Play It Again, Mr Sandman

HIGHLIGHTS

SLEEP AND MEMORY IN THE NEWS

Purple haze

Play it again, Mr Sandman A recent flurry of reports in the UK media focused on a paper In a scene familiar to all, a fractious in Nature Neuroscience on the addictive properties of the child is sent to bed in the belief that psychoactive component of the sleep that will surely follow will marijuana. They concerned a allow the child to get some much report by Steven Goldberg needed ‘rest’.But the idea that sleep is that self-administration simply a rest period has been repeat- behaviour is maintained by edly challenged over the years. delta-9-tetrahydrocannabinol (THC) in squirrel monkeys. Initially, the challenge was provided Previous studies that have by the electrophysiological descrip- tried to establish reliable self- tions of the sleep–wake cycle. More administration behaviour in recent findings have linked sleep and animals with THC have been the hippocampus with the consolida- unsuccessful, indicating that tion of neuronal temporalcodes for marijuana might have less spatial memory. However, we still potential for abuse than other drugs such as heroin and know little about sleep. Two recent cocaine. The press interest papers in Science provide thought- was stimulated by the likely provoking additions to this literature. impact of these findings on the In the first paper, Robert Stickgold polarized debate in the UK and colleagues focused on the effect media regarding the issue of of extended mental activity on hypn- whether to decriminalize marijuana. So how did the agogic mentation — the replay of media present the story? mental imagery at the onset of sleep. The experiment was designed to Marijuana “is as addictive evaluate the source and the function as heroin” of hypnagogic images. The partici- pants played the computer game A study into the addictiveness of cannabis Tetris® for extended periods over has concluded that the three days and were asked to report drug can be as compulsive mentation during the first hour of as cocaine or heroin. The attempted sleep each evening. Three The second study provides evi- the RA neurons during sleep matched findings will come as a groups participated in the experi- dence for the role of sleep in birdsong their sensorimotor activity,and there- blow to those campaigning ment: novices, experts and amnesic learning. Dave and Margoliash record- by may provide a form of song replay for the legalisation of patients with bilateral medial tem- ed the activity of single neuronsin the for motor learning. marijuana. The research by Steven Goldberg… used a poral lobe damage. All subjects forebrain nucleus robustus archistri- In conclusion, these two studies standard test for reported intrusive stereotypical atalis (RA) of zebra finches. This area indicate that the replay of sensory addictiveness in laboratory images of the blocks used in the is analogous to the motor cortex in experience during sleep may have animals and found little game at sleep onset. This was true mammals and its descending projec- complex effects on different forms of difference between the even for the amnesic patients who tions represent the output of the fore- learning and memory. So although it effects of cocaine, heroin could not recall playing the game. brain song system. Recordings from may be some time before the secrets and cannabis. The Independent One interpretation of this result is RA in individual birds were made of the Sandman are finally revealed, that hypnagogic images do not while each bird was singing and again these two studies demonstrate that A detail missing from the piece require intact declarative memory during playback of the bird’s song we are now able to tackle this prob- was that self-administration of systems. Another intriguing aspect of while it was asleep. The timing and lem with a wide range of techniques. THC was obtained in monkeys this study is that although playing structure of the neural activity elicited Peter Collins that had previously been Tetris might be expected to involve by the playback of song duringsleep trained to self-administer References and links cocaine — a standard test of procedural learning (which is intact matched the activity recorded during ORIGINAL RESEARCH PAPERS Stickgold, R. the addictive properties of in amnesic subjects), the amnesic singing. Activity during singing leads et al. Replaying the game: hypnagogic images in psychoactive drugs. Future normals and amnesics. Science 290, 350–353 patients in this study did not show the sounds that are produced, thus the research will be required to (2000) | Dave, A. S. & Margoliash, D. Song replay the same level of improvement as the matching auditory responses repre- during sleep and computational rules for establish whether drug naïve novice players. Further work will be sent a prediction of the following sensorimotor vocal learning. Science 290, monkeys will also self- required to clarify this area, but it sound based on the sequence of the 812–816 (2000) administer marijuana at the FURTHER READING Brainard, M. S. & Doupe, does seem that the source of hypna- preceding sounds. Such predictions low doses used in this study. A. J. Auditory feedback in learning and And this may be important in gogic images and the improved per- may lie at the heart of the computa- maintenance of vocal behaviour. Nature Rev. Neurosci. 1, 31–40 (2000) the final analysis of the abuse formance may rely on different areas tions involved in vocal learning. ENCYCLOPEDIA OF LIFE SCIENCES Amnesia potential of marijuana. of the brain. Moreover, the spontaneous activityof WEB SITE Daniel Margoliash Peter Collins