Why is time so variable? | Joe Paton

[Applause]

[Applause] [Music]

thank the organizers for inviting me to

thank the organizers for inviting me to take part in today it’s been a really

take part in today it’s been a really

take part in today it’s been a really inspiring day of ideas and performances

inspiring day of ideas and performances

inspiring day of ideas and performances and I hope I can hold your focus for the

and I hope I can hold your focus for the

and I hope I can hold your focus for the last little bit of time that we have

last little bit of time that we have

last little bit of time that we have here and time is a really broad and

here and time is a really broad and

here and time is a really broad and fascinating subject it touches on a lot

fascinating subject it touches on a lot

fascinating subject it touches on a lot of different areas physicists and

of different areas physicists and

of different areas physicists and philosophers theorized about what time

philosophers theorized about what time

philosophers theorized about what time is time is a coordinate it’s a measure

is time is a coordinate it’s a measure

is time is a coordinate it’s a measure of duration it’s the ever existing

of duration it’s the ever existing

of duration it’s the ever existing entropy in the universe neuroscientists

entropy in the universe neuroscientists

entropy in the universe neuroscientists and psychologists try to understand how

and psychologists try to understand how

and psychologists try to understand how we perceive time

we perceive time

we perceive time well more generally how the brain makes

well more generally how the brain makes

well more generally how the brain makes use of it my name is Joe Patton and I’m

use of it my name is Joe Patton and I’m

use of it my name is Joe Patton and I’m a neuroscientist at gym probably more

a neuroscientist at gym probably more

a neuroscientist at gym probably more research here in Lisbon and I got

research here in Lisbon and I got

research here in Lisbon and I got interested in time for a particular

interested in time for a particular

interested in time for a particular reason and that is that what I

reason and that is that what I

reason and that is that what I ultimately want to understand is how the

ultimately want to understand is how the

ultimately want to understand is how the brain produces something we call

brain produces something we call

brain produces something we call adaptive behavior how do we and other

adaptive behavior how do we and other

adaptive behavior how do we and other animals learn through experience to

animals learn through experience to

animals learn through experience to behave in ways that are good for us and

behave in ways that are good for us and

behave in ways that are good for us and it turns out that time will role in that

it turns out that time will role in that

it turns out that time will role in that ability and to give you a sense of that

ability and to give you a sense of that

ability and to give you a sense of that I want to start with a visual analogy if

I want to start with a visual analogy if

I want to start with a visual analogy if you look at this image it’s a scene

you look at this image it’s a scene

you look at this image it’s a scene right it happens to be of Native

right it happens to be of Native

right it happens to be of Native Americans who are hunting deer our

Americans who are hunting deer our

Americans who are hunting deer our ability to perceive the scene and

ability to perceive the scene and

ability to perceive the scene and describe it of course depends on the the

describe it of course depends on the the

describe it of course depends on the the particular structure of luminance and if

