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Episode 29: Time Perception and Dopamine
22 Plays4 years ago
In this half-hour episode, Rolf and Joe discuss research by Jennifer Mitchell and colleagues ("Dopamine, time perception, and future time perspective") showing that the drug tolcapone, which selectively increases dopamine in frontal cortical regions, has the effect of reducing the error in estimating how much time has passed. Individuals tend to systematicaly underestimate how much time has passed (think of impatient kids asking "are we there yet?"), and in this double-blind study, tolcapone nearly eliminated this effect, most dramatically for a 60 second interval.
Implications of the study are discussed, including what this says about an "internal clock", whether you should rush to get this drug, and how time perception is related to depression, anxiety, and other mood disorders. We do not discuss the role of tolcapone in ending the world.
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Transcript
Introduction to Cognation Show
00:00:10
Speaker
Welcome to Cognation, the show about psychology, neuroscience, technology, philosophy, and anything else we happen to be interested in today. I'm Joe Hardy. And I'm Ralph Nelson. Welcome to the show.
Exploring Time Perception and Dopamine
00:00:26
Speaker
On today's show, we're going to talk about the perception of time. And in particular, we're going to talk about an interesting finding that shows the involvement of dopamine in time perception. So we'll be looking from a paper called Dopamine, Time Perception, and Future Time Perspective. It's a paper by Jennifer Mitchell, Don Weinstein, Taylor Vegas, and Andrew Kaiser from 2018.
00:00:55
Speaker
Right, and these guys are at. I think somewhere at Berkeley. Yeah, you see San Francisco and they did the research. They actually use the scanner at Berkeley and it looks like Taylor Vega is at and Andrew Kaiser also have an appointment at Northern California Healthcare System in Martinez. So I guess that's the VA. Yeah, so it's a cool paper. A really interesting work actually and raises a lot of interesting questions. We were interested in.
00:01:24
Speaker
thinking about how the brain processes time, which is what led us to this work in particular. And they have a very interesting take on it. So I think it should be a good conversation.
How Dopamine Affects Time Perception and Accuracy
00:01:37
Speaker
So the bottom line on this paper is a really interesting one, which is that they find that taking a dopamine increasing drug can improve your perception of time, which is really cool. So in general,
00:01:55
Speaker
people tend to be not exactly accurate on how long an event lasts. And you get worse the longer it is. In particular, people tend to have a bias to say things are longer than they are, I guess, or to think that a minute is done before that it is. In other words, people are by default a little bit antsy about time. Right, exactly. And there's different ways to measure time perception. There's a lot of different ways, actually.
00:02:24
Speaker
The one that we're talking about today is really about understanding that a certain amount of time has passed. So press a button when five seconds has passed or 10 seconds has passed or 60 seconds has passed. Most of the findings they have here are actually from 60 seconds. Press a button when a minute has passed. And you can't count too, that's the thing. They said it was okay to count.
00:02:51
Speaker
I think they said they monitored whether people were using counting strategies. They did. They definitely said that. People were allowed to count? They were allowed to count. Yeah, exactly. They didn't really care because they had found previously or believed previously that it didn't matter whether you were counting or not.
00:03:12
Speaker
Oh, maybe that's, I guess your counting would just speed up if you're, you know, if you're proceeding, it's happening slower. That was what I was thinking too. Like, what's the effect of counting? I mean, I was doing this thing the other day where I was recording just like a talk track of me saying one, two, three, you know, like once a second, uh, for like a test that I was doing an audio test that I was doing. And what I found was that it was, I was definitely going faster.
00:03:41
Speaker
If I wasn't looking at a stopwatch, I was counting faster than a second. And the longer I looked away from the clock, I kept speeding up again. That's interesting. So counting doesn't help because the speed that you're going is going to change directly in relation to how your time estimation is changing anyway.
00:04:02
Speaker
Right, that seems to be what they're saying. Yeah, and it seems like they got the biggest effects on, as Rolf said, really, not everyone, but the general trend was strongly in the direction that people would press the button before the minute was up, when they were trying to wait a minute. I think maybe by an average of what, around six seconds or so? Maybe it was more like three seconds, but yeah, something like that.
00:04:29
Speaker
What was it exactly? But yeah, the, you know, you didn't really see it as much. Yeah, about three seconds. Three seconds. Yeah, I see. That's right. Three seconds. So you didn't you didn't really get the effect so readily or noticeable with a five second time, but was still there. You know, just just sort of increased continuously across like longer and longer times.
