Synchronizing Back-propagation Activated Calcium Spikes: A Model forAttentional Control

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Recent experiments show that synchronized burst firing plays an important role in attentional control. It was found that during attentional control, bursts in the prefrontal cortex (PFC) synchronized with the local field potential (LFP) from distant brain areas. Back-propagation activated calcium spikes (BACs), a dendritic mechanism elicited by the coincidence of a back-propagating somatic action potential and input at the tuft, could be a new explanation for attentional control. BACs could implement the selection of relevant sensory information by acting as a coincidence detector of sensory information received at the proximal somatic dendrites and feedback information reflecting its relevance received at the tuft. To inform distant brain areas about the relevant sensory information BACs could be synchronized by oscillatory inhibition from Martinotti cells and in turn excite distant Martinotti cells that project the oscillation to pyramidal cells downstream. In this modeling study we investigated (i) the firing rate, degree of phase-locking and the ratio of BACs of a multi-compartment pyramidal cell model for varying frequencies of oscillatory inhibition and (ii) the characteristics of a network model representing two different brain areas developed to reproduce the experimental findings with an emphasis on the synchronization induced by BAG bursts between brain areas. By varying the frequency of the oscillatory inhibition we found a resonance in the firing rate of the pyramidal cell model at low frequencies that resulted from synchronized bursting. These bursts were predominantly elicited by BACs when the excitatory input was equally distributed to the basal dendrite and tuft and were highly phase locked. In the network model we could reproduce the observation that synchronization of activity in one area to the LFP in another was associated with bursts. These findings yield new insights about the possible role of synchronized BAG bursts in attentional control. Not only couid BAG bursts implement the selection of relevant sensory information, they could also couple to distant brain areas by synchronization.
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