particular structure of luminance and if

particular structure of luminance and if this were a colored image color and

this were a colored image color and

this were a colored image color and space if we were to remove that

space if we were to remove that

space if we were to remove that structure by say shuffling the location

structure by say shuffling the location

structure by say shuffling the location of all the pixels in this image of

of all the pixels in this image of

of all the pixels in this image of course it would be impossible to tell

course it would be impossible to tell

course it would be impossible to tell what this is an image of now likewise if

what this is an image of now likewise if

what this is an image of now likewise if we were to remove the influence of time

we were to remove the influence of time

we were to remove the influence of time on our experience we might have a

on our experience we might have a

on our experience we might have a similarly unintelligible mess for

similarly unintelligible mess for

similarly unintelligible mess for instance all of our experiences might be

instance all of our experiences might be

instance all of our experiences might be compressed into one moment right which

compressed into one moment right which

compressed into one moment right which is reflected in this famous quote it’s

is reflected in this famous quote it’s

is reflected in this famous quote it’s often attributed to the physicist John

often attributed to the physicist John

often attributed to the physicist John wheeler but what he actually read on the

wheeler but what he actually read on the

wheeler but what he actually read on the wall of a bathroom somewhere which says

wall of a bathroom somewhere which says

wall of a bathroom somewhere which says that time is Nature’s Way to keep

that time is Nature’s Way to keep

that time is Nature’s Way to keep everything from happening at once but

everything from happening at once but

everything from happening at once but actually I think about time a little bit

actually I think about time a little bit

actually I think about time a little bit differently because event

differently because event

differently because event have order they have a direction and

have order they have a direction and

have order they have a direction and there’s some smoothness to how they

there’s some smoothness to how they

there’s some smoothness to how they evolve right so if we were to remove

evolve right so if we were to remove

evolve right so if we were to remove time from our experience I imagine that

time from our experience I imagine that

time from our experience I imagine that events would become jumbled untethered

events would become jumbled untethered

events would become jumbled untethered from the surrounding moments kind of

from the surrounding moments kind of

from the surrounding moments kind of like shuffling the frames of a movie

like shuffling the frames of a movie

like shuffling the frames of a movie that constitutes your entire life now

that constitutes your entire life now

that constitutes your entire life now imagine trying to take that and using it

imagine trying to take that and using it

imagine trying to take that and using it to learn about the consequences of your

to learn about the consequences of your

to learn about the consequences of your actions in order to learn how to behave

actions in order to learn how to behave

actions in order to learn how to behave adaptively it’s impossible we’re more

adaptively it’s impossible we’re more

adaptively it’s impossible we’re more basically imagine being a young child

basically imagine being a young child

basically imagine being a young child you know when you come into this world

you know when you come into this world

you know when you come into this world you’re a blank slate a tabula rasa and

you’re a blank slate a tabula rasa and

you’re a blank slate a tabula rasa and you have to learn in large part do the

you have to learn in large part do the

you have to learn in large part do the relationships between events and time

relationships between events and time

relationships between events and time how to understand really understand

how to understand really understand

how to understand really understand anything about the world in addition to

anything about the world in addition to

anything about the world in addition to behave adaptively we need to have a

behave adaptively we need to have a

behave adaptively we need to have a sense of in what moment to act so time

sense of in what moment to act so time

sense of in what moment to act so time is really fundamental in that it it

is really fundamental in that it it

is really fundamental in that it it provides the structured order to our

provides the structured order to our

provides the structured order to our experience that we need in order to

experience that we need in order to

experience that we need in order to understand the world and make

understand the world and make

understand the world and make predictions and also because we need it

predictions and also because we need it

predictions and also because we need it to behave at the right time so when I

to behave at the right time so when I

to behave at the right time so when I was setting up my research group I was I

was setting up my research group I was I

was setting up my research group I was I was super excited because I felt like I

was super excited because I felt like I

was super excited because I felt like I had identified this problem one of these

had identified this problem one of these

had identified this problem one of these problems that my lab would focus on how

problems that my lab would focus on how

problems that my lab would focus on how does the brain deal with time which was

does the brain deal with time which was

does the brain deal with time which was super important for understanding how we

super important for understanding how we

super important for understanding how we and other animals learn to interact with