00:04:51
Speaker
But the cool thing is, and they include a really amazing graph here, which I think lays it out pretty clearly, that
Tolkapone's Role in Time Perception and Parkinson's Treatment
00:05:03
Speaker
When you are taking the tolkapone, which is the dopamine drug, your inaccuracy goes down to almost zero or is significantly reduced. So in all time courses, it's reduced a little bit so that you're more accurate in each case. But at 60 seconds, it's a really noticeable difference where it's a consistent difference of about three seconds and then less than half of a second with the people on dopamine.
00:05:42
Speaker
And we hope we're saying it correctly, because this is the first time I've ever heard of this drug. But spelled T-O-L-C-A-P-O-N-E. Tolkapon, that's what we're saying, is a catechol O methyltransferase inhibitor. So it's referred to by the acronym COMPT.
00:05:58
Speaker
That's right. Exactly. I think it's probably worth taking a time out here to talk a little bit about the drug.
00:06:05
Speaker
So a comped inhibitor. And so this catechol O methyltransferase is a enzyme that breaks down dopamine, essentially, or reduces the amount of dopamine that's available specifically in the frontal part of the brain, in the frontal cortex.
00:06:30
Speaker
So by taking this drug, Tolkapon, you inhibit that enzyme. So you increase the amount of the availability of dopamine essentially. Yeah. And they call it, they say it increases dopamine tone in the frontal cortex. I'm not exactly, I'm sure that's a term that people that, um, that, uh, research this are familiar with. I don't know exactly what tone means.
00:06:56
Speaker
Right. I mean, I think what they're suggesting is it's not like you're flooding the system with a bunch of dopamine. You're not like releasing a bunch of dopamine into synapses, but rather just increasing the availability of dopamine to be used in neural processing.
00:07:16
Speaker
Yeah, and we should say the reason why they use this toll capone instead of other methods of increasing dopamine availability is because toll capone particularly targets dopamine pathways in the frontal cortex.
00:07:33
Speaker
When we had a show before about effects of dopamine, we were mainly talking about dopamine in the striatal areas, which is involved more in reinforcement learning and some other sorts of behavior.
00:07:51
Speaker
That's right, exactly. Yeah, so Tocapone is actually a drug that is used in Parkinson's disease. So folks who are familiar with this stuff might be aware that there's a breakdown in dopamine-releasing neurons in parts of the brain that control movement.
00:08:11
Speaker
or initiate movement in Parkinson's disease. So this drug is used with some others, for example, L-Dopa and other drugs you may have heard of in Parkinson's disease to improve the initiation of movement, essentially. Okay, should we get into exactly what they're doing here? Yeah.
00:08:36
Speaker
OK, so if you're in this very nicely, carefully controlled study, one of the things I appreciated about the study is to make sure that participants don't know that they're in the experimental group. They give them an extra drug that makes their pee clear so they can't notice it just accidentally. So I think it's kind of clever. So you go into this experiment.
00:09:07
Speaker
Half of them get a placebo and half of them get talcapone.
00:09:11
Speaker
And then they do a couple tasks. One of them is this time estimation task. Between five seconds and 60 seconds, they just sit there and estimate when it's been 60 seconds. And that's the main result. And then to make sure that it's not just that their motor system is faster, that it's just responding faster, they give a simple reaction time test where they just have to press a button as fast as they can when a target appears.
00:09:40
Speaker
That's right. And there's no difference between drug and placebo on the reaction time test. Right. So it's not just that in general, people are faster at these sorts of things or better at tasks in general. Right, exactly. So that's cool. That's an interesting thing. And as Ralph was saying earlier, the big result here is that in the group that took the drug while
00:10:09
Speaker
Everyone took the drug because it was a crossover design, but in the sessions where people took the drug, their perception of time as measured by the accuracy of selecting when a minute was up, for example, was improved when they were on the drug to the point where it was on average across subjects, essentially perfectly accurate.
00:10:31
Speaker
So this is great. Now we can have a drug that gets rid of our poor time perception. Well, I mean, there's a little bit more complicated than that, of course. And we don't have all the information we would need to fully evaluate that claim. But it's an interesting result in terms of understanding how time perception works. So it certainly does seem that, on average,
00:10:59
Speaker
The perception of time was essentially slowed down. Am I saying that correctly? Slowed down. Yeah, I find it very confusing because it is confusing because they're asked to judge the duration of a minute. And if you say 50 seconds, that almost seems like time is going faster, but I think it means that time is going slower.
