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. Author manuscript; available in PMC: 2012 Jan 20.
Published in final edited form as: J Neurosci. 2011 Jul 20;31(29):10579–10592. doi: 10.1523/JNEUROSCI.1592-11.2011

Fig. 4. Combined LTP and LTD of Parallel Fiber Inputs Depolarizes Fusiform Cells.

Fig. 4

(Panels A1–C2 illustrate modelling data). A1. Two-compartment fusiform cell model driven by both auditory nerve (AN) activity and PF inputs arising from a population of granule cells. The PF excitatory inputs synapse onto the dendrite and PF inhibitory inputs and AN inputs synapse onto the soma. A2. The model spike response to a depolarizing step in input current. A3. The model membrane response to the mixed direct PF excitatory and indirect cartwheel inhibitory input with control synapse parameters (ge=0.009 mS/cm2 and gi=0.0162 mS/cm2, black curve) and with combined LTP and LTD synapse parameters (ge=0.0115 mS/cm2 and gi=0.014 mS/cm2, red curve). B1. Model EPSC (top), IPSC (middle) and fusiform cell membrane response (bottom) to two PF inputs (control synapse parameters are shown in black, and combined LTP and LTD synapse parameters in red). B2. Same as (B1) but now in response to a high frequency Poisson distributed PF discharge (1.6KHz). C1. Average resting model membrane potential (Vrest) for control vs. LTP/D synapse parameters during high frequency Poisson drive of PF shown in (B2). C2 Average model input resistance Rm for the same conditions as (C1).

(Panels D1–D3 illustrate experimental data) D1. Schematic representation of the placement of recording pipette (left) allowing injection of simulated high frequency train (control) of PSCs (EPSCs + IPSCs) mimicking PF activity shown in B2. D2. Current clamp experiments showing membrane potential measurements of fusiform cells in response to simulated PF activity in control (black trace) and after application of combined LTP and LTD in simulated trains (red trace). Recruitment of combined LTP and LTD was produced by modulating the injected control train of PSCs by enhancing EPSCs and reducing IPSCs by the percentage that was determined by our in vitro experiments shown in Fig. 3F. D3. Average resting membrane potential in response to simulated PF activity shown in D1 and D2 for control (−62± 0.5 mV, n=5) and after application of combined LTP and LTD (−59 ± 1 mV, n=5, p<0.01).