RESUMEN
BACKGROUND: Little is known about time perception, its putative role as cognitive endophenotype, and its neuroanatomical underpinnings in adults with attention deficit hyperactivity disorder (ADHD). METHOD: Twenty adults with ADHD, 20 unaffected first-degree relatives and 20 typically developing controls matched for age and gender undertook structural magnetic resonance imaging scans. Voxel-based morphometry with DARTEL was performed to obtain regional grey-matter volumes. Temporal processing was investigated as a putative cognitive endophenotype using a temporal reproduction paradigm. General linear modelling was employed to examine the relationship between temporal reproduction performances and grey-matter volumes. RESULTS: ADHD participants were impaired in temporal reproduction and unaffected first-degree relatives performed in between their ADHD probands and typically developing controls. Increased grey-matter volume in the cerebellum was associated with poorer temporal reproduction performance. CONCLUSIONS: Adults with ADHD are impaired in time reproduction. Performances of the unaffected first-degree relatives are in between ADHD relatives and controls, suggesting that time reproduction might be a cognitive endophenotype for adult ADHD. The cerebellum is involved in time reproduction and might play a role in driving time performances.
Asunto(s)
Trastorno por Déficit de Atención con Hiperactividad/patología , Trastorno por Déficit de Atención con Hiperactividad/fisiopatología , Sustancia Gris/patología , Percepción del Tiempo/fisiología , Adulto , Trastorno por Déficit de Atención con Hiperactividad/diagnóstico por imagen , Endofenotipos , Femenino , Sustancia Gris/diagnóstico por imagen , Humanos , Imagen por Resonancia Magnética , Masculino , Persona de Mediana Edad , Núcleo Familiar , Adulto JovenRESUMEN
BACKGROUND: There is evidence of executive function impairment in obsessive compulsive disorder (OCD) that potentially contributes to symptom development and maintenance. Nevertheless, the precise nature of these executive impairments and their neural basis remains to be defined. METHOD: We compared stopping and shifting, two key executive functions previously implicated in OCD, in the same task using functional magnetic resonance imaging, in patients with virtually no co-morbidities and age-, verbal IQ- and gender-matched healthy volunteers. The combined task allowed direct comparison of neural activity in stopping and shifting independent of patient sample characteristics and state variables such as arousal, learning, or current symptom expression. RESULTS: Both OCD patients and controls exhibited right inferior frontal cortex activation during stopping, and left inferior parietal cortex activation during shifting. However, widespread under-activation across frontal-parietal areas was found in OCD patients compared to controls for shifting but not stopping. Conservative, whole-brain analyses also indicated marked divergent abnormal activation in OCD in the caudate and thalamus for these two cognitive functions, with stopping-related over-activation contrasting with shift-related under-activation. CONCLUSIONS: OCD is associated with selective components of executive function, which engage similar common elements of cortico-striatal regions in different abnormal ways. The results implicate altered neural activation of subcortical origin in executive function abnormalities in OCD that are dependent on the precise cognitive and contextual requirements, informing current theories of symptom expression.
Asunto(s)
Encéfalo/fisiopatología , Función Ejecutiva/fisiología , Trastorno Obsesivo Compulsivo/fisiopatología , Adulto , Nivel de Alerta/fisiología , Estudios de Casos y Controles , Núcleo Caudado/fisiopatología , Cognición/fisiología , Lóbulo Frontal/fisiopatología , Neuroimagen Funcional , Humanos , Imagen por Resonancia Magnética , Persona de Mediana Edad , Neostriado/fisiopatología , Lóbulo Parietal/fisiopatología , Análisis y Desempeño de Tareas , Tálamo/fisiopatologíaRESUMEN
Though stimulant drugs such as cocaine are considered highly addictive, some individuals report recreational use over long periods without developing dependence. Difficulties in response inhibition have been hypothesized to contribute to dependence, but previous studies investigating response inhibition in recreational cocaine users have reported conflicting results. Performance on a stop-signal task was examined in 24 recreational cocaine users and 32 healthy non-drug using control participants matched for age, gender and verbal intelligence during functional magnetic resonance imaging scanning. The two groups were further matched on traumatic childhood histories and the absence of family histories of addiction. Results revealed that recreational cocaine users did not significantly differ from controls on any index of task performance, including response execution and stop-signal reaction time, with the latter averaging 198 ms in both groups. Functional magnetic resonance imaging analyses indicated that, compared with controls, stopping in the recreational users was associated with increased activation in the pre-supplementary motor area but not the right inferior frontal cortex. Thus, findings imply intact response inhibition abilities in recreational cocaine users, though the distinct pattern of accompanying activation suggests increased recruitment of brain areas implicated in response inhibition. This increased recruitment could be attributed to compensatory mechanisms that enable preserved cognitive control in this group, possibly relating to their hypothetical resilience to stimulant drug dependence. Such overactivation, alternatively, may be attributable to prolonged cocaine use leading to neuroplastic adaptations.
