Eye-tracking data analysis and neuroergonomics

In 1945, the physicist Felix Bloch of Stanford University, along with Edward Purcell of Harvard University, succeeded in measuring the so-called nuclear spin resonance of liquids. Both researchers received the Nobel Prize in physics for this detection. The effect is based on the fact that the nucleons of atoms have their own rotation; this rotation is the spin that generates a magnetic field. If (a probe of) a material is brought in a strong homogeneous magnetic field, the single spins of the nucleons perform a precession movement around the direction of the magnetic field of the electromagnet (they behave like a spinning top influenced by a force, in this case that of the magnetic field). Simultaneously, another electric inductor generates another weaker altering magnetic field perpendicular to the measuring field (the frequency of which is changed slowly). If the frequency of the measuring field matches the precession movement of the respective nuclear spins, its direction tilts as a result of this resonance process. The energy necessary for this tilting is measured by the measuring coil as increased current consumption. Because atoms have different resonance frequencies, depending on their number of protons and neutrons, the type of the atoms can be detected. This method of nuclear spin resonance is used for magnetic resonance tomography and magnetic resonance imaging (MRI), which are especially prominent in the medical field. Using the MRI technique generally involves having the test person or patient rest in a lying position, back down, on a sliding bed which is then slid into an electric inductor, which generates a high-frequency magnetic field. In an adjacent room, a computer that is connected to the magnetic resonance tomography machine receives the data output. The received data are typically sectional images of the body that can be combined into a spatial picture containing coordinates not only of the body surface but also of internal organs and the skeleton. In 1992, Seiji Ogawa and coworkers discovered that with this nuclear spin tomography the oxygenation of the hemoglobin in blood cells was being detected. Consequently, it was possible to indirectly track the blood flow of the brain to a nearly exact measurement in space and time. Assumedly, the brain areas that show a large blood supply are also those areas that are especially active, which means that this technology permits the measurement of a fully conscious person lying in the scanner tube. In addition to medical uses, this sort of technology is used in basic and applied research settings, where, for example, participants solve different types of problems or perform various types of tasks while in the scanner. This form of MRI coupled with tasks is called functional magnetic resonance imaging (fMRI).