Nicotine enhances sustained attention in the rat under specific task conditions
Although nicotine has cognitive enhancing effects in both animals and humans, most studies in humans have only shown consistent improvements in sustained attention. Moreover, many studies with smokers have been criticised, since nicotine may simply be relieving withdrawal-induced deficits. The present study investigated the effect of nicotine on sustained attention in drug-naïve rats using a five-choice serial reaction time task. Initially, the task was demonstrated to satisfy some of the criteria for the construct validity of a vigilance task: reducing signal length and either increasing or decreasing the inter-trial interval significantly (P<0.05) impaired performance. Whether nicotine (0.05–0.4 mg/kg, SC) reversed the deficits induced by a signal length of 0.25 s (weak signal) or an inter-trial-interval of either 20 s (low event rate) or 1 s (high event rate) was assessed. Nicotine (0.15 mg/kg) improved accuracy and decreased omission errors under low event rate conditions only. However, nicotine (0.05/0.15 mg/kg) improved reaction time and increased anticipatory responses under both weak signal and low event rate conditions. There was no effect of nicotine on performance under high event rate conditions. Under the low event rate condition, nicotine enhanced the ability of rats to maintain attention (i.e. accuracy) throughout a session. These findings suggest (i) that nicotine’s effect on attention depends upon task characteristics; (ii) these effects on attention may reflect self-reports by smokers that nicotine aids concentration, particularly in stressful situations, and (iii) nicotinic agonists may have therapeutic benefits in patient populations suffering from attentional deficits.
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