Switching from tonic firing to bursting: implications on learning and memory

The brain's ability to learn and remember information relies on synaptic plasticity, the process by which neurons change the strength of their connections in response to their spiking activity. In parallel, the switch between different brain states, such as from active to quiet wakefulness, involves a transition in neuronal activity from tonic firing to bursting. It raises questions about how switches between different states affect synaptic plasticity and memory consolidation.

Recent research has revealed that bursting leads to a homeostatic reset of synaptic efficacy, where synaptic efficacy returns to a baseline value regardless of its starting point, causing the network to forget any learned information. To address this issue, we propose a new mechanism called burst-driven structural plasticity, that combines early changes in synaptic efficacy with long-lasting morphological changes such as spine growth or new protein synthesis.

Using a conductance-based neuronal model with a calcium-based plasticity rule, we demonstrate the utility of the proposed mechanism in a network that learns to recognize hand-written digits from the MNIST dataset. Our results show that the combination of switching from tonic firing to bursting with structural plasticity improves memory consolidation and enhances network robustness to noise. Conversely, blocking bursting and its burst-driven structural plasticity leads to forgetting.

In conclusion, this study highlights the importance of firing patterns in synaptic plasticity and proposes a solution to bridge the gap between the switches from tonic firing to bursting, learning and memory consolidation.