Neurophysics

Neurophysics (or neurobiophysics) is the branch of biophysics dealing with the development and use of physical techniques to gain information about the nervous system on a molecular level. Neurophysics is an interdisciplinary science which applies the approaches and methods of experimental biophysics to study the nervous system. Neurophysics aim to describe various cerebral activities using physics with the purpose of studying them and combining them with other neurosciences to better understand neural processes. The properties studied are for the most part electrical, mechanical or fluidic. The term "neurophysics" is a portmanteau of "neuron" and "physics".

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

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 in human in 1924 , 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 the its activity. The Functional Magnetic Resonance Imaging (fMRI) technique, discovered by Seiji Ogawa in 1990, reveales 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. An other technique, the Two Photons Microscopy (2P), invented by Winfried Denk (for which he has been awarded the Brain Prize in 2015), John H. Strickler and Watt W. Webb in 1990 at Cornell University, 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. Nowadays, 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 yet an unknown mechanism and theorists have come up with physical hypotheses explaining its mechanisms. Some theories relie on the idea that consciousness could be explained by the disturbances in the cerebral electromagnectic field generated by the action potentials trigerred during brain activity. These theories are called electromagnetic theories of consciousness. An other group of hypotheses suggest that consciousness can not be explained by classical dynamics but with quantum mechanics its phenomena. These hypotheses are gathered into the idea of quantum mind and were first introduced by Eugene Wigner.

Neurophysics institutes

• The Theoretical Neurophysics Laboratory, University of Bremen
• Department of Neurophysics, Max-Planck Institute
• Center of Functionally Integrative Neuroscience, Neurophysics group, Aarhus University
• W. M. Keck Center for Neurophysics, UCLA
• Neurophysics Program, Georgia State University
• Neurophysics at the Institute of Neurology, University College of London

Awards

Among the list of prices 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". 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 developped techniques which contributed widely to a better understanding of the nervous sytem, such as Neher and Sakmann in 1991 for the patch clamp, but also Lauterbur and Mansfield for their work on magnetic resonance imaging (MRI) in 2003.

See also

• Action potential
• Brain
• Biophysics
• Electrical engineering
• Electrophysiology
• Molecular neuroscience
• Neural engineering
• Neuroimaging
• Neurophysiology
• Neuroscience
• Psychophysics
• Quantum mind
• Soliton model in neuroscience

Books

• Wulfram Gerstner and Werner M. Kistler, Spiking Neuron Models, Single Neurons, Populations, Plasticity, Cambridge University Press (2002) ISBN 0-521-89079-9 ISBN 0-521-81384-0
• Alwyn Scott, Neuroscience: A Mathematical Primer, Birkhäuser (2002) ISBN 0-387-95403-1
• Graben, Peter; Zhou, Changsong; Thiel, Marco; Kurths, Jürgen (2008), "Foundations of Neurophysics", Lectures in Supercomputational Neurosciences, Berlin, Heidelberg: Springer, pp. 3–48, doi:10.1007/978-3-540-73159-7, ISBN 978-3-540-73159-7