Long-term potentiation
Siegfried Othmer
Long-term potentiation
In many a lecture in times past, when it came to specify the mechanism by which learning was taking place at the level of the neuron, the answer given was ‘long-term potentiation,’ and then the discussion would move on to other matters. From the very beginning this response struck me as entirely unsatisfactory.
I am reminded of Skinner’s accusation that the use of ‘placebo’ in a scientific discussion served more to terminate inquiry than to promote it. The placebo model was a shape-shifter that was whatever it needed to be in the situation at hand, and it was pointless to inquire further. The same seemed to be going on here. Everybody in the room knew that it would not be worthwhile to inquire further into just how long-term potentiation actually addressed the problem at hand.
We are dealing here the persistent strengthening of synaptic coupling based on changes in patterns of activity, facilitating a lasting increase in signal transmission between two neurons. Missing from the discussion is the obligatory contingency of such enhancement on the prevailing context. The enhanced transmission had to be available only selectively.
Bringing context into the mix, however, involves a rather large variable space. What could possibly accommodate a repository of such large dimensionality? Consider the astrocyte network, which chaperones our excitatory glutamate synapses and modulates their level of activation on longer timescales. This network offers situational awareness on a larger spatial scale, and with a longer time horizon, than that of a single neuron.
Seen in this more encompassing perspective, neurofeedback operating on the neuronal dance mediates the training of astrocyte networks as the repository of the critical information bearing on neuronal activation and excitability. ILF Neurofeedback gives this task its deserved priority by zeroing in on the frequency domain in which astrocytes command the stage. This is the domain of core state regulation first and foremost, the realm of the resting state networks. Finally, ultra-low frequency training is deemed to target homeostatic mechanisms that govern homeodynamics in the ILF regime.
Neurofeedback in the EEG range also serves to train the astrocyte network. With endogenous neuromodulation, it does so with with emphasis on state regulation, whereas with operant conditioning it does so in an event-related manner that brings the engaged brain and functional particularity into the picture. Hence, there is a natural complementarity between endogenous neuromodulation and operant conditioning on the one hand, and between training in the ILF and the EEG range on the other.
Siegfried Othmer, Ph.D.
Chief Scientist, The EEG Institute
Los Angeles