SUMMARYPrevious results show that when unrestrained crayfish sleep, the electrical activity of the brain changes from multiple spikes (frequencies above 300Hz) on a flat baseline to continuous slow waves at a frequency of 15-20Hz. To study the temporal organization of such activity, we developed a tethered crayfish preparation that allows us to place electrodes on visually identified regions of the brain. Recording the electrical activity of different brain areas shows that when the animal is active (awake), slow waves are present only in the central complex. However, simultaneously with the animal becoming limp (sleeping), slow waves spread first to deuto-and then to protocerebrum, suggesting that the central complex of the crayfish brain acts as the sleep generator.

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Early adverse life stress has been associated to behavioral disorders that can manifest as inappropriate or aggressive responses to social challenges. In this study, we analyzed the effects of artificial rearing on the open field and burial behavioral tests and on GFAP, c-Fos immunoreactivity, and glucose metabolism measured in anxiety-related brain areas. Artificial rearing of male rats was performed by supplying artificial milk through a cheek cannula and tactile stimulation, mimicking the mother's licking to rat pups from the fourth postnatal day until weaning. Tactile stimulation was applied twice a day, at morning and at night, by means of a camel brush on the rat anogenital area. As compared to mother reared rats, greater aggressiveness, and boldness, stereotyped behavior (burial conduct) was observed in artificially reared rats which occurred in parallel to a reduction of GFAP immunoreactivity in somatosensory cortex, c-Fos immunoreactivity at the amygdala and primary somatosensory cortex, and lower metabolism in amygdala (as measured by 2-deoxi-2-[ fluoro]-d-glucose uptake, assessed by microPET imaging). These results could suggest that tactile and/or chemical stimuli from the mother and littermates carry relevant information for the proper development of the central nervous system, particularly in brain areas involved with emotions and social relationships of the rat. © 2017 Wiley Periodicals, Inc. Develop Neurobiol 77: 1413-1429, 2017.

Although sleep is a very conspicuous behavior in all animals that we are frequently in contact with and possibly in many others, its scientific study was for many years restricted to very few of them. However, since the end of the XX century there have been studies about sleep in several animals and currently many of them attempt to found, first, if all animals sleep and second, if their sleep is similar to that of other animals. An important objective of this search is to identify the animal species in which sleep originated, which might gives us clues about the need that was fulfilled by such behavior. The search started with insects, among the most developed arthropods, but has now been expanded to include other invertebrates, among them crustaceans. In this work we review some aspects of sleep in invertebrates, focusing on the crustacean crayfish, animals in which both, behavioral and electrophysiological studies have been conducted and whose results show surprising similarities with sleep in mammals.