title: Unblocking in Pavlovian fear conditioning.
abstract: Six experiments used rats to study blocking and unblocking of fear learning. An excitatory stimulus (A) blocked fear learning to a neutral stimulus (B). Unblocking of B occurred if the AB compound signaled an increase in unconditioned stimulus (US) intensity or number. Assessments of associative change during blocking showed that more was learned about B than A. Such assessments during unblocking revealed that more was learned about B than A following an increase in US intensity but not US number. These US manipulations had no differential effects on single-cue learning. The results show that variations in US intensity or number produce unblocking of fear learning, but for each there is a different profile of associative change and a potentially different mechanism.
authors.affiliation: School of Psychology, University of New South Wales, Sydney, Australia.
authors.forename: Laura
authors.initials: L
authors.lastname: Bradfield
authors.forename: Gavan P
authors.initials: GP
authors.lastname: McNally
mesh_terms: D000818:Animals; D001143:Arousal; D001245:Association Learning; D001288:Attention; D003214:Conditioning, Classical; D004193:Discrimination Learning; D005239:Fear; D005795:Generalization, Stimulus; D007266:Inhibition, Psychological; D008297:Male; D009042:Motivation; D009043:Motor Activity; D051381:Rats; D017208:Rats, Wistar