Rat psychomotor vigilance task with fast response times using a conditioned lick behavior

Investigations into the physiological mechanisms of sleep control require an animal psychomotor vigilance task (PVT) with fast response times (<300 ms). Rats provide a good PVT model since whisker stimulation produces a rapid and robust cortical evoked response, and animals can be trained to lick following stimulation. Our prior experiments used deprivation-based approaches to maximize motivation for operant conditioned responses. However, deprivation can influence physiological and neurobehavioral effects. In order to maintain motivation without water deprivation, we conditioned rats for immobilization and head restraint, then trained them to lick for a 10% sucrose solution in response to whisker stimulation. After approximately 8 training sessions, animals produced greater than 80% correct hits to the stimulus. Over the course of training, reaction times became faster and correct hits increased. Performance in the PVT was examined after 3, 6 and 12 h of sleep deprivation achieved by gentle handling. A significant decrease in percent correct hits occurred following 6 and 12 h of sleep deprivation and reaction times increased significantly following 12 h of sleep deprivation. While behaviorally the animals appeared to be awake, we observed significant increases in EEG delta power prior to misses. The rat PVT with fast response times allows investigation of sleep deprivation effects, time-on-task and pharmacological agents. Fast response times also allow closer parallel studies to ongoing human protocols.

Research highlights▶ The psychomotor vigilance task is a widely used test of simple reaction times and is a sensitive measure of sleep deprivation. ▶ Sucrose can be used as a reinforcer to maintain responding in conditioned learning paradigms without the need for deprivation. ▶ A significant decrease in percent correct hits occurred following 6 and 12 h of sleep deprivation and reaction times increased significantly following 12 h of sleep deprivation. ▶ Increases in EEG delta power and lower EMG power were observed prior to misses during sleep deprivation sessions. ▶ An increase in evoked response peak amplitudes was observed during conditioning, suggesting that plasticity may occur with conditioned learning.