Sub- and suprathreshold adaptation currents have opposite effects on frequency tuning.
Natural stimuli are often characterized by statistics that can vary over orders of magnitude. Experiments have shown that sensory neurons continuously adapt their responses to changes in these statistics, thereby optimizing information transmission. However, such adaptation can also alter the neuronal transfer function by attenuating if not eliminating responses to the low frequency components of time varying stimuli,which can create ambiguity in the neural code. We recorded from electrosensory pyramidal neurons before and after pharmacological inactivation of either calcium-activated (I(AHP)) or KCNQ voltage-gated potassium currents (I(M)). We found that blocking each current decreased adaptation in a similar fashion but led to opposite changes in the neuronal transfer function. Indeed, blocking I(AHP) increased while blocking I(M) instead decreased the response to low temporal frequencies. To understand this surprising result, we built a mathematical model incorporating each channel type. This model predicted that these differential effects could be accounted for by differential activation properties. Our results show that the mechanisms that mediate adaptation can either increase or decrease the response to low frequency stimuli. As such, they suggest that the nervous system resolves ambiguity resulting from adaptation through independent control of adaptation and the neuronal transfer function.
Department of Physiology, McGill University, 3655 Sir William Osler, room 1137, Montreal, QC, H3G 1Y6, Canada.
Tara
T
Deemyad
Jens
J
Kroeger
Maurice J
MJ
Chacron
D000222:Adaptation, Physiological / Q000502:physiology*; D000473:Alkanes / Q000494:pharmacology; D000818:Animals; D000873:Anthracenes / Q000494:pharmacology; D005260:Female; D005399:Fishes; D066298:In Vitro Techniques; D051656:KCNQ Potassium Channels / Q000502:physiology*; D008297:Male; D008959:Models, Neurological; D026902:Potassium Channel Blockers / Q000494:pharmacology; D024681:Potassium Channels, Calcium-Activated / Q000502:physiology*; D017966:Pyramidal Cells / Q000502:physiology*; D011806:Quinolinium Compounds / Q000494:pharmacology
C112297:10,10-bis(4-pyridinylmethyl)-9(10H)-anthracenone; C110349:6,10-diaza-3(1,3),8(1,4)dibenzena-1,5(1,4)diquinolinacyclodecaphane; D000473:Alkanes; D000873:Anthracenes; D051656:KCNQ Potassium Channels; D026902:Potassium Channel Blockers; D024681:Potassium Channels, Calcium-Activated; D011806:Quinolinium Compounds