00:11:28
Speaker
Time is going slower, right? So actually their perception of this time is going faster, more veridical, but relative to their previous experience, not on the drug, time is going faster. With Tocopone. With Tocopone. So their time perception on, the reason why I emphasize the idea that time, the average is more accurate is that to understand whether
00:11:56
Speaker
This drug actually improves a person's ability to accurately say how much time has passed, but you really need to look at as the variability. Yes. And they didn't really get into that too much. So, but it's more just that on average, the, the responses is more vertical. It's more correct.
00:12:18
Speaker
Yes, so that but yeah still very very cool and it's a strong, you know, uh in terms of just like if you just look at the The pattern of effects is a strong effect I mean the actual statistics come out to be a little bit marginal in the sense that it's like kind of close on the Statistical significance it does come out statistically significant, but you kind of have to look at it a certain way Yeah So that that's not awesome for them. There were there were 66 participants, which is not a huge number but it's
00:12:47
Speaker
You're giving people a drug. It's a lot. That's an expensive, time-consuming study. So it's good that they were able to get something. But yeah, it's not overwhelming in terms of the effect. But yeah, I mean, in general, directionally what they were expecting and a cool result. Yes.
Brain Areas and Implications for Mood Disorders
00:13:10
Speaker
OK. And I think what is really interesting about this is
00:13:18
Speaker
Well, it doesn't necessarily indicate that there's a single place in the brain where time, you know, a single dedicated area in the brain where time perception happens. I mean, the first thing you might take from this is, okay, they showed that giving tolkopone to the frontal lobe or giving dopamine to frontal areas makes time perception better. You might think that that's what part of the, there's a part of the frontal lobes that's dedicated to that.
00:13:46
Speaker
It seems like more likely it's just a general increase in accuracy and working memory and sort of executive function all the stuff that the frontal lobe does. But I wouldn't say that they found a single place in the brain that that keeps track of time or that measures time.
00:14:03
Speaker
Right, no, definitely not. I wouldn't say that either. Just to follow up on that. So in terms of when we think of what's going on in the brain in terms of timekeeping, there's been a long history of research into this. And there are some areas in the brain that are implicated in certain kinds of timekeeping, like keeping the beat or timekeeping over the course of a day.
00:14:28
Speaker
So we have circadian rhythms that keep us in tune over the course of 24 hours. And we can synchronize up with beats or repeated actions. But in terms of, we don't have a single centralized clock in our brain that sort of syncs up with the world. So this is why we can be poor at estimating things like how long is 60 seconds. Because we just don't have any mechanism in our brain to do that.
00:14:58
Speaker
We have to change it for each task that we do. We need a new timer for each task that we do. Yeah, exactly. I mean, you might have a very different result in terms of accuracy for a person doing a tapping task, for example, where you have to tap once per half a second or once per second or what have you.
00:15:20
Speaker
Right. So this might be something that, um, if you're, you might look at this and say, well, I'm a drummer. I want to have better timing. That wouldn't necessarily have something like that. Maybe that's too short of time perception. Right. Exactly. And different, a different kind of time perception as well. Although it'd be interesting to see, uh, I'm sure that's been studied, the relationship between that is not something I know about, but that would, I'd be interested to learn more about that.
00:15:50
Speaker
But yeah, I mean, the really interesting thing that they bring out here is the relationship between this type of time perception, the underlying genetics, and different mood disorders. Yeah, it seems strange that time perception would be closely related to stuff like depression and stress, but it makes sense, I guess, when you think about it.
00:16:19
Speaker
Yeah, they report that the drug effect of the improvement in time perception from the drug is related to whether people drink alcohol too much, whether they're impulsive, and whether they tend to be depressed.
00:16:40
Speaker
So they measured using psychological scales, those different things of, you know, sort of like alcohol use, depression and impulsivity. And they found that people who were, you know, more prone, for example, towards hazardous drinking had larger drug effects of the tolkopon. In other words, the tolkopon was more helpful in making their time perception accurate
00:17:08
Speaker
if they, or had a history of hazardous drinking. So how do you make sense out of this? I mean, I guess if you think about impulsivity, which plays a part in drug addiction or any of these other problems, chronic gambling, something like that, a lot of impulsivity might be, and this is what they relate in the paper, a lot of impulsivity might be related to
00:17:36
Speaker
not being able to perceive time correctly because it seems like things are taking longer than they are, right? Right. Yeah. You're impatient. You're impatient. Time seems to extend longer than it does. Exactly. Or there may be some third factor that's related to both. So something about the fact that you're feeling irritated or annoyed or what have you is making it feel like time is going slowly.
