14 research outputs found
Concept-modulated model-based offline reinforcement learning for rapid generalization
The robustness of any machine learning solution is fundamentally bound by the
data it was trained on. One way to generalize beyond the original training is
through human-informed augmentation of the original dataset; however, it is
impossible to specify all possible failure cases that can occur during
deployment. To address this limitation we combine model-based reinforcement
learning and model-interpretability methods to propose a solution that
self-generates simulated scenarios constrained by environmental concepts and
dynamics learned in an unsupervised manner. In particular, an internal model of
the agent's environment is conditioned on low-dimensional concept
representations of the input space that are sensitive to the agent's actions.
We demonstrate this method within a standard realistic driving simulator in a
simple point-to-point navigation task, where we show dramatic improvements in
one-shot generalization to different instances of specified failure cases as
well as zero-shot generalization to similar variations compared to model-based
and model-free approaches
Context Meta-Reinforcement Learning via Neuromodulation
Meta-reinforcement learning (meta-RL) algorithms enable agents to adapt
quickly to tasks from few samples in dynamic environments. Such a feat is
achieved through dynamic representations in an agent's policy network (obtained
via reasoning about task context, model parameter updates, or both). However,
obtaining rich dynamic representations for fast adaptation beyond simple
benchmark problems is challenging due to the burden placed on the policy
network to accommodate different policies. This paper addresses the challenge
by introducing neuromodulation as a modular component to augment a standard
policy network that regulates neuronal activities in order to produce efficient
dynamic representations for task adaptation. The proposed extension to the
policy network is evaluated across multiple discrete and continuous control
environments of increasing complexity. To prove the generality and benefits of
the extension in meta-RL, the neuromodulated network was applied to two
state-of-the-art meta-RL algorithms (CAVIA and PEARL). The result demonstrates
that meta-RL augmented with neuromodulation produces significantly better
result and richer dynamic representations in comparison to the baselines
Sliced Cramer synaptic consolidation for preserving deeply learned representations
Deep neural networks suffer from the inability to preserve the learned data representation (i.e., catastrophic forgetting) in domains where the input data distribution is non-stationary, and it changes during training. Various selective synaptic
plasticity approaches have been recently proposed to preserve network parameters, which are crucial for previously learned tasks while learning new tasks.
We explore such selective synaptic plasticity approaches through a unifying lens
of memory replay and show the close relationship between methods like Elastic
Weight Consolidation (EWC) and Memory-Aware-Synapses (MAS). We then propose a fundamentally different class of preservation methods that aim at preserving the distribution of the network’s output at an arbitrary layer for previous tasks
while learning a new one. We propose the sliced Cramer distance as a suitable ´
choice for such preservation and evaluate our Sliced Cramer Preservation (SCP) ´
algorithm through extensive empirical investigations on various network architectures in both supervised and unsupervised learning settings. We show that SCP
consistently utilizes the learning capacity of the network better than online-EWC
and MAS methods on various incremental learning tasks
A Domain-Agnostic Approach for Characterization of Lifelong Learning Systems
Despite the advancement of machine learning techniques in recent years,
state-of-the-art systems lack robustness to "real world" events, where the
input distributions and tasks encountered by the deployed systems will not be
limited to the original training context, and systems will instead need to
adapt to novel distributions and tasks while deployed. This critical gap may be
addressed through the development of "Lifelong Learning" systems that are
capable of 1) Continuous Learning, 2) Transfer and Adaptation, and 3)
Scalability. Unfortunately, efforts to improve these capabilities are typically
treated as distinct areas of research that are assessed independently, without
regard to the impact of each separate capability on other aspects of the
system. We instead propose a holistic approach, using a suite of metrics and an
evaluation framework to assess Lifelong Learning in a principled way that is
agnostic to specific domains or system techniques. Through five case studies,
we show that this suite of metrics can inform the development of varied and
complex Lifelong Learning systems. We highlight how the proposed suite of
metrics quantifies performance trade-offs present during Lifelong Learning
system development - both the widely discussed Stability-Plasticity dilemma and
the newly proposed relationship between Sample Efficient and Robust Learning.
