F MRI STUDY OF TASTE CORTEX USING FOCAL STIMULI

这项提议的短期目标是确定人类大脑皮质味觉加工的位置是否取决于味觉刺激在舌头上的位置。我们将构建并测试一种味觉刺激器，将化学味觉刺激施加到舌头的离散部分，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，在右撇子受试者中，无论舌头的一侧受到刺激，初级味觉皮质以及一些二级或更高级别皮质味觉区域的味觉加工将主要发生在右半球。我们还假设，来自舌后瓦状乳突的味觉信息将在初级味觉皮质的不同部分处理，而不是来自前舌的菌状乳突。长期目标包括比较左撇子和右撇子受试者，以及检查对刺激其他味蕾区域的反应。一个长期的目标是了解对味觉系统外周损害的生物学反应的性质和局限性。人类味觉系统的外周部分包括5个不同的味蕾区域，至少由3个脑神经的4个分支支配。因此，外周病变或疾病导致的味觉功能丧失很少是完全的。例如，其中一种味觉神经鼓索经常在口腔手术、中耳手术或疾病(如贝尔氏麻痹)中受损。剩下的完好无损的味蕾和它们的神经纤维通常可以调节相对正常的感觉。中央补偿机制可能是这种复苏的部分原因。揭示这种代偿机制的一个必要步骤是建立中枢激活的正常模式，这是选择性刺激味蕾个别区域的结果。

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.