Failure to delay gratification following septal lesions in rats: Implications for an animal model of disinhibitory psychopathology

It has been proposed that dysfunction within a neural system composed of the medial septum, the posterior hippocampus and the orbito-frontal cortex (SHF system) may constitute the physiological basis of several disinhibitory syndromes in humans—psychopathy, hyperkinesis, alcoholism and extraversion. Consequently, the syndrome produced by lesions of the SHF system in animals is offered as a tentative behavioral model that may elucidate basic psychological components of human disinhibitory psychopathology. As predicted from this model, rats with septal lesions, like disinhibited humans, were less likely to delay gratification than controls when given a choice between waiting 10 sec for an assured reinforcement and an immediately available, though infrequently delivered, reinforcement. Inquiry into the nature of this deficit suggested that these rats are subject to an interference effect, such that the influence of future rewards on behavior could be disrupted or ‘eclipsed’ by the presence of more immediate, prominent, motivationally significant cues. The possibility that various disinhibitory syndromes in humans may also be due to a similar rigid focus of attention upon the most immediate or prominent motivationally significant event was briefly discussed.