抄録
In comparison with the barrel cortex, the primary gustatory area in the insular cortex is thought to have much less distinct functional columns. In order to better understand the inter-columnar information processing in which GABAA IPSPs are thought to be involved, we examined the differences in the spatiotemporal pattern of excitation spread between the barrel and insular cortices, using voltage-sensitive dye imaging. The excitation evoked by stimulation of layer IV of the barrel cortex spread upwardly into layer II/III, where the excitation spread horizontally into neighboring columns partially, but leaving the layer V/VI unexcited. By contrast, the excitation in layer IV of the insular cortex spread upwardly into layer II/III as well as into layer V/VI downwardly, while the horizontal spread in layer II/III was much less prominent. An application of bicuculline prolonged the time course and enlarged the extent of horizontal spread in layer II/III across the neighboring columns fully, while it just prolonged the time course of vertical spread in the insular cortex, leaving the horizontal spread almost unchanged. These results suggest that the involvement of GABAA receptors in the lateral inhibition in layers II/III is much more prominent in the barrel cortex than in the insular cortex. In the insular cortex, the sensory information arising from thalamus would be forwarded bi-directionally to the superficial and deep layers, and the reciprocal inhibition between the two layers within a same column is remarkable. [J Physiol Sci. 2007;57 Suppl:S150]
