Barry J. Everitt

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29, 31, and 45; right 17, 35, and 37). 17. Although the improvement in WM performance with cholinergic enhancement was a nonsignificant trend in the current study (P 5 0.07), in a previous study (9) with a larger sample (n 5 13) the effect was highly significant (P , 0.001). In the current study, we analyzed RT data for six of our seven subjects because the(More)
Drug addiction is increasingly viewed as the endpoint of a series of transitions from initial drug use--when a drug is voluntarily taken because it has reinforcing, often hedonic, effects--through loss of control over this behavior, such that it becomes habitual and ultimately compulsive. Here we discuss evidence that these transitions depend on(More)
Emotions are multifaceted, but a key aspect of emotion involves the assessment of the value of environmental stimuli. This article reviews the many psychological representations, including representations of stimulus value, which are formed in the brain during Pavlovian and instrumental conditioning tasks. These representations may be related directly to(More)
We used a novel computerized decision-making task to compare the decision-making behavior of chronic amphetamine abusers, chronic opiate abusers, and patients with focal lesions of orbital prefrontal cortex (PFC) or dorsolateral/medial PFC. We also assessed the effects of reducing central 5-hydroxytryptamine (5-HT) activity using a tryptophan-depleting(More)
Impulsive choice is exemplified by choosing a small or poor reward that is available immediately, in preference to a larger but delayed reward. Impulsive choice contributes to drug addiction, attention-deficit/hyperactivity disorder, mania, and personality disorders, but its neuroanatomical basis is unclear. Here, we show that selective lesions of the(More)
Stimulant addiction is often linked to excessive risk taking, sensation seeking, and impulsivity, but in ways that are poorly understood. We report here that a form of impulsivity in rats predicts high rates of intravenous cocaine self-administration and is associated with changes in dopamine (DA) function before drug exposure. Using positron emission(More)
Five experiments examined the effects of destruction of the dorsal noradrenergic bundle (DNAB), arising in the locus coeruleus, both on brightness and spatial visual discrimination, and selective attention. An analogue o Leonard's 5-choice serial reaction task for human subjects was used. Hungry rats were trained to detect brief (0.5 sec) flashes of light(More)
Dissociable effects of bilateral excitotoxic lesions of different regions of the rat neocortex, including medial prefrontal and anterior cingulate cortices, were investigated in a five-choice serial reaction time task that provides several indices of the accuracy and speed of attentional function. Whereas medial prefrontal cortical lesions impaired(More)
Dopamine release within the nucleus accumbens (NAcc) has been associated with both the rewarding and locomotor-stimulant effects of abused drugs. The functions of the NAcc core and shell were investigated in mediating amphetamine-potentiated conditioned reinforcement and locomotion. Rats were initially trained to associate a neutral stimulus (Pavlovian CS)(More)
Rationale: Inability to tolerate delays to reward is an important component of impulsive behaviour, and has been suggested to reflect dysfunction of dopamine systems. Objectives: The present experiments examined the effects of signalling a delayed, large reward on rats' ability to choose it over a small, immediate reward, and on the response to amphetamine,(More)