Single spikes drive sequential propagation and routing of activity in a cortical network

Abstract

Single spikes can trigger repeatable firing sequences in cortical networks. The mechanisms that support reliable propagation of activity from such small events and their functional consequences remain unclear. By constraining a recurrent network model with experimental statistics from turtle cortex, we generate reliable and temporally precise sequences from single spike triggers. We find that rare strong connections support sequence propagation, while dense weak connections modulate propagation reliability. We identify sections of sequences corresponding to divergent branches of strongly connected neurons which can be selectively gated. Applying external inputs to specific neurons in the sparse backbone of strong connections can effectively control propagation and route activity within the network. Finally, we demonstrate that concurrent sequences interact reliably, generating a highly combinatorial space of sequence activations. Our results reveal the impact of individual spikes in cortical circuits, detailing how repeatable sequences of activity can be triggered, sustained, and controlled during cortical computations.

Extreme distributions in the preconfigured developing brain

“…It has been suggested that extreme distributions of neural parameters might have several useful properties 1,2,10,27 . For instance, the log-normal distribution of synaptic sizes might promote the formation and propagation of neuronal sequences 10,28 , while at the same time optimizing storage capacity 27 . Moreover, the extreme distribution of firing rates might result in an environment with an optimal balance between a large amount of “specialist” neurons complemented by few “generalists”.…”

The purpose of weights in excitable brain networks

“…A number of recent simulation studies have started to highlight general principles of spike communication. Overall, these studies have demonstrated that spike transmission occurs mostly along strong and sparse links [62,71,31,67].…”

“…The heavy-tailed distributions of synaptic weights enhance the dynamical repertoire of the system, and increase its response speed and stability [41,62,71,67]. However, given the predominance of strong links in communication, it remains unclear whether weak links are of functional importance or whether they can be discarded without noticeable consequences.…”

Multi-Scale Spiking Network Model of Human Cerebral Cortex

“…Due to the stochastic input to the network and its sensitivity to small perturbations, the triggered spike sequences are not fixed but will differ between trials. Future work may investigate whether subnetworks with strong synapses, such as those modeled for turtle cortex by Riquelme et al (2023), can support repeatable and precisely timed spike sequence in the human cortical network.…”