I know the feeling of rushing around to get somewhere on time is common among my peers and I. Admittedly, it's a terrible habit; I have some sort of inner voice, not necessarily an internal clock, that tells me I can get anywhere in Denver in less than or equal to 15 minutes. Thankfully, we, as humans, have an internal clock that helps us tell time, maintain circadian rhythm, etc. However, recent research has shown that it's not one internal clock that helps us tell how much time has passed, i.e. if you've been driving too long or if you've been spending too much time eating breakfast, but that there is a secondary clock that interacts with our main internal clock.
For a great period of time, the striatum was thought to be the crux of our inner clock, using the brain's surrounding cortex to integrate temporal information. New research published in the Journal of Neuroscience has expanded on this and found that the hippocampus actually plays the main role in remembering how much time has passed, which makes sense, given the hippocampus' role in memory. To assess this role, researchers trained rats to discriminate between different time intervals and rewarded the rats based on what odor they chose, correlating to a specific time interval. To make things more interesting, these researchers selectively inactivated the hippocampus with a GABA-A agonist, and found that without an active hippocampus, rats were only able to tell the difference between largely different time intervals, such as 2 minutes versus 10 minutes.
This research highlights a new take on telling time: we don't necessarily think of memory when it comes to telling how much time has elapsed, do we? It's really clever, really, that our brain uses episodic memory to assist with determining how much time has elapsed. The brain identifies when specific events occurred, then uses the internal clock (striatum) to determine how long ago that event occurred from the present.
Given the role of the hippocampus and striatum in memory and time telling, it would be interesting to assess the effects of neurodegenerative diseases on the brains ability to tell time/elapsed time. It is known that patients with Parkinson's Disease have trouble telling time, but what of their ability to tell how much time has passed since they started eating their bagel?
What do you guys think? My hippocampus and striatum tell me I'm late to class...again.
References:
Jacobs NS, Allen TA, Nguyen N, F ortin NJ. 2013. Critical role of the hippocampus in memory for elapsed time. J Neurosci. 33(34):13888-13893.
Hmmm... This makes sense to me. If someone has short term memory loss they typically have a difficult time telling how much time has passes since the last time they... forgot something. This suggests to me that it is natural that the hippocampus tells us how much time has recently passed. After all, without the memory of where we've been it would be very difficult to remember how much time it took to get to where we are now.
ReplyDeleteI wonder what would happen if the hippocampus was upregulated? Would our perception of time become clearer? Sounds like an interesting field of research.
Well, I guess my hippocampus seems to be incorrectly calibrated because I definitely have trouble being on time. This is a very interesting post though. Do you suppose that people who are late regularly train themselves to be late? From your article it would seem that if you are late a few times your brain would remember you being late and then that would become your current memory of "15" minutes, which in reality may be 20 minutes. So, do we basically teach our brain to remember time spans incorrectly?
ReplyDeleteI really enjoyed this post! Do you think our teachers would accept the excuse that our hippocampus is incorrectly calibrated when we are late?
Great post Dylan, this got me thinking about how my dog's memory works, that is that I started to think if my dog is able to tell if I have been gone for two hours or eight hours. According to the Animal's Planet article, "Do dogs understand the concept of time (2013) dogs do have the ability to tell how much time has passed since their owners last departure. I would imagine that this would also fall into the functioning of the dog's hippocampus. So the next time you hear a dog owner say that they have to get back to their dog you can let them know that the dog will be expecting them.
ReplyDeleteDo dogs understand the concept of time [Internet]. c2013. New York City: Discovery Communications [cited 2013 Dec 2]. Available from: http://animal.discovery.com/pets/do-dogs-understand-the-concept-of-time.htm