F MRI STUDY OF TASTE CORTEX USING FOCAL STIMULI

这项提议的短期目标是确定人类皮层味觉处理的位置是否取决于味觉刺激在舌头上的位置。我们将构建和测试一个味觉刺激器，将化学味觉刺激应用于舌头的离散部分，并使用功能磁共振成像（fMRI）观察由此产生的中枢激活。我们假设，在右手受试者中，初级味觉皮层以及一些第二或更高层次的皮层味觉区域的味觉处理将主要在右半球，而不管舌头的哪一侧受到刺激。我们还假设来自舌头后端腭状乳头的味觉信息将在初级味觉皮层的不同部分处理，而不是来自舌头前端真菌状乳头的味觉信息。长期目标包括比较左撇子和右撇子受试者，以及检查对其他味蕾区刺激的反应。长期目标是了解味觉系统外围损伤的生物反应的性质和局限性。人类味觉系统的外围部分包括5个不同的味蕾区，由3个颅神经的至少4个分支支配。因此，由周围病变或疾病引起的味觉功能丧失很少是完全的。例如，在口腔手术、中耳手术或疾病（如贝尔氏麻痹）中，其中一种味觉神经——鼓室索经常受到损伤。剩下的完整的味蕾和支配它们的神经纤维通常可以调节相对正常的感觉。中枢代偿机制可能对这种恢复负有部分责任。揭示这种补偿机制的必要步骤是建立正常的中央激活模式，这种模式是由味蕾的个别区域的选择性刺激引起的。

The short term goals of this proposal are to determine whether the location of cortical taste processing in humans depends on the location of the taste stimulus on the tongue. We will construct and test a taste stimulator for applying chemical taste stimuli to discrete parts of the tongue and observe the resulting central activation with functional magnetic resonance imaging (fMRI). We hypothesize that taste processing in the primary gustatory cortex as well as in some second or higher order cortical taste areas will be mostly in the right hemisphere in right handed subjects regardless of the side of the tongue that was stimulated. We also hypothesize that taste information from the vallate papillae on the posterior tongue will be processed in a different part of the primary gustatory cortex than that from the fungiform papillae on the anterior tongue. Long term goals include the comparison of left and right handed subjects, and examination of responses to stimulation of other taste bud fields. A long term objective is to understand the nature and limitations of the biological response to peripheral damage to the taste system. The peripheral part of the human taste system includes 5 distinct fields of taste buds, innervated by at least 4 branches of 3 cranial nerves. Thus loss of taste function resulting from peripheral lesions or disease is rarely complete. For example, one of the taste nerves, the chorda tympani, is often damaged during oral surgery, middle ear surgery, or from disease (e.g. Bell's Palsy). The remaining intact taste buds and their innervating nerve fibers can often mediate relatively normal perception. Central compensatory mechanisms may be partially responsible for this recovery. A necessary step for revealing such compensatory mechanisms is to establish normal patterns of central activation resulting from selective stimulation of the individual fields of taste buds.