Resonant behavior and frequency preferences of thalamic neurons

E. Puil*, H. Meiri, Y. Yarom

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

85 Scopus citations

Abstract

1. We studied the voltage responses of thalamocortical neurons to a periodic current input of variable frequency, in slices of mediodorsal thalamus (guinea pig). The ratio of the Fourier transform of the voltage response to the Fourier transform of the oscillatory current input was used to calculate the frequency response of the neurons at different resting and imposed membrane potentials. 2. Most neurons displayed a resonant hump in the frequency response curve. A narrow band of low-frequency (2-4 Hz) resonance occurred near the resting level [-66 + 8 mV (SD)] and at imposed membrane potentials in a range of -60 to 80 mV. An additional wide band (12-26 Hz) of peak resonant frequencies was observed at depolarized levels. 3. The low- frequency resonance was insensitive to tetrodotoxin (TTX) application in concentrations (0.5-1 μM) that blocked a depolarization activated inward rectifier and Na+-dependent action potentials. TTX, however, eliminated the wideband resonant hump centered at 12-26 Hz that we observed at depolarized membrane potentials. 4. Application of Ni2+ (0.5-1 mM) reversibly blocked all slow spikes and greatly reduced the low-frequency resonant humps, without changing the resting potential. Octanol in concentrations of 50 μM had similar effects. 5. Application of Cs+ (3-5 mM), a blocker of the hyperpolarization activated inward rectifier, produced a 5- to 10-mV depolarization and completely blocked the rectification. Cs+ did not alter the low-frequency resonant hump or its dependence on membrane voltage. 6. We conclude from these investigations that the interactions of the low threshold Ca2+ current with the passive properties are required for the generation of the 2- to 6-Hz resonant behavior and frequency selectivity of mediodorsalis neurons. A comparison of the resonant frequencies and their dependence on membrane potential to rhythmic activities of neurons in vivo, suggests to us that the resonant behavior has an important role in generating the characteristic rhythmic activity in the thalamus.

Original languageEnglish
Pages (from-to)575-582
Number of pages8
JournalJournal of Neurophysiology
Volume71
Issue number2
DOIs
StatePublished - 1994
Externally publishedYes

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