The 2020 Time Vortex and other Tales of Perception

Posted by Laura Beebe on October 22, 2020 in Behavioral Neuroscience, Drugs, Memory, Neurodegenerative disorders, neuropsychology | Leave a comment

As we approach the end of 2020, I feel time warp as I think back to the early Spring… When I was quarantined in my home, the days seemed to rush past, but I still felt stuck in a huge temporal abyss.  Looking back at that time, I don’t sense the normal pattern of memories I was accustomed to in non-pandemic years!  It turns out I’m not the only one who felt this way.  Many people around the world reported anecdotally that their sense of time became distorted during periods of lockdown, and scientists are conducting longitudinal studies to assess these commonalities.  Why did this happen, and how can time feel different even though the length of days remains the same? 

At a cellular level, our bodies track the rhythm of day and night via a circadian clock.  But how we perceive the passing of time, and what it means to us, may be defined in totally different ways.  Our memories of past events exist on the scale of split seconds, days, years and decades.  When we look back, what do we see? 

We know that humans experience time subjectively.  Even when there’s not a global pandemic, a common set of behavioral patterns indicates that we perceive events in a way that is not tied to standard time passage. For example, scientists have observed that humans tend to recall recent events as occurring longer ago than they actually happened- a phenomenon called backwards telescoping.  Conversely, we usually recall long-ago events as occurring much more recently than they actually happened (forward telescoping).  Additionally, whether the events are personal or general news items makes a difference for how we recall and order them (Janssen 2006).  We don’t understand exactly why telescoping phenomena arise.  However, certain neurodegenerative diseases (like Alzheimer’s) can worsen these effects, perhaps via pathologies in the hippocampus, a brain area related to learning and memory.  (El Haj 2017)

It is impossible to directly understand how another human perceives time passing, but we can somewhat infer this process by measuring behavior.  By asking someone to describe when “x” event occurred – either a momentary “blip” in a laboratory setting, a distant emotional memory, or a habitual pattern (when did you last reach for your phone?) – we can start to learn about how people form their unique understanding of time.  On the level of seconds to minutes, psychologists can ascertain behavioral differences between humans based on pre-existing conditions, like whether or not the subject smokes cigarettes.  For instance, one study found that nicotine withdrawal perturbed study participants’ ability to both reproduce time (replicate an on-screen stimulus by holding down their mouse) and also discriminate between time intervals (decide which of 2 presented time intervals is longer).  Additionally, the behavioral effects may be different between men and women.  (Ashare and Kable 2015) 

For some humans with a disorder called dyschronometria, or “lost time syndrome”, perception of time passage can seem totally unlinked to the steady ticks of Earth clocks.  Jeannie Campbell, a woman who developed dyschronometria after suffering a cerebellar stroke, recently described her experience in an interview.  She notes observations like visiting the bulletin board at work for only a perceived second, to realize later that she was actually standing there for 15 minutes.  How and why does her brain produce this perceptual phenomenon? 

No cortex, no problem 

Early studies in rats that lack a neocortex show that they are able to accurately estimate short periods of time (Jaldow 1989). The neocortex is a “higher order” brain structure known for its role in sensory perception, spatial reasoning, and motor planning.  Some think of it as “the crowning achievement of evolution” (Rakic 2009), and gives humans the ability to consciously take in our surroundings and respond with actions.  But when this structure is removed in rats, the animals are still capable of performing a timed operant learning task (meaning that they can be reliably trained to press a lever and receive food, despite some sensorimotor shortcomings). This would suggest that for perceiving short, “in the moment” time intervals, cortical brain structures, i.e. those that would control conscious thought in humans, are not strictly necessary.  

The cerebellum, a brain structure also implicated in directing our bodily movements through space, may play an important role in how we sense the immediate flow of time.  Indeed, many people who suffer a cerebellar stroke (like Jeannie Campbell) can develop some form of dyschronometria, although it usually resolves. Patients with cerebellar lesions often display perceptual timing deficits on the sub-second scale, and they may also have difficulty integrating information about space and time to effectively plan their movements.  (Piras 2014)  

Pharmacological manipulations

We’ve seen evidence that specific brain areas control particular aspects of time perception.  But how, on a molecular scale, do our brains concoct the sensation of time passing?  Certain drugs can influence how “fast” or “slow” time seems to move.  Cocaine, a stimulant that produces feelings of euphoria through dopamine release, has been shown with behavior to speed up time perception in humans and rats.  (Most precisely, researchers observe  “a horizontal leftward shift in the temporal response function” after cocaine administration in rats).  (Cheng 2006)  But if rats receive extended behavioral training in advance of their time perception test, the time “speeding up” effects of cocaine seem to dissipate (Cheng 2007).  

