Local neurons, in contrast, fired low-amplitude Ca2+ spikes and displayed spike frequency adaptation caused by Ca2+-dependent potassium currents. Fast GABA (LN-PN and LN-LN connections) and nicotinic cholinergic synaptic currents (PN-LN connections) were modeled by first order activation schemes. The equations for all intrinsic and synaptic currents are given in the Supplemental Information and are based on Bazhenov et al., 2001a and Bazhenov et al., 2001b. In Figure 1, Figure 2 and Figure 3 we simulated isolated networks of LNs. The population of LNs and the specific
connectivity are shown in the respective figures. In the following figures we this website simulated networks including both excitatory PNs and inhibitory LNs. Drawing from the basic anatomy of the insect AL, the PNs received inputs from LNs and projected random connections back to LNs.
The AL model simulated in Figure 5 included 20 LNs and 100 PNs. LN-PN connections were determined such that each PN occupied a position on the grid in Figure 5. We tested the network with a larger population of LNs and PNs with random connectivity to obtain the same result (propagating waves of activity in the 2D plane). With random connections the population of PNs simulated did not cover all points on the 2D grid. However, the waves of activity could be clearly seen despite gaps in the grid of PNs. We also simulated a network with chromatic number three and were able to generate 2D wave-fronts that propagated along orthogonal directions. Intracellular recordings (Figure 1 and Figure 7) Oxymatrine selleck chemicals were made from local neurons in adult locusts (Schistocerca americana) obtained from a crowded colony. Animals were immobilized and stabilized with wax with one antenna secured. The brain was exposed, desheathed, and superfused with locust saline as previously described ( Laurent and Davidowitz, 1994). Intracellular electrodes were sharp glass micropipettes (O.D = 1.0 mm, Warner Instruments, 80–230 MΩ, Sutter P97 horizontal puller,
Sutter Instruments) and were filled with 0.5 M potassium acetate and 5% neurobiotin (Vector Laboratories). Data were digitally acquired (5 kHz sampling rate, LabView software and PCI-6602 DAQ and PCI- MIO-16E-4 hardware, National Instruments), stored on a PC hard drive, and analyzed off-line using MATLAB (The MathWorks, Inc.). Odor puffs were dilute grass volatiles delivered as described in Brown et al. (2005). This work was supported by grants from the US National Institute of Deafness and other Communication Disorders (C.A. and M.B.), the US National Institute of Neurological Disorders and Stroke (M.B.) and a US National Institute of Child Health and Human Development intramural award (M.S.). The authors would like to thank Professor Gilles Laurent for many stimulating discussions and insightful suggestions and Stacey Brown Daffron for providing examples of recordings from LNs made in vivo. C.