Further, we make recommendations for the formulation and use of metrics to
guide the continuing development of Lifelong Learning systems and assess their
progress in the future.Comment: To appear in Neural Network
Dose-Dependent Effects of Closed-Loop tACS Delivered During Slow-Wave Oscillations on Memory Consolidation
Sleep is critically important to consolidate information learned throughout the day. Slow-wave sleep (SWS) serves to consolidate declarative memories, a process previously modulated with open-loop non-invasive electrical stimulation, though not always effectively. These failures to replicate could be explained by the fact that stimulation has only been performed in open-loop, as opposed to closed-loop where phase and frequency of the endogenous slow-wave oscillations (SWOs) are matched for optimal timing. The current study investigated the effects of closed-loop transcranial Alternating Current Stimulation (tACS) targeting SWOs during sleep on memory consolidation. 21 participants took part in a three-night, counterbalanced, randomized, single-blind, within-subjects study, investigating performance changes (correct rate and F1 score) on images in a target detection task over 24 h. During sleep, 1.5 mA closed-loop tACS was delivered in phase over electrodes at F3 and F4 and 180° out of phase over electrodes at bilateral mastoids at the frequency (range 0.5–1.2 Hz) and phase of ongoing SWOs for a duration of 5 cycles in each discrete event throughout the night. Data were analyzed in a repeated measures ANOVA framework, and results show that verum stimulation improved post-sleep performance specifically on generalized versions of images used in training at both morning and afternoon tests compared to sham, suggesting the facilitation of schematization of information, but not of rote, veridical recall. We also found a surprising inverted U-shaped dose effect of sleep tACS, which is interpreted in terms of tACS-induced faciliatory and subsequent refractory dynamics of SWO power in scalp EEG. This is the first study showing a selective modulation of long-term memory generalization using a novel closed-loop tACS approach, which holds great potential for both healthy and neuropsychiatric populations
Supplementary information files for Context meta-reinforcement learning via neuromodulation
Supplementary files for article Context meta-reinforcement learning via neuromodulation
Meta-reinforcement learning (meta-RL) algorithms enable agents to adapt quickly to tasks from few samples in dynamic environments. Such a feat is achieved through dynamic representations in an agent’s policy network (obtained via reasoning about task context, model parameter updates, or both). However, obtaining rich dynamic representations for fast adaptation beyond simple benchmark problems is challenging due to the burden placed on the policy network to accommodate different policies. This paper addresses the challenge by introducing neuromodulation as a modular component to augment a standard policy network that regulates neuronal activities in order to produce efficient dynamic representations for task adaptation. The proposed extension to the policy network is evaluated across multiple discrete and continuous control environments of increasing complexity. To prove the generality and benefits of the extension in meta-RL, the neuromodulated network was applied to two state-of-the-art meta-RL algorithms (CAVIA and PEARL). The result demonstrates that meta-RL augmented with neuromodulation produces significantly better result and richer dynamic representations in comparison to the baselines. </p
Context meta-reinforcement learning via neuromodulation
Meta-reinforcement learning (meta-RL) algorithms enable agents to adapt quickly to tasks from few samples in dynamic environments. Such a feat is achieved through dynamic representations in an agent’s policy network (obtained via reasoning about task context, model parameter updates, or both). However, obtaining rich dynamic representations for fast adaptation beyond simple benchmark problems is challenging due to the burden placed on the policy network to accommodate different policies. This paper addresses the challenge by introducing neuromodulation as a modular component to augment a standard policy network that regulates neuronal activities in order to produce efficient dynamic representations for task adaptation. The proposed extension to the policy network is evaluated across multiple discrete and continuous control environments of increasing complexity. To prove the generality and benefits of the extension in meta-RL, the neuromodulated network was applied to two state-of-the-art meta-RL algorithms (CAVIA and PEARL). The result demonstrates that meta-RL augmented with neuromodulation produces significantly better result and richer dynamic representations in comparison to the baselines.</p
The Benefits of Closed-Loop Transcranial Alternating Current Stimulation on Subjective Sleep Quality
Background: Poor sleep quality is a common complaint, affecting over one third of people in the United States. While sleep quality is thought to be related to slow-wave sleep (SWS), there has been little investigation to address whether modulating slow-wave oscillations (SWOs) that characterize SWS could impact sleep quality. Here we examined whether closed-loop transcranial alternating current stimulation (CL-tACS) applied during sleep impacts sleep quality and efficiency. Methods: CL-tACS was used in 21 participants delivered at the same frequency and in phase with endogenous SWOs during sleep. Sleep quality was assessed in the morning following either verum or sham control stimulation during sleep, with order counterbalanced within participants. Results: Higher sleep quality and efficiency were found after verum stimulation nights compared to control. The largest effects on sleep quality were found immediately following an adaptation night in the laboratory for which sleep quality was reduced. Conclusions: Applying CL-tACS at the same frequency and phase as endogenous SWOs may offer a novel method to improve subjective sleep quality after a night with poor quality sleep. CL-tACS might be helpful for increasing sleep quality and efficiency in otherwise healthy people, and in patients with clinical disorders that involve sleep deficits