Stimulus-dependent spatial patterns of response in SI cortex.
BACKGROUND
Recently we reported that vibrotactile flutter stimulation of a skin locus at different amplitudes evokes an optical response confined to the same local region of the primary somatosensory cortex (SI), where its overall magnitude varies proportionally to the flutter amplitude. In this report, we characterize the impact of the flutter amplitude on the spatial patterns of activity evoked within the responding SI region.


RESULTS
In order to characterize the spatial pattern of activity within the responding SI region, images of the flutter-evoked SI optical response were segmented and analyzed with spatial frequency analysis. The analysis revealed that: (1) dominant spatial frequencies in the optical intrinsic signal emerge within the responding SI region within 3-5 sec of stimulus onset; (2) the stimulus-evoked activity is spatially organized in a form of several roughly parallel, anterior-posteriorly extended waves, spaced 0.4-0.5 mm apart; (3) the waves themselves exhibit spatial periodicities along their long axis; and (4) depending on the flutter stimulus amplitude, these periodicities can range from fine 0.15 mm "ripples" at 50 microm amplitude to well-developed 0.5 mm fluctuations at the amplitude of 400 microm.


CONCLUSIONS
The observed spatiointensive fractionation on a sub-macrocolumnar scale of the SI response to skin stimulation might be the product of local competitive interactions within the stimulus-activated SI region and may be a feature that could yield novel insights into the functional interactions that take place in SI cortex.
Chiu
Joannellyn S
JS
Department of Biomedical Engineering, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA. jchiu@email.unc.edu
Tommerdahl
Mark
M
Whitsel
Barry L
BL
Favorov
Oleg V
OV
D000818:Animals; D011930:Reaction Time / Q000502:physiology; D012453:Saimiri; D012879:Skin Physiological Phenomena; D013003:Somatosensory Cortex / Q000502:physiology*; D014732:Vibration