LI, K. T. | Search bioRxiv

bioRxiv2024

Synfire Chain Dynamics Unravelling Theta-nested Gamma Oscillations for Balancing Prediction and Dodge in Navigation

Theta-nested gamma oscillations, widely observed in experiments, play a crucial role in navigation, yet their functional roles and the origin of the positive correlation between theta frequency and motion velocity remain unclear. We propose that the objects survival relies on both prediction and dodge - predicting future events and staying alert to unpredictable ones, the latter of which has seldom been considered in goal-navigation tasks. By building a biologically plausible spiking neuronal network model and reproducing experimental results, we leverage synfire chain properties - length and separation - to elucidate the functional roles of theta-nested gamma oscillations: theta oscillations for self-location awareness, gamma oscillations for predictive capabilities and their coupling for enhancing functionality. The positive correlation between theta frequency and motion velocity is demonstrated to optimally balance representing predictable events for planning and staying alert to unexpected events. Our study offers a new avenue for unravelling the neural mechanisms of navigation.

neuroscience↗

bioRxiv2022

Synaptic degeneration in neuronal circuits hinders memory recall, memory rescue, and learning

Neurodegeneration is a characteristic of Alzheimers disease (AD), but its effect on neural activity dynamics underlying memory deficits is unclear. Here, we studied the effects of synaptic degeneration on neural activities associated with memory recall, memory rescue by slow-gamma stimulation, and learning a new memory, in an integrate-and-fire neuronal network. Our results showed that reducing connectivity decreases the neuronal synchronisation of memory neurons at slow-gamma frequencies and impairs memory recall performance. Although slow-gamma stimulation rescued memory recall and slow-gamma oscillations, the rescue with reduced connectivity caused a side effect of activating mixed memories. During the learning of a new memory, reducing connectivity caused an impairment in storing the new memory, but did not affect previously stored memories. Our results reveal potential computational mechanisms underlying the memory deficits caused by synaptic degeneration in AD.

neuroscience↗