لذت برای محرک های بصری و بویایی با تحریک غذاهای پرانرژی که در بی اشتهایی عصبی کاهش می یابد

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.

Energy-rich foods are particularly aversive in patients suffering from anorexia nervosa (AN). Such persons are indeed characterized by an everyday avoidance to eat high-fat and sweet foods and by an obsessive fear of gaining weight (American Psychiatric Association, 1994, Crisp et al., 2006 and Kaye, 2008). Several investigators advocated that palatable foods as reinforcers are avoided in AN patients due to low sensitivity to reward or a diminished ability to experience sensory pleasure (physical anhedonia), and suggested a possible etiological role of dysfunctioning brain reward systems (dopamine and opioid systems) (Davis & Woodside, 2002, Berridge, 2007 and Kaye, 2008). Although recent neuroimaging and psychophysiological studies have begun to address the hypothesis of altered reward or appetitive systems in AN patients (Friederich et al., 2006, Wagner et al., 2007 and Soussignan et al., 2010), the issue remains to be clarified because studies based on self-report scales of physical anhedonia and measurement of sensory pleasure in AN patients provided conflicting results. In some studies, as compared to controls, AN women were found to be anhedonic (Bydlowski et al., 2002, Davis & Woodside, 2002 and Deborde et al., 2006) and reported higher dislike for the sight of high energy foods (Bossert et al., 1991, Stoner et al., 1996, Stormark & Torkildsen, 2004 and Herpertz et al., 2008), for fat taste (Drewnowski et al., 1987, Sunday & Halmi, 1990 and Simon et al., 1993), and the smell of food (Schreder et al., 2008). In some studies, AN patients evinced unchanged hedonic responses to low-caloric food pictures (Bossert et al., 1991 and Stoner et al., 1996), olfactory stimuli (Lombion-Pouthier et al., 2006), and sweet taste (Drewnowski et al., 1987). Finally, AN patients reported a decreased pleasure when sweet solutions were swallowed but not spat out (Eiber et al., 2002), suggesting that they exhibited an excessive fear of gaining weight rather than a diminished ability to experience pleasure. Taken together, currently available studies do not make clear whether the low sensitivity to food reinforcement in AN patients relies on (i) a general decrease in pleasure responses to any kind of actual and imagined events (i.e., anhedonia), (ii) a specific reduction in pleasure responses to food cues, or (iii) a reduction to cues carried by high energy-density foods as a consequence of fear of gaining weight. Further, little is known on how hedonic experience in AN patients relates to hunger/satiety states since in healthy people the expression of pleasure for olfactory and visual food cues fluctuates as a function of motivational states (Cabanac & Duclaux, 1973, Soussignan et al., 1999, Stoeckel et al., 2007 and Jiang et al., 2008). 1.1. Sensory modality and hedonic experience Most of the above studies have gauged taste as the elicitor of hedonic responses, restricting exploration to stimuli that directly relate to food intake, hence excluding the differentiation of pleasure responses to food and non-food stimuli. The investigation of other sensory contributions to flavor perception and pleasure in a variety of situations could indeed provide better understanding of the cues that are meaningful to AN patients. Olfaction and vision provide such alternative cues bearing information on the hedonic value and energetic content of a given food before consumption, and thus may contribute to expectancies involved in anticipatory hunger and pleasure (Thibault and Booth, 2006), and in the amount of food to be ingested (de Wijk et al., 2004). To the best of our knowledge, investigations on sensory pleasure in AN patients have studied only one sensory modality at a time and few have considered either odor or visual cues using both food and non-food stimuli as a function of hunger/satiety. Those studies using food pictures found lower hedonic ratings in AN patients as compared to controls (Santel et al., 2006 and Herpertz et al., 2008), but the effect of motivational state (hunger vs. satiety) was assessed only in one study using a rating scale with a low discriminative power (Santel et al., 2006). Furthermore, studies on hedonic responses to odors raised contradictory findings, but they were limited in the sense that they used only a single food odorant (Schreder et al., 2008), or odorants that were not categorically differentiated by the subjects as belonging to food vs. non-food sources (Lombion-Pouthier et al., 2006). 1.2. Liking and wanting of food Recent studies have suggested at least two neural systems involved in food reward mechanisms, one mediating food hedonics (“liking”), the other mediating the incentive to eat (“wanting”) (Berridge, 1996 and Berridge, 2007). Alterations of liking and wanting have been suggested to be involved in some eating disturbances (Mela, 2006). In one study, wanting was particularly affected in AN patients when high caloric foods were concerned (Stoner et al., 1996). However, this finding was not confirmed in a later study showing that AN patients' wanting appears similar than in healthy controls (Schreder et al., 2008). Thus, whether liking and wanting are similarly affected and whether they are dependent on an individual's motivational state remain to be clarified in anorexia nervosa. 1.3. Aims of the current study The aims of this study are twofold. First, we shall examine whether decreased hedonic responsiveness usually reported in AN patients is specific to olfactory and visual cues carried by foods of high energy density and dependent on an individual's metabolic state, or whether it represents a generalized disturbed affective state (i.e., physical anhedonia). This will be investigated by using the level of depression as a covariate because AN patients were previously reported to be slightly depressive (Bydlowski et al., 2002), and because this affective state has a strong influence on hedonic responses to sensory stimuli (Steiner et al., 1993 and Schaal et al., 2010). Secondly, we shall assess whether hedonic responsiveness to food stimuli (liking) and the desire to ingest these foods (wanting) are differentially affected in anorexia.