Ketamine, a dissociative anaesthetic, is also dopaminergic in its secondary mode of action. However, administration of ketamine alone does not affect internal clock speed in rats (Cheng 2006).  Cocaine appears to affect time perception by prompting dopamine release specifically within part of the brain known as the dosal striatum.  While ketamine doesn’t have the same effect on its own, giving rats a small amount of ketamine in addition to a larger cocaine dose seems to perpetuate the classic increase in internal clock speed, even with advance behavioral training (Cheng 2007).  Scientists speculate that in this case, it’s not just dopamine that makes a difference in time perception.  Ketamine prompts a second neuromodulator, glutamate, to act on neurons within the dorsal striatum, “unlocking” the traditional cocaine effect (Cheng 2007).   

Studies like these illustrate a piece of the vast network of neuromodulators, acting within a complex map of brain structures, to create a nuanced and deeply personal sense of perceived time.  Humans are most likely too short-lived to disentangle all the many gears of the clocks in our brains, but we are sure to spend many, many more hours trying.  

References

Cheng, R. K., Ali, Y. M., & Meck, W. H. (2007). Ketamine “unlocks” the reduced clock-speed effects of cocaine following extended training: Evidence for dopamine-glutamate interactions in timing and time perception. Neurobiology of Learning and Memory, 88(2), 149–159. https://doi.org/10.1016/j.nlm.2007.04.005

Cheng, R. K., MacDonald, C. J., & Meck, W. H. (2006). Differential effects of cocaine and ketamine on time estimation: Implications for neurobiological models of interval timing. Pharmacology Biochemistry and Behavior, 85(1), 114–122. https://doi.org/10.1016/j.pbb.2006.07.019

Piras, F., Piras, F., Ciullo, V., Danese, E., Caltagirone, C., & Spalletta, G. (2014). Time dysperception perspective for acquired brain injury. Frontiers in Neurology, 4 JAN. https://doi.org/10.3389/fneur.2013.00217

Rakic, P. (2009). Evolution of the neocortex: A perspective from developmental biology. In Nature Reviews Neuroscience (Vol. 10, Issue 10, pp. 724–735). Nature Publishing Group. https://doi.org/10.1038/nrn2719

Jaldow, E. J., Oakley, D. A., & Davey, G. C. L. (1989). Performance of Decorticated Rats on Fixed Interval and Fixed Time Schedules. European Journal of Neuroscience, 1(5), 461–470. https://doi.org/10.1111/j.1460-9568.1989.tb00352.x

Why quarantine has made time feel so weird, explained – Vox. (n.d.). Retrieved October 22, 2020, from https://www.vox.com/2020/5/7/21248259/why-time-feels-so-weird-right-now-quarantine-coronavirus-pandemic

COVID19 – Timing Research Forum. (n.d.). Retrieved October 22, 2020, from http://timingforum.org/covid19/

Janssen, S. M. J., Chessa, A. G., & Murre, J. M. J. (2006). Memory for time: How people date events. Memory and Cognition, 34(1), 138–147. https://doi.org/10.3758/BF03193393

El Haj, M., Janssen, S. M. J., & Antoine, P. (2017). Memory and time: Backward and forward telescoping in Alzheimer’s disease. Brain and Cognition, 117, 65–72. https://doi.org/10.1016/j.bandc.2017.06.005

A Woman With Dyschronometria Shares Her Experience Of Losing Track Of Time : NPR. (n.d.). Retrieved October 22, 2020, from https://www.npr.org/2020/05/18/858236566/a-woman-with-dyschronometria-shares-her-experience-of-losing-track-of-time

Ashare, R. L., & Kable, J. W. (2014). Sex differences in time perception during smoking abstinence. Nicotine and Tobacco Research, 17(4), 449–454. https://doi.org/10.1093/ntr/ntu260