Grill H J, Roitman M F, Kaplan J M
University of Pennsylvania, Graduate Groups of Psychology and Neuroscience, Philadelphia.
Am J Physiol. 1996 Sep;271(3 Pt 2):R677-87. doi: 10.1152/ajpregu.1996.271.3.R677.
We used conjoint manipulation of taste and physiological state to address the theoretical issue of signal integration. The interaction between taste (glucose concentration) and state (food deprivation) was evaluated using the taste reactivity method in which oral motor responses elicited by direct intraoral infusion are measured. The time frame of the typical taste reactivity paradigm, where observation is limited to the infusion period, was expanded to include the postinfusion interval. In each test session, rats received a series of trials consisting of 15-s intraoral infusions and 45-s postinfusion observation intervals. Two experiments were run in which glucose concentration was varied and rats were run nondeprived and after 24 h food deprivation. In experiment 1, glucose concentrations (0, 3.2, 6.25, 12.5, and 25%) were randomly presented during each test session. In experiment 2, individual glucose concentrations (0, 6.25, or 25%) were presented during separate sessions. For both, a deprivation condition was flanked by nondeprived (baseline) sessions. Concentration-response functions were comparable in both experiments. In each experiment, the shape of the concentration-response function was dramatically different during and after infusions. During infusions, there were no increases in glucose-elicited rhythmic oral responses beyond a very dilute concentration. After infusions, the concentration-response functions appeared linear across the concentration range. In both experiments, deprivation elevated responding only in the after-infusion periods. In experiment 1, the concentration-response function was uniformly elevated (on average, 27%) by deprivation, which if taken at face value would suggest an additive combination of taste and state feedback signals. In experiment 2, however, deprivation increased responding (approximately 30%) for 6.25%, but not for 0 or 25%, suggesting a stimulus specificity of the taste-state integration. Clearly then, the taste-state profiles differed as a function of experimental design. In the GENERAL DISCUSSION, we suggest that the uniform elevation of responding to all glucose concentrations, and to water, seen in experiment 1, may be an artifact of the random presentation of all stimuli during individual sessions. Experiment 2, in which stimuli were presented in a between-sessions design, may provide a truer reflection of the underlying integrative process.
我们采用味觉与生理状态的联合操控来解决信号整合的理论问题。使用味觉反应方法评估味觉（葡萄糖浓度）与状态（食物剥夺）之间的相互作用，该方法通过测量经口腔直接灌注引发的口腔运动反应。典型味觉反应范式的时间框架（观察仅限于灌注期）被扩展至包括灌注后间隔期。在每个测试环节中，大鼠接受一系列试验，包括15秒的口腔内灌注和45秒的灌注后观察间隔期。进行了两项实验，其中葡萄糖浓度有所变化，且大鼠分别在未剥夺食物和食物剥夺24小时后进行实验。在实验1中，每次测试环节随机呈现葡萄糖浓度（0%、3.2%、6.25%、12.5%和25%）。在实验2中，单独的测试环节分别呈现单个葡萄糖浓度（0%、6.25%或25%）。对于这两项实验，剥夺食物条件的测试环节两侧均为未剥夺食物（基线）的测试环节。两项实验中的浓度 - 反应函数具有可比性。在每个实验中，灌注期间和灌注后的浓度 - 反应函数形状显著不同。在灌注期间，除了非常稀的浓度外，葡萄糖引发的节律性口腔反应没有增加。灌注后，浓度 - 反应函数在整个浓度范围内呈线性。在两项实验中，剥夺食物仅在灌注后阶段提高反应。在实验1中，剥夺食物使浓度 - 反应函数平均均匀升高27%，如果仅从表面看，这表明味觉和状态反馈信号是相加组合。然而，在实验2中，剥夺食物使6.25%葡萄糖浓度的反应增加（约30%），但对0%和25%葡萄糖浓度则没有增加，这表明味觉 - 状态整合具有刺激特异性。显然，味觉 - 状态特征因实验设计而异。在“一般讨论”部分，我们认为在实验1中观察到的对所有葡萄糖浓度以及水的反应均匀升高，可能是由于在单个测试环节中所有刺激随机呈现造成的假象。实验2采用测试环节间呈现刺激的设计，可能更真实地反映了潜在的整合过程。