00:18:06
Speaker
Yes. But it's just, yeah, I mean, it's very interesting. They indicate that there have been studies on this COPT gene, you know, this methyltransferase that breaks down and reduces the availability of dopamine, that this gene is related to frontal cognitive function. So there's a relationship between hazardous alcohol use, behavioral impulsivity, and mood disorders, and this gene.
00:18:37
Speaker
And just very interesting that that there's also then this relationship between those things and time perception. And that is then this drug kind of comes in and is related to all to, you know, in both directions. So yeah, all of these things are all very closely connected. Yeah, part of the same cognitive systems.
00:18:58
Speaker
So the obvious question then becomes, and probably I'm guessing where they're coming from, although they don't really get into it directly here too much, is, well, if people were highly impulsive and had, for example, drinking problems, could that be helped with a drug like this, for example?
00:19:22
Speaker
Yeah. Yeah. So this is an interesting time to think about who would benefit from this kind of drug. Right. I mean, there's no there isn't research so we don't know, you know, the hope is that it could be a useful thing for depression. Right. Depression or obsessive compulsive disorder, you know, anxiety. Yeah, yeah. Particularly related to, you know, drug or alcohol use.
00:19:48
Speaker
This particular drug has some side effects that might make it hard to implement in that context. But maybe there's better drugs that could be made that would have less side effects. You do have these movement-related side effects with this drug at high doses over time.
00:20:13
Speaker
It's not something you're just going to want to take because you want to improve your video game skills. Right. No, exactly. Exactly. With its relationship to Parkinson's disease, you can imagine that there would be this movement effects, but those are some of the listed side effects. You might have spontaneous movements, like twitching and other kinds of things like that.
00:20:37
Speaker
that could be disruptive and there probably are other more physiological effects. And then when you go off the drug, you could have other movement problems as well. So it's not like something you would just want to be taking casually.
00:20:54
Speaker
Well, one other thing that this may indicate, I don't know, is that maybe you could get some benefit by training time perception or increasing, you know, if you could behaviorally change time perception by increasing those tasks so that you could get people with depression or anxiety to more realistically perceive time. Yeah, that's a good point. That's a good point.
00:21:18
Speaker
I mean, if it is the case that depression or anxiety can be made worse by inaccurate time perception, then that could be something to target. Exactly. I mean, I like what they said in the beginning of the paper in trying to explain how to think about this.
00:21:40
Speaker
they say, as anyone who has ever known, as anyone who has ever taken a long car trip knows, individuals have different thresholds for deciding to ask, are we there yet? And I think that really kind of sums up the vibe of it, right? Like some, you know, like kids, for example, are like, are we there? Are we there yet? Yeah.
00:22:04
Speaker
You can imagine that their child's perception of how much time has passed, when a minute has passed, would be very different than an adult's. And that's one of the things they mentioned in the discussion.
00:22:22
Speaker
was that this is a group of people taken from San Francisco Bay Area and mostly younger people. And you might see different results with older people or people from different cultures or different parts of the world.
00:22:40
Speaker
It does make a lot of sense if, I mean, if we think of brain development as continuing till the mid-20s, you might be looking at, and we also certainly kids are more, you know, younger kids are more impulsive and teenagers are more impulsive than adults. So that could be an issue. It really, yeah, it makes me just sort of question or think about why would it be, just thinking evolutionarily here for a second,
00:23:09
Speaker
Why would it be that people would in general have this misapprehension of time where they think that a minute goes by faster than it really does?