and other animals learn to interact with

and other animals learn to interact with their environment and very few people

their environment and very few people

their environment and very few people were studying it there’s not a lot known

were studying it there’s not a lot known

were studying it there’s not a lot known about it and so I thought great I have

about it and so I thought great I have

about it and so I thought great I have job security security for the next few

job security security for the next few

job security security for the next few decades but I kept running up against

decades but I kept running up against

decades but I kept running up against this kind of uncomfortable reality and

this kind of uncomfortable reality and

this kind of uncomfortable reality and that is that we’re pretty terrible at

that is that we’re pretty terrible at

that is that we’re pretty terrible at timing stuff exhibit a clocks this

timing stuff exhibit a clocks this

timing stuff exhibit a clocks this happens to be a clock made by a

happens to be a clock made by a

happens to be a clock made by a two-year-old

two-year-old

two-year-old and father’s day but the fact that

and father’s day but the fact that

and father’s day but the fact that humanity created this machine and all of

humanity created this machine and all of

humanity created this machine and all of its predecessors sundials hourglasses

its predecessors sundials hourglasses

its predecessors sundials hourglasses water clocks astrolabes and all the

water clocks astrolabes and all the

water clocks astrolabes and all the different ways that we’ve we’ve learned

different ways that we’ve we’ve learned

different ways that we’ve we’ve learned we’ve invented machines to tell time is

we’ve invented machines to tell time is

we’ve invented machines to tell time is the existence proof that our innate

the existence proof that our innate

the existence proof that our innate sense of time isn’t very reliable if it

sense of time isn’t very reliable if it

sense of time isn’t very reliable if it were we wouldn’t need clocks to tell us

were we wouldn’t need clocks to tell us

were we wouldn’t need clocks to tell us what time it is

so time can you know stand still they

so time can you know stand still they can fly it can disappear based on a

can fly it can disappear based on a

can fly it can disappear based on a number of different factors for example

number of different factors for example

number of different factors for example I’m going to show you two video clips

I’m going to show you two video clips

I’m going to show you two video clips okay a flashing colored grids and I want

okay a flashing colored grids and I want

okay a flashing colored grids and I want you to look straight at the center of

you to look straight at the center of

you to look straight at the center of the video clips and I want you to tell

the video clips and I want you to tell

the video clips and I want you to tell me which one lasted longer and don’t

me which one lasted longer and don’t

me which one lasted longer and don’t cheat don’t count don’t look at your

cheat don’t count don’t look at your

cheat don’t count don’t look at your watch or anything like that

watch or anything like that

watch or anything like that just give me your gut impression okay

just give me your gut impression okay

just give me your gut impression okay here we go

now it’s a second okay so everyone who

now it’s a second okay so everyone who thought that the first clip lasted

thought that the first clip lasted

thought that the first clip lasted longer raise your hand and everyone

longer raise your hand and everyone

longer raise your hand and everyone thought that the second thought lasted

thought that the second thought lasted

thought that the second thought lasted longer raise your hand

longer raise your hand

longer raise your hand awesome that worked perfectly okay so

awesome that worked perfectly okay so

awesome that worked perfectly okay so the vast majority of you thought that

the vast majority of you thought that

the vast majority of you thought that the first clip lasted longer but in fact

the first clip lasted longer but in fact

the first clip lasted longer but in fact they’re identical in duration and that’s

