Daniel Rigaud

Hedonic reactivity to visual and olfactory cues: Rapid facial electromyographic reactions are altered in anorexia nervosa

Though it has been suggested that hedonic processing is altered in anorexia nervosa (AN), few studies have used objective measures to assess affective processes in this eating disorder. Accordingly, we investigated facial electromyographic, autonomic and subjective reactivity to the smell and sight of food and non-food stimuli, and assessed more particularly rapid facial reactions reflecting automatic processing of pleasantness. AN and healthy control (HC) women were exposed, before and after a standardized lunch, to pictures and odorants of foods differing in energy density, as well as to non-food sensory cues. Whereas the temporal profile of zygomatic activity in AN patients was typified by a fast drop to sensory cues within the 1000 ms following stimulus onset, HC showed a larger EMG reactivity to pictures in a 800-1000 ms time window. In contrast, pleasantness ratings discriminated the two groups only for high energy density food cues suggesting a partial dissociation between objective and subjective measures of hedonic processes in AN patients. The findings suggest that the automatic processing of pleasantness might be altered in AN, with the sensitivity to reward being modulated by controlled processes.

Alliesthesia to food cues: heterogeneity across stimuli and sensory modalities.

Negative alliesthesia to olfactory and visual stimuli was assessed in 29 normal-weight women who, on alternate days, were either fasting or in a postprandial state after an ad libitum lunch. The participants were alternatively exposed to food and non-food pictures and odorants, and then rated for their hedonic appreciation (liking) and their desire to ingest (wanting) the evoked foods. While negative alliesthesia was observed only for food stimuli, it did not equally affect all food categories in either sensory modality. The stimuli representing foods eaten in typical local main dishes or having high energy density (e.g., pizza, bacon, beef, cheese) evoked clear negative alliesthesia, whereas this was not the case for those less consumed within a customary meal or associated with desserts (i.e., fruits). Furthermore, the visual food stimuli triggered a more negative shift in liking than did the food odours. Finally, the shift in wanting between pre- and post-meal state was more important than the shift in liking. These results suggest that alliesthesia may be influenced by both metabolic and non-metabolic factors.

Pleasure for visual and olfactory stimuli evoking energy-dense foods is decreased in anorexia nervosa

Although patients with anorexia nervosa have been suggested to be anhedonic, few experiments have directly measured their sensory pleasure for a range of food and non-food stimuli. This study aimed to examine whether restrictive anorexia nervosa (AN-R) patients displayed: i) a generalized decline in sensory pleasure or only in food-related sensory pleasure; ii) a modification of hedonic responses to food cues (liking) and of the desire to eat foods (wanting) as a function of their motivational state (hunger vs. satiety) and energy density of foods (high vs. low). Forty-six female participants (AN-R n=17; healthy controls (HC) n=29) reported before/after lunch their pleasure for pictures/odorants representing foods of different energy density and non-food objects. They also reported their desire to eat the foods evoked by the sensory stimuli, and completed the Physical Anhedonia Scale and the Beck Depression Inventory. AN-R and HC participants did not differ on liking ratings when exposed to low energy-density food or to non-food stimuli. The two groups also had similar physical anhedonia scores. However, compared to HC, AN-R reported lower liking ratings for high energy food pictures regardless of their motivational state. Olfactory pleasure was reduced only during the pre-prandial state in the AN-R group. The wanting ratings showed a distinct pattern since AN-R participants reported less desire to eat the foods representing both low and high energy densities, but the effect was restricted to the pre-prandial state. Taken together these results reflect more the influence of core symptoms in anorexia nervosa (fear of gaining weight) than an overall inability to experience pleasure.