Efficient Learning of Sequences in Structured Recurrent Networks: A Biologically Plausible Model for Cortical Sequence Learning

Keskeiset käsitteet

A biologically plausible model for learning complex, non-Markovian sequences in recurrent networks of structured neurons, using a fully local, always-on plasticity rule that enables efficient and robust sequence learning.

Tiivistelmä

The content presents a framework for learning sequences in recurrent networks of structured neurons, inspired by the interplay between development and learning in the cortex. The key aspects are:

The network consists of two populations of neurons - an output population and a latent population. During early development, a sparse, random scaffold of somato-somatic connections is formed between the neurons.

After the development phase, the network learns a target sequence by adapting the somato-dendritic synapses using a local, error-correcting plasticity rule. The somatic scaffold transports the teacher's nudging signal to the dendritic compartments, which then use this signal to update the synaptic weights.

This process leads to the formation of a robust dynamical attractor in the latent population that can generate the desired output sequence independently of the external teacher.

The model is shown to be resource-efficient, allowing the learning of complex sequences using only a small number of neurons. It also demonstrates high robustness to various disturbances and parameter variations, making it a biologically plausible model of sequence learning in the brain.

The authors demonstrate the model's capabilities in a mock-up of birdsong learning, where the network learns and robustly reproduces a long, non-Markovian sequence (a sample of Beethoven's "Für Elise").

Tilastot

"Behavior can be described as a temporal sequence of actions driven by neural activity."
"To learn complex sequential patterns in neural networks, memories of past activities need to persist on significantly longer timescales than relaxation times of single-neuron activity."
"Our model is resource-efficient, enabling the learning of complex sequences using only a small number of neurons."
"We demonstrate these features in a mock-up of birdsong learning, in which our networks first learn a long, non-Markovian sequence (a sample of Beethoven's "Für Elise") that they can then reproduce robustly despite external disturbances."

Lainaukset

"By applying a fully local, always-on plasticity rule we are able to learn complex sequences in a recurrent network comprised of two populations."
"Importantly, our model makes efficient use of its neuronal resources, allowing the learning of complex sequences with only a small number of neurons."
"We show that the attractor dynamics imprinted into our latent population via our local learning rule are able to withstand strong external disturbances."

Tärkeimmät oivallukset

ELiSe: Efficient Learning of Sequences in Structured Recurrent Networks

by Laur... klo arxiv.org 09-30-2024

https://arxiv.org/pdf/2402.16763.pdf

Syvällisempiä Kysymyksiä

How could this model be extended to handle more complex, hierarchical sequence structures, such as those observed in human language or music?

To extend the model for handling more complex, hierarchical sequence structures, such as those found in human language or music, several modifications could be implemented. First, the architecture could be expanded to include multiple layers of recurrent networks, each responsible for different levels of abstraction. For instance, lower layers could focus on phonetic or rhythmic patterns, while higher layers could capture syntactic or semantic relationships. This hierarchical structure would allow the model to learn and represent sequences at varying levels of complexity, similar to how human language is structured.
Additionally, incorporating attention mechanisms could enhance the model's ability to focus on relevant parts of the input sequence while ignoring less pertinent information. This would be particularly beneficial in processing long sequences, where certain elements may be more critical for understanding context or meaning. Furthermore, integrating temporal hierarchies, where different time scales are represented, could help the model learn dependencies that span across longer durations, akin to musical phrases or sentences in language.
Lastly, the model could benefit from incorporating feedback loops that allow for the dynamic adjustment of synaptic weights based on the hierarchical context, enabling it to adaptively learn from the structure of the sequences it encounters. This would enhance its robustness and flexibility in learning complex, structured sequences.

What are the potential limitations of this approach, and how could it be further improved to address them?

Despite its advantages, the proposed model has several potential limitations. One significant limitation is its reliance on local plasticity rules, which may restrict the model's ability to learn global patterns that require coordination across distant neurons. This could hinder its performance in tasks that involve complex interactions between different parts of the network.
Another limitation is the model's dependency on the initial scaffold of connections. If the initial configuration is not conducive to learning the desired sequences, the model may struggle to adapt effectively. Additionally, while the model demonstrates robustness to disturbances, it may still be vulnerable to specific types of noise or disruptions that could disrupt the learning process.
To address these limitations, future improvements could include the integration of global learning mechanisms that allow for the adjustment of weights across the entire network, rather than relying solely on local updates. This could enhance the model's ability to capture global dependencies and improve its overall learning capacity. Furthermore, implementing adaptive scaffolding techniques that can evolve based on the learning context could help optimize the initial configuration for better performance.
Lastly, exploring hybrid models that combine the strengths of this approach with other learning paradigms, such as reinforcement learning or unsupervised learning, could provide a more comprehensive framework for tackling complex sequence learning tasks.

What insights from this model of sequence learning in the cortex could be applied to the development of more efficient and robust artificial sequence learning systems?

The insights gained from this model of sequence learning in the cortex can significantly inform the development of more efficient and robust artificial sequence learning systems. One key takeaway is the importance of local learning rules that allow for continuous adaptation based on local error signals. This principle can be applied to artificial neural networks to enhance their ability to learn from real-time data, making them more responsive to changes in input patterns.
Additionally, the model's emphasis on resource efficiency highlights the potential for developing smaller, more compact neural networks that can still achieve high performance. This could lead to advancements in edge computing, where computational resources are limited, yet the need for effective sequence learning remains critical.
The concept of a developmental scaffold, where initial connections are sparse and evolve over time, can also be translated into artificial systems. By starting with a simple architecture and allowing it to grow and adapt based on the learning task, artificial systems could achieve greater flexibility and robustness.
Moreover, the model's ability to recover from disturbances suggests that incorporating mechanisms for resilience and fault tolerance in artificial systems could enhance their reliability in real-world applications. This could involve designing networks that can maintain performance despite noise or unexpected changes in input.
Overall, the principles of local plasticity, resource efficiency, adaptive scaffolding, and resilience derived from this model can guide the design of next-generation artificial sequence learning systems, making them more aligned with biological processes and better suited for complex, dynamic environments.