Document Detail

Threshold firing frequency-current relationships of neurons in rat somatosensory cortex: type 1 and type 2 dynamics.
MedLine Citation:
PMID:  15381746     Owner:  NLM     Status:  MEDLINE    
Neurons and dynamical models of spike generation display two different types of threshold behavior, with steady current stimulation: type 1 [the firing frequency vs. current (f-I) relationship is continuous at threshold) and type 2 (discontinuous f-I)]. The dynamics at threshold can have profound effects on the encoding of input as spikes, the sensitivity of spike generation to input noise, and the coherence of population firing. We have examined the f-I and frequency-conductance (f-g) relationships of cells in layer 2/3 of slices of young (15-21 DIV) rat somatosensory cortex, focusing in detail on the nature of the threshold. Using white-noise stimulation, we also measured firing frequency and interspike interval variability as a function of noise amplitude. Regular-spiking (RS) pyramidal neurons show a type 1 threshold, consistent with their well-known ability to fire regularly at very low frequencies. In fast-spiking (FS) inhibitory interneurons, although regular firing is supported over a wide range of frequencies, there is a clear discontinuity in their f-I relationship at threshold (type 2), which has not previously been highlighted. FS neurons are unable to support maintained periodic firing below a critical frequency fc, in the range of 10 to 30 Hz. Very close to threshold, FS cells switch irregularly between bursts of periodic firing and subthreshold oscillations. These characteristics mean that the dynamics of RS neurons are well suited to encoding inputs into low-frequency firing rates, whereas the dynamics of FS neurons are suited to maintaining and quickly synchronizing to gamma and higher-frequency input.
T Tateno; A Harsch; H P C Robinson
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Publication Detail:
Type:  In Vitro; Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Journal of neurophysiology     Volume:  92     ISSN:  0022-3077     ISO Abbreviation:  J. Neurophysiol.     Publication Date:  2004 Oct 
Date Detail:
Created Date:  2004-09-21     Completed Date:  2004-11-22     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  0375404     Medline TA:  J Neurophysiol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  2283-94     Citation Subset:  IM    
Department of Physiology, University of Cambridge, Cambridge CB2 3EG, United Kingdom.
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MeSH Terms
Action Potentials / physiology
Models, Neurological
Nerve Net / physiology
Neural Conduction / physiology
Neurons / classification,  physiology*
Rats, Wistar
Receptors, AMPA / physiology
Sensory Thresholds / physiology*
Somatosensory Cortex / cytology,  physiology*
Synaptic Membranes / physiology
Reg. No./Substance:
0/Receptors, AMPA

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