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Biomedical subjects

Dana M Small

Publications and source records attributed to Dana M Small.

10 recordsLinked to original sources
PubMed2006

Central gustatory processing in humans.

The purpose of this chapter is to provide a general overview of the central representation of gustatory information in the human brain. The anatomical pathways for the two primary animal models (rodent and nonhuman primate) are provided followed by the presumed human gustatory pathway. The section on the gustatory pathway describes what is known about how taste intensity, quality and affective value are represented in the human brain. The chapter concludes with a review of flavor processing.

Affect↗
PubMed2005

Increased taste intensity perception exhibited by patients with chronic back pain.

There is overlap between brain regions involved in taste and pain perception, and cortical injuries may lead to increases as well as decreases in sensitivity to taste. Recently it was shown that chronic back pain (CBP) is associated with a specific pattern of brain atrophy. Since CBP is characterized by increased sensitivity to pain, we reasoned that the sense of taste might also be enhanced in CBP. Detection and recognition thresholds were established for a sour taste and ratings of both suprathreshold taste intensity and pleasantness-unpleasantness perception were collected for sweet, sour, salty and bitter stimuli in 11 CBP patients and 11 matched control subjects. As a control, ratings were also collected for visual assessment of degree of grayness. There was no difference between CBP and control subjects for visual grayness rating. On the other hand, CBP patients in comparison to control subjects rated gustatory stimuli as significantly more intense but no more or less pleasant and showed a trend towards a lower detection threshold (i.e. increased sensitivity). The selectivity of the taste disturbance suggests interaction between pain and taste at specific brain sites and provides further evidence that CBP involves specific brain abnormalities.

Adult↗
PubMed2005

Differential neural responses evoked by orthonasal versus retronasal odorant perception in humans.

Odors perceived through the mouth (retronasally) as flavor are referred to the oral cavity, whereas odors perceived through the nose (orthonasally) are referred to the external world. We delivered vaporized odorants via the orthonasal and retronasal routes and measured brain response with fMRI. Comparison of retronasal versus orthonasal delivery produced preferential activity in the mouth area at the base of the central sulcus, possibly reflecting olfactory referral to the mouth, associated with retronasal olfaction. Routes of delivery produced differential activation in the insula/operculum, thalamus, hippocampus, amygdala, and caudolateral orbitofrontal cortex in orthonasal > retronasal and in the perigenual cingulate and medial orbitofrontal cortex in retronasal > orthonasal in response to chocolate, but not lavender, butanol, or farnesol, so that an interaction of route and odorant may be inferred. These findings demonstrate differential neural recruitment depending upon the route of odorant administration and suggest that its effect is influenced by whether an odorant represents a food.

Appetite↗
PubMed2005

Odor/taste integration and the perception of flavor.

Perceptions of the flavors of foods or beverages reflect information derived from multiple sensory afferents, including gustatory, olfactory, and somatosensory fibers. Although flavor perception therefore arises from the central integration of multiple sensory inputs, it is possible to distinguish the different modalities contributing to flavor, especially when attention is drawn to particular sensory characteristics. Nevertheless, our experiences of the flavor of a food or beverage are also simultaneously of an overall unitary perception. Research aimed at understanding the mechanisms behind this integrated flavor perception is, for the most part, relatively recent. However, psychophysical, neuroimaging and neurophysiological studies on cross-modal sensory interactions involved in flavor perception have started to provide an understanding of the integrated activity of sensory systems that generate such unitary perceptions, and hence the mechanisms by which these signals are "functionally united when anatomically separated". Here we review this recent research on odor/taste integration, and propose a model of flavor processing that depends on prior experience with the particular combination of sensory inputs, temporal and spatial concurrence, and attentional allocation. We propose that flavor perception depends upon neural processes occurring in chemosensory regions of the brain, including the anterior insula, frontal operculum, orbitofrontal cortex and anterior cingulate cortex, as well as upon the interaction of this chemosensory "flavor network" with other heteromodal regions including the posterior parietal cortex and possibly the ventral lateral prefrontal cortex.

Animals↗
PubMed2005

Monetary incentives enhance processing in brain regions mediating top-down control of attention.

To evaluate the effect of an abstract motivational incentive on top-down mechanisms of visual spatial attention, 10 subjects engaged in a target detection task and responded to targets preceded by spatially valid (predictive), invalid (misleading) or neutral central cues under three different incentive conditions: win money (WIN), lose money (LOSE), and neutral (neither gain nor lose). Activation in the posterior cingulate cortex was correlated with visual spatial expectancy, defined as the degree to which the valid cue benefited performance as evidenced by faster reaction times compared to non-directional cues. Winning and losing money enhanced this relationship via overlapping but independent limbic mechanisms. In addition, activity in the inferior parietal lobule was correlated with disengagement (the degree to which invalid cues diminished performance). This relationship was also enhanced by monetary incentives. Finally, incentive enhanced the relationship of activation in the visual cortex to visual spatial expectancy and disengagement for both types of incentive (WIN and LOSE). These results show that abstract incentives enhance neural processing within the attention network in a process- and valence-selective manner. They also show that different cognitive and motivational mechanisms may produce a common effect upon unimodal cortices in order to enhance processing to serve the current behavioral goal.

