Searches Conducted
We initially did a broad search of several of the major biological and medical databases, initially including the following 14 key words: sleep, REM, NREM, EEG, electroencephalography, telemetry, actigraphy, active sleep, quiet sleep, spindles, K complex, slow wave sleep, delta wave, sleep rebound.
We excluded from all of our searches cats, rats, mice, and humans because we felt valid data for sleep quotas are already available for these species (so much of basic sleep neurobiology is based on these species). We also excluded any papers dated prior to 1953.
Here's What We Did:
We first entered a genus species name, several key words, and included specific limits. For example, we entered Galago and then the following key words: sleep OR REM OR NREM OR EEG OR telemetry OR actigraphy OR active sleep OR quiet sleep OR spindles OR K complex OR slow wave sleep OR delta wave OR sleep rebound into the Medline (Ovid) database. We limited our initial searches to animals, the English language, and the following animal types in seriatim: cattle, chick embryo, dogs, goats, guinea pigs, hamsters, horses, rabbits, sheep, swine. The publication years were limited to 1953-2005. These search parameters returned over 4,000 titles. The search in the ‘Web of Science database returned over 27,000 titles. The search in the CAB database returned over 1,800 titles. Perusal of hundreds of the titles revealed that the search was too broad so we then delimited the next series of searches in the following way:
We reduced the keyword list to REM or NREM or EEG or telemetry and again limited our search to the English language, the years from 1953-2005, and included all of the animal types except cats, rats, humans, or mice. We next reviewed previous compilations of papers containing data on sleep quotas in mammals. These compilations were by Meddis (1983), Elgar et al. (1988), and Zepelin (1989). We found that our searches had captured all of the references contained in these compilations. We then reviewed recent proceedings of the Sleep Research Society, which publishes abstracts from its annual conferences. We perused all of the abstracts contained under the heading of 'Phylogeny' for the last three years. This added another three titles to our list.
Over the next several weeks, Dr. McNamara studied the titles/abstracts of each of these 2,256 references, indicating which to discard and which to obtain. Ultimately, about 400 were retained for further analysis. Of these 400, only 181 contained data on sleep quotas. Of those 181 papers, only 141 contained EEG data. These are the data we used in our preliminary analyses. The complete reference list can be viewed here.
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