Arousal-related associative response characteristics of dorsal lateral geniculate nucleus neurons during acoustic pavlovian fear conditioning

This research determined whether fear-conditioned, acoustic stimuli induce thalamic arousal reflected in associative responses in dorsal lateral genic ulate nucleus (dLGN) neurons. Rabbits received a Pavlovian discriminative f ear conditioning procedure in which one tone conditioned stimulus (CS+) was always paired with an aversive unconditioned stimulus (US) and another ton e (CS-) was never paired with the US. Responses of single dLGN neurons to r andom CS+ and CS- presentations were then recorded. Nine of 15 recorded neu rons demonstrated significantly greater firing during the CS+ versus the CS -. Their spontaneous activity demonstrated tonic firing during increased ne ocortical arousal and burst firing during decreased neocortical arousal. Th e results demonstrate that dLGN neurons show associative responses to fear- conditioned, acoustic stimuli and present a model for investigating the neu ral circuits by which such stimuli affect sensory processing at the thalami c level.