Haemodynamic response

The Neurovascular coupling (composed of Greek neuron nerve cell and Latin vas, (blood) vessel) is a physiological mechanism for regulating the blood supply to the brain in order to meet the increased demand of the activated nerve tissue of oxygen and glucose by local increase in blood flow; this mechanism can be used for the presentation of neuronal activity.

Hemodynamic response

Cortical activation leads with a latency of a few seconds to an increase of blood flow by 10-40 %. This is so pronounced that the relative oxygen content of the blood, the so-called oxygenation increases, although the metabolic activity, and thus the oxygen consumption of the relevant neural tissue increases.

As the blood flow response is mediated, is still largely unclear. It is assumed that the interaction of several factors, such as pH, potassium ions and adenosine. Some newer models assume a crucial role of neuroglia in the blood flow regulation.

Functional Imaging

The display of functional processes in the brain has advanced greatly in recent years. Such techniques can document the specific function of the institutions themselves, while anatomical- morphological methods such as CT and MRI show only the structure of the living body. For the measurement of brain activity for a long time on electrophysiological methods ( EEG) was limited. Newer methods, however, make use of the fact that an increase in activity causes in a specific area of ​​the brain, for example, movement, perception or cognitive performance in a localized increase in blood flow in this region.

There are nuclear medicine (PET, SPECT), magnetic resonance and optical spectroscopy (NIRS ) approaches in functional brain imaging. As standard, the functional magnetic resonance imaging (fMRI ) has been proven on the basis of oxygen saturation dependent BOLD contrast.