RESUMEN
BACKGROUND & AIMS: The study of intrinsic fluctuations in the blood oxygen level-dependent signal of functional magnetic resonance imaging can provide insight into the effect of physiologic states on brain processes. In an effort to better understand the brain-gut communication induced by the absorption and metabolism of nutrients in healthy lean and obese individuals, we investigated whether ingestion of nutritive and non-nutritive sweetened beverages differentially engages the hypothalamus and brainstem vagal pathways in lean and obese women. METHODS: In a 2-day, double-blind crossover study, 11 lean and 11 obese healthy women underwent functional magnetic resonance imaging scans after ingestion of 2 beverages of different sucrose content, but identical sweetness. During scans, subjects rested with eyes closed. RESULTS: Blood oxygen level-dependent fluctuations demonstrated significantly greater power in the highest frequency band (slow-3: 0.073-0.198 Hz) after ingestion of high-sucrose compared with low-sucrose beverages in the nucleus tractus solitarius for both groups. Obese women had greater connectivity between the right lateral hypothalamus and a reward-related brain region and weaker connectivity with homeostasis and gustatory-related brain regions than lean women. CONCLUSIONS: In a functional magnetic resonance imaging study, we observed sucrose-related changes in oscillatory dynamics of blood oxygen level-dependent fluctuations in brainstem and hypothalamus in lean and obese women. The observed frequency changes are consistent with a rapid vagally mediated mechanism due to nutrient absorption, rather than sweet taste receptor activation. These findings provide support for altered interaction between homeostatic and reward networks in obese individuals.
Asunto(s)
Tronco Encefálico/fisiopatología , Sacarosa en la Dieta/administración & dosificación , Hipotálamo/fisiopatología , Obesidad/fisiopatología , Delgadez/fisiopatología , Administración Oral , Adulto , Bebidas , Mapeo Encefálico/métodos , Tronco Encefálico/metabolismo , Estudios Cruzados , Sacarosa en la Dieta/metabolismo , Método Doble Ciego , Femenino , Homeostasis , Humanos , Hipotálamo/metabolismo , Imagen por Resonancia Magnética , Obesidad/metabolismo , Obesidad/psicología , Oscilometría , Oxígeno/sangre , Recompensa , Saciedad , Delgadez/metabolismo , Delgadez/psicología , Factores de Tiempo , Nervio Vago/fisiopatología , Adulto JovenRESUMEN
The beneficial effects of mindful awareness and mindfulness meditation training on physical and psychological health are thought to be mediated in part through changes in underlying brain processes. Functional connectivity MRI (fcMRI) allows identification of functional networks in the brain. It has been used to examine state-dependent activity and is well suited for studying states such as meditation. We applied fcMRI to determine if Mindfulness-Based Stress Reduction (MBSR) training is effective in altering intrinsic connectivity networks (ICNs). Healthy women were randomly assigned to participate in an 8-week Mindfulness-Based Stress Reduction (MBSR) training course or an 8-week waiting period. After 8 weeks, fMRI data (1.5T) was acquired while subjects rested with eyes closed, with the instruction to pay attention to the sounds of the scanner environment. Group independent component analysis was performed to investigate training-related changes in functional connectivity. Significant MBSR-related differences in functional connectivity were found mainly in auditory/salience and medial visual networks. Relative to findings in the control group, MBSR subjects showed (1) increased functional connectivity within auditory and visual networks, (2) increased functional connectivity between auditory cortex and areas associated with attentional and self-referential processes, (3) stronger anticorrelation between auditory and visual cortex, and (4) stronger anticorrelation between visual cortex and areas associated with attentional and self-referential processes. These findings suggest that 8 weeks of mindfulness meditation training alters intrinsic functional connectivity in ways that may reflect a more consistent attentional focus, enhanced sensory processing, and reflective awareness of sensory experience.
