Sleep Research

Sleep has been of interest for many centuries as we are all practitioners of sleep. There have been many theories about sleep. One of the latest theories is that sleep is a natural recurring resting state in which mind and body restore their biochemical and physiological processes that are progressively degraded during prior wakefulness. Since the discovery of the electroencephalogram (EEG) in 1924, it is possible to gain insight in the activity of the brain. From that time on, both humans and animals have been extensively studied in the field of sleep research. Advancements in technology have made it easier to measure brain activity in non-restricted individuals. Studies of sleeping animals have increased our knowledge of the basic mechanisms of sleep. Such studies have revealed that impaired sleep quality increases the chance of developing cardiovascular and neurological disorders. 

How Sleep is Measured

Sleep can be measured by physical activity correlated to resting periods. Identifying sleep duration is often used when studying circadian rhythm. Another way to measure sleep is by EEG that measures the electrical signals in the brain. In this way, the different stages during sleep can be identified. Sleep is determined by physiological changes in EEG together with the EMG (electromyogram – muscle movement) and EOG (electrooculogram - eye movement) (see Figure 1). Other variables including temperature, blood pressure and neuroendocrine function can be added to gain extra information about the circadian process.

Figure 1: Comparative location of EEG/EMG and EOG electrodes in human and animals. A human, B & C rat.
EEG human mouse rat

The EEG recordings are classified into five frequency bands:

  • Delta (0.5 to 4 Hz)
  • Theta (4 to 8 Hz)
  • Alpha (8 to11.5 Hz)
  • Beta1 (11.5 to 15 Hz) and Beta2 (15 to 35 Hz)
  • Gamma (30-100+ Hz)


According to the frequency contents, EMG/EOG muscular activities the sleep stages can be subdivided between rapid eye movement (REM) sleep and non-REM sleep (light and slow wave sleep). 

Learn more about sleep stages classification.

List of measured sleep parameters (but not limited to):

1) Onset to slow-wave
2) Onset to paradoxical (Small Animal)
3) Onset to REM (Large Animal)

Small Animal Implantable Telemetry System – The system is composed of receiver plates (placed below the cage). The signals are then routed through a matrix (MX2) interface into a PC for real time signal collection using network standards (Router and Switch).

Learn more about mouse and small animal telemetry specifications from DSI.

System image

Large Animal Implantable Telemetry System (PhysioTel Digital) – The system is composed of receiver plates placed in the cage that allow group housing of animals and larger cages. The signal are then routed through a matrix interface into a PC for real time signal collection using network standards (Router and Switch).

Learn more about large animal telemetry specifications from DSI.

PTD NHP cage

Hardwired Monitoring System – DSI’s hardwired solutions provide a minimally invasive method to offer continuous measurement (EEG, EMG, EOG, etc.) during central nervous system studies with small animals.  Hardwired solutions allow the use of a tether to monitor up to 12 EEG/EMG channels.    

A setup would include use of electrodes, wires, and commutators. EEG and/or EMG signals from this tethered approach are brought into DSI’s Ponemah software platform by the use of digital signal conditioners/amplifiers.

Learn more about Signal Conditioners and accessories from DSI.


NeuroScore Software – After data acquisition has taken place, DSI’s NeuroScore™ software can be used to efficiently analyze chronic data sets common to neuroscience studies.  This modular platform offers sleep scoring, seizure detection, video synchronization, and batch processing capabilities. 

Learn more about NeuroScore software from DSI.

Neuroscore, Sleep Scoring, Rodent Sleep Scoring, cns software


Ashley, Noah T., et al. "Photoperiod alters duration and intensity of non-rapid eye movement sleep following immune challenge in Siberian hamsters (Phodopus sungorus)." Chronobiology International, 29.6 (2012): 683-692.

Authier, S., et al. "Video-electroencephalography in conscious non human primate using radiotelemetry and computerized analysis: refinement of a safety pharmacology model." Journal of Pharmacological and Toxicological Methods, 60.1 (2009): 88-93.

Crofts, H. S., et al. "Investigation of the sleep electrocorticogram of the common marmoset (Callithrix jacchus) using radiotelemetry." Clinical Neurophysiology, 112.12 (2001): 2265-2273.

Bastlund, Jesper F., et al. "Spontaneous epileptic rats show changes in sleep architecture and hypothalamic pathology." Epilepsia 46.6 (2005): 934-938.

Datta, Subimal, and Robert Ross MacLean. "Neurobiological mechanisms for the regulation of mammalian sleep–wake behavior: reinterpretation of historical evidence and inclusion of contemporary cellular and molecular evidence." Neuroscience & Biobehavioral Reviews,31.5 (2007): 775-824.

Hadjimarkou MM, Benham R, Schwarz JM, Holder MK, Mong JA.  Estradiol suppresses rapid eye movement sleep and activation of sleep-active neurons in the ventrolateral preoptic area.  European Journal of Neuroscience 2008; 27: 1780-1792.

Horner RL Brooks D Kozer LF Leung E Hamrahi H Render-Teixeira CL/ Makin H Kimoff RJ Phillipson EA Sleep architecture in a canine model of obstructive sleep apnea Journal of Sleep and Sleep Disorders Research 1998; 21: 791-934

Ivarsson M, Paterson LM, Hutson PH.  Antidepressants and REM sleep in Wistar-Kyoto and Sprague-Dawley rats.  European Journal of Pharmacology 2005; 522: 63-71.

Mavanji, Vijayakumar, et al. "Elevated sleep quality and orexin receptor mRNA in obesity-resistant rats." International Journal of Obesity 34.11 (2010): 1576-1588.

Morairty SR, Hedley L, Flores J,  Martin R, Kilduff TS.  Selective 5HT2A and 5HT6 Receptor Antagonists Promote Sleep in Rats. SLEEP 2008; 31: 34-44. 

Morrow JD and Opp MR. Sleep-wake behavior and responses of interleukin-6-deficient mice to sleep deprivation. Brain, Behavior and Immunity 2005; 19 1: 28-39.

Olviadoti MD, Opp MR.  Effects of I.C.V. administration of interleukin-1 on sleep and body temperature of interleukin-6-deficient mice.  Neuroscience 2008; 153: 338-348.

Tang X, Sanford LD.  Telemetric Recording of Sleep and Home Cage Activity in Mice.  SLEEP 2002; 25: 677-685.

Wisor JP, Schmidt MA, Clegern WC. Cerebral microglia mediate sleep/wake and neuroinflammatory effects of methamphetamine. Brain, Behavior, and Immunity, 25 (2011) 767–776.

The above list contains the most widely used definitions of the frequency bands. However, exact band limits may differ slightly between laboratories, species or protocols.