EEG Primer - Part 1

As you think, see, sense, dream, or try to solve a crossword puzzle or start to learn how to drive, the brain is constantly active, engrossing all the information it is presented with, compressing and re-connecting the existing data, and integrating all of it into an experience for you. Everything you see, understand, learn is all shaped by the brain. Based on thoughts, emotions and previous experiences the brain creates its own narratives and it is what ultimately drives your behavior

EEG stands for Electroencephalogram. It is the continuous recording of electrical brain activity. The brain is made up of 100’s of billion of brain cells called neurons. These neurons have axons that release neurotransmitters and then dendrites that receive them. When the dendrites of the neurons receive the neurotransmitters from the axons of other neurons it causes an electrical polarity change inside of the neuron. This polarity change is what the EEG recording. It is the post-synaptic dendritic currents from cortical pyramidial cells. The activity from one single neuron is way too small to be detected with EEG equipment. But when thousands of neurons work together, they generate an electrical field which is strong enough to spread through bone and skull that is recorded on the head surface by the EEG. It is like how a single subtle earthquake might not be noticeable, but if a number of of them occur at the same time and location, it will be with much more impact and will definitely be noticeable.

The EEG, Electroencephalography, is a way of recording electrical activity that is produced by the brain. To ensure that the data is collected from similar scalp positions across all respondents, electrodes are accumulated in elastic caps.

Even though the name of EEG (Electroencephalogram) might intimidate people and seem like somewhat daunting, the biophysics behind EEG is surprisingly simple. The EEG calculates the electrical activity produced by the neurons, hence allowing you to analyze which areas of the brain are active at a specific time.

Small voltage fluctuations measured at the electrodes are digitized after recording and then sent to an amplifier. The data amplified allows it to be displayed as a series of voltage values.

The number of electrodes and the quality of the amplifier and the digitization along with the quantity of snapshots the device can take adds up to the price difference between EEG equipments.

100 years ago EEG time course was plotted on a piece of paper. Now the technology has advanced to the extent that EEG is one the fastest and quickest imaging techniques available allowing taking thousands of snaps per second.

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