Adult↗
PubMed2005

Taste and olfactory intensity perception changes following left insular stroke.

The authors tested suprathreshold intensity perception of gustatory and olfactory stimuli in a 70-year-old right-handed man following a left posterior insular stroke and compared his results with those of age-matched controls. Both modalities revealed significant differences between left (ipsilateral to lesion) and right (contralateral) ratings of intensity. In both gustation and olfaction, these differences were driven primarily by trends toward increased contralateral sensitivity relative to controls. Intensity changes were most pronounced for unpleasant odors and for tastes perceived strongly as either pleasant (sweet) or unpleasant (salty, bitter). These results show that a left posterior insula lesion may affect taste and olfactory perception similarly by increasing sensitivity contralateral to the lesion. One possible mechanism is release from inhibition at the cortical level.

Aged↗
PubMed2004

Experience-dependent neural integration of taste and smell in the human brain.

Flavor perception arises from the central integration of peripherally distinct sensory inputs (taste, smell, texture, temperature, sight, and even sound of foods). The results from psychophysical and neuroimaging studies in humans are converging with electrophysiological findings in animals and a picture of the neural correlates of flavor processing is beginning to emerge. Here we used event-related fMRI to evaluate brain response during perception of flavors (i.e., taste/odor liquid mixtures not differing in temperature or texture) compared with the sum of the independent presentation of their constituents (taste and/or odor). All stimuli were presented in liquid form so that olfactory stimulation was by the retronasal route. Mode of olfactory delivery is important because neural suppression has been observed in chemosensory regions during congruent taste-odor pairs when the odors are delivered by the orthonasal route and require subjects to sniff. There were 2 flavors. One contained a familiar/congruent taste-odor pair (vanilla/sweet) and the other an unfamiliar/incongruent taste-odor pair (vanilla/salty). Three unimodal stimuli, including 2 tastes (sweet and salty) and one odor (vanilla), as well as a tasteless/odorless liquid (baseline) were presented. Superadditive responses during the perception of the congruent flavor compared with the sum of its constituents were observed in the anterior cingulate cortex (ACC), dorsal insula, anterior ventral insula extending into the caudal orbitofrontal cortex (OFC), frontal operculum, ventral lateral prefrontal cortex, and posterior parietal cortex. These regions were not present in a similar analysis of the incongruent flavor compared with the sum of its constituents. All of these regions except the ventrolateral prefrontal cortex were also isolated in a direct contrast of congruent - incongruent. Additionally, the anterior cingulate, posterior parietal cortex, frontal operculum, and ventral insula/caudal OFC were also more active in vanilla + salty minus incongruent, suggesting that delivery of an unfamiliar taste-odor combination may lead to suppressed neural responses. Taken together with previous findings in the literature, these results suggest that the insula, OFC, and ACC are key components of the network underlying flavor perception and that taste-smell integration within these and other regions is dependent on 1) mode of olfactory delivery and 2) previous experience with taste/smell combinations.

Adult↗
PubMed2003

Dissociation of neural representation of intensity and affective valuation in human gustation.

We used a 2 x 2 factorial design to dissociate regions responding to taste intensity and taste affective valence. Two intensities each of a pleasant and unpleasant taste were presented to subjects during event-related fMRI scanning. The cerebellum, pons, middle insula, and amygdala responded to intensity irrespective of valence. In contrast, valence-specific responses were observed in anterior insula/operculum extending into the orbitofrontal cortex (OFC). The right caudolateral OFC responded preferentially to pleasant compared to unpleasant taste, irrespective of intensity, and the left dorsal anterior insula/operculuar region responded preferentially to unpleasant compared to pleasant tastes equated for intensity. Responses best characterized as an interaction between intensity and pleasantness were also observed in several limbic regions. These findings demonstrate a functional segregation within the human gustatory system. They also show that amygdala activity may be driven by stimulus intensity irrespective of valence, casting doubt upon the notion that the amygdala responds preferentially to negative stimuli.

Adult↗
PubMed2003

Feeding-induced dopamine release in dorsal striatum correlates with meal pleasantness ratings in healthy human volunteers.

Seven healthy subjects underwent two [(11)C]raclopride positron emission tomography (PET) scans, one following a 16-h fast and the other after consumption of a favorite meal (following a 16-h fast) in counterbalanced fashion. Before and after each scan subjects gave ratings of hunger/fullness and desire to eat. In addition, meal pleasantness ratings were collected immediately after consumption of the favorite meal. PET data were analyzed using brain parametric maps to generate regions of statistically significant change, as well as regions of interest manually drawn on each individual's coregistered anatomical image. [(11)C]Raclopride binding potential was compared across the two states (hungry and full). A significant reduction in binding potential was observed in the full compared to the hungry state in the dorsal putamen and caudate nucleus, indicative of dopamine release. There were no changes elsewhere in the striatum. A correlation was observed between the reduction in [(11)C]raclopride binding and meal pleasantness ratings, but not with desire to eat (hunger) or satiety after eating. These results suggest that feeding is associated with dopamine release in the dorsal, but not the ventral striatum, and that the amount of dopamine released correlates with the degree of experienced pleasure.

Adult↗