arXiv subjects

Elia Turner

Publications and source records attributed to Elia Turner.

3 recordsLinked to original sources

arXiv2025

Models of attractor dynamics in the brain

Attractor dynamics are a fundamental computational motif in neural circuits, supporting diverse cognitive functions through stable, self-sustaining patterns of neural activity. In these lecture notes, we review four key examples that demonstrate how autoassociative neural network models can elucidate the computational mechanisms underlying attractor-based information processing in biological neural systems performing cognitive functions. Drawing on empirical evidence, we explore hippocampal spatial representations, visual classification in the inferotemporal cortex, perceptual adaptation and priming, and working-memory biases shaped by sensory history. Across these domains, attractor network models reveal common computational principles and provide analytical insights into how experience shapes neural activity and behavior. Our synthesis underscores the value of attractor models as powerful tools for probing the neural basis of cognition and behavior.

q-bio.NC↗

arXiv2021

Charting and navigating the space of solutions for recurrent neural networks

Recurrent Neural Networks (RNNs) were recently successfully used to model the way neural activity drives task-related behavior in animals, operating under the implicit assumption that the obtained solutions are universal. Observations in both neuroscience and machine learning challenge this assumption. Animals can approach a given task with a variety of strategies, and training machine learning algorithms introduces the phenomenon of underspecification. These observations imply that every task is associated with a space of solutions. To date, the structure of this space is not understood, limiting the approach of comparing RNNs with neural data. Here, we characterize the space of solutions associated with various tasks. We first study a simple two-neuron network on a task that leads to multiple solutions. We trace the nature of the final solution back to the network's initial connectivity and identify discrete dynamical regimes that underlie this diversity. We then examine three neuroscience-inspired tasks: Delayed and interval discrimination, and Time reproduction. For each task, we find a rich set of solutions. Variability can be found directly in the neural activity of the networks, and additionally by testing the trained networks' ability to extrapolate, as a perturbation to a system often reveals hidden structure. Furthermore, we relate extrapolation patterns to specific dynamical objects and effective algorithms found by the networks. We introduce a tool to derive the reduced dynamics of networks by generating a compact directed graph describing the essence of the dynamics with regards to behavioral inputs and outputs. Using this representation, we can partition the solutions to each task into a handful of types and partially predict them from neural features. Our results shed light on the concept of the space of solutions and its uses in Machine learning and in Neuroscience.

q-bio.NC↗

arXiv2019

Sparse Matrix Multiplication and Triangle Listing in the Congested Clique Model

We multiply two $n \times n$ matrices $S,T$ over semirings in the Congested Clique model, where $n$ fully connected nodes communicate synchronously using $O(\log n)$-bit messages, within $O(nz(S)^{1/3} nz(T)^{1/3}/n + 1)$ rounds of communication, where $nz(A)$ denotes the number of non-zero elements in a matrix $A$. By leveraging the sparsity of the input matrices, our algorithm greatly reduces communication compared with general algorithms [Censor-Hillel et al., PODC 2015], improving upon the state-of-the-art for matrices with $o(n^2)$ non-zero elements. Our algorithm exhibits the additional strength of surpassing previous solutions also when only one matrix is sparse. This allows efficiently raising a sparse matrix to a power greater than 2. As applications, we speed up 4-cycle counting and APSP in sparse graphs. Our algorithmic contribution is a new \emph{deterministic} method of restructuring the input matrices in a sparsity-aware manner, which assigns each node with element-wise multiplication tasks that are not necessarily consecutive but are balanced, yielding communication-efficient multiplication. Moreover, this new deterministic method for restructuring matrices may be used to restructure the adjacency matrix of input graphs, enabling faster solutions for graph related problems. As an example, we present a new deterministic algorithm which solves the triangle listing problem in $O(m/n^{5/3} + 1)$ rounds, a complexity that was previously obtained by a \emph{randomized} algorithm [Pandurangan et al., SPAA 2018] and matches the lower bound of $\tildeΩ(n^{1/3})$ when $m=n^2$ of [Izumi and Le Gall, PODC 2017, Pandurangan et al., SPAA 2018]. Our triangle listing algorithm implies triangle counting with the same complexity of $O(m/n^{5/3} + 1)$ rounds, which is a \emph{cubic} improvement over the previous $O(m^2/n^3)$-round algorithm [Dolev et al., DISC 2012].

cs.DS↗