RESUMEN
A novel, five-term relational reasoning paradigm was employed during functional magnetic resonance imaging to investigate neural correlates of the symbolic distance effect (SDE). Prior to scanning, participants learned a series of more-than (E>D>C>B>A) or less-than (A
Asunto(s)
Formación de Concepto , Generalización del Estimulo , Conceptos Matemáticos , Lóbulo Parietal/fisiología , Solución de Problemas , Aprendizaje por Asociación , Femenino , Humanos , Lógica , Imagen por Resonancia Magnética , Masculino , Estimulación Luminosa , Corteza Prefrontal/fisiología , Tiempo de Reacción , Adulto JovenRESUMEN
This study focused on genetic and behavioural aspects of one important component of the motivation to eat - how appetitive arousal is elicited through the presentation of food-associated stimuli. Individuals with Prader-Willi syndrome, a genetic disorder associated with hyperphagia, and control participants completed a computerised response task in the presence of motivational stimuli. In controls, appetitive arousal was specific to particular stimuli. In contrast, individuals with PWS showed a non-specific pattern of arousal. Over-activation of the anticipatory motivation system may be one consequence of the genetic disorder in PWS.
Asunto(s)
Apetito , Nivel de Alerta , Conducta Alimentaria/psicología , Hiperfagia/psicología , Síndrome de Prader-Willi/psicología , Adulto , Señales (Psicología) , Femenino , Humanos , Hambre , Hiperfagia/complicaciones , Masculino , Motivación , Estimulación Luminosa/métodos , Síndrome de Prader-Willi/complicaciones , Encuestas y Cuestionarios , Análisis y Desempeño de TareasRESUMEN
BACKGROUND: Research into the excessive eating behaviour associated with Prader-Willi syndrome (PWS) to date has focused on homeostatic and behavioural investigations. The aim of this study was to examine the role of the reward system in such eating behaviour, in terms of both the pattern of food preferences and the neural substrates of incentive in the amygdala and orbitofrontal cortex (OFC). METHOD: Participants with PWS (n = 18) were given a food preference interview to examine food preferences and to inform the food-related incentive task to be conducted during the neuroimaging. Thirteen individuals with PWS took part in the positron emission tomography (PET) study, the design of which was based on a previous study of non-obese, non-PWS controls. For the task, participants were asked to consider photographs of food and to choose the food they would most like to eat in two conditions, one of high and one of low incentive foods, tailored to each participant's preferences. For comparison of the food preference data, 12 non-PWS individuals were given one part of the interview. RESULTS: Individuals with PWS expressed relative liking of different foods and showed preferences that were consistent over time, particularly for sweet foods. The participants with PWS did give the foods in the high incentive condition a significantly higher incentive value than the foods in the low incentive condition. However, activation of the amygdala and medial OFC was not associated with the prospect of highly valued foods as predicted in those with PWS. CONCLUSIONS: It would appear that incentive motivation alone plays a less powerful role in individuals with PWS than in those without the syndrome. This is likely to be due to the overriding intrinsic drive to eat because of a lack of satiety in those with PWS, and the impact of this on activity in the incentive processing regions of the brain. Activity in such reward areas may not then function to guide behaviour selectively towards the consumption of high preference foods.
Asunto(s)
Preferencias Alimentarias/psicología , Motivación , Síndrome de Prader-Willi/psicología , Adolescente , Adulto , Anciano , Encéfalo/diagnóstico por imagen , Conducta Alimentaria/psicología , Femenino , Humanos , Procesamiento de Imagen Asistido por Computador/métodos , Entrevistas como Asunto/métodos , Masculino , Persona de Mediana Edad , Tomografía de Emisión de Positrones/métodos , Reino UnidoRESUMEN
OBJECTIVE: To investigate the neural basis of the abnormal eating behaviour in Prader-Willi syndrome (PWS), using brain imaging. We predicted that the satiety response in those with PWS would be delayed and insensitive to food intake. DESIGN AND PARTICIPANTS: The design of this study was based on a previous investigation of the neural activation associated with conditions of fasting and food intake in a nonobese, non-PWS group. The findings were used to generate specific hypotheses regarding brain regions of interest for the current study, in which 13 adults with PWS took part (mean +/- s.d. age = 29 +/- 6; BMI = 31.5 +/- 5.1; IQ = 71 +/- 8, six were female). MEASUREMENTS: Regional cerebral blood flow was measured using positron emission tomography in three sessions: one following an overnight fast and two following disguised energy controlled meals of similar volume and appearance--one of 1674 kJ (400 kcal) and another of 5021 kJ (1200 kcal). Subjective ratings of hunger, fullness and desire to eat, and blood plasma levels of glucose, insulin, leptin, ghrelin and PYY were measured before and after each imaging session. RESULTS: The neural representation of hunger, after an overnight fast, was similar to that found in nonobese individuals in the control study. In contrast, after food intake, the patterns of neural activation previously associated with satiety were not found, even after the higher-energy load. Lateral and medial orbitofrontal cortical activation was associated with consumption of the 400- and 1200-kcal meals, respectively. The medial orbitofrontal activation, however, was only found in those who had shown a large percentage change in fullness ratings following the higher-energy meal. CONCLUSION: We conclude that there is a dysfunction in the satiety system in those with PWS. These findings suggest that brain regions associated with satiety are insensitive even to high-energy food intake in those with the syndrome. This may be the neural basis of the hyperphagia seen in PWS.