they’re identical in duration and that’s

they’re identical in duration and that’s because in a lot of studies have shown

because in a lot of studies have shown

because in a lot of studies have shown this the rate at which sensory stimuli

this the rate at which sensory stimuli

this the rate at which sensory stimuli change can alter your perception of time

change can alter your perception of time

change can alter your perception of time okay and here I’m showing data from one

okay and here I’m showing data from one

okay and here I’m showing data from one of those studies so what’s plotted along

of those studies so what’s plotted along

of those studies so what’s plotted along the vertical axis here is the relative

the vertical axis here is the relative

the vertical axis here is the relative estimated duration of a stimulus that

estimated duration of a stimulus that

estimated duration of a stimulus that has dynamics it’s changing it’s

has dynamics it’s changing it’s

has dynamics it’s changing it’s flickering like those stimulation before

flickering like those stimulation before

flickering like those stimulation before and along the horizontal axis is the

and along the horizontal axis is the

and along the horizontal axis is the speed of that change how fast is the

speed of that change how fast is the

speed of that change how fast is the stimulus flickering and what you can see

stimulus flickering and what you can see

stimulus flickering and what you can see is that the stimulus changes faster and

is that the stimulus changes faster and

is that the stimulus changes faster and faster people show a tendency to

faster people show a tendency to

faster people show a tendency to overestimate duration okay so sensory

overestimate duration okay so sensory

overestimate duration okay so sensory change is one factor that can affect

change is one factor that can affect

change is one factor that can affect your perception of time but there are

your perception of time but there are

your perception of time but there are others and what I want to suggest you

others and what I want to suggest you

others and what I want to suggest you today this is sort of the central idea

today this is sort of the central idea

today this is sort of the central idea is that this variability in our innate

is that this variability in our innate

is that this variability in our innate timekeeping isn’t some shortcoming it’s

timekeeping isn’t some shortcoming it’s

timekeeping isn’t some shortcoming it’s not a problem that evolution hasn’t

not a problem that evolution hasn’t

not a problem that evolution hasn’t gotten around to fixing yet but rather

gotten around to fixing yet but rather

gotten around to fixing yet but rather it’s a feature that ultimately serves

it’s a feature that ultimately serves

it’s a feature that ultimately serves our best interests

and I think it’s telling that when we

and I think it’s telling that when we look into the brain we find that those

look into the brain we find that those

look into the brain we find that those same brain systems that seem to be

same brain systems that seem to be

same brain systems that seem to be critical for guiding adaptive behavior

critical for guiding adaptive behavior

critical for guiding adaptive behavior also seem to be responsible for

also seem to be responsible for

also seem to be responsible for variability in time perception and the

variability in time perception and the

variability in time perception and the brain system I’ll spend a lot of time

brain system I’ll spend a lot of time

brain system I’ll spend a lot of time focusing on today is that of dopamine

focusing on today is that of dopamine

focusing on today is that of dopamine neurons in the midbrain so here I’m

neurons in the midbrain so here I’m

neurons in the midbrain so here I’m showing a side or a sagittal view of the

showing a side or a sagittal view of the

showing a side or a sagittal view of the human brain with one side cutaway and

human brain with one side cutaway and

human brain with one side cutaway and the dopamine neurons I’ll focus on today

the dopamine neurons I’ll focus on today

the dopamine neurons I’ll focus on today are located in the midbrain their cell

are located in the midbrain their cell

are located in the midbrain their cell bodies here and this branching portion

bodies here and this branching portion

bodies here and this branching portion here represents the projections or the

here represents the projections or the

here represents the projections or the axons where the signals that these cells

axons where the signals that these cells

axons where the signals that these cells are carrying are being projected to and

are carrying are being projected to and

are carrying are being projected to and these neurons they use a

these neurons they use a

these neurons they use a neurotransmitter they release a

neurotransmitter they release a

neurotransmitter they release a neurotransmitter neuromodulator dopamine

neurotransmitter neuromodulator dopamine

neurotransmitter neuromodulator dopamine which alters the way recipient neurons

which alters the way recipient neurons

which alters the way recipient neurons respond to other inputs and it can do it

respond to other inputs and it can do it

respond to other inputs and it can do it in the current moment or it can alter in

