Embedding Robust Multi-Timescale Computation in Neuromorphic Hardware using Distributed Representations

Core Concepts

Distributed representations using high-dimensional random vectors can be leveraged to embed robust multi-timescale dynamics into attractor-based recurrent spiking neural networks, enabling the implementation of arbitrary finite state machines in neuromorphic hardware.

Abstract

The paper presents a method for embedding arbitrary finite state machines (FSMs) into recurrent spiking neural networks (RSNNs) using the principles of vector symbolic architectures (VSAs). The key insights are:

Each state of the FSM is represented by a high-dimensional random vector (hypervector) that serves as a fixed-point attractor in the RSNN dynamics. The hypervectors follow a sparse block structure, where only one neuron in each block is active at a time.

Transition dynamics between attractor states are encoded by superimposing additional heteroassociative outer-product terms in the recurrent weight matrix. These terms are bound to the input hypervectors, and become effective when the corresponding input is applied as a mask, triggering the transition.

This approach enables the robust embedding of arbitrary state machines into RSNNs, without requiring fine-tuning or significant platform-specific optimization. It is validated through simulations with non-ideal weights, a closed-loop memristive hardware setup, and implementation on Intel's Loihi 2 neuromorphic chip.

The distributed and representation-invariant nature of VSAs allows the same high-level algorithm to be seamlessly deployed across different neuromorphic hardware platforms, advancing VSAs as a promising abstraction layer for cognitive algorithms in neuromorphic computing.

Stats

The network is able to perform the correct walk between attractor states for various input sequences, despite the presence of significant non-idealities in the synaptic weights.

Quotes

"Programming recurrent spiking neural networks (RSNNs) to robustly perform multi-timescale computation remains a difficult challenge."
"We embed finite state machines into the RSNN dynamics by superimposing a symmetric autoassociative weight matrix and asymmetric transition terms."
"This work demonstrates the effectiveness of VSA representations for embedding robust computation with recurrent dynamics into neuromorphic hardware, without requiring parameter fine-tuning or significant platform-specific optimisation."

Key Insights Distilled From

Distributed Representations Enable Robust Multi-Timescale Computation in Neuromorphic Hardware

by Madison Cott... at arxiv.org 05-03-2024

https://arxiv.org/pdf/2405.01305.pdf

Deeper Inquiries

How can the proposed VSA-based approach be extended to learn and adapt the embedded state machines in an online fashion, rather than programming them in a fixed manner

To extend the VSA-based approach to learn and adapt the embedded state machines in an online fashion, we can leverage Hebbian learning rules to update the synaptic weights based on the network's activity. By introducing plasticity mechanisms that adjust the weights in response to the network's performance and input patterns, the RSNN can dynamically adapt to changing requirements. This adaptation can be achieved by incorporating online learning rules that update the weights based on the network's response to inputs and desired output states. By continuously adjusting the synaptic strengths based on the network's performance, the RSNN can learn to transition between states more effectively and adapt to new tasks or patterns in real-time.

What are the limitations of the VSA framework in terms of the complexity of state machines that can be effectively embedded, and how could these limitations be addressed

The VSA framework, while powerful in its ability to represent complex data structures and algorithms, may have limitations in embedding highly intricate state machines with a large number of states and transitions. The complexity of the state machines that can be effectively embedded using VSAs may be limited by the dimensionality of the hypervectors used to represent states and transitions. To address these limitations, one approach could be to explore hierarchical or modular representations, where complex state machines are broken down into smaller, more manageable components that can be embedded using VSAs. Additionally, techniques such as dimensionality reduction or sparsity constraints can be employed to handle larger state machines within the VSA framework. By optimizing the representation and learning mechanisms, the VSA framework can potentially handle more complex state machines effectively.

Given the representation-invariant nature of VSAs, how could this approach be combined with other neuromorphic computing paradigms, such as reservoir computing or spiking neural networks with structural plasticity, to further enhance the flexibility and adaptability of the embedded cognitive algorithms

Combining the representation-invariant nature of VSAs with other neuromorphic computing paradigms, such as reservoir computing or spiking neural networks with structural plasticity, can enhance the flexibility and adaptability of the embedded cognitive algorithms. Reservoir computing can provide a rich dynamical substrate for processing information, while VSAs can offer a high-level abstract representation of cognitive algorithms. By integrating these approaches, the system can benefit from both the computational power of reservoir computing and the robustness and flexibility of VSAs. Additionally, incorporating structural plasticity in spiking neural networks can enable the network to adapt its connectivity based on the input patterns and task requirements, further enhancing the adaptability and efficiency of the cognitive algorithms embedded using VSAs. This integration can lead to more robust and flexible cognitive computing systems that can efficiently process complex information and adapt to changing environments.