This is an application for a project that will use fMRI to investigate central representation of taste in the human brain. There are 2 specific aims.
Specific aim I is to evaluate whether the performance of a task influences brain responses to sapid stimuli. We know that there are anticipatory neurons interspersed with taste-responsive neurons in the cortical gustatory areas and we know that these cortical taste regions participate in affective decision-making. Therefore, it is very likely that performance of a task, such as judging pleasantness or detecting the presence of a taste, affects the response of gustatory neurons or evokes a response within the gustatory areas that could hinder or interact with detection of the response to taste. Systematic investigation of how judging perceptual attributes of a taste interact with the gustatory response is therefore clearly needed.
Specific aim II is to evaluate the general prediction that quality-specific responses can be isolated when intensity and affective value are controlled, and that such responses can be functionally grouped according the physiological meaning of the quality. Although the issue of taste-quality coding has dominated the rat and primate electrophysiological work in gustation, to date, no study has addressed this issue in humans. Since there is likely to be overlapping representation of taste intensity, affect, and quality coding, we propose to examine brain responses to taste quality while systematically manipulating or controlling for the intensity and affective value of the stimulus. Because affective value can be intrinsic to the stimulus, or the result of changes in internal state we will test the hypothesis that while the intrinsic pleasantness of a sweet taste may influence quality coding, quality coding should be independent from transient changes in pleasantness associated with satiety. We will use standard fMRI as well as 2 novel techniques, fMRI-adaptation, and effective connectivity analyses, to examine if quality is represented as spatially segregated responses (e.g. chemotopy), spatially overlapping but distinct neuronal population responses or as unique patterns of interconnectivity within a network of cortical gustatory areas. This research will provide fundamental information about human gustation and it will provide important baseline data for future studies of gustatory processing in the obese and individuals with an eating, drug or alcohol disorder.
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