Study On The Relationship Between Neuronal Oscillations And Synaptic Plasticity In Rats With Vascular Dementia

ObjectiveVarious frequencies of neural oscillations could be benefit for integrations of distributed neurons activities. Recently, more and more studies were reported that neural oscillations could contribute to the information communication of multiple layers of brain regions through the same-rhythm coupling and/or cross-rhythm coupling. Both forms of interactions were demonstrated to be closely associated with the cognitive functions whose alterations were involved in mediating the cognitive deficits observed in some neuropsychiatric illnesses. One of our previous studies showed that vascular dementia rats (VD) rats had serious cognitive deficits. In the present study, we investigated the coordination between hippocampal CA3and CA1through local field potential (LFP) to explore the underlying mechanism of cognitive impairment of VD rats at the network level. Furthermore, it was wondered whether the neural information flow (NIF) indices based on LFP could be used to measure the synaptic plasticity.MethodsIn this study, we established VD animal model by two-vessel occlusion (2VO) method. Wistar rats were used. Local field potentials (LFPs) of CA3and CA1were recorded followed by the induction of long-term potentiation (LTP) in the same CA3-CA1pathway.Results1. Significant decreases of LTP were found in VD group.2. The same-rhythm couplings at theta and gamma frequency bands between CA3and CA1regions were remarkably reduced in VD rats, measured by PLV; The strength of CA3driving CA1at these two rhythms was also decreased in VD rats, measured by the approach of gPDC.3. The CA3theta-CA1gamma cross frequency phase-phase coupling (PPC, measured by n:m phase locking) and phase-amplitude coupling (PAC, measured by modulation index) were both reduced in VD rats. To further distinguish the roles of the CA1gamma amplitude and the phase coupling between CA3theta and CA1gamma amplitude on PAC results, we calculated the CA1gamma power in one CA3theta circle and the phase coupling between CA3theta and CA1gamma amplitude (measured by phase amplitude coupling_phase locking value, PAC_PLV; phase amplitude couplingconditional mutual information, PAC_CMI), respectively. Our results showed no significant difference of CA1gamma power in one CA3theta circle between the two groups. However, the indices of PAC_PLV, PAC_CMI were considerably reduced in VD rats.Conclusions1. The altered phase coupling between CA3theta and CA1gamma amplitude produced the decreased CA3theta-CA1gamma PAC in VD rats.2. The depressed coordination between CA3and CA1regions might be the mechanism of the impaired cognition in VD rats at the neural network level3..NIF indices, based on LFPs, are probably used to measure the synaptic plasticity.