Abstract
Communication between cortical sites is mediated by long-range synaptic connections. However, these connections are relatively static, while everyday cognitive tasks demand a fast and flexible routing of information in the brain. Synchronization of activity between distant cortical sites has been proposed as the mechanism underlying such a dynamic communication structure. Here, we study how oscillatory activity affects the excitability and input-output relation of local cortical circuits and how it alters the transmission of information between cortical circuits. To this end, we develop model circuits showing fast oscillations by the PING mechanism, of which the oscillatory characteristics can be altered. We identify conditions for synchronization between two brain circuits and show that the level of intercircuit coherence and the phase difference is set by the frequency difference between the intrinsic oscillations. We show that the susceptibility of the circuits to inputs, i.e., the degree of change in circuit output following input pulses, is not uniform throughout the oscillation period and that both firing rate, frequency and power are differentially modulated by inputs arriving at different phases. As a result, an appropriate phase difference between the circuits is critical for the susceptibility windows of the circuits in the network to align and for information to be efficiently transferred. We demonstrate that changes in synchrony and phase difference can be used to set up or abolish information transfer in a network of cortical circuits.
Highlights
Evidence for oscillatory neural activity is found throughout the brain, in several frequency bands and both at the single neuron as well as the network level
We showed that two brain circuits, both showing oscillatory activity emerging from local circuit activation according to the Pyramidal Interneuron Network Gamma (PING) mechanism, synchronized their activity across a range of frequency differences, levels of internal synchronization and I/E-ratios of the projections
The frequency at which synchronization occurred was determined by the sending circuit, while the level of coherence and the phase difference was set by the frequency difference between the two intrinsic oscillations
Summary
Evidence for oscillatory neural activity is found throughout the brain, in several frequency bands and both at the single neuron as well as the network level. Oscillations are linked to a wide range of higher level cognitive functions (Buzsáki and Draguhn, 2004), such as attention (Steinmetz et al, 2000; Gregoriou et al, 2009; Bosman et al, 2012; Saalmann et al, 2012), memory (Fujisawa and Buzsáki, 2011; Watrous et al, 2013), and rule representation (Buschman et al, 2012), as well as circuit level computations such as input selection (Börgers et al, 2008) and tuning (Womelsdorf et al, 2012; Moldakarimov et al, 2014). Over the course of the last two decades, considerable insight has been gained into the generation of oscillatory activity at the level of single neurons and neural circuits (Tiesinga and Sejnowski, 2009; Wang, 2010; Buzsáki and Wang, 2012).
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