The responsiveness of neurons in the insular gustatory cortex of the macaque monkey is independent of hunger

2004

Anat. Rec.

Self Cite

136

In primates, stimuli to sensory systems influence motivational and emotional behavior via neural relays to the orbitofrontal cortex. This article reviews studies on the effects of stimuli from multiple sensory modalities on the brain of humans and some other higher primates. The primate orbitofrontal cortex contains the secondary taste cortex, in which the reward value of taste is represented. It also contains the secondary and tertiary olfactory cortical areas, in which information about the identity and also about the reward value of odors is represented. A somatosensory input is revealed by neurons that respond to the viscosity of food in the mouth, to the texture (mouth feel) of fat in the mouth, and to the temperature of liquids placed into the mouth. The orbitofrontal cortex also receives information about the sight of objects from the temporal lobe cortical visual areas. Information about each of these modalities is represented separately by different neurons, but in addition, other neurons show convergence between different types of sensory input. This convergence occurs by associative learning between the visual or olfactory input and the taste. In that emotions can be defined as states elicited by reinforcers, the neurons that respond to primary reinforcers (such as taste and touch), as well as learn associations to visual and olfactory stimuli that become secondary reinforcers, provide a basis for understanding the functions of the orbitofrontal cortex in emotion. In complementary neuroimaging studies in humans, it is being found that areas of the orbitofrontal cortex are activated by pleasant touch, by painful touch, by taste, by smell, and by more abstract reinforcers such as winning or losing money. Damage to the orbitofrontal cortex in humans can impair the learning and reversal of stimulus-reinforcement associations and thus the correction of behavioral responses when these are no longer appropriate because previous reinforcement contingencies change. It is striking that humans and other catarrhines, being visual specialists like other anthropoids, interface the visual system to other sensory systems (e.g., taste and smell) in the orbitofrontal cortex. © 2004 Wiley-Liss, Inc.Key words: emotion; orbitofrontal cortex; reward; reinforcement; taste; olfaction; vision; touch; reversal learning; face expression Despite being visual specialists, it is notable that anthropoid primates such as hominoids (e.g., humans) and Old World monkeys still have important stimuli from other sensory modalities. This review examines how sensory systems influence motivational and emotional behavior via neural relays to the orbitofrontal cortex.In primates, the prefrontal cortex is the part of the cortex that receives projections from the mediodorsal nucleus of the thalamus (with which it is reciprocally connected) and is situated in front of the motor and premotor cortices (areas 4 and 6) in the frontal lobe. Based on the divisions of the mediodorsal nucleus, the prefrontal cortex may be divided into three main ...

Section: Neurophysiology Of Orbitofrontal Cortex Tastementioning

confidence: 92%

Convergence of sensory systems in the orbitofrontal cortex in primates and brain design for emotion

2004

Anat. Rec.

Self Cite

136

“…Some neurons in the primary taste cortex respond to particular combinations of taste and oral texture stimuli, but do not respond to olfactory stimuli or visual stimuli such as the sight of food (17) Neurons in the primary taste cortex do not represent the reward value of taste, that is, the appetite for a food, in that their firing is not decreased to zero by feeding the taste to satiety (18,19) .…”

Section: The Primary Taste Cortexmentioning

confidence: 99%

Taste, olfactory and food texture reward processing in the brain and the control of appetite

2012

Proc. Nutr. Soc.

Self Cite

106

Complementary neuronal recordings and functional neuroimaging in human subjects show that the primary taste cortex in the anterior insula provides separate and combined representations of the taste, temperature and texture (including fat texture) of food in the mouth independently of hunger and thus of reward value and pleasantness. One synapse on, in the orbitofrontal cortex (OFC), these sensory inputs are for some neurons combined by learning with olfactory and visual inputs, and these neurons encode food reward in that they only respond to food when hungry, and in that activations correlate with subjective pleasantness. Cognitive factors, including word-level descriptions, and attention modulate the representation of the reward value of food in the OFC and a region to which it projects, the anterior cingulate cortex. Further, there are individual differences in the representation of the reward value of food in the OFC. It is argued that over-eating and obesity are related in many cases to an increased reward value of the sensory inputs produced by foods, and their modulation by cognition and attention that over-ride existing satiety signals. It is proposed that control of all rather than one or several of these factors that influence food reward and eating may be important in the prevention and treatment of overeating and obesity.

“…Similarly, the gustatory responses of neurons in the primary taste cortical regions of the insula and frontal operculum were found to be unaffected by satiety Scott et al 1985;Yaxley et al 1988). Visual responses to food at the level of the inferotemporal cortex [a visual area known to project to orbitofrontal cortex (Barbas 1988;Morecraft et al 1992)] were also not modulated by satiety (Rolls et al 1977).…”

Section: Introductionmentioning

confidence: 97%

Hunger and satiety modify the responses of olfactory and visual neurons in the primate orbitofrontal cortex

Critchley

Journal of Neurophysiology

1996

432

288

SUMMARYAND CONCLUSIONS1. The primate orbitofiontal cortex is the site of convergence of information from primary taste and primary olfactory cortical regions. In addition, it receives projections from temporal lobe visual areas concerned with the representation of objects such as foods. Previous work has shown that the responses of gustatory neurons in the secondary taste area within the orbitofrontal cortex are modulated by hunger and satiety, in that they stop responding to the taste of a food on which an animal has been fed to behavioral satiation, yet may continue to respond to the taste of other foods.2. This study demonstrates a similar modulation of the responses of olfactory and visual orbitofrontal cortex neurons after &ding to satiety. Seven of nine olfactory neurons that were responsive to the odors of foods, such as blackcurrant juice, were found to decrease their responses to the odor of the satiating food in a selective and statistically significant manner.3. It also was found for eight of nine neurons that had selective responses to the sight of food, that they demonstrated a sensoryspecific reduction in their visual responses to foods after satiation.4 The responses of orbitofiontal cortex neurons selective for foods in more than one modality also were analyzed before and after feeding to satiation. Satiety often affected the responses of these multimodal neurons across all modalities, but a sensoryspecific effect was not always demonstrable for both modalities.5. These findings show that the olfactory and visual representations of food, as well as the taste representation of food, in the primate orbitofi=ontal cortex are modulated by hunger. Usually a component related to sensory-specific satiety can be demonstrated. The findings link at least part of the processing of olfactory and visual information in this brain region to the control of feedingrelated behavior.