Electroencephalography is the neurophysiological measurement of electrical activity in the brain as recorded by electrodes placed on the scalp or, in special cases, subdurally or in the cerebral cortex. The resulting traces are known as an electroencephalogram (EEG) and represent a summation of post-synaptic potentials from a large number of neurons.
The use of EEG in neuroscience research delivers a number of benefits. One is that EEG is non-invasive for the research subject. Furthermore, the need to restrict the subject‘s movements is clearly lower than in other fields of neuroscience such as functional magnetic resonance imaging (fMRI). A further benefit is that many EEG applications record spontaneous brain activity, which means that the subject does not need to be able to cooperate with the researcher (as is necessary, for instance, during behavioral testing in neuropsychology). Also, EEGs have a high temporal resolution compared with techniques such as fMRI and PET and are capable of detecting changes in electrical activity in the brain on a time scale in the millisecond region.
In conventional scalp EEG, the recording is obtained by applying electrodes to the scalp using a conductive gel or paste, usually after preparing the scalp area by light abrasion to reduce electrode-scalp impedance. Many systems typically use electrodes which are each attached to an individual wire. Some systems use caps in which electrodes are embedded. This latter method is particularly common when high-density arrays of electrodes are required.
In addition to internal artifacts such as those produced by blinking, there are many artifacts which originate from outside the patient. Movement by the patient generates huge artifacts. Sweating or changes in temperature may cause electrode drifts. Spikes can originate from a momentary change in impedance at a given electrode.
Brain Products EEG amplifiers are equipped with a number of noise reduction techniques such as active noise cancellation and active electrodes. High common mode rejection as well as low amplifier noise ensure maximum data quality. Our huge product range includes a range of electrodes and caps with custom or standard montages as well as a variety of requisite accessories.