Up to 6 attractor memories could be simultaneously augmented and hence selleck compound periodically reactivated (Lundqvist et al., 2011 and Lundqvist et al., 2012). We used the SPLIT simulator developed for simulations of large, biophysically detailed network models, which can run on a single processor as well as on massively parallel machines (Hammarlund and Ekeberg, 1998). The presented model has previously been scaled up to the size of 22 million neurons and 11 billion synapses on a supercomputer (Djurfeldt et al., 2008). The network simulated here typically consisted of 14,553 cells connected by 1.8 million synapses. Simulations were typically performed on
128 nodes of the supercomputer at the Center for Parallel Computers at KTH Royal Institute of Technology, Stockholm, Sweden. The simulation time step was 0.1 ms and it took 81 s to simulate 1 s of network activity. www.selleckchem.com/products/SNS-032.html Local field potentials (LFPs) were estimated by calculating the average soma potential for all pyramidal cells in local populations at every time step, similarly to the approach adopted by Ursino and La Cara (2006). Although LFP is more directly linked to the synaptic activity (Logothetis, 2003), the averaged membrane potentials have been reported to be correlated with LFPs (Okun et al., 2010). In particular,
low-pass-filtered components of synaptic currents reflected in membrane potentials appear to carry the portion of the power spectral content of extracellular potentials that is relevant to our key findings (Lindén et al., 2010). As regards the phase
response of estimated extracellular potentials, the delays of different frequency check details components are spatially dependent (Lindén et al., 2010). However, irrespective of the LFP synthesis, phase-related phenomena reported in this study remain qualitatively unaffected since they hinge on relative rather than absolute phase values. All analyses in this study were performed using MATLAB. In the first step, LFPs were subsampled at the frequency of 1 kHz and correspondingly, spikes obtained in the majority of cases from pyramidal cells, except the analysis of the preferred phase of firing of basket cells, were binned at 1 ms resolution. Then a low-pass filter was applied to the LFP signals with the cut-off frequency of 250 Hz in the forward and reverse directions to avoid any phase distortions. The analyses carried out in this work fall into the following categories: spectral quantification, estimation of coherence and phase locking, analysis of spike timing with respect to LFP phase, instantaneous firing rate estimation, spiking variability quantification and examination of the spatiotemporal structure of spiking activity.