Multiple mechanisms govern the dynamics of depression at neocortical synapses of young rats |
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Authors: | Galit Fuhrmann Anna Cowan Idan Segev Misha Tsodyks Christian Stricker |
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Affiliation: | Department of Neurobiology, Weizmann Institute of Science, Rehovot 76100, Israel;Center for Neural Computation;and Department of Neurobiology, The Hebrew University, Jerusalem 91904, Israel;Institute of Neuroinformatics, University of Zürich and Swiss Federal Institute of Technology (ETH), Winterthurerstrasse 190, CH-8057 Zürich, Switzerland;Division of Neuroscience, John Curtin School of Medical Research;and Australian National University Medical School, Canberra, ACT 0200, Australia |
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Abstract: | Synaptic transmission between pairs of excitatory neurones in layers V ( N = 38) or IV ( N = 6) of somatosensory cortex was examined in a parasagittal slice preparation obtained from young Wistar rats (14–18 days old). A combined experimental and theoretical approach reveals two characteristics of short-term synaptic depression. Firstly, as well as a release-dependent depression, there is a release-independent component that is evident in smaller postsynaptic responses even following failure to release transmitter. Secondly, recovery from depression is activity dependent and is faster at higher input frequencies. Frequency-dependent recovery is a Ca2+-dependent process and does not reflect an underlying augmentation. Frequency-dependent recovery and release-independent depression are correlated, such that at those connections with a large amount of release-independent depression, recovery from depression is faster. In addition, both are more pronounced in experiments performed at physiological temperatures. Simulations demonstrate that these homeostatic properties allow the transfer of rate information at all frequencies, essentially linearizing synaptic responses at high input frequencies. |
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