Amplitude-dependency of response of SI cortex to flutter stimulation Public Deposited

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Creator
  • Tannan, Vinay
    • Affiliation: School of Medicine, UNC/NCSU Joint Department of Biomedical Engineering
  • Tommerdahl, Mark Allen
    • Affiliation: School of Medicine, UNC/NCSU Joint Department of Biomedical Engineering
  • Chiu, Joannellyn S
    • Affiliation: School of Medicine, UNC/NCSU Joint Department of Biomedical Engineering
  • Whitsel, Barry
    • Affiliation: School of Medicine, Department of Cell Biology and Physiology
  • Simons, Stephen B
    • Affiliation: School of Medicine, UNC/NCSU Joint Department of Biomedical Engineering
  • Favorov, Oleg
    • Affiliation: School of Medicine, UNC/NCSU Joint Department of Biomedical Engineering
Abstract
  • Abstract Background It is established that increasing the amplitude of a flutter stimulus increases its perceived intensity. Although many studies have examined this phenomenon with regard to the responding afferent population, the way in which the intensity of a stimulus is coded in primary somatosensory cortex (SI) remains unclear. Results Optical intrinsic signal (OIS) imaging was used to study the evoked responses in SI of anesthetized squirrel monkeys by 25 Hz sinusoidal vertical skin displacement stimulation. Stimuli were 10 sec duration with a 50 sec inter-stimulus interval. Stimulus amplitude ranged from 50 to 400 microns and different amplitudes were interleaved. Control levels of activity were measured in the absence of stimulation, and used to compare with activation levels evoked by the different stimulus amplitudes. Stimulation of a discrete skin site on the forelimb evoked a prominent increase in absorbance within the forelimb representational region in cytoarchitectonic areas 3b and 1 of the contralateral hemisphere. An increase in stimulus amplitude led to a proportional increase in the magnitude of the absorbance increase in this region of areas 3b and 1 while surrounding cortex underwent a decrease in absorbance. Correlation maps revealed that as stimulus amplitude is increased, the spatial extent of the activated region in SI remains relatively constant, and the activity within this region increases progressively. Additionally, as stimulus amplitude is increased to suprathreshold levels, activity in the surround of the activated SI territory decreases, suggesting an increase in inhibition of neuronal activity within these regions. Conclusion Increasing the amplitude of a flutter stimulus leads to a proportional increase in absorbance within the forelimb representational region of SI. This most likely reflects an increase in the firing rate of neurons in this region of SI. The relatively constant spatial extent of this stimulus-evoked increase in absorbance suggests that an increase in the amplitude of a 25 Hz skin stimulus does not evoke a larger area of SI neuronal activation due to an amplitude-dependent lateral inhibitory effect that spatially funnels the responding SI neuronal population.
Date of publication
Identifier
  • 15969752
  • doi:10.1186/1471-2202-6-43
Resource type
  • Article
Rights statement
  • In Copyright
Rights holder
  • Stephen B Simons et al.; licensee BioMed Central Ltd.
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Journal title
  • BMC Neuroscience
Journal volume
  • 6
Journal issue
  • 1
Page start
  • 43
Language
  • English
Is the article or chapter peer-reviewed?
  • Yes
ISSN
  • 1471-2202
Bibliographic citation
  • BMC Neuroscience. 2005 Jun 21;6(1):43
Access
  • Open Access
Publisher
  • BioMed Central Ltd
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