Memory for emotional material: a comparison of central versus peripheral beta blockade

The connection between affect and memory is poorly understood. A possible p sychopharmacological linking mechanism is the sympathetic arousal that occu rs in response to threatening or emotive material. Cahill et al. (1994) rep orted that a single administration of 40 mg propranolol hydrochloride, a no n-selective beta-adrenergic blocker, to healthy young adults significantly reduced delayed recall of emotive material, with recall of matched neutral material unaffected. This study differed importantly from the original Cahi ll ct al, (1994) procedure in that only the emotionally arousing narrative was employed. Using the same slide presentation as Cahill et al. (1994), an experiment was carried out in order to determine whether beta-adrenergic b lockade significantly reduces recall of emotive material via a central or p eripheral mode of action. Thirty-six healthy young adults were recruited as subjects. Subjects were randomly allocated to three groups: (a) placebo (b ) 40 mg propranolol hydrochloride (a beta blocker which readily crosses the blood-brain barrier) and (c) 40 mg nadolol (a beta blocker which does not cross the blood-brain barrier). The three groups were matched for age, sex, intelligence, personality factors, and general memory functioning. Subject s viewed a series of 11 slides accompanied by a narrative, divisible into t hree phases. The emotionally arousing component of the narrative was introd uced during phase II. Both central and peripheral beta blockade produced th e expected effects on the sympathetic nervous system, as demonstrated by re liable reductions in systolic and diastolic blood pressure. In a surprise m emory test I week later, subjects were asked to recall as much as possible of the story and slides, and also completed a forced choice recognition mem ory test. All three groups showed heightened recall and recognition for the central (emotive) section of the story. There was no differential effect o f beta blockade (either central or peripheral) relative to placebo. Beta bl ockade markedly reduced systolic and diastolic blood pressure, but resulted in no significant effect on memory for both emotional and neutral material .