Psychedelic Information Theory
Shamanism in the Age of Reason
References
The stuff dreams are made of: anatomical substrates of REM sleep
Siegel, JM; Nature Neuroscience, V9.6, p721, 06/2006
Where do dreams come from? Why do we dream? A recent paper1 brings us closer to answering the first question, although the answer to the second question remains elusive. Rapid eye movement (REM) sleep was discovered in 1953. Its hallmarks are periods of rapid eye movements, low-voltage electroencephalogram (EEG) and muscle tone suppression that recur throughout the night in a 90-minute rhythm (in humans) and are accompanied by dreams. A physiologically identical state is present in most mammals2. Less elaborate dreams can occur in non-REM sleep as well. In the new paper, Lu et al.1 combine studies of neuronal activation, staining for the protein encoded by the immediate-early gene c-fos, identification of the neurotransmitters of activated cells and brain lesions to determine the dynamics of the regulation of the REM sleep–generating system in the rat. Work in the cat3,4 has defined the location of ‘REM sleep–on’ neurons, cells selectively active during REM sleep and believed to trigger this state. These cells are concentrated in the brainstem ventral to the locus coeruleus, in a region known as the subcoeruleus. Damage to this area reduces or disrupts REM sleep. The new paper1 and previous work5 in the rat show that REM-on cells are found in the sublaterodorsal (SLD) nucleus (analogous to the subcoeruleus region in the cat) and also in a region just rostral to the locus coeruleus1. These findings suggest a universal localization of the REM-on region in mammals (Fig. 1). The brainstem location of the REM sleep– generating mechanism3 indicates that REM sleep may have evolved primarily in service to the brainstem, with any forebrain functions having developed relatively recently. Injection of glutamate agonists or GABA