From latent inhibition to retrospective revaluation: an attentional-associative model

Abstract

This chapter summarizes my work with Jeffrey Gray (1934–2004) on latent inhibition (LI), i.e., the retardation in the generation of the conditioned response (CR) during the pairing of the conditioned stimulus (CS) and the unconditioned stimulus (US) following CS preexposure. From 1996 to 2004, we published a series of articles on (a) a neural network model that describes LI and other classical conditioning paradigms (Schmajuk, Lam, & Gray,1996), (b) the mapping of variables in the model onto brain structures and neurotransmitters (Schmajuk, Cox, & Gray, 2001; Schmajuk, Gray, & Larrauri, 2005), (c) the application of the model to the description of the effect of brain lesions and drug administration on LI and the characterization of the neural activity and neurotransmitter release in different brain areas during LI (Buhusi, Gray, & Schmajuk, 1998; Schmajuk, Buhusi, & Gray, 1998), and (d) how the absence of LI, regarded as a positive symptom of schizophrenia, is caused by hippocampal dysfunction and ameliorated by DA blockers (Schmajuk, Christiansen, & Cox, 2000; Schmajuk, 2001; Schmajuk, 2002). After 2004, still guided by Jeffrey's suggestions, Jose Larrauri and I (Schmajuk & Larrauri, 2006) successfully applied the model to data that seem to challenge the power of existing models of classical conditioning. Namely, recovery from blocking (the reduced responding to one CS of a conditioned compound when the other CS was separately conditioned first), backward blocking (the reduced responding to one CS of a conditioned compound when the other CS was separately conditioned following compound conditioning), the counteraction between LI and overshadowing (the reduced responding to one or both CSs of a conditioned compound compared with their individual conditioning), and super LI (decreased responding to a preexposed CS after a delay following conditioning,).