00:23:22
Speaker
You might have something with, uh, you know, you were talking about cultural influences. Um, it could be that, you know, on the Savannah, we evolved to perceive 60 seconds as 60 seconds, but we're more impulsive because there's a lot more going on now. I mean, that's a total speculation that doesn't, you know, yeah, that's certainly, you know, it would be interesting to explore, you know, how,
00:23:49
Speaker
your ability to wait 60 seconds is influenced by cultural things going on. But I mean, of course on the Savannah, 60 seconds had no meaning. Right. 60 seconds didn't, you know, it's an externally imposed timeframe doesn't mean anything, right? Right. Yeah. It's important to us culturally now. But yeah, it couldn't be something that evolved because we didn't have
00:24:16
Speaker
But we did have the sun and people were, you know, people have been paying attention to time for as long as people have, you know, as long as we know of, you know, people have been recording when the sun reaches different parts of the sky at different times of the year. And really paying attention to that, because that has a lot of impacts on a lot of things in terms of, well, certainly being outside where you can see during the day.
00:24:43
Speaker
how warm or cold it is, and then also related to the changing of the seasons, of course. That's right. And people are out of touch with a lot of that stuff now, less connected with changing of seasons and longer term kinds of time givers. I mean, if you're outdoors less, I guess you have less access to the things that are changing over the course of the day. Absolutely, yeah.
00:25:07
Speaker
Yeah, and I yeah, it's interesting because I'm just trying to think about what it make a difference if you were more tuned into the diurnal clock, you know, like a passing of a day, would that help you in determining the length of a minute or not? Because it's sort of very different, right? Because like a minute is like this arbitrary cut on
00:25:32
Speaker
an hour, which is an arbitrary cut on a day. A day, obviously, is a certain length. A day has meaning to our bodies already, certainly, yeah. Right. But it is a subdivision, and it's like a regular subdivision. So it's not necessarily, I guess, I mean, it is arbitrary that we chose to break it out into that many subdivisions. But it's a constant ratio of a real thing that's happening in the world. So it could be related, or it could not be related. Yeah, both are possible.
00:26:04
Speaker
So I don't think we should probably give this drug to our kids, although it's tempting. Well, is it something that you think would make them wait longer to eat marshmallows? That's right. I mean, or wait longer to say, are we there yet? I mean, that's the one that I was thinking of specifically in the car.
00:26:26
Speaker
But yeah, I wonder if it would have that effect on people, whether it would have a real behavioral effect. Because that was one of the things that came out of the paper was that people didn't notice that they were on the drug when they were on the drug. Yeah, that's right. So you could imagine that maybe it wouldn't have that large of an effect that you would notice it behaviorally in that way. Yeah.
00:26:50
Speaker
But it's cool. And dopamine is interesting. I mean, there's so many things that dopamine is involved in so many different aspects of cognition. It's just interesting that it plays into this storyline here as well.
Connectivity and Mental Health
00:27:04
Speaker
So there's one more thing from the paper that I think is worth mentioning. And that's the, let's see, they got an increase in activity that was closely related to the strength of the effect.
00:27:20
Speaker
You're talking about the FMRI result? Yeah. Yeah. So they were looking at these different, one of these connectivity, functional connectivity kind of results. So it looks like the connection from the right inferior frontal gyrus to the right putamen, this connection is strongest when tocopone causes an increase in duration estimation.
00:27:46
Speaker
So in other words, when Tocopone is having this, when it's correcting this mistaken time perception, it has the strongest connection between the right inferior frontal gyrus and the right putamen. Yeah, so overall, that is a very interesting paper, super interesting topics in terms of thinking about dopamine time perception, you know, some of these behavioral disorders, how they're related,
00:28:12
Speaker
how it's related to different parts of the brain and genetics. Just a lot of cool pieces coming together. So, you know, big shout out to the authors there on this.
Summary and Listener Engagement
00:28:22
Speaker
Just really nice paper. And it's just strange to think that your perception of time can be affected like this.
00:28:30
Speaker
But it's also I think one of the bottom lines we really get at here is this connection of time perception to impulsivity and depression and stress and anxiety that that seems to be important and and that they're all connected in in a way. Yeah, absolutely. Absolutely. Yeah. And we'd love to hear your thoughts if you have any thoughts on on the show or, you know, this one or any of anything that you talk about. We'd love to hear from you. You can find us on email.
00:28:59
Speaker
at Cognation Podcast, all one word, at gmail.com, cognationpodcast at gmail.com. You can tweet at me, at jlhardyphd. And you can try to tweet at me at roflnelson, but I probably won't see it.
00:29:21
Speaker
I'll see it and then I'll let you know. Tweet at us if you want to let us know something or have something we want us to talk about on the show or you want to be on the show, anything. Just let us know. Thanks for listening. Thank you. Bye.