Abstract

The brain is the most complicated system known to man; it constitutes one of the greatest scientific challenges for the 21st century. Being composed of atoms, the brain appears to be governed by known laws of physics, and to understand it, knowledge of physics is indeed essential. The proper description of brain function involves phenomena on a wide range of time and length scales, from molecular interactions to the level or the cortex and even society. The term “neurophysics” refers to the use of physics in the study of neuroscience.

The goal of neurophysics is to explain the brain in physical terms. We know a lot about the structure of the brain, how ions diffuse, how electrical signals are transmitted, and how the brain uses energy and synthesizes proteins and other substances, but a full explanation will include also concepts such as evolution, maturation, and deterioration of the brain, perception, thinking, learning, memory, sleep, consciousness, mind. A very large body of knowledge of these phenomena have been accumulated but the central question of how the brain processes information, remains to be answered properly. Some phenomena such as consciousness may even require additions or modifications to the presently accepted physical laws.

In addition to giving the basis for understanding the brain, physics is also needed in the development of brain-research technology.  In this lecture, emphasis is put on macrosopic measures of human brain activity that can be obtained with modern brain imaging methods such as magnetoencephalography (MEG), electroencephalography (EEG), transcranial magnetic stimulation (TMS), magnetic resonance imaging (MRI), near infrared spectroscopy (NIRS), and positron emission tomography (PET). At the dawn of the new millennium, for the first time in the history of mankind, the human being can now look into his or her own brain and observe how different neuronal circuits are activated during a mental task. The role of the physicist in these developments is becoming more important as we proceed from present-day technology to the powerful brain scanners of the future and from phenomenological descriptions to true understanding of the brain.

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