Recurrent Network Models of Sequence Generation and Memory

• Published in: Neuron (Cambridge, Mass.) Vol. 90; no. 1; pp. 128 - 142
• Main Authors: Rajan, Kanaka, Harvey, Christopher D., Tank, David W.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 06.04.2016; Elsevier Limited
• Subjects: Algorithms; Animals; Behavior; Brain research; Choice Behavior - physiology; Decision Making; Investigations; Memory, Short-Term - physiology; Mice; Models, Neurological; Neural Pathways - physiology; Neurons; Neurons - physiology; Parietal Lobe - physiology; Stem cells
• ISSN: 0896-6273; 1097-4199
• DOI: 10.1016/j.neuron.2016.02.009

Sequential activation of neurons is a common feature of network activity during a variety of behaviors, including working memory and decision making. Previous network models for sequences and memory emphasized specialized architectures in which a principled mechanism is pre-wired into their connectivity. Here we demonstrate that, starting from random connectivity and modifying a small fraction of connections, a largely disordered recurrent network can produce sequences and implement working memory efficiently. We use this process, called Partial In-Network Training (PINning), to model and match cellular resolution imaging data from the posterior parietal cortex during a virtual memory-guided two-alternative forced-choice task. Analysis of the connectivity reveals that sequences propagate by the cooperation between recurrent synaptic interactions and external inputs, rather than through feedforward or asymmetric connections. Together our results suggest that neural sequences may emerge through learning from largely unstructured network architectures. •Sequences emerge in random networks by modifying a small fraction of their connections•Analysis reveals new circuit mechanism for input-dependent sequence propagation•Sequential activation may provide a dynamic mechanism for short-term memory Rajan et al. show that neural sequences similar to those observed during memory-based decision-making tasks can be generated by minimally structured networks. Sequences may effectively mediate the short-term memory engaged in these tasks.