Food choice and neural reward systems in adolescents with anorexia nervosa and atypical anorexia nervosa

Abstract

Background: Adolescence is a critical developmental period for the study of anorexia nervosa (AN), an illness characterized by extreme restriction of food intake. The maturation of the reward system during adolescence combined with recent neurobiological models of AN led to the hypothesis that early on in illness, restrictive food choices would be associated with activity in nucleus accumbens reward regions, rather than caudate regions identified among adults with AN.

Methods: Healthy adolescents (HC, n = 41) and adolescents with AN or atypical AN (atypAN, n = 76) completed a Food Choice Task during fMRI scanning. Selection of high-fat foods and choice-related activation in nucleus accumbens and anterior caudate regions-of-interest (ROIs) were compared between individuals with AN/atypAN and HC. Associations were examined between choice-related activation and choice preferences among the AN group. Exploratory analyses examined associations between choice-related activation and psychological assessments among the patient group.

Results: Adolescents with AN or atypAN selected fewer high-fat foods than HC (t = -5.92, p < .001). Counter to predictions, there were no significant group differences in choice-related activation in the ROIs. Among individuals with AN or atypAN, choice-related neural activity in the anterior caudate was significantly negatively associated with high-fat food selections in the task (r = -.32, p = .024). In exploratory analyses, choice-related anterior caudate activation was positively associated with psychological measures of illness severity among patients (p's < .05, uncorrected).

Conclusions: In this large cohort of adolescents with AN/atypAN, there was no evidence of altered reward system engagement during food choice. While there was no group difference in choice-related caudate activation, the associations with choices and psychological measures continue to suggest that this neural region is implicated in illness. Longitudinal analyses will clarify whether neural variability relates to longer-term course.

Keywords: Anorexia nervosa; adolescence; caudate; neuroimaging; reward.

Figure 1

Food choice task. Participants completed the Food Choice Task with fMRI scanning. The task comprises two rating phases (A, B) and a choice phase (C). During the Choice phase, on each trial, participants indicated their preference for a changing food item (shown on the right) relative to a repeating neutral-rated reference item (on the left)

Figure 2

Food choice task behavior. (A) Low-fat items were rated higher on healthiness than high-fat items. Individuals with AN or atypAN rated food, and high-fat foods in particular, as lower in healthiness compared to HC. (B) The AN group rated high-fat foods lower in tastiness relative to HC. (C) The AN group was less likely to choose high-fat foods than the HC group; groups did not differ on low-fat selections. (D) Choice was influenced more by tastiness among HC relative to individuals with AN or atypAN, whereas choice was influenced more by healthiness among individuals with AN or atypAN relative to HC. (E) Tastiness and healthiness ratings were more strongly associated among individuals with AN or atypAN than HC. (F) Associations between the proportion of high-fat food choices on the task and actual caloric intake at the multi-item meal. * indicates p < .01

Figure 3

Region of interest (ROI) analyses. (A) There were no significant differences between groups in choice-related activation of striatal regions. Evidence was strong for the absence of a difference between groups in the nucleus accumbens (left) and inconclusive for the anterior caudate (right). (B) Choice of high-fat foods was not associated with activation of the nucleus accumbens during choice (left) but was negatively associated with choice-related anterior caudate activation among individuals with AN or atypAN (right). *p < .01

Figure 4

Associations between choice-related activation in striatal regions of interest (ROIs) and psychological assessments among individuals with AN or atypAN. Associations between (A) TFEQ restraint subscale, (B) Global EDE-Q score, (C) SRHI total score, (D) SPSRQ-C reward sensitivity, and choice-related nucleus accumbens activation (left column) and choice-related anterior caudate activation (right column). Analyses were adjusted for age and IQ, p-values are uncorrected for multiple comparisons.