Forebrain monoamines and associative learning: I. Latent inhibition and conditioned inhibition.
Two experiments evaluated the effects of depletion of forebrain norepinephrine (NE) or serotonin (5-HT) on two forms of internal inhibition. Experiment 1 examined the role of NE and 5-HT depletion on latent inhibition: rats with dorsal bundle or raphe lesions or vehicle control rats were trained to one of two pre-exposure conditions (single vs multiple stimuli) or to a non-pre-exposure control prior to conditioning. The results of this experiment showed that latent inhibition was attenuated under either condition of pre-exposure following depletion of 5-HT but that attenuation was present in NE depleted rats only when pre-exposed to multiple stimuli. Experiment 2 assessed the rate at which a conditioned inhibitor was established following NE or 5-HT depletion. The results of Experiment 2 indicated that the formation of a conditioned inhibitor was unimpaired following depletion of either NE or 5-HT. The results of Experiment 1 demonstrate that 5-HT and NE have different effects on associative processes: 5-HT apparently affects a habituation-like process, whereas NE is an important influence on more complex mechanisms involving the comparison of new with previously acquired information. The findings of Experiment 2 are consistent with behavioral investigations which show that conditioned inhibition affects output processes rather than the salience of stimuli.
D000818:Animals; D001245:Association Learning / Q000502:physiology*; D001921:Brain / Q000502:physiology*; D003214:Conditioning, Classical / Q000502:physiology*; D006185:Habituation, Psychophysiologic / Q000502:physiology; D007858:Learning / Q000502:physiology*; D008125:Locus Coeruleus / Q000502:physiology; D008297:Male; D009433:Neural Inhibition; D009434:Neural Pathways / Q000502:physiology; D009638:Norepinephrine / Q000378:metabolism*; D011903:Raphe Nuclei / Q000502:physiology; D051381:Rats; D011919:Rats, Inbred Strains; D012701:Serotonin / Q000378:metabolism*; D013687:Telencephalon / Q000502:physiology
D012701:Serotonin; D009638:Norepinephrine