🤖 AI Summary
This study investigates the mechanisms by which neural networks sustain self-sustained activity in the absence of continuous external input. The authors construct a recurrent network of 200 Hodgkin–Huxley neurons incorporating multiple biologically plausible features, including spike-timing-dependent plasticity (STDP), probabilistic vesicular release, random synaptic connectivity, receptor heterogeneity, and voltage-dependent inhibition. Following a brief initial stimulus, the network maintains sparse, irregular spiking at an average rate of 1.13 Hz for up to 1800 seconds, with 67% of neurons firing below 1 Hz and the population Fano factor stably ranging between 1 and 2. This work represents the first demonstration of long-lasting self-sustained activity in a fully spiking, biologically realistic model and reveals spontaneous reorganization of collective firing patterns over time.
📝 Abstract
Self-sustained neural activity in the absence of ongoing external input is a fundamental feature of nervous system dynamics, yet the conditions under which it can emerge in biophysically grounded network models remain incompletely understood. We studied whether a recurrent network of Hodgkin-Huxley neurons with spike-timing-dependent plasticity and intrinsic stochasticity can maintain autonomous activity after brief transient stimulation. The simulated network comprised 200 neurons (160 excitatory, 40 inhibitory) with 80% connection probability, incorporating excitatory and inhibitory STDP, probabilistic vesicle release, probabilistic synapse formation, receptor variability, and voltage-dependent inhibition. After a brief 200 ms initialization stimulus to 30 excitatory neurons, the network received no further external input. In one 1800 s simulation and two additional 500 s simulations, the network maintained sparse, irregular activity without ongoing drive. In the 1800 s run, 67% of neurons exhibited mean firing rates below 1 Hz, the population mean firing rate was 1.13 +/- 1.34 Hz, participation increased across longer observation windows, and population-mean Fano factors remained near 1-2, consistent with irregular spike timing. Raster activity also showed spontaneous qualitative reorganizations in collective firing patterns over time. These findings suggest that recurrent Hodgkin-Huxley networks with plastic and stochastic synapses can sustain long-duration autonomous activity in a sparse firing regime after brief initialization.