The Benefits of Sleep

           “If you die in your dream then you’ll die in real life too!” This was a belief I often heard whispered with reverence on the playground in my younger years. Older kids would nod sagely, as if they had a friend who had died in such a manner. For as kids, sleep was special and mysterious- and we all wanted more of it. But as we grow older, the specialness of sleep seems to fade as we focus more on getting at least the minimal amount of sleep needed for functioning. According to the Center for Disease Control, one in three Americans is sleep deprived, usually chronically. And this lack of sleep, however, impacts the important role sleep has in maintaining our mental health. Without adequate rest, we are prone to act in irrational and non-adaptive ways (such as binging on sweets or becoming easily upset).

        Although much research has focused on the detrimental effects of sleep deprivation, further research is need to understand what happens during this portion of non-consciousness. As far as we can tell, every living thing from trees to flies has some form of sleep or quiescence (quiet resting) during which it recovers from previous activity. In smaller, simpler organisms, this quiescence might only include clearing cellular debris but in more complicated organisms this sleep period is also important for changes in the brain. In humans, sleep is a privileged period of time when the brain doesn’t have to take in external information. Instead the mind prioritizes shuffling and re-organizing information learned during the day. We call this process of organizing and solidifying information memory consolidation. Most scientists agree that this process is always going on, but is especially prevalent during sleep. Memory consolidation is one reason why consistent sleep is so important for our daily lives.

        When we are sleep deprived, we restrict our brain’s ability to organize and prepare for the next day. This means that we are more likely to be forgetful, impulsive, and moody. College students who assume that they will do better in the exam by pulling an all-nighter are actually making it more difficult for themselves to succeed. Sleep deprivation is especially damaging because the part of our brain necessary for forming memories, the hippocampus, is particularly sensitive to sleep deprivation. It’s almost like a switch where at a certain point you are unable to learn and retain almost any information you are studying late into the night.

In addition to impairing memory, not getting enough sleep can also lead to motor control problems. If you’ve ever noticed that you seem to be less coordinated after staying up all night (or not getting enough sleep for a prolonged period of time), the loss of sleep is probably to blame. Coordinated motor control, especially for fine motor control is actually a complicated mental ability. So when you are sleep deprived, you aren’t able to respond as quickly or accurately to your surroundings. This problem has serious implications for professional truckers or others who drive long distances. In America, more than 1550 people are now killed by sleep-deprived automotive drivers.

The above mentioned problems are only a few of the consequences of sleep deprivation on the brain. In recent years there has been an escalating interest in the cognitive effects of sleep and why sleep is so important for a huge variety of mental abilities. But despite the accumulating evidence of sleep’s importance, Americans still tend to habitually stay up late and rise too early- putting us at a constant disadvantage. Thankfully, there are a few simple tricks that have been shown to help the chronically sleep deprived get some rest. First, going to sleep and waking at a consistent time each day helps us set our internal clock so it’s easier to fall asleep and we get quality rest. Another simple trick is treating your bedroom as a place reserved for sleep. Avoid watching TV or playing video games in bed as this creates a mental association between your bed and these activities instead of sleep. These tricks, along with avoiding caffeine in the evening, can greatly improve your ability to get restful sleep.

So maybe the schoolyard wisdom about dying in your dreams doesn’t hold up to modern science. In fact, the relationship seems to go the other way: a prolonged lack of sleep can actually cause death. But schoolyard children are right to think of sleep with awe and wonder.

There is some truth in the thought that sleep is a special period of time important to our health and well-being. We should retain some of that awe and wonder from our childhood years and realize how special sleep is.


Footnotes:
I would like to say a special word of thanks to ComSciCon16 for helping me craft this piece. It's a wonderful convention/program that has provided me with lots of feedback, as well as helping me make connections with other interested science communicators.  

Why does memory change as we age? What changes?

As the baby boomer generation begins to enter seniority, concerns over mental performance for that age group are drastically increasing. Supposed brain training games like luminosity are attempting to cash in on this generational concern, but how is memory actually changing as the brain ages? Research seems to indicate that while episodic and source memories are affected by normal aging, semantic and procedural memory stay rather intact. Scientists believe this is due to how different regions of the brain atrophy during aging.

