Sleep is believed to play an important role in memory consolidation. We induced sleep on demand by expressing the temperature-gated nonspecific cation channel Transient receptor potential cation channel (UAS-TrpA1) in neurons, including those with projections to the dorsal Fan-Shaped body (FB). When the temperature was raised to 31°C, flies entered a quiescent state that meets the criteria for identifying sleep. When sleep was induced for 4 hours after a massed-training protocol for courtship conditioning that is not capable of inducing long-term memory (LTM) by itself, flies develop an LTM. Activating the dorsal FB in the absence of sleep did not result in the formation of LTM after massed training.

Background Extended wakefulness disrupts acquisition of short term memories in mammals. However, the underlying molecular mechanisms triggered by extended waking and restored by sleep are unknown. Moreover, the neuronal circuits that depend on sleep for optimal learning remain unidentified. Results Learning was evaluated using Aversive Phototaxic Suppression (APS). In this task, flies learn to avoid light that is paired with an aversive stimulus (quinine /humidity). We demonstrate extensive homology in sleep deprivation induced learning impairment between flies and humans. Both 6 h and 12 h of sleep deprivation are sufficient to impair learning in Canton-S (Cs) flies. Moreover, learning is impaired at the end of the normal waking-day in direct correlation with time spent awake. Mechanistic studies indicate that this task requires intact mushroom bodies (MBs) and requires the Dopamine D1-like receptor (dDA1). Importantly, sleep deprivation induced learning impairments could be rescued by targeted gene expression of the dDA1 receptor to the MBs. Conclusion These data provide direct evidence that extended wakefulness disrupts learning in Drosophila. These results demonstrate that it is possible to prevent the effects of sleep deprivation by targeting a single neuronal structure and identify cellular and molecular targets adversely affected by extended waking in a genetically tractable model organism.

Starvation, which is common in the wild, appears to initiate a genetic program that allows fruitflies to remain awake without the sleepiness and cognitive impairments that typically follow sleep deprivation.

It is a common experience to sacrifice sleep to meet the demands of our 24-h society. Current estimates reveal that as a society, we sleep on average 2 h less than we did 40 years ago. This level of sleep restriction results in negative health outcomes and is sufficient to produce cognitive deficits and reduced attention and is associated with increased risk for traffic and occupational accidents. Unfortunately, there is no simple quantifiable marker that can detect an individual who is excessively sleepy before adverse outcomes become evident. To address this issue, we have developed a simple and effective strategy for identifying biomarkers of sleepiness by using genetic and pharmacological tools that dissociate sleep drive from wake time in the model organism Drosophila melanogaster. These studies have identified a biomarker, Amylase, that is highly correlated with sleep drive. More importantly, both salivary Amylase activity and mRNA levels are also responsive to extended waking in humans. These data indicate that the fly is relevant for human sleep research and represents a first step in developing an effective method for detecting sleepiness in vulnerable populations.Drosophila ͉ saliva ͉ sleep deprivation I t has been suggested that forced and self-inflicted sleep loss have reached epidemic proportions in Western industrialized populations (1, 2), costing billions of dollars in lost productivity and creating hazardous conditions on our roadways (3), in our skies (4), and in our hospitals (5). The National Highway Traffic Safety Administration estimates that 20% of motor vehicle crashes are attributed to sleepiness and fully 37% of adult drivers report falling asleep at the wheel at some point in their lives. Moreover, both regional and long-haul pilots accumulate sleep debt during trips, fall asleep in the cockpit, and experience levels of sleepiness that are associated with performance decrements (6, 7). In the hospital setting, training demands frequently disrupt the sleep of medical residents, which is then associated with increased attentional failures and medical errors (8). Indeed, after a heavy call rotation, the driving performance of medical residents was similar to those with a blood alcohol level of 0.05 g % (9) and is associated with increased risk of falling asleep while driving (10).Given the magnitude of this problem, it is not surprising that the sleep community, public health officials, and others have devoted considerable attention toward minimizing the negative impact of sleep loss on public health and safety (11). In addition to more focused basic research and increased educational campaigns to create public awareness, both regulatory and legislative initiatives have been implemented to address this problem. A general theme that has emerged from all of these efforts has been the importance of identifying a simple and quantifiable biomarker of sleepiness (11)(12)(13). A biomarker of sleepiness should be responsive to increasing levels of sleep debt and should only be activated by period...

These data indicate that sleep plays an important and phylogenetically conserved role in the developing brain.