Bitterness suppression as revealed by split-tongue taste stimulation in humans.

QHCl-sucrose and QHCl-NaCl mixtures administered to the anterior part of the human tongue led to substantial bitterness suppression as determined by the method of magnitude estimation. In the QHCl-sucrose condition components separated by the tongue's midline and those spatially mixed produced equal amounts of bitterness suppression. However, the QHCl-NaCl mixture produced significantly more bitterness suppression with the spatially mixed than with the spatially separated stimulus components. It is concluded that bitterness suppression in mixtures with sucrose occurs centrally and in mixtures with NaCl both peripherally and centrally.