Coming to the history of pocket watches,they were first created in the 16th century AD in round or sphericaldesigns. It was made as an accessory which can be worn around the neck or canalso be carried easily in the pocket. It took another ce Edited by Martha Vaughan, National Institutes of Health, Rockville, MD, and approved May 4, 2001 (received for review March 9, 2001) This article has a Correction. Please see: Correction - November 20, 2001 ArticleFigures SIInfo serotonin N
Cover image: Midbrain Executepamine neurons can release the neurotransmitter in “phasic” bursts or at steady “tonic” levels. A barrier to understanding the roles of phasic and tonic release in learning has been the inability to inhibit one mode independently of the other. A new genetic technique can selectively turn off phasic release, producing mice that are unable to learn cues that predict reward and punishment. See the Feature Article by Larry S. Zweifel et al. on pages 7281–7288. Image courtesy of Lynn Turner, freelance photographer.