One of the fundamental capacities of neural network is the plasticity serving for learning and memory, while its abnormal changes are considered as implications of neurodegenerative disorder (NDD). Our studies, with the approach of in vivo extracellular recording, focused on how the plasticity and neural disorder affects the neuronal decoding at the neural network level, which might lead to a new approach for evaluation and new medical treatments for neurodegenerative disorder. In this study, we chose the rat barrel cortex for measuring the activity-dependent plasticity and observed how the NDD induced by diabetes impairs the CA1 area of hippocampus. The two observations reciprocally indicate the neural mechanisms underlying the plasticity change in NDD and ageing. On the aspects of engineering technology, we used an in vivo extracellular neurophysiology platform to record evoked and spontaneous spikes from different brain regions. Based on the various characteristics of neuronal signal, we analyzed the temporal latency of neuronal firing, waveform of evoked potential (EP) and coordination between neuronal firing and local field potential to evaluate the changes of neural coding caused by plasticity or neural disorder. Our results indicate that the whisker pairing stimuli of vibrissa system can change the neural coding in rat barrel cortex which corresponds well with the description of spike-timing dependent plasticity(STDP), emphasizing the importance of timing order in synaptic excitatory potentials. Meanwhile, revealed by latency analysis, the diabetes, as a NDD, affects the spike timing accuracy in barrel cortex, which results in the changes of receptive field of neurons. Finally, it was firstly found that the phase-locking relationship between single neuron firing and hippocampal slow oscillation indicated the diabetes also impairs the neural coordination in CA1 area of hippocampus, which might be a network level mechanism for diabetes induced memory deterioration.
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