Trends in Neurosciences
OpinionShort-term synaptic plasticity as a temporal filter
Section snippets
Synaptic depression and temporal processing
Many sensory neurons in the cortices of mammalian species, sensory systems of invertebrate species, and electrosensory midbrains of some species of fish, respond strongly to low-temporal frequency stimuli, for example <10 Hz (see Fig. 1a,b), and weakly or not at all to ongoing high-temporal frequencies 6, 10, 17, 18, 19. Many of these neurons, paradoxically, respond strongly to sensory transients and the onsets of high-temporal frequency stimuli, even though most of the power in these stimuli
The interplay between synaptic depression and synaptic facilitation
The use of synaptic depression for low-pass temporal filtering presents a paradox. If all the inputs to a neuron experience short-term depression, it might not respond to low-temporal frequency information in the presence of depressing high-temporal frequency stimulation. For many behaviors this would defeat the function of the low-pass filter. For example, as stated above, ongoing high-temporal frequency electrosensory information does not impair behavioral responses to biologically relevant
Conclusions
Independently evolved sensory systems, including the visual system of mammals and electrosensory systems of weakly electric fish, have convergently employed synaptic depression as a mechanism for low-pass temporal filtering. Because other mechanisms exist for achieving this filtering, it is probable that synaptic depression serves some common functional demands in these systems beyond low-pass filtering. Future studies should examine the hypothesis that the depression-induced phase advances in
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