Asunto(s)
Trastornos Relacionados con Cocaína/psicología , Función Ejecutiva/fisiología , Inhibición Psicológica , Corteza Motora/fisiopatología , Corteza Prefrontal/fisiopatología , Adulto , Encéfalo/fisiopatología , Estudios de Casos y Controles , Estimulantes del Sistema Nervioso Central , Cocaína , Trastornos Relacionados con Cocaína/fisiopatología , Femenino , Lóbulo Frontal/fisiopatología , Neuroimagen Funcional , Humanos , Imagen por Resonancia Magnética , Masculino , Tiempo de Reacción , Análisis y Desempeño de Tareas , Adulto JovenRESUMEN
BACKGROUND: Obsessive-compulsive disorder (OCD) has been associated with response inhibition deficits under motivationally neutral contingencies. We examined response inhibition performance in the presence of reward and punishment. We further investigated whether the hypothesized difficulties in flexibly updating behaviour based on external feedback in OCD would also lead to a reduced ability to adjust to changes in the reward and punishment contingencies. METHOD: Participants completed a go/no-go task that used punishments or rewards to promote response activation or suppression. The task was administered to OCD patients free of current Axis-I co-morbidities including major depression (n = 20) and a group of healthy controls (n = 32). RESULTS: Compared with controls, patients with OCD had increased commission errors in punishment conditions, and failed to slow down immediately after receiving punishment. The punishment-induced increase in commission errors correlated with self-report measures of OCD symptom severity. Additionally, patients did not differ from controls in adapting their overall response style to the changes in task contingencies. CONCLUSIONS: Individuals with OCD showed reduced response control selectively under punishment conditions, manifesting in an impulsive response style that was related to their current symptom severity. This stresses failures of cognitive control in OCD, particularly under negative motivational contingencies.
Asunto(s)
Inhibición Psicológica , Trastorno Obsesivo Compulsivo/fisiopatología , Desempeño Psicomotor/fisiología , Castigo , Recompensa , Adaptación Psicológica/fisiología , Adulto , Estudios de Casos y Controles , Femenino , Humanos , Masculino , Pruebas Neuropsicológicas/estadística & datos numéricos , Trastorno Obsesivo Compulsivo/tratamiento farmacológico , Trastorno Obsesivo Compulsivo/psicología , Tiempo de Reacción/fisiología , Autoinforme , Inhibidores Selectivos de la Recaptación de Serotonina/uso terapéutico , Índice de Severidad de la EnfermedadRESUMEN
BACKGROUND: Obsessive-compulsive disorder (OCD) has been associated with impairments in stop-signal inhibition, a measure of motor response suppression. The study used a novel paradigm to examine both thought suppression and response inhibition in OCD, where the modulatory effects of stimuli relevant to OCD could also be assessed. Additionally, the study compared inhibitory impairments in OCD patients with and without co-morbid depression, as depression is the major co-morbidity of OCD. METHOD: Volitional response suppression and unintentional thought suppression to emotive and neutral stimuli were examined using a novel thought stop-signal task. The thought stop-signal task was administered to non-depressed OCD patients, depressed OCD patients and healthy controls (n=20 per group). RESULTS: Motor inhibition impairments were evident in OCD patients, while motor response performance did not differ between patients and controls. Switching to a new response but not motor inhibition was affected by stimulus relevance in OCD patients. Additionally, unintentional thought suppression as measured by repetition priming was intact. OCD patients with and without depression did not differ on any task performance measures, though there were significant differences in all self-reported measures. CONCLUSIONS: Results support motor inhibition deficits in OCD that remain stable regardless of stimulus meaning or co-morbid depression. Only switching to a new response was influenced by stimulus meaning. When response inhibition was successful in OCD patients, so was the unintentional suppression of the accompanying thought.