Kinetics of fast short-term depression are matched to spike train statistics to reduce noise.
Short-term depression (STD) is observed at many synapses of the CNS and is important for diverse computations. We have discovered a form of fast STD (FSTD) in the synaptic responses of pyramidal cells evoked by stimulation of their electrosensory afferent fibers (P-units). The dynamics of the FSTD are matched to the mean and variance of natural P-unit discharge. FSTD exhibits switch-like behavior in that it is immediately activated with stimulus intervals near the mean interspike interval (ISI) of P-units (approximately 5 ms) and recovers immediately after stimulation with the slightly longer intervals (>7.5 ms) that also occur during P-unit natural and evoked discharge patterns. Remarkably, the magnitude of evoked excitatory postsynaptic potentials appear to depend only on the duration of the previous ISI. Our theoretical analysis suggests that FSTD can serve as a mechanism for noise reduction. Because the kinetics of depression are as fast as the natural spike statistics, this role is distinct from previously ascribed functional roles of STD in gain modulation, synchrony detection or as a temporal filter.
Khanbabaie
Reza
R
Department of Cellular and Molecular Medicine, University of Ottawa, 451 Smyth Rd., Ottawa, Ontario K1H 8M5, Canada. skhanbab@uottawa.ca
Nesse
William H
WH
Longtin
Andre
A
Maler
Leonard
L
D000200:Action Potentials / Q000502:physiology*; D000344:Afferent Pathways / Q000502:physiology; D000818:Animals; D001581:Benzothiadiazines / Q000494:pharmacology; D001921:Brain / Q000166:cytology; D004558:Electric Stimulation / Q000379:methods; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D005260:Female; D005399:Fishes / Q000502:physiology; D066298:In Vitro Techniques; D008297:Male; D008959:Models, Neurological; D009433:Neural Inhibition / Q000502:physiology*; D009474:Neurons / Q000145:classification / Q000502:physiology*; D009622:Noise; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology; D013997:Time Factors; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
D001581:Benzothiadiazines; D018691:Excitatory Amino Acid Antagonists; D005680:gamma-Aminobutyric Acid; C004639:cyclothiazide