in the current moment or it can alter in

in the current moment or it can alter in more permanent ways the strength of the

more permanent ways the strength of the

more permanent ways the strength of the connections between neurons okay

connections between neurons okay

connections between neurons okay something we call synaptic plasticity

something we call synaptic plasticity

something we call synaptic plasticity and now it’s really interesting when you

and now it’s really interesting when you

and now it’s really interesting when you consider the way these neurons can kind

consider the way these neurons can kind

consider the way these neurons can kind of change or teach the strength of

of change or teach the strength of

of change or teach the strength of connections between neurons when you

connections between neurons when you

connections between neurons when you consider that these cells carry a really

consider that these cells carry a really

consider that these cells carry a really really useful instructive signal they

really useful instructive signal they

really useful instructive signal they seem to teach the brain to choose those

seem to teach the brain to choose those

seem to teach the brain to choose those behaviors that are going to result in

behaviors that are going to result in

behaviors that are going to result in reward and they act sort of like a

reward and they act sort of like a

reward and they act sort of like a teacher that tells you only if you’re

teacher that tells you only if you’re

teacher that tells you only if you’re surprised surprised at whether things

surprised surprised at whether things

surprised surprised at whether things are better or worse than expected now

are better or worse than expected now

are better or worse than expected now why is a teacher based on surprise

why is a teacher based on surprise

why is a teacher based on surprise useful well if you think about it if

useful well if you think about it if

useful well if you think about it if you’re surprised by some particular

you’re surprised by some particular

you’re surprised by some particular outcome that’s an indication that you

outcome that’s an indication that you

outcome that’s an indication that you should update your expectations you

should update your expectations you

should update your expectations you should learn something so the next time

should learn something so the next time

should learn something so the next time you encounter that situation you’re less

you encounter that situation you’re less

you encounter that situation you’re less surprised okay these updated

surprised okay these updated

surprised okay these updated expectations about the quality of the

expectations about the quality of the

expectations about the quality of the current situation can be used to guide

current situation can be used to guide

current situation can be used to guide your behavior towards those situations

your behavior towards those situations

your behavior towards those situations of the highest quality okay but why am I

of the highest quality okay but why am I

of the highest quality okay but why am I telling you all this about dopamine

telling you all this about dopamine

telling you all this about dopamine neurons and learning and rewards I

neurons and learning and rewards I

neurons and learning and rewards I thought this was a talk about time well

thought this was a talk about time well

thought this was a talk about time well one of the reasons is that these neurons

one of the reasons is that these neurons

one of the reasons is that these neurons project very very densely to another

project very very densely to another

project very very densely to another part of the brain called the striatum

part of the brain called the striatum

part of the brain called the striatum which you can see here in pink which the

which you can see here in pink which the

which you can see here in pink which the work of many labs including mine is

work of many labs including mine is

work of many labs including mine is shown to be critical for

shown to be critical for

shown to be critical for keeping time so if we can bring down the

keeping time so if we can bring down the

keeping time so if we can bring down the lights a little bit this would be a

lights a little bit this would be a

lights a little bit this would be a little bit more clear but I’m showing

little bit more clear but I’m showing

little bit more clear but I’m showing you is a slice now through a mouse brain

you is a slice now through a mouse brain

you is a slice now through a mouse brain what we’ve done is we’ve labeled

what we’ve done is we’ve labeled

what we’ve done is we’ve labeled dopamine neurons on one side of the

dopamine neurons on one side of the

dopamine neurons on one side of the brain where the protein that fluoresce

brain where the protein that fluoresce

brain where the protein that fluoresce is red and what you’re actually looking

is red and what you’re actually looking

is red and what you’re actually looking at here are the axon terminals the

at here are the axon terminals the

at here are the axon terminals the projections of these these nerve cells

projections of these these nerve cells

projections of these these nerve cells and basically everything you’re seeing

and basically everything you’re seeing

and basically everything you’re seeing here in red is this brain area the

here in red is this brain area the

here in red is this brain area the striatum so you can just see how densely

striatum so you can just see how densely

striatum so you can just see how densely these neurons project to this area as as

these neurons project to this area as as

these neurons project to this area as as opposed to other areas where they do

opposed to other areas where they do

opposed to other areas where they do project like these ones out here and now

project like these ones out here and now

project like these ones out here and now synaptic plasticity remember those those

synaptic plasticity remember those those

synaptic plasticity remember those those changes in strength in the connections

changes in strength in the connections

changes in strength in the connections between neurons in this particular area

between neurons in this particular area

between neurons in this particular area is thought to be important for shaping

is thought to be important for shaping

is thought to be important for shaping the actions we take in a given situation

the actions we take in a given situation

the actions we take in a given situation and if you were to look at the activity

and if you were to look at the activity

and if you were to look at the activity of single neurons in this area during

of single neurons in this area during

of single neurons in this area during behavior you might see something like

behavior you might see something like

behavior you might see something like the following so here I’m visualizing

the following so here I’m visualizing

the following so here I’m visualizing real data each circle here represents an

real data each circle here represents an

real data each circle here represents an individual neuron in this brain area the

