RESUMEN
BACKGROUND: This study aimed to determine whether patients with post-traumatic stress disorder (PTSD) show difficulty in recruitment of the regions of the frontal and parietal cortex implicated in top-down attentional control in the presence and absence of emotional distracters. METHOD: Unmedicated individuals with PTSD (n = 14), and age-, IQ- and gender-matched individuals exposed to trauma (n = 15) and healthy controls (n = 19) were tested on the affective number Stroop task. In addition, blood oxygen level-dependent responses, as measured via functional magnetic resonance imaging, were recorded. RESULTS: Patients with PTSD showed disrupted recruitment of lateral regions of the superior and inferior frontal cortex as well as the parietal cortex in the presence of negative distracters. Trauma-comparison individuals showed indications of a heightened ability to recruit fronto-parietal regions implicated in top-down attentional control across distracter conditions. CONCLUSIONS: These results are consistent with suggestions that emotional responsiveness can interfere with the recruitment of regions implicated in top-down attentional control; the heightened emotional responding of patients with PTSD may lead to the heightened interference in the recruitment of these regions.
Asunto(s)
Atención/fisiología , Función Ejecutiva/fisiología , Lóbulo Frontal/fisiopatología , Imagen por Resonancia Magnética/métodos , Lóbulo Parietal/fisiopatología , Trastornos por Estrés Postraumático/fisiopatología , Trastornos de Estrés Traumático/fisiopatología , Adulto , Femenino , Humanos , Imagen por Resonancia Magnética/instrumentación , Masculino , Trastornos por Estrés Postraumático/etiología , Trastornos de Estrés Traumático/complicaciones , Test de StroopRESUMEN
This fMRI study investigates neural activity associated with the interfering effects of emotional distracters. While in the scanner, participants made simple motor responses to target stimuli that were preceded and followed by positive, negative, or neutral images. Despite instructions to disregard the pictorial images, participants were slower to respond in the presence of positive or negative relative to neutral distracters, and significantly slower for negative relative to positive distracters. Enhanced activity in the amygdala and visual cortex was evident during trials that included positive and negative distracters. In contrast, increased activity in inferior frontal gyrus (BA 47) was only observed during trials that involved negative distracters. Connectivity analysis showed that activity in right amygdala correlated with activity in cingulate gyrus, posterior cingulate, middle temporal cortex, and was negatively correlated with activity in lateral superior frontal gyrus, middle frontal/orbital gyrus, and parietal cortex. The pattern of neural activity observed was interpreted within the framework of current cognitive models of attention. During a task demonstrating behavioural interference in the context of emotional distracters, increased activity in neural regions implicated in emotional processing (the amygdala) was associated with reduced activity in regions thought to be involved in exerting attentional control over task-relevant sensory representations (a frontoparietal network).
Asunto(s)
Amígdala del Cerebelo/fisiología , Emociones/fisiología , Lóbulo Frontal/fisiología , Imagen por Resonancia Magnética , Lóbulo Parietal/fisiología , Adulto , Femenino , Humanos , Masculino , Análisis y Desempeño de TareasRESUMEN
RATIONALE: The serotonin (5-HT) system is considered important for decision-making. However, its role in reward- and punishment-based processing has not yet been clearly determined. OBJECTIVES: The present study examines the effect of 5-HTTLPR genotype and tryptophan depletion on reward- and punishment-related processing, using a task that considers decision-making in situations of subtlety of choice. Thus, it considers that response choice often occurs in situations where both options are desirable (e.g., choosing between mousse au chocolat or crème caramel cheesecake from a menu) or undesirable. It also considers that response choice is easier when the reinforcements associated with the options are far apart, rather than close, in value. MATERIALS AND METHODS: Healthy volunteers underwent acute tryptophan depletion (ATD) or control procedures and genotyping of the 5-HTTLPR for long and short allele variants. We then examined the effects and interactions of ATD and the serotonin promoter polymorphism genotype on two aspects of decision-making: (a) decision form, choosing between two objects to gain the greater reward or lesser punishment and (b) between-object reinforcement distance, the difference in reinforcements associated with two options. RESULTS: ATD and LL homozygosity had comparable interactions with decision form and between-object reinforcement distance. Specifically, both modulated the effect of between-object reinforcement distance when deciding between objects both associated with punishment. Moreover, ATD and genotype interacted with ATD disproportionately affecting the performance of the LL homozygous group. CONCLUSIONS: These results suggest that serotonin is particularly associated with punishment, rather than reward-related processing, and that individual sensitivity to punishment-related information and tryptophan depletion varies with genotype.
Asunto(s)
Conducta de Elección/fisiología , Genotipo , Polimorfismo Genético/genética , Proteínas de Transporte de Serotonina en la Membrana Plasmática/genética , Triptófano/fisiología , Adulto , Alelos , Aminoácidos/administración & dosificación , Cápsulas , Toma de Decisiones/fisiología , Método Doble Ciego , Femenino , Juego de Azar/psicología , Tamización de Portadores Genéticos , Homocigoto , Humanos , Masculino , Persona de Mediana Edad , Motivación , Reconocimiento Visual de Modelos , Regiones Promotoras Genéticas/genética , Castigo , Refuerzo en Psicología , Triptófano/administración & dosificaciónRESUMEN
BACKGROUND: From a cognitive neuroscience perspective, the emotional attentional bias in post-traumatic stress disorder (PTSD) could be conceptualized either as emotional hyper-responsiveness or as reduced priming of task-relevant representations due to dysfunction in 'top-down' regulatory systems. We investigated these possibilities both with respect to threatening and positive stimuli among traumatized individuals with and without PTSD. METHOD: Twenty-two patients with PTSD, 21 trauma controls and 20 non-traumatized healthy participants were evaluated on two tasks. For one of these tasks, the affective Stroop task (aST), the emotional stimuli act as distracters and interfere with task performance. For the other, the emotional lexical decision task (eLDT), emotional information facilitates task performance. RESULTS: Compared to trauma controls and healthy participants, patients with PTSD showed increased interference for negative but not positive distracters on the aST and increased emotional facilitation for negative words on the eLDT. CONCLUSIONS: These findings document that hyper-responsiveness to threat but not to positive stimuli is specific for patients with PTSD.