Cortical control of appropriate tongue protrusion during licking in cats--increase in regional cerebral blood flow (rCBF) of the contralateral area P and in tongue protrusion after the unilateral area P lesion.

Adequate tongue protrusion may be regulated by cat bilateral area P (the motor cortex for jaw and tongue movements) (Hiraba and Sato, Somatosens Mot Res 2005b;22:183-192). The ICMS (intracortical microstimulation) in the unilateral area P evoked motor effects of tongue protrusion without deviation (Hiraba and Sato, Somatosens Mot Res 2004;23:1-12), and cats with the unilateral lesion of area P showed abnormal tongue protrusion without deviation during licking (Hiraba and Sato, Somatosens Mot Res 2005b;22:183-192). Further, the measurements of the regional cerebral blood flow (rCBF) in the bilateral jaw and tongue motor cortical areas were shown to have the same activity rate during the lateral licking (Hiraba and Sato, Somatosens Mot Res 2005c;22:307-317). We assumed from these results that cortical control for tongue protrusion was executed by networks between the bilateral area P including inhibitory interneurons. We prepared the measurable cats of the rCBF in the contralateral side after the unilateral area P lesion. Changes in the rates of rCBF and tongue protrusion during licking were examined over a long time course of about 1-2 months after the unilateral area P lesion. All cats after the unilateral area P lesion showed increased rate (double or triple in comparison with the normal ones) of rCBF of the contralateral area P in the early (0-20 days) phase. On the other hand, increased rates of tongue protrusion were about 120% in the early phase, and about 180% in the middle (21-35 days) and late (36-last days) phases. The results support the organization of networks between bilateral area P including the inhibitory interneurons.