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 geniculate nucleus (dLGN) neurons. Rabbits received a Pavlovian discriminative fear conditioning procedure in which one tone conditioned stimulus (CS+) was always paired with an aversive unconditioned stimulus (US) and another tone (CS-) was never paired with the US. Responses of single dLGN neurons to random CS+ and CS- presentations were then recorded. Nine of 15 recorded neurons demonstrated significantly greater firing during the CS+ versus the CS-. Their spontaneous activity demonstrated tonic firing during increased neocortical arousal and burst firing during decreased neocortical arousal. The results demonstrate that dLGN neurons show associative responses to fear-conditioned, acoustic stimuli and present a model for investigating the neural circuits by which such stimuli affect sensory processing at the thalamic level.