I’ve officially been at the Marine Biological Laboratory in Woods Hole, Massachusetts for one week and it has been a hell of a week. From meeting amazing people while flying across the country to struggles while putting together my materials and experimental design for this study. If there’s one thing I love, it’s a challenge and boy has this trip been challenging! 

First I suppose I should explain why I’m even here at the MBL. If you’ve been keeping up with the podcast, as I’m sure you loyal Fact Finders have, you may have heard me talk about studying sleep-like behavior in cuttlefish. I say “sleep-like” because technically speaking, it hasn’t been proven that the cuttlefish are actually sleeping. To be considered sleep there are three criteria that need to be met:

  1. Decreased responsiveness to the environment
  2. Can be easily aroused and reverted back to wakefulness—consider trying to wake up a hibernating bear with a loud clap of your hands vs waking up a sleeping friend. One is going to be much more difficult than the other.
  3. And finally, Increased threshold to arousal—which just means the level of stimuli that creates a startle response while you’re awake must be higher to create the same response while you’re asleep.
  4. I’m also going to add that it must be homeostatically regulated—meaning if you are sleep deprived, the next opportunity you have to rest you will compensate by sleeping more.

Try not to get numbers 1 and 3 confused. They are similar, but not the same. Decreased responsiveness is pretty easy to visualize because you can think of times when you’ve fallen asleep in class and woken up to find out the class has ended and there’s a whole different room of people surrounding you—that’s decreased awareness of/responsiveness to your surroundings. Increased threshold to arousal also deals with responsiveness to your environment but in a different way. Here we’re looking at specific physiological measures of alertness like your heart rate, blood pressure, respiratory rate, etc.

What the cuttlefish have been known to do is enter a state of quiescence, which according to the Merriam-Webster dictionary is defined as “inactivity or repose.” Experiments have been done to show that this state of quiescence induces 1) decreased responsiveness to their environment and 2) they can be easily aroused to revert back to the awake state. They have even shown disrupting rest in the cuttlefish for 48 hours leads to them compensating by sleeping more, demonstrating homeostatic regulation. The critical evidence missing to demonstrate this is indeed sleep are experiments determining whether there are differences in arousal thresholds between the quiescent and wake states. And so concludes my crash course in classifying sleep and why we currently cannot definitively say cuttlefish are sleeping! Lowkey, I’m about 90% sure it’s sleep. As the great Randy Newman once said, 

“I could be wrong now,

But I don’t think so!”

 It is a jungle out there in these journal streets tho. One must have rigorous experimental design and the evidence must show beyond reasonable doubt that arousal thresholds are higher during quiescence for this to be considered sleep as we know it. The design and evidence must then be evaluated by multiple expert eyes who can suss out any errors in theory, design, or analyses before we come to any conclusions as a community. On the show we’ve also talked about the dangers of confirmation bias, and it is something I stay aware of. I’m constantly making sure I’m taking into account the fact that at this point, it is equally as likely the animals will have similar arousal thresholds while awake and while quiescent. Whether or not I do find a difference between states, either of these findings would hold value to the scientific community because sleep remains a giant mystery. All discoveries are welcome, so long as they withstand the rigor of the scientific process and I have no problem being wrong considering nature is always full of surprises. The function of sleep remains elusive, although different theories exist and actively compete with one another for dominance in the field. I personally stand along the lines that sleep is essential for learning and memory and is specifically of importance when it comes to social and emotional learning. But before I can begin conducting experiments to prove or disprove this in cuttlefish, I need to first determine whether the cuttlefish are experiencing sleep as we have traditionally defined it, or perhaps discover this is an entirely new type of sleep altogether.