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Thursday, 7 July 2011

Sources of information

Sources of information

Neuroscientists, along with researchers from allied disciplines, study how the human brain works. Such research has expanded considerably in recent decades. The "Decade of the Brain", an initiative of the United States Government in the 1990s, is considered to have marked much of this increase in research.[22]
Information about the structure and function of the human brain comes from a variety of experimental methods. Most information about the cellular components of the brain and how they work comes from studies of animal subjects, using techniques described in the brain article. Some techniques, however, are used mainly in humans, and therefore are described here.

Computed tomography of human brain, from base of the skull to top, taken with intravenous contrast medium

EEG

By placing electrodes on the scalp it is possible to record the summed electrical activity of the cortex, in a technique known as electroencephalography (EEG).[23] EEG measures mass changes in population synaptic activity from the cerebral cortex, but can only detect changes over large areas of the brain, with very little sensitivity for sub-cortical activity. EEG recordings can detect events lasting only a few thousandths of a second. EEG recordings have good temporal resolution, but poor spatial resolution.

MEG

Apart from measuring the electric field around the skull it is possible to measure the magnetic field directly in a technique known as magnetoencephalography (MEG).[24] This technique has the same temporal resolution as EEG but much better spatial resolution, although not as good as Magnetic Resonance Imaging (MRI). The greatest disadvantage of MEG is that, because the magnetic fields generated by neural activity are very weak, the method is only capable of picking up signals from near the surface of the cortex, and even then, only neurons located in the depths of cortical folds (sulci) have dendrites oriented in a way that gives rise to detectable magnetic fields outside the skull.

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