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Differential synaptic processing separates stationary from transient inputs to the auditory cortex


Sound features are blended together en route to the central nervous system before being discriminated for further processing by the cortical synaptic network. The mechanisms underlying this synaptic processing, however, are largely unexplored. Intracortical processing of the auditory signal was investigated by simultaneously recording from pairs of connected principal neurons in layer II/III in slices from A1 auditory cortex. Physiological patterns of stimulation in the presynaptic cell revealed two populations of postsynaptic events that differed in mean amplitude, failure rate, kinetics and short-term plasticity. In contrast, transmission between layer II/III pyramidal neurons in barrel cortex were uniformly of large amplitude and high success (release) probability (Pr). These unique features of auditory cortical transmission may provide two distinct mechanisms for discerning and separating transient from stationary features of the auditory signal at an early stage of cortical processing.

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Figure 1: Two layer II/III cortico–cortical excitatory connection phenotypes.
Figure 2: Differing properties of HPCs and LPCs.
Figure 3: Short-term plasticity at LFCs and HFC connections.
Figure 4: Time course of recovery from short-term depression at HPCs.
Figure 5: Differential dependence of short-term plasticity on [Ca2+]o in HPCs.
Figure 6: Differential dependence of short term plasticity on [Ca2+]o in LPCs.
Figure 7: Equivalent connections were not observed in barrel cortex.
Figure 8: Synchronous spontaneous synaptic input onto connected layer II/III cells.


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We thank D. Feldman for his assistance in preparing Barrel cortex slices and C. Trouth for cell reconstruction and camera lucida drawings of neurons. This work was supported by an Intramural Research award to C.McB.

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Correspondence to Chris J. McBain.

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Atzori, M., Lei, S., Evans, D. et al. Differential synaptic processing separates stationary from transient inputs to the auditory cortex. Nat Neurosci 4, 1230–1237 (2001).

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