RESUMEN
Human lesion and functional imaging data suggest a central role for the amygdala in the processing of negative stimuli. To determine whether the amygdala's role in affective processing extends beyond negative stimuli, subjects viewed pictures that varied in emotional content (positive vs negative valence) and arousal level (high vs low) while undergoing functional magnetic resonance imaging. Amygdala activation, relative to a low arousal and neutral valence picture baseline, was significantly increased for both positively and negatively valenced stimuli and did not differ for the two valences. There were no laterality effects. Whereas arousal level appeared to modulate the amygdala response for negative stimuli, all positively valenced pictures (both high and low in arousal) produced significant amygdala responses. These results clearly demonstrate a role for the amygdala in processing emotional stimuli that extends beyond negative and fearful stimuli.
Asunto(s)
Afecto/fisiología , Amígdala del Cerebelo/fisiología , Nivel de Alerta/fisiología , Emociones/fisiología , Estimulación Luminosa/métodos , Adolescente , Adulto , Análisis de Varianza , Femenino , Humanos , Imagen por Resonancia MagnéticaRESUMEN
OBJECTIVE: The authors' goal was to determine potential hemodynamic consequences of methylphenidate on functional magnetic resonance imaging (MRI) blood-oxygen-level-dependent (BOLD) contrast. METHOD: BOLD and perfusion changes were recorded from the motor cortex of six healthy subjects while they performed flexion-extension movements of the right index finger (finger tapping) at varying rates before and after oral methylphenidate administration. RESULTS: Functional MRI signals increased monotonically with faster movement rates. Subjects' heart rates increased modestly after methylphenidate administration, but no changes in finger tapping performance or functional MRI signals were observed. CONCLUSIONS: Methylphenidate does not alter BOLD neural-hemodynamic coupling. Consequently, functional MRI can be used to map neural systems that subserve cognitive operations (e.g., attention and executive processes) in subjects taking methylphenidate.
Asunto(s)
Encéfalo/irrigación sanguínea , Imagen por Resonancia Magnética/métodos , Metilfenidato/farmacología , Destreza Motora/efectos de los fármacos , Oxígeno/sangre , Flujo Sanguíneo Regional/efectos de los fármacos , Adulto , Humanos , Imagen por Resonancia Magnética/estadística & datos numéricos , Masculino , Persona de Mediana Edad , Corteza Motora/irrigación sanguínea , Corteza Motora/efectos de los fármacos , Corteza Motora/fisiología , Destreza Motora/fisiologíaRESUMEN
Seven male and five female volunteers underwent double-blind infusions of the alpha 2-adrenoceptor antagonist idazoxan (100 and 200 micrograms/mg) and placebo in random order. Blood pressure, plasma norepinephrine, growth hormone and subjective responses were measured. The higher dose of idazoxan produced increases in blood pressure, norepinephrine and growth hormone and slight increases in anxiety. Both subject age and sex appeared to influence the magnitude of responses.
Asunto(s)
Antagonistas de Receptores Adrenérgicos alfa 2 , Nivel de Alerta/efectos de los fármacos , Idazoxan/farmacología , Adulto , Nivel de Alerta/fisiología , Presión Sanguínea/efectos de los fármacos , Presión Sanguínea/fisiología , Relación Dosis-Respuesta a Droga , Método Doble Ciego , Femenino , Hormona de Crecimiento Humana/sangre , Humanos , Infusiones Intravenosas , Masculino , Persona de Mediana Edad , Norepinefrina/sangre , Factores SexualesRESUMEN
BACKGROUND: Several classes of antidepressant drugs act on alpha 2-adrenergic receptors. Studies of patients with disorders responsive to treatment with these drugs report group differences in ex vivo measures of alpha 2-binding and in vivo responses mediated by alpha 2-receptors. Measurement of regional brain metabolic response to an alpha 2-antagonist may be a useful method for further definition of the role alpha 2-receptor regulation plays in the treatment of neuropsychiatric disorders. METHODS: Regional brain glucose metabolism was measured before and after infusion with 200 micrograms/kg idazoxan with use of 18F-fluoro-2-deoxyglucose positron emission tomography in 13 healthy men. Arterial drug concentration, behavioral responses, and cardiovascular responses were also measured. RESULTS: The absolute and normalized glucose metabolic rate significantly increased in primary visual cortex. Significant increases and decreases occurred in normalized metabolic rates in prefrontal cortical regions. Measurement of metabolic effects occurred during the peak cardiovascular response. CONCLUSIONS: Our findings are consistent with regionally specific effects of alpha 2-blockade. This method may be useful for the study of alpha 2-receptor function in humans.