Pulling an “all-nighter” in the library may seem depressing and emotionally-taxing, and these feelings are usually further exaggerated the next day. However, researchers from UC Berkeley have found new explanations as to why the brain functions in a way to amplify these feelings.

According to a report by a team led by Ninad Gujar in Journal of Neuroscience, the reward system of the brain secretes increased amounts of dopamine, a potent neurotransmitter, during mental states caused by sleep deprivation. In other words, receiving a compliment or a good grade the day after an “all-nighter” would feel more rewarding than it would in a rested, sober state of mind.

Jane Lubischer, biology professor, compared the human neurophysiology to tests done in animals explaining how the reward system in the brain functions.

“The neurons reward system starts in the ventral tegmental area of the brainstem and projects upward to the nucleus accumbens, located near the thalamus,” Lubischer said. “The thalamus is the gateway between our sensory inputs and the more higher-thinking parts of our brain. Now with the reward system, when stimulated, the synapses [neuron endings] at the nucleus accumbens release dopamine and cause this feeling of ‘reward,’ often with feelings of happiness.”

Gujar’s research suggests that sleep deprivation, in Lubischer’s words, “sets this balance out of whack and makes us react in an exaggerated way.” According to Lubischer, the relationship between sensory inputs and higher thinking and analysis exist in a fragile balance—a balance that sleep deprivation can easily affect.

“[Emotional response and cognitive thinking] should be in a sort of equilibrium,” Lubischer said. “But when you exaggerate the emotional response, then you’ve thrown the cognitive thinking out of balance, which plays into risky behavior and people making not-so-smart decisions.”

Erika Ferro, a graduate student in physiology, is no stranger to all-nighters and sleep deprivation as a student. Ferro said she has similar feelings of exaggerated emotions after a night with little sleep.

“I generally see that my emotions get hypersensitive after I don’t get any sleep,” Ferro said. “That research does make some sense, because everything, positive or negative, is just more dramatic when I haven’t had enough sleep.”

Using MRI machines to track brain activity, the researchers found similar results in 27 male subjects, between 18 and 30 years old. While exposed to images that evoke positive and negative feelings, those sleep deprived ranked the images higher or lower scores than the scores by subjects with a good night’s sleep.

The MRI’s relieved that the sleep-deprived subjects secreted more dopamine in the reward system.

“This suggests that people without much sleep would be more willing to act in risky behavior or do something not well thought out,” Lubischer said. “Remember, that comes in to play when the emotional part of your brain is overpowering your cognitive thinking.”

Dopamine has a suspicious reputation due to many of the stimulators that act on it, including some addictive drugs. The mechanism these drugs take on the reward system are unknown, but with the secretion of dopamine comes feelings of euphoria and positive reinforcement.

“Getting a reward stimulates this region, but we know that many drugs of addiction hit this pathway like a hammer,” Lubischer said. “However, this doesn’t mean that not getting sleep will get you ‘high,’ per se. But it is interesting how lack of sleep affects this pathway.”

Sleep’s role, apart from physical recovery, remains a large mystery, but this type of research is starting to probe into how sleep affects our health and physiology. According to Lubischer, our brain consolidates memories and knowledge while sleeping.

“In the state of unconsciousness, the brain shuts off all its connections with the outside world,” Lubischer said. “This gateway becomes disconnected from these stimuli, and the thalamus and the cortex start doing this little ping pong game. Brain waves become long, slow, and synchronized. This oscillation is more visible in deeper stages of sleep.”

REM sleep, differs from other stages of deep sleep and according to Lubischer, brain activity during REM mirrow conscious brain activity.

“This is when we dream and so it’s hard to say the brian every rests, because there’s all this activity,” Lubischer said. “The body rests but the brain gets temporarily disconnected.”

We all know that sleep is good, but scientists have yet to grasp why. However, in studies of rats, severely sleep-deprived subjects die.

“We know that every species needs some sort of rest and quiescence in brain activity,” Lubischer said. “However, I don’t think humans would die, just shut down and sleep.”

Yet sleep is a hard thing to find in pursuit of a college degree. It’s even harder with procrastination, which Sokun Hourn, a senior in biochemistry, said she does too often.

“With work, classes and friends, it’s hard to study in advance,” Hourn said. “So I tend to do it all in the crunch period. I can function under the pressure, but I wouldn’t call it fun. Last semester I pulled 15 all-nighters in total, three of them consecutive.”

Lubischer’s recommendations for remedying lack of sleep are simple—get more sleep.

“Make it up, as much as you can and as soon as possible,” Lubischer said. “And don’t drive.”