individual neuron in this brain area the

individual neuron in this brain area the striatum and the brightness of the red

striatum and the brightness of the red

striatum and the brightness of the red color indicates how electrically active

color indicates how electrically active

color indicates how electrically active that cell is and if you look at the

that cell is and if you look at the

that cell is and if you look at the activity of these cells you see there’s

activity of these cells you see there’s

activity of these cells you see there’s a diversity of responding okay in this

a diversity of responding okay in this

a diversity of responding okay in this diversity can actually be used to read

diversity can actually be used to read

diversity can actually be used to read out the passage of time and this becomes

out the passage of time and this becomes

out the passage of time and this becomes more clear if we just reorder the cells

more clear if we just reorder the cells

more clear if we just reorder the cells by when they’re active if you do that

by when they’re active if you do that

by when they’re active if you do that you see this kind of wave of activity

you see this kind of wave of activity

you see this kind of wave of activity that moves over the population and just

that moves over the population and just

that moves over the population and just like the hands of a clock move across

like the hands of a clock move across

like the hands of a clock move across its face

its face

its face so does this wave of activity across

so does this wave of activity across

so does this wave of activity across this population of neurons okay so you

this population of neurons okay so you

this population of neurons okay so you can read out time from these cells here

can read out time from these cells here

can read out time from these cells here but what’s the evidence that the brain

but what’s the evidence that the brain

but what’s the evidence that the brain is actually doing that well to get at

is actually doing that well to get at

is actually doing that well to get at that you need to ask the animal this

that you need to ask the animal this

that you need to ask the animal this happens to be a rat where we recorded

happens to be a rat where we recorded

happens to be a rat where we recorded this activity about its sense of time if

this activity about its sense of time if

this activity about its sense of time if we were working with a person we could

we were working with a person we could

we were working with a person we could ask them to describe their sensations

ask them to describe their sensations

ask them to describe their sensations using language but we as a society don’t

using language but we as a society don’t

using language but we as a society don’t like to insert electrodes or other

like to insert electrodes or other

like to insert electrodes or other devices into the human brain unless we

devices into the human brain unless we

devices into the human brain unless we absolutely have to you might hit a blood

absolutely have to you might hit a blood

absolutely have to you might hit a blood vessel or you might cause an infection

vessel or you might cause an infection

vessel or you might cause an infection however we’re a little more tolerant of

however we’re a little more tolerant of

however we’re a little more tolerant of doing this in an animal model organism

doing this in an animal model organism

doing this in an animal model organism like a rat

like a rat

like a rat but how do you ask a rat about its time

but how do you ask a rat about its time

but how do you ask a rat about its time perception well one way to do that is to

perception well one way to do that is to

perception well one way to do that is to train them to make a judgement okay was

train them to make a judgement okay was

train them to make a judgement okay was the interval you just experienced longer

the interval you just experienced longer

the interval you just experienced longer or shorter than one-and-a-half seconds

or shorter than one-and-a-half seconds

or shorter than one-and-a-half seconds and you train them until they’re really

and you train them until they’re really

and you train them until they’re really really good at this at this judgment and

really good at this at this judgment and

really good at this at this judgment and here I’m showing behavioral data from a

here I’m showing behavioral data from a

here I’m showing behavioral data from a rat that’s been trained to do this

rat that’s been trained to do this

rat that’s been trained to do this we’re on what I’m plotting on the

we’re on what I’m plotting on the

we’re on what I’m plotting on the vertical axis here is the probability

vertical axis here is the probability

vertical axis here is the probability that they they categorize an interval as

that they they categorize an interval as

that they they categorize an interval as long they judge it as longer than

long they judge it as longer than

long they judge it as longer than one-and-a-half seconds against the

one-and-a-half seconds against the

one-and-a-half seconds against the different intervals that we present to

different intervals that we present to

different intervals that we present to them and what you can see is that for

them and what you can see is that for

them and what you can see is that for these these intervals that are near

these these intervals that are near

these these intervals that are near one-and-a-half seconds the difficult

one-and-a-half seconds the difficult

one-and-a-half seconds the difficult ones their choices are variable

ones their choices are variable

ones their choices are variable sometimes they’re going to judge this

sometimes they’re going to judge this

sometimes they’re going to judge this interval is longer than one-and-a-half

interval is longer than one-and-a-half

interval is longer than one-and-a-half seconds and sometimes they’re going to

seconds and sometimes they’re going to

seconds and sometimes they’re going to judge it as shorter and we think that

judge it as shorter and we think that

judge it as shorter and we think that most of this variability in their

most of this variability in their

most of this variability in their judgments is actually due to variability

judgments is actually due to variability

judgments is actually due to variability in their sense of time so then we can

in their sense of time so then we can

in their sense of time so then we can compare the judgments that animals make

compare the judgments that animals make

compare the judgments that animals make to either observations or manipulations

to either observations or manipulations

to either observations or manipulations of neural activity that we make in the

of neural activity that we make in the

of neural activity that we make in the in laboratory in order to try and

in laboratory in order to try and

in laboratory in order to try and identify candidate neural signals for

identify candidate neural signals for

identify candidate neural signals for timing so the first piece of evidence

timing so the first piece of evidence

timing so the first piece of evidence that those waves of activity I showed

that those waves of activity I showed

that those waves of activity I showed you are actually involved in keeping

you are actually involved in keeping

you are actually involved in keeping time is that if you inject a drug into

time is that if you inject a drug into

time is that if you inject a drug into the striatum that just perturbs activity

the striatum that just perturbs activity

the striatum that just perturbs activity a little bit it doesn’t mess up the

a little bit it doesn’t mess up the

a little bit it doesn’t mess up the animal’s behavior very much at all while

animal’s behavior very much at all while

animal’s behavior very much at all while they’re performing this task they get

they’re performing this task they get

they’re performing this task they get worse so here I’m showing in orange data

worse so here I’m showing in orange data

worse so here I’m showing in orange data collected on days when we injected this

collected on days when we injected this

collected on days when we injected this drug into the striatum okay and in green

drug into the striatum okay and in green

drug into the striatum okay and in green I’m showing data on days on alternate

I’m showing data on days on alternate

I’m showing data on days on alternate days when we just injected saline or

days when we just injected saline or

days when we just injected saline or saltwater so you can see just by messing

saltwater so you can see just by messing

saltwater so you can see just by messing up activity a little bit in this area

up activity a little bit in this area

up activity a little bit in this area you produce a market decrease in the

you produce a market decrease in the

you produce a market decrease in the sensitivity of animals judgments to time

sensitivity of animals judgments to time

sensitivity of animals judgments to time but what about those ways of activity if

