Changes in brain activity related to eating chocolate: From pleasure to aversion

Neuropsychology/Cognitive Neuroscience Unit, and Northwestern Cognitive Brain Mapping Group, Northwestern University School of Medicine, Chicago, IL 60611, USA.
Brain (Impact Factor: 9.2). 10/2001; 124(Pt 9):1720-33.
Source: PubMed


We performed successive H(2)(15)O-PET scans on volunteers as they ate chocolate to beyond satiety. Thus, the sensory stimulus and act (eating) were held constant while the reward value of the chocolate and motivation of the subject to eat were manipulated by feeding. Non-specific effects of satiety (such as feelings of fullness and autonomic changes) were also present and probably contributed to the modulation of brain activity. After eating each piece of chocolate, subjects gave ratings of how pleasant/unpleasant the chocolate was and of how much they did or did not want another piece of chocolate. Regional cerebral blood flow was then regressed against subjects' ratings. Different groups of structures were recruited selectively depending on whether subjects were eating chocolate when they were highly motivated to eat and rated the chocolate as very pleasant [subcallosal region, caudomedial orbitofrontal cortex (OFC), insula/operculum, striatum and midbrain] or whether they ate chocolate despite being satiated (parahippocampal gyrus, caudolateral OFC and prefrontal regions). As predicted, modulation was observed in cortical chemosensory areas, including the insula and caudomedial and caudolateral OFC, suggesting that the reward value of food is represented here. Of particular interest, the medial and lateral caudal OFC showed opposite patterns of activity. This pattern of activity indicates that there may be a functional segregation of the neural representation of reward and punishment within this region. The only brain region that was active during both positive and negative compared with neutral conditions was the posterior cingulate cortex. Therefore, these results support the hypothesis that there are two separate motivational systems: one orchestrating approach and another avoidance behaviours.

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Available from: Alan Charles Evans, Dec 27, 2013
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    • "This explanation fits well with other research investigating the reward value attributed to a given stimulus. For example,Small et al. (2001)showed modulation of the medial orbitofrontal cortex the more a participant found chocolate pleasant and rewarding (see also Rolls, 2000). In a seminal meta-analysis of 93 neuroimaging studies of positive-valence aesthetic appraisal spanning four different sensory modalities (vision, audition, olfaction and gustation),Brown et al. (2011)attempted to establish core neurobiological features common across all aesthetic contexts (as opposed to the other major neuroaesthetics meta-analysis, performed byVartanian and Skov (2014), which focused on visual studies only). "
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    • "When participants ate chocolate despite being satiated, they evaluated it as less rewarding and showed changed activation patterns (caudolateral OFC, prefrontal regions). Cingulate activation was independent from reward associated with chocolate consumption (Small et al. 2001). Another study further supported the notion of a satiety-dependent activation in the OFC (O'Doherty et al. 2000). "
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    • "Several studies have suggested that the right insula functionally relates to stimulus intensity (Small et al., 2003; Spetter et al., 2010). Although several authors also associated this region with taste pleasantness (Nitschke et al., 2006; Small et al., 2001), these studies were unable to rule out taste intensity effects, because taste concentration was not explicitly manipulated and/ or subjective intensity ratings were not measured. We found no significant association between the second factor and pleasantness ratings. "
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