Neurobiology Reviews: Does the Brain Have Prediction-Error Neurons? NO
There is a recent paper in JNeurosci, Stimulus-specific prediction error neurons in mouse auditory cortex, where the authors stated that ‘Our data reveal that the auditory cortex learns to suppress responses to self-generated sounds along multiple acoustic dimensions simultaneously. We identify a distinct population of auditory cortex neurons that are not responsive to passive sounds or to the expected sound but that encode prediction errors. These prediction error neurons are abundant only in animals with a learned motor-sensory expectation, and encode one or two specific violations rather than a generic error signal. Together, these findings reveal that cortical predictions about self-generated sounds have specificity in multiple simultaneous dimensions and that cortical prediction error neurons encode specific violations from expectation.”
Simply, some neurons were silent when things went as expected, but were activated when they didn’t. This observation is consistent with the predictive coding and processing phenomenon in neurobiology, which states that the brain is constantly generating predictions with an internal model, which it often updates, when there is an error in prediction.
How?
In spite of the numerous studies that have presented prediction/error in neuroscience, there is no explicit mechanism to show how it occurs. Neurons silent or firing are vague generalities that don’t describe how.
When neurons fire or are activated, it means electrical impulses are passing through, when they are silent, it roughly implies — no electrical impulses. The important question becomes, for what the brain seems to predict or correct, what is the role of electrical impulses?
Since some neurons were silent when things went as expected, it means that there were no distributions of electrical impulses to them, by others.
The authors said some neurons were activated by prediction error. This means that electrical impulses of these activated neurons are in a set.
Also, electrical impulses are often preceded or succeeded by chemical impulses. This means that the chemical impulses are also in sets.
Since firing or activation involves electrical impulses, which also involves chemical impulses, how do sets of impulses organize information to relate with the external world?
There is the concept of reward prediction error, about dopamine neurons.
There is a paper in PNAS, Understanding dopamine and reinforcement learning: The dopamine reward prediction error hypothesis, stating a definition, “reward prediction error is the difference between a weighted average of past rewards and the reward that has just been experienced. When those are the same, there is no error, and the system does not learn.”
It stated another definition, “reward prediction error term should be viewed as the difference between one’s rational expectations of all future rewards and any information (be it an actual reward or a signal that a reward is coming up) that leads to a revision of expectations. If, for example, we predict that we will receive one reward every 1 min for the next 10 min and a visual cue indicates that, instead of these 10 rewards, we will receive one reward every 1 min for 11 min, then a prediction error exists when the visual cue arrives, not 11 min later when the final (and at that point, fully expected) reward actually arrives.”
The paper explained that, “Three groups of dopamine secreting neurons send axons along long-distance trajectories that influence brain activity in many areas: the A8 and A10 groups of the ventral tegmental area (VTA) and the A9 group of the substantia nigra pars compacta (SNc).”
Since dopamine secreting neurons send fibers to many parts of the brain, when they influence brain activity [or chemical impulses, then electrical impulse actions] there, shouldn’t they be seen as part of the collective in those areas?
Simply, when dopamine contributes elsewhere, isn’t it part of a formation with other chemical impulses, rather than isolated? If it is not isolated, and it is part of what holds information, how does a set of chemical impulses organize information or prepare experiences?
Conceptually, in a set, chemical impulses get rationed or filled into a formation. This formation gets distributed, as electrical impulses, continuing the process, across clusters of neurons and circuits, or arrays of loops.
It is hypothesized that loops or sets of chemical impulses often have a formation. This formation is how information is organized. The experience of reward though ascribed to dopamine, could be a formation of dopamine and other chemical impulses. For example, JKL, where dopamine, as a ration, could be K, but has the most percentage for the rewarding experience. Formation is also how memory is proposed to be held, including emotions, modulations and feelings. It is proposed that, in a set, electrical impulses act like they are interacting with chemical impulses, not just ‘triggering the release’ of chemical impulses.
It is established in brain science that electrical impulses leap from node to node, going faster, in myelinated axons, in what is called saltatory conduction.
It is theorized here that in a set of neurons, some electrical impulses break off to go ahead of others, to ‘interact’ with [or trigger the release of] chemical impulses, like they had before. This early-split or go-before is what explains the observation of predictive coding or processing. If the input matches, no follow-up. If not, the follow-up or incoming ones go in another direction.
This means that in the bundle of electrical impulses, some go ahead of others to drive chemical impulses like before, if the input matches, distribution or shares for processing continues in another direction, if not, the remaining part of the electrical impulses in the bundle is called up to interact differently, making its distribution go in other directions from what that of ‘the match’ would have been.
For example, in reading something, seeing the letters wed, first, for someone may indicate a day of the week, or a coupling event for others, if it matches with the day of the week, the electrical impulses are distributed, after interaction with chemical impulses, to continue reading the sentence. If it is not for the day of the week, the incoming one [or follow-up] takes off, interacting differently and distributed in another direction to match with a coupling event.
It similarly applies to a knock on the door at a particular time and a delivery of cake. If — at other times — it matches, electrical impulses interact with the formation of reward and the follow-up stays away. If it is not cake, the follow-up interacts differently, going in another direction, whose distribution may include towards the formation of disappointment.
E = E2 + E1
E1 + C1
E2 + C2
Where
· E1 is the go before of electrical impulse
· E2 is the follow-up of electrical impulse if E1 does not match
· C1 is the chemical impulse formation, for the interaction like prior
· C2 is the chemical impulse formation, for the subsequent interaction
The observation of prediction and error are processes of splits, interaction and distribution of electrical and chemical impulses.
There are no prediction error neurons in the brain. Distribution of electrical signals in another direction, or through certain neurons, when the early split does not match, does not mean that there are neurons just for prediction error. Also, it is not prediction or error, electrical impulses are in loop and early-split is a feature, so is rationing for formation, as well as distribution or shares.
There is another recent paper in Neuron, Neuronal activity drives IGF2 expression from pericytes to form long-term memory, stating that, “Learning significantly increased pericytic Igf2 expression in the hippocampus, particularly in the highly vascularized stratum lacunosum moleculare and stratum moleculare layers of the dentate gyrus. Igf2 increases required neuronal activity. Regulated hippocampal Igf2 knockout in pericytes, but not in fibroblasts or neurons, impaired long-term memories and blunted the learning-dependent increase of neuronal immediate early genes (IEGs). Thus, neuronal activity-driven signaling from pericytes to neurons via IGF2 is essential for long-term memory.”
Simply, pericytes produce IGF2 whose surge is associated with long-term memory. There are several assistants across the brain, for the mind, but the human mind, conceptually, is the collection of all the electrical and chemical impulses of nerve cells, with their features, interactions, loops and arrays.
Everything else is the brain, just impulses are the mind. Impulses are involved in all functions, including thoughts, movements, regulation, feeling, emotion, memory and so forth. Blood vessels, glial cells, oxygen, glucose, genes, nerve cells and so forth, as part of the brain all aid impulses, but the core of functions is impulses, their features and interactions.
There could be applicable cases to explore pericytes for degenerative diseases, but the features, interactions of impulses would have to lead the way, in setting up the architecture for how information is organized and projection of CNS pathology.