but what about those ways of activity if

but what about those ways of activity if the animal is actually looking at where

the animal is actually looking at where

the animal is actually looking at where that wave is and using it to tell much

that wave is and using it to tell much

that wave is and using it to tell much time it’s past if that wave goes a

time it’s past if that wave goes a

time it’s past if that wave goes a little faster they should think time is

little faster they should think time is

little faster they should think time is passing faster and if that wave is going

passing faster and if that wave is going

passing faster and if that wave is going slower they should you think that time

slower they should you think that time

slower they should you think that time is passing slower and indeed if we

is passing slower and indeed if we

is passing slower and indeed if we record from populations of neurons

record from populations of neurons

record from populations of neurons during this task we see something very

during this task we see something very

during this task we see something very similar so when that wave goes more

similar so when that wave goes more

similar so when that wave goes more quickly as you can see in this red curve

quickly as you can see in this red curve

quickly as you can see in this red curve animals show a system at

animals show a system at

animals show a system at tendency to judge intervals as being

tendency to judge intervals as being

tendency to judge intervals as being long particularly for those intervals

long particularly for those intervals

long particularly for those intervals that are near the decision boundary and

that are near the decision boundary and

that are near the decision boundary and the reverse is true when that wave

the reverse is true when that wave

the reverse is true when that wave progresses more slowly okay so you have

progresses more slowly okay so you have

progresses more slowly okay so you have this clock it’s variable sometimes it

this clock it’s variable sometimes it

this clock it’s variable sometimes it goes faster sometimes it goes slower and

goes faster sometimes it goes slower and

goes faster sometimes it goes slower and that predicts the judgments that animals

that predicts the judgments that animals

that predicts the judgments that animals are going to make but what’s responsible

are going to make but what’s responsible

are going to make but what’s responsible for that variability in clock speed and

for that variability in clock speed and

for that variability in clock speed and this is where we come back to dopamine

this is where we come back to dopamine

this is where we come back to dopamine so if you look through the psychological

so if you look through the psychological

so if you look through the psychological literature and you try and find

literature and you try and find

literature and you try and find situations where your your timekeeping

situations where your your timekeeping

situations where your your timekeeping seems to be systematically altered on

seems to be systematically altered on

seems to be systematically altered on the right what I’m showing our cases

the right what I’m showing our cases

the right what I’m showing our cases where time appears to drag and this can

where time appears to drag and this can

where time appears to drag and this can get confusing because this is sort of

get confusing because this is sort of

get confusing because this is sort of akin to having a fast internal clock you

akin to having a fast internal clock you

akin to having a fast internal clock you think that more time has passed and

think that more time has passed and

think that more time has passed and actually has and these are things like

actually has and these are things like

actually has and these are things like fear anxiety boredom and pain and on the

fear anxiety boredom and pain and on the

fear anxiety boredom and pain and on the right I’m going to show cases where time

right I’m going to show cases where time

right I’m going to show cases where time appears to fly and again this is akin to