For example, Nyberg and colleagues found that episodic recall varied according to age but that semantic memory did not show this negative relationship. Thus older adults might struggle with remembering if they took their vitamin supplements that morning, but seemed to have no problem identifying the current president. In addition, memories for how to carry out actions seem completely spared. In studies using animal models, researchers found that aged animals performed equally well on an obstacle course compared to the younger animals (as long as gross motor control was normalized across groups). This explains why my 62-year-old mother is one of the best nurse anesthetists at her workplace, even when she might feel that some of her memory is eroding.

So why aren’t all memories made equal with respect to aging? Shouldn’t all types of memory decline equally as we age? Region-specific atrophy seems to be one of the key components in this dissociation longevity between the types of memories. In an imaging study conducted by Yonelinas and colleagues, healthy older adults showed reductions in hippocampal volume when recollection was diminished. Meanwhile recognition performance was dependent on entorhinal volume. These regions of the brain, found in the medial temporal lobe, tend to decrease in volume to a greater extent during aging than other regions. Whether these volume changes are due to the dying-off of neurons or reduction in synaptic connections, this seems to be a major cause of memory complaints in older adults.

So it is rather unfair to say that memory declines as we age, when not all memory is created equal. It is noticeable in daily life to recognize that you can’t call to mind where you met someone or how to use a computer function that your children just taught you. It is not immediately obvious that your memory of how to drive a car or ride a bike is still almost completely intact. I believe this is due to our limited connotation of the word ‘memory.’ When taking all forms of memory into account, healthy aging does not cause nearly the impairment that might be felt by an older adult. Because we rely so heavily on episodic and source memory in our social lives, we might not realize the multitudes of semantic and procedural memories that have been spared. Maybe brain-training games are effective, but it is important to also remember that an aging mind isn’t deficient in all memory types and that much expertise is actually spared.

Churchill, J. D., Stanis, J. J., Press, C., Kushelev, M., & Greenough, W. T. (2003). Is procedural memory relatively spared from age effects?.Neurobiology of Aging, 24(6), 883-892.

Nyberg, L., Bäckman, L., Erngrund, K., Olofsson, U., & Nilsson, L. G. (1996). Age differences in episodic memory, semantic memory, and priming: Relationships to demographic, intellectual, and biological factors. The Journals of Gerontology Series B: Psychological Sciences and Social Sciences, 51(4), P234-P240.

Yonelinas, A. P., Widaman, K., Mungas, D., Reed, B., Weiner, M. W., & Chui, H. C. (2007). Hippocampus, 17(11), 1134-1140.

Memory in the aging brain: doubly dissociating the contribution of the hippocampus and entorhinal cortex.

Why do we forget?

Thanks to brain training companies, it seems everyone is trying to increase his or her memory. It’s easy to argue that better memory can only positively impact your life, but in fact forgetting serves an equally important role in cognition. Specifically, forgetting is necessary for two reasons- forgetting (especially of details) allows for automatized skills and semantic encoding and forgetting is emotionally adaptive to neglect some painful or negative memories.

First let us examine the case of AJ, a woman with highly superior autobiographic memory. If you were to ask AJ what happened 20 years ago on April 11, she could list exactly what she wore that day, along with all of her activities. Her memory is able to retain an episodic account of nearly every day of her life. However, this ability deeply intrudes on her life. She reports, “Most have called it a gift but I call it a burden. I run my entire life through my head every day and it drives me crazy” (Parker et al., 2006, p. 35). Imagine every time you went to the grocery store, you remembered every other instance of a trip to buy milk. It would be cognitively taxing and unnecessary to sustain all these individual memories. And in fact, a study by Logan and Crump (2009) demonstrated the necessity of losing detailed memory in professional typists, who aren’t able to verbalize where keys are located or how their hands are moving. Yet these workers are still extremely proficient in their job, and when they are asked to explicitly focus on what their hands are doing, their performance suffers. These typists do not have detailed memory of every time they sat down at a keyboard, but their skill demonstrates that a composite of all those experiences meshed together have given them their proficiency. Thus, forgetting may allow for details of episodes to be removed so that abstraction and generalized skill learning can occur.

