Sleep Research Lab, Jawahar Lal Nehru University (JNU), Delhi

Conceivably from the Vedic or post-Vedic period, it is said generation after generation that there are five prominent characteristics of an ideal student. It is said in Sanskrit that

In the above line “Svan Nidra” represents the nature of sleep in a dog. It was believed that the dog has light sleep only as it always remains watchful, so a student should also have similar behavior. It also suggests that an ideal student should not spend more time in sleep. It is virtually a misconception that the dogs’ sleep is light in nature. Similar to human sleep, the dog also exhibits different stages of sleep such as Rapid Eye Movement sleep (REM sleep: the deepest stage of sleep) and Non-REM sleep (NREM sleep: also called deep sleep). These two stages of sleep have been found only in birds and mammals. However, dual sleep stages have not been observed in reptiles, amphibians, and fishes. It still remains an enigma that why dual sleep stages have evolved in the higher animals only, such as in birds and mammals? What does the sleeping brain do to our mind and body? We are attempting to address these questions in our laboratory at the School of Life Sciences, Jawaharlal Nehru University, New Delhi.

Human spend a third of their lives sleeping, and most of us think we sleep to restore body and brain metabolic expenditure. This could be true, but we don’t actually know why we sleep? If rats are continuously deprived of sleep, they die after 12-14 days. Why do the rats die without sleep? Is it that sleep is indispensable for their survival? On the other hand, humans can sustain their life till eleven days without sleeping and show no immediate visible ill effects apart from feeling sleepy. This obviously does not tell us much about why we sleep, only that we have a very powerful mechanism to make us sleep. But on the other hand, many evidences demonstrate that sleep fulfills multiple functions, and most of them are imperative for our survival.

In our laboratory, we have demonstrated that short-term (6 hrs only) total sleep deprivation soon after training impairs the consolidation of trace and fear-conditioned memories in the rodents. The sleep-deprived animals (sleep deprivation performed soon after training for only 6 hrs) demonstrated skill deficit in obtaining fruit juice during testing compared to non-sleep deprived and stress control animals. Also, short-term (6 hrs) total sleep deprivation soon after training-induced learning deficit in fear conditioning. The sleep-deprived animals exhibited significantly less fear responses during testing compared to non-sleep deprived and stress control animals. These suggest that sleep, after learning of a task, plays an important role in memory consolidation. At the same time, our studies also suggest that a few hours of sleep deprivation soon after experiencing a traumatic event may be beneficial in removing the negative emotional memories of the events and hence would minimize the chance for the development of panic disorders in those subjects. Further, we have shown that each sleep stage possibly contributes differently to the learning processes. For example, we have observed that NREM sleep plays an important role in the consolidation of fear conditioned memories while REM sleep plays an important role in non-fear conditioned memories in the rat. In addition, we have demonstrated that sleep plays an important role in a dynamic rearrangement of neuronal circuitries underlying ocular dominance plasticity in the visual cortex in the cat.

Sleep also plays an important role in the modulation of several physiological functions. For example, heart rate and blood pressure decrease during NREM sleep but increase during REM sleep. During NREM sleep, pulmonary ventilation is diminished (as a result blood pH may also decrease), which otherwise remains elevated during wakefulness and REM sleep. The respiratory groups of neurons in the brainstem perceive the elevated hydrogen ion concentration through chemosensors and in turn accelerate pulmonary ventilation to help protect neural damage from an altered blood pH.

Therefore, to help maintain physiological range of blood CO2, it seems obligatory that the subject should periodically go from NREM sleep to a high ventilation state, which occurs during either wakefulness or REM sleep. We have recently proposed that since frequent arousal from sleep may not be physiologically and cognitively sensible, therefore, intermittent REM sleep between NREM sleep would thus be favored to help maintain optimum CO2 level and long-lasting sleep periods.

The reptiles may not require REM sleep as they are intermittent breathers, and that is why REM sleep might have evolved in higher animals only such as the mammals and birds.

Although REM sleep is present in almost all the terrestrial mammals, but it is absent in aquatic mammals. The aquatic mammals are obligate swimmers and have to surface at regular intervals for breathing. Also, these animals live in thermally challenging environments, where the conductive heat loss is approximately ninety times greater than air. Therefore, they have to be mobile most of the time. As an adaptation, they have evolved unihemispheric sleep, during which they can move as well as take rest. The activity of the postural muscles and the temperature regulating machinery remain suspended during REM sleep. Therefore, REM sleep is not at all suitable for the aquatic mammals, and thus nature has possibly eliminated its expression in these mammals. Interestingly, using the disk-over water, multiple or single platform, and wire-mesh grid platform methods, in which, water is used as the surrounding medium, REM sleep can completely be abolished even in terrestrial mammals. Our laboratory has recently proposed that aquatic conditions, as well as gravity, inhibit the expression of REM sleep, and that is why REM sleep might be absent in the aquatic mammals. However, it remains to be investigated that if REM sleep is also altered in the crew members on a ship in the deep sea.

Training Opportunities In Sleep Research Lab, Jawarhar lal Nehru University (JNU), Delhi

Our laboratory offers training at the masters, Ph.D. and post-doctoral levels to understand the basic neurobiology of sleep, learning and memory and cognition for short term (3-4 months) or long term (one year and beyond). The training program is specially designed to enhance the number of trained personal in our country in the field of neurobiological and neurobehavioral research related to basic and applied research on sleep and learning and memory. The enrolment in the Ph.D. program is exclusively through the entrance test followed by interview. The students having junior research fellowship (USC, CSIR, ICMR etc) may apply directly (no need to turn up in the entrance examination conducted by JNU) but selection is made through interview board (for detail see our web site: https://admissions.jnu.ac.in/). The interested master and post-doctoral trainee may directly approach to laboratory director Dr. Sushil K. Jha through email: sushilkjha@mail.jnu.ac.in or meet personally in the Room # 208, School of Life Sciences, Jawaharlal Nehru University, New Delhi-110067. (Also see our web site http://www.jnu.ac.in/FacultyStaff/ShowProfile.asp?SendUserName=sushilkjha).