title: Conditioned stimulus familiarity determines effects of MK-801 on fear extinction.
abstract: Six experiments studied the role of conditioned stimulus (CS) familiarity in determining the effects of the N-methyl-d-aspartate (NMDA) receptor antagonist MK-801 on fear extinction. Systemic administration of MK-801 (0.1 mg/kg) impaired initial extinction but not reextinction learning. MK-801 impaired reextinction learning when the CS was relatively novel during reextinction training but not initial extinction learning when the CS was relatively familiar during initial extinction training. A context change failed to reinstate the sensitivity of initial fear extinction learning about a relatively familiar CS to MK-801. These experiments show that CS familiarity is an important determinant of effects of MK-801 on fear extinction learning: MK-801 impaired extinction learning about novel stimuli but spared extinction learning about familiar stimuli.
authors.affiliation: School of Psychology, University of New South Wales, Sydney, Australia.
authors.forename: Wan Yee Macy
authors.initials: WY
authors.lastname: Chan
authors.forename: Gavan P
authors.initials: GP
authors.lastname: McNally