As mentioned before, forgetting not only benefits cognition, but also assists in emotional stability. Joorman and colleagues (2009), among many others, have demonstrated that depression is linked to an inability to forget negative memories. Perhaps if we were able to remember every embarrassing moment and social faux pas, we would be less likely to take social risks or even engage with others at all. Forgetting negative experiences can help us stay open to new social experiences or maintain important relationships. Going back to the case of AJ, she was diagnosed with both depression and anxiety, maybe because she couldn’t forget her negative experiences. Thus, AJ exemplifies that there is no evolutionary benefit to remembering every negative experience.

Memory is unequivocally important for many functions, but forgetting also serves a purpose in maintaining healthy functioning. Without forgetting, we might be less positive about the future and unwilling to take the big risks that advance science and other fields. We would also be unable to garner abstract information from multiple situations or sources we encounter. Like tow sides of the same coin, forgetting and remembering balance each other.

Works Cited

Joormann, J., Hertel, P. T., LeMoult, J., & Gotlib, I. H. (2009). Training forgetting of negative material in depression. Journal of abnormal psychology, 118(1), 34.

Logan, G. D., & Crump, M. J. (2009). The Left Hand Doesn't Know What the Right Hand Is Doing The Disruptive Effects of Attention to the Hands in Skilled Typewriting. Psychological Science, 20(10), 1296-1300.

Nørby, S. (2015). Why Forget? On the Adaptive Value of Memory Loss.Perspectives on Psychological Science, 10(5), 551-578.

Parker, E. S., Cahill, L., & McGaugh, J. L. (2006). A case of unusual autobiographical

            remembering. Neurocase, 12(1), 35-49.

Remember that one time when.....

How much of our personality, our soul, is composed of our memories?  I think who we are stems from what we've done and how we've learned from those actions.  But imagine an existence where you could no longer form memories.  This is the situation faced by neurological patient H.M.- now know as Henry Molaison.

Henry Molaison passed away in 2008.

Henry suffered from debilitating seizures caused by tissue in his temporal lobes.  Historically, patients before him had undergone surgery to remove the epicenter in the brain that caused the seizures and this usually solved the problem.  But for Henry, the seizures were caused by 2 epicenters- one on each temporal lobe.  So when surgeon Scoville removed the defective tissue in 27 year old Henry Molaison, he had to take large portions from both sides.

But a strange thing happened when Henry recovered from his surgery.  He was no longer able to form new memories.  Semantic information (facts and dates) from before his surgery was untouched but when it came to recalling simple episodic information (like what he had eaten for breakfast), he couldn't recall a thing.

Neuroscientists Brenda Milner and Suzanne Corkin took on the case of H.M. in the hopes of learning more about memory and its storage in the human brain.  They found that the hippocampus, which was almost completely removed, is vital for processing memories.  You could view it as a sort of clearing house where short term memory gets transferred into long term storage.  But without this structure, Henry could no longer process his memories.  In other words, he was forever stuck in the mindset of his 27 year old self.

Hi-lighted in yellow is the portion that H.M. lost.

A similar deficit was found in a Korsakoff's syndrome patient mentioned by Oliver Sacks in his book The Man Who Mistook His Wife for a Hat.  This man was also unable to form new memories, leaving him trapped in a time that has already passed.

Now while there are some technical differences on the types of memories and amount of retrieval between these patients, they both hold an amount of melancholy in my mind.  To be deprived of the ever changing world.  To be able to grow and expand.  These two men lost so much.

I am a firm believer that our genetics set the blue print but our experiences are really what make us unique. And our capacity to change is what makes us so fantastic.  My heart goes out to these two men and all who suffer from anterograde amnesia.  It's a hard world to imagine.

But what about you?  Would you rather suffer anterograde amnesia (where you can't form new memories) or retrograde amnesia (where you can't remember your past from a certain point back)?  It's no easy choice.