Sleep in various species of laboratory animals.

There are distinct differences, but also marked similarities between the quantitative and qualitative sleep parameters of various species of laboratory animals. The increasing use of computers and the automatic, powerful methods of EEG analysis in sleep research give rise to the belief that in the near future the sleep of the various species may be better differentiated. However, one commonly encountered problem when attempting to compare sleep patterns of different species is the use of different brain areas as recording sites. This is further accentuated by the use of different reference electrodes (for example, monopolar or bipolar recordings, different distance of the recording electrode pair). We propose, therefore, that one agrees on two definite electrodes which would provide a reference recording and could be used besides others. A suitable placement for a monopolar recording in sleep studies could be the placement of one electrode above the occipital cortex and of the other, indifferent electrode, in the os frontale, nasal to the brain.