CEMI Field Theory Closing the Loop". Journal of Consciousness Studies: Controversies in Science and the Humanities. 20 (1–2): 153–168. ISSN   1355-8250.
  11. ↑ "Announcement of The Brain Prize 2020". Lundbeckfonden. Retrieved 2020-10-29.


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