Conditions: Healthy
Keywords: N/A healthy volunteers
Allocation: RANDOMIZED | Intervention model: PARALLEL
Enrollment: 60
Healthy volunteers: yes

Brief summary:
This study involves 60 healthy volunteers aged between 18 and 50 recruited from the general community. It involves doing a set of simple memory tests while inside a fMRI machine. The subject is given a very low dose of an anesthetic drug intravenously while in the scanner. The subject then sees a sequence of pictures on a screen, and presses a button if they remember seeing the picture before. While this is happening, the scanner will be capturing images that tell us what parts of the brain are active. Hypothesis: patterns of hippocampal and amygdala activation during the encoding and retrieval of memory,as measured by fMRI, will be altered by intravenous anesthetics such that suppression of hippocampal and amygdala activities will be dissociable. This dissociation pattern will be different between the drugs propofol and thiopental.

Detailed description:
Background: Subclinical doses of propofol produce anterograde amnesia, characterized by an early failure of memory consolidation. It is unknown how propofol affects the amygdala-dependent emotional memory system, which modulates consolidation in the hippocampus in response to emotional arousal and neurohumoral stress. We present an event-related functional magnetic resonance imaging study of the effects of propofol on the emotional memory system in human subjects.

Methods: Sixty healthy subjects were randomized to receive propofol, at an estimated brain concentration of 0.90 μgml-1, thiopental, at an estimated brain concentration of 3.0 μgml-1, or placebo. During drug infusion, emotionally arousing and neutral images were presented in a continuous recognition task, while blood-oxygen-level-dependent activation responses were acquired. After a drug-free interval of 2 h, subsequent memory for successfully encoded items was assessed. Imaging analysis was performed using statistical parametric mapping and behavioural analysis using signal detection models.

Arms:
arm 1: Placebo given in low dose to gauge subject's responses to visual stimuli. arm 2: Propofol given at 0.90 μgml-1 to gauge subject's responses to visual stimuli. arm 3: Thiopental given at 3.0 μgml-1 to gauge subject's responses to visual stimuli.

Interventions: intervention 1: Placebo intervention 2: Propofol intervention 3: Thiopental
Intervention descriptions: intervention 1: A low dose given intravenously one time for just under an hour while the subject is shown visually stimulating images in an MRI machine. intervention 2: A low dose of propofol 0.90 μgml-1, given intravenously while the subject is shown visually stimulating images in an MRI machine. intervention 3: A low dose of thiopental 3.0 μgml-1, given intravenously while the subject is shown visually stimulating images in an MRI machine.

Protocol document: