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EEG Changes | EEG Changes Before/After Migraine 

When you see the EEG change, is the brain actually changing?

The EEG is a physiological measure. If you watch your EEG change while you're doing neurofeedback training - you have changed your brain. Try it - it's quite easy to do (click here for an example).  With neurofeedback, you can target training any frequency at any site.  For most people, you'll quickly watch their EEG change, based upon rewards.  This is basic operant conditioning principles and learning theory 



Skinner, Pigeons and Pecking

This technique got interesting when Dr. Barry Sterman in the late '60's trained cats to change their EEG.  Cats who increased SMR activity didn't go into seizures nearly as fast as other cats.  All had been exposed to a toxic rocket fuel. No one expected such profound changes in brain behavior by training a change in the EEG.  There are still many professionals who are not aware that 1) that the EEG is easily changed, and 2) training the EEG over time can have a profound impact on behavior, affect, attention, and resilience or stability.

 But what's really happening?  Neuroscience and neurophysiology are gaining a much clearer understanding of the EEG and it's underlying mechanisms.  We're not trying to teach a neurophysiology class here.  If you want to understand in detail the electrochemistry and detailed neurophysiology that lead up the EEG, we suggest you take an up-to-date neurophysiology course or read a current neurophysiology text book. 

There are an estimated 100 billion neurons in the cortex. If you look under any electrode, there may only be a few hundred thousand - a very tiny percent.  If you are seeing changes under one electrode at one site, does that mean you are only changing those few hundred thousand neurons?
 
But in simple terms, what does the EEG tell you?

The EEG sums the electrical activity of neurons.  If you see an increase in amplitude in a particular EEG band - say 12-15 hz, in simple terms, it means more neurons are doing the same thing at the same time.

Since the EEG is by definition sum of electrical potential of neuronal activity, the only way to see changes occur in the EEG is when many neurons shift towards being more ready to fire (excitatory) or to not fire (inhibitory) at the same time. 

It's electro-chemical reactions that in fact produce neurotransmitters and that produce the EEG.   Electrochemistry and neurochemistry are opposite sides of the same coin. When a neuron finally fires, the firing releases neurotransmitters.  These go into to the synapses between neurons and may bind to receptor sites for many other neurons. It's firing in essence produces messages that will influence whether other neurons will fire.  Each neuron gathers information from other neurons which help it determine whether it's going to fire or be inhibited from firing.  Medications often target those neurotransmitters.  So it should be expected that many medications do affect the EEG.

It's estimated a neuron can influence up to 1 million additional neurons.  Why is that important?  When you place an electrode over a site on the head, it's probably only covering about 100,000 neurons.  So are you only training 100,000 neurons right under the electrode?  Absolutely not. Each of those neurons affect huge number of other neurons.  The neurons it affects may be local or at a much further distance.  The neurons under the electrodes influence other neurons to fire or not fire, which in turn encourage others to do the same.  The pathways can influence areas all over the brain and body.  Remember that many nerves are bundles of axons that are the end point of neurons in the brain.

There are well-documented feedback loops between neurons at the cortex and the thalamus (thalamo-cortical loop).  This thalamus has rich connections down to the brain stem.

It's all about feedback loops in the brain

When someone starts to change their EEG, they are influencing feedback loops that connect throughout the brain.  Often, the effect of training the EEG at just one site has profound effects on how well someone maintains an alert and awake state.  That goes far beyond the effect of just the neurons under the electrode.

Or, it allows someone to fall asleep more quickly or wake or more easily.  Those are system arousal functions. It's the brain stem and reticular activating system that are well known in neurophysiology.  The brain stem plays the primary role of how a person maintains an alert and awake state.

Neurofeedback rapidly affects an alert or awake state.  It's clear that the feedback loops being impacted go from the cortex down to the brainstem and back.  Those loops - which are well known in neuroscience, are the only explanation we know of how training 100,000 neurons can have such a profound system wide effect.   It would be nice to see this proven out in sophisticated imaging studies.  But there is no other possible explanation for the process.  We've discussed it with very knowledgeable neuroscientists.  They agree these pathways are being influenced with changes in the EEg.

It's because all those neurons constantly talk to each other and are influenced by each other that neurofeedback  works.

Additional technical explanation.  Each neuron has dendrites – which gather up information from other neurons.  These dendrites gather excitatory or inhibitory information.  The neuron computes the total.  For example – lets say the neuron receives 500 excitatory messages (neurotransmitters) from other neurons and 800 inhibitory messages from other neurons.  In essence, the neuron adds up the votes. With more inhibitory "votes" or messages, the neuron's charge would be lowered and would be less likely to fire.  But if the situation is reversed, the neuron will decide to fire, that firing will send an impulse down it’s axon, which is it’s single output process.  When the impulse reaches the end of the axon, it releases neurotransmitter molecules, such as serotonin or dopamine.  These float across the synaptic cleft and bind to receptors on the next neuron.  (This axon could communicated up to 1 million neurons.  Which means, that once it fires, it could tell 1 million neurons that they should fire.)