Effects of lithium on latent inhibition in the rat

1. A latent inhibition paradigm was used to test the proposition that lithium increases rats' capacity to ignore an irrelevant stimulation. 2. In latent inhibition, non-reinforced presentations of the stimulus in the preexposure phase are said to lead the animal to ignore this stimulus, therefore reducing its later associability with a UCS. 3. Lithium (as chloride, 0.15 mEq/kg, for 6 days) counteracted the latent inhibition and impaired the acquisition of the conditioned response in the nonpreexposed condition. These results were attributed to an increased focus on stimuli of high salience, produced by lithium. 4. This interpretation was supported in a second experiment which demonstrated that enhancing opportunities for detailed inspective exploration of the apparatus before the initiation of conditioning markedly impaired the learning of rats treated for up to 7 days with 0.15 mEq/kg lithium chloride. 5. These findings are discussed within the context of the hypothesis that lithium narrows the breadth of attention onto stimuli of high salience at the expense of the processing of stimuli of low salience.