Asunto(s)
Mapeo Encefálico , Encéfalo/fisiología , Meditación/psicología , Vías Nerviosas/fisiología , Adulto , Femenino , Humanos , Interpretación de Imagen Asistida por Computador , Imagen por Resonancia Magnética , Persona de Mediana Edad , Estrés Psicológico/prevención & control , Estrés Psicológico/psicología , Adulto JovenRESUMEN
BACKGROUND & AIMS: Abuse history is common in irritable bowel syndrome (IBS) and is associated with greater pain reporting, psychologic distress, and poorer health outcome. These effects may be mediated by enhanced responses to aversive visceral stimuli. We investigated the effects of IBS and abuse history on pain reporting and brain activation in response to rectal distentions. METHODS: Ten female patients with IBS and 10 controls were included. Half of patients in each group reported a history of abuse. Brain functional magnetic resonance imaging (fMRI) images and pain ratings were obtained during rectal distentions. Statistical parametric mapping identified activation in subregions of the dorsal cingulate cortex and covariation with rated pain. RESULTS: (1) Distention-elicited pain correlated with anxiety and activation of the posterior (PCC) and middle (MCC) dorsal cingulate subregions. (2) Subjects with a history of abuse showed greater activation in the left MCC (P = .022; t = 5.61) and PCC (P = .033; t = 5.00) than subjects without abuse. (3) Those with IBS and abuse reported greater pain than all others (P = .004), had more activity in the left MCC (P = .021; t = 5.29) and PCC (P = .049; t = 4.81), and had less activity in the left supragenual anterior cingulate (sACC) (P = .01; t = 4.86). CONCLUSIONS: Pain ratings during rectal distention are associated with activation of dorsal cingulate regions implicated in homeostatic afferent processing, and prior abuse enhances this activation. Patients with IBS and abuse report more pain, greater MCC/PCC activation, and reduced activity of a region implicated in pain inhibition and arousal (sACC). These findings suggest a possible explanation for the clinical observation of greater pain reporting and poorer outcome in IBS patients with a history of abuse.
Asunto(s)
Giro del Cíngulo/fisiopatología , Síndrome del Colon Irritable/fisiopatología , Síndrome del Colon Irritable/psicología , Imagen por Resonancia Magnética , Dolor/fisiopatología , Dolor/psicología , Delitos Sexuales/psicología , Adolescente , Adulto , Vías Aferentes/fisiopatología , Anciano , Estudios de Casos y Controles , Femenino , Giro del Cíngulo/patología , Humanos , Síndrome del Colon Irritable/patología , Persona de Mediana Edad , Dolor/patología , Dimensión del Dolor , Estimulación Física , Recto/patología , Recto/fisiopatología , Índice de Severidad de la EnfermedadRESUMEN
The neurocognitive pathways by which placebo effects operate are poorly understood. Positron emission tomography (PET) imaging was used to assess the brain response of patients with chronic abdominal pain (irritable bowel syndrome; IBS) to induced intestinal discomfort both before and after a 3-week placebo regimen. A daily symptom diary was used to measure symptom improvement. Increases in right ventrolateral prefrontal cortex (RVLPFC) activity from pre- to post-placebo predicted self-reported symptom improvement, and this relationship was mediated by changes in dorsal anterior cingulate (dACC), typically associated with pain unpleasantness. These results are consistent with disruption theory [Lieberman, M.D., 2003. Reflective and reflexive judgment processes: a social cognitive neuroscience approach. In: Forgas, J.P., Williams, K.R., von Hippel, W. (Eds.), Social Judgments: Explicit and Implicit Processes. Cambridge Univ. Press, New York, pp. 44-67], which proposes that activation of prefrontal regions associated with thinking about negative affect can diminish dACC and amygdala reactivity to negative affect stimuli. This is the first study to identify a neural pathway from a region of the brain associated with placebos and affective thought to a region closely linked to the placebo-related outcome of diminished pain unpleasantness.