A recent study suggests that electric fields might be used to inform working memory, allowing the brain to overcome representational drift or the inconsistency of individual neurons.
As the brain strives to keep information in mind, such as the list of groceries we need to buy on the way home, a new study suggests that the most consistent and reliable representation of that information is not the electrical activity of the individual neurons involved, but a general electric field they collectively produce.
In a new study, scientists at The Picower Institute for Learning and Memory at the University of London discovered that regardless of which specific neurons were involved, the overall electric field that was generated provided a stable and consistent signal of the information the animals were tasked to remember.
According to Dimitris Pinotsis, the conductor of an orchestra in which each neuron is a single musician in a sense, the field imposes itself on the neurons, as the conductor of an orchestra in which the neuron is identified. Even if the musicians change, the conductor continues to coordinate who is in the chairs for the same results.
Pinotsis, an associate professor at the University of London and a research affiliate at The Picower Institute at MIT, believes the brain can still function. Even after individual parts changes, the field ensures that the same output of the ensemble of neurons is achieved. The brain does not require individual neurons, only the conductor, the electric field.
Electric fields may therefore offer the brain a level of information representation and integration that is more abstract than the level of individual information encoded by single neurons or circuits, according to co-authors.
Even as information flows, the brain may employ this technique to perform on a more holistic level.
Measurements and mathematical modeling
Pinotsis and Miller investigated whether the electric field was stable and if it contained information related to the task. Using direct measurements of neural activity in animals as they performed a working memory game, and subsequent mathematical analysis to isolate and estimate the electric fields. It was not possible to just measure the electric fields directly, because the implanted electrode arrays they used measure neural activity individually and EEG electrodes that sit on the outside of the skull pick up patterns that are much too broad and general to reflect the specific information.
Miller said that each detail must be recorded and then taken the required half-step up mathematically.
During the game, animals were shown a dot on one of six positions on the edge of a screen that would then disappear. After a brief pause, they would then have to direct their eyes from the screens center to the position they just saw marked. Pinotsis and Miller were also recording the electrical activity of neurons on the brain surface.
Even when comparing rounds of the game where the position to be remembered was the same, there was a lot of noise. First of all, consistent with representational drift, the participation of individual neurons varied, but also the electrodes picked up activity non only from neurons involved in the task, but also from cells that were working on unrelated things.
Pinotsis used a mathematical technique to track correlated activity among neurons during the delay period, demonstrating their connectivity and thus the information flow among them. From there, he calculated the electric field their activity was producing around the brain surface they occupied.
As Miller shook hands, the fields were above the brain, but they were still above them.
The estimated electric fields demonstrated properties, indicating that they were more consistent than the underlying neural activity was when the direction to be remembered was the same. They differed in different but consistent ways based on which cued position was to be remembered in mind. This proved that when the scientists trained software called a decoder to guess which direction the animals were holding in mind, the decoder was comparatively better able to do it based on the electric fields than based on the neural activity.
Miller said this is not to say that the differences between individual neurons are significant unsettling noise. Even as people repeat the same tasks, thoughts and sensations of people and animals can vary minute by minute, resulting in different neurons behaving differently than they did just. The whole field, therefore, is always consistent in its representation.
This material, which we call representational drift or noise, may be real computations the brain is doing, but the reason is that at that next level up of electric fields, you may remove that drift and only have a signal, according to Miller.
The researchers claim that the field appears to be a means the brain can employ to sculpt information flow to achieve the desired result. By imposing that a particular field emerge, it directs the activity of the participating neurons.
One of the next questions the scientists are looking at is whether electric fields might be a way of controlling neurons?
We are now using this study to research whether information flows from the macroscale level of the electric field down to the microscale level of individual neurons, according to Pinotsis. We are now using this experiment to investigate whether a conductor''s style alters the way an individual member of an orchestra plays her instrument.
