Rolls � PPT presentation on taste + eating

Greg Detre

Thursday, 01 June, 2000

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Rolls � PPT presentation on taste + eating�� 1

Distinct Groups of Gustatory Neurons� 1

Gustatory Responses in Secondary Taste Cortex� 1

Effects of Hunger and Satiety on Neuronal Taste Processing at Different Stages of the Taste Pathway� 1

In contrast, in the secondary taste cortex, in the caudolateral part of the orbitofrontal cortex, it was found that the responses of neurons to the taste of the glucose decreased to zero while the monkey ate it to satiety� 2

In the secondary taste cortex, it was also found that the decreases in the responsiveness of the neurons were relatively specific to the food which one has been fed to satiety� 2

Summary� 2

Taste Processing in the Secondary Taste Pathways� 2

2. Sensory Specific Satiety� 2

Summary� 3

Distinct Groups of Gustatory Neurons

Responsiveness of neurons in the insular part of the primary taste cortex was determined by measuring the responses of each neuron to the prototypical stimuli plus water and blackcurrant juice

Profiles of these sensitivities were then compared with each other

It was shown that there were groups of neurons that responded primarily to each of the prototypical stimuli, to water, and to blackcurrant juice, as well as other groups of neurons that responded to combinations of these

Gustatory Responses in Secondary Taste Cortex

As researchers studied the area anterior to the primary taste cortex, they discovered a secondary taste cortex (caudolateral orbitofrontal cortex)

Using the same technique as above, they found the mean sensitivity of neurons here to be 0.39

So, this tuning is much finer than that of neurons in NTS, and finer than that of neurons in the primary frontal opercular and insular taste cortices

Clusters of different types of neurons also found in here

Effects of Hunger and Satiety on Neuronal Taste Processing at Different Stages of the Taste Pathway

Responses of single neurons at different stages of taste system have been analyzed during feeding macaque monkeys to satiety with 20% glucose solution

Normal control of feeding

Responsiveness of taste neurons in NTS is not attenuated by feeding to satiety

In the primary taste cortex, both in the frontal operculum and in the insular part, hunger does not modulate the responsiveness of single neurons to gustatory stimuli

In contrast, in the secondary taste cortex, in the caudolateral part of the orbitofrontal cortex, it was found that the responses of neurons to the taste of the glucose decreased to zero while the monkey ate it to satiety

In contrast, in the secondary taste cortex, in the caudolateral part of the orbitofrontal cortex, it was found that the responses of neurons to the taste of the glucose decreased to zero while the monkey ate it to satiety

Eating behaviour turned from avid acceptance to active rejection of the glucose

Same neuronal responses were produced, when thirsty animal drank water until satiety

In the secondary taste cortex, it was also found that the decreases in the responsiveness of the neurons were relatively specific to the food which one has been fed to satiety

If fed glucose solution to satiety, neuronal responsiveness decreased to the taste of the glucose but not to the taste of blackcurrant juice.

Summary

Taste Pathway

NTS-->VPMpc (Thalamus)-->Primary Taste Cortex (Frontal Operculum and Insula)-->Secondary Taste Cortex (Caudolateral Orbitofrontal Cortex)

As we go up in the taste pathway to the higher levels, the gustatory neuron sensitivity (tuning) gets finer and finer. The neurons become more specific in the response to the different taste stimuli.

Hunger and satiety motivational states affect the responsiveness of gustatory neurons only in the secondary taste cortex

Taste Processing in the Secondary Taste Pathways

1.Convergence of olfactory and taste inputs

3 types of neurons responding to:

a) Taste, vision, or olfactory

b) Taste and visual inputs

c) Taste and olfactory inputs

d) Olfactory and visual inputs

2. Sensory Specific Satiety

-The term sensory-specific satiety was coined because sensory factors such as similarity of color, shape, flavor, and texture are usually more important then metabolic equivalence in terms of protein, carbohydrates and fat content in influencing how food interacts with this type of satiety

-the effects of hunger

-the reward value of odor

Summary

there are 3 types of neurons responding and converging with three different sensory modalities in the orbital frontal cortex

sensory-specific satiety has a significant effect on the control of feeding related behaviors since taste representations as well as olfactory representations of food are modulated by hunger