Abstract
The synchronous activity of groups of neurons is increasingly thought to be important in cortical information processing and transmission. However, most studies of processing in the primary auditory cortex (AI) have viewed neurons as independent filters; little is known about how coordinated AI neuronal activity is expressed throughout cortical columns and how it might enhance the processing of auditory information. To address this, we recorded from populations of neurons in AI cortical columns of anesthetized rats and, using dimensionality reduction techniques, identified multiple coordinated neuronal ensembles (cNEs), which are groups of neurons with reliable synchronous activity. We show that cNEs reflect local network configurations with enhanced information encoding properties that cannot be accounted for by stimulus-driven synchronization alone. Furthermore, similar cNEs were identified in both spontaneous and evoked activity, indicating that columnar cNEs are stable functional constructs that may represent principal units of information processing in AI.
Highlights
How individual neurons work together to encode sensory information and influence behavior remains one of the fundamental questions in systems neuroscience
Member neurons was significantly higher than that of random groups of neurons (p < 0.001, Wilcoxon signed-rank test; Figure 10—figure supplement 1E). For both spectro-temporal receptive field (STRF) peak-trough differences (PTD) and mutual information (MI), we found that the distribution of uniqueness index (UI) values was significantly skewed towards 0, and was significantly different from a uniform distribution, which would be obtained if coordinated neuronal ensembles (cNEs) were composed of randomly selected neurons from population recordings (p < 0.001, Kolmogorov–Smirnov test)
For groups containing more than three members, the coincidence ratios (CRs) values for most control models were always near or at 0. These results suggest that member neurons of cNEs have more coincident activity than expected, further supporting the hypothesis that coordinated cNE events are driven by higher-thansecond-order correlations and cannot be explained via stimulus-induced synchronization or shared receptive field properties, including those not reflected in STRFs
Summary
How individual neurons work together to encode sensory information and influence behavior remains one of the fundamental questions in systems neuroscience. Technological advances in large-scale recordings, including calcium imaging and high-density multi-channel electrodes, have allowed the monitoring of the simultaneous activity of large populations of neurons This has led to the demonstration of coordinated activity within groups of recorded neurons, identified and verified by statistical approaches (Billeh et al, 2014; Gourévitch and Eggermont, 2010; Lopes-dos-Santos et al, 2013; Miller et al, 2014; Peyrache et al, 2010; Pipa et al., 2008).
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