appears to fly and again this is akin to

appears to fly and again this is akin to having a slow internal clock you think

having a slow internal clock you think

having a slow internal clock you think that last time has passed and actually

that last time has passed and actually

that last time has passed and actually happens and these are things like your

happens and these are things like your

happens and these are things like your motivation to approach or engage with

motivation to approach or engage with

motivation to approach or engage with the situation attentional load pleasure

the situation attentional load pleasure

the situation attentional load pleasure and novelty now interestingly most of

and novelty now interestingly most of

and novelty now interestingly most of these cases here on the Left are

these cases here on the Left are

these cases here on the Left are associated with decreased dopamine

associated with decreased dopamine

associated with decreased dopamine signaling and most of these situations

signaling and most of these situations

signaling and most of these situations here on the right are associated with

here on the right are associated with

here on the right are associated with increased dopamine signaling in addition

increased dopamine signaling in addition

increased dopamine signaling in addition conditions where dope the dopaminergic

conditions where dope the dopaminergic

conditions where dope the dopaminergic system is damaged such as Parkinson’s

system is damaged such as Parkinson’s

system is damaged such as Parkinson’s disease people with Parkinson’s disease

disease people with Parkinson’s disease

disease people with Parkinson’s disease display kind of peculiar timing deficits

display kind of peculiar timing deficits

display kind of peculiar timing deficits so there’s a lot of kind of indirect

so there’s a lot of kind of indirect

so there’s a lot of kind of indirect evidence that dopamine neurons may be

evidence that dopamine neurons may be

evidence that dopamine neurons may be exerting some kind of control over your

exerting some kind of control over your

exerting some kind of control over your perception of time but how do we

perception of time but how do we

perception of time but how do we directly test this idea so recently

directly test this idea so recently

directly test this idea so recently bassam Matala and sofia swat is in the

bassam Matala and sofia swat is in the

bassam Matala and sofia swat is in the lab devised and and carried out a series

lab devised and and carried out a series

lab devised and and carried out a series of experiments to directly test whether

of experiments to directly test whether

of experiments to directly test whether dopamine neurons can control your time

dopamine neurons can control your time

dopamine neurons can control your time perception or at least the time

perception or at least the time

perception or at least the time perception of mice so what they did was

perception of mice so what they did was

perception of mice so what they did was they first trained mice to perform this

they first trained mice to perform this

they first trained mice to perform this judgment was the interval longer shorter

judgment was the interval longer shorter

judgment was the interval longer shorter than one-and-a-half seconds that you

than one-and-a-half seconds that you

than one-and-a-half seconds that you just experienced

just experienced

just experienced remember the data I plotted before which

remember the data I plotted before which

remember the data I plotted before which is showing the probability that an

is showing the probability that an

is showing the probability that an animal makes a long judgment as a

animal makes a long judgment as a

animal makes a long judgment as a function of the different intervals

function of the different intervals

function of the different intervals because that would be important and

because that would be important and

because that would be important and that’s what they did was they measured

that’s what they did was they measured

that’s what they did was they measured the activity of dopamine neurons using

the activity of dopamine neurons using

the activity of dopamine neurons using an optical technique where we engineered

an optical technique where we engineered

an optical technique where we engineered dopamine neurons to light up when they

dopamine neurons to light up when they

dopamine neurons to light up when they were active this gave us a fast and

were active this gave us a fast and

were active this gave us a fast and continuous measure of the activity of

continuous measure of the activity of

continuous measure of the activity of these cells that we could then compare

these cells that we could then compare

these cells that we could then compare to the judgments that animals were

to the judgments that animals were

to the judgments that animals were making from childhood trial and what

making from childhood trial and what

making from childhood trial and what they observed was striking when they

they observed was striking when they

they observed was striking when they when the activity of these neurons was

when the activity of these neurons was

when the activity of these neurons was higher as you can see in this blue curve

higher as you can see in this blue curve

higher as you can see in this blue curve animals clocks appeared to slow down

animals clocks appeared to slow down

animals clocks appeared to slow down they were more likely to underestimate

they were more likely to underestimate

they were more likely to underestimate duration and the reverse was true when

duration and the reverse was true when

duration and the reverse was true when these cells were less active they were

these cells were less active they were

these cells were less active they were more likely to overestimate duration if

more likely to overestimate duration if

more likely to overestimate duration if as if their clock had sped up okay so

as if their clock had sped up okay so

as if their clock had sped up okay so there was this correlation between the

there was this correlation between the

there was this correlation between the activity of these neurons and the

activity of these neurons and the

activity of these neurons and the pattern the judgments about time that

pattern the judgments about time that

pattern the judgments about time that animals were making but of course

animals were making but of course

animals were making but of course correlation doesn’t imply causation so

correlation doesn’t imply causation so

correlation doesn’t imply causation so the next they went a step further and

the next they went a step further and

the next they went a step further and they applied a technique from a

they applied a technique from a

they applied a technique from a relatively new field called optogenetics

relatively new field called optogenetics

relatively new field called optogenetics the name of the name should make sense

the name of the name should make sense

the name of the name should make sense in a moment

in a moment

in a moment in order to transiently manipulate the

in order to transiently manipulate the

in order to transiently manipulate the activity of these cells during this

activity of these cells during this

activity of these cells during this behavior so what is optogenetics in our

behavior so what is optogenetics in our

behavior so what is optogenetics in our eyes we have proteins that coupled to

eyes we have proteins that coupled to

eyes we have proteins that coupled to light-sensitive molecules if these

light-sensitive molecules if these

light-sensitive molecules if these molecules observe a photon they change

molecules observe a photon they change

molecules observe a photon they change shape and this kicks off a series of

shape and this kicks off a series of

shape and this kicks off a series of steps that ultimately results in a

steps that ultimately results in a

steps that ultimately results in a message being sent to your brain and

message being sent to your brain and

message being sent to your brain and that’s how we see but this process is

that’s how we see but this process is

that’s how we see but this process is kind of complicated it involves a number

kind of complicated it involves a number

kind of complicated it involves a number different proteins and genes and in the

different proteins and genes and in the

different proteins and genes and in the end of the 90s in the early 2000s people

end of the 90s in the early 2000s people

end of the 90s in the early 2000s people were wondering if they could kind of

were wondering if they could kind of

were wondering if they could kind of harness that general idea to make

harness that general idea to make

harness that general idea to make neurons controllable with light and what

neurons controllable with light and what

neurons controllable with light and what these people did is they identified

these people did is they identified

these people did is they identified another similar kind of protein that’s

another similar kind of protein that’s

another similar kind of protein that’s expressed by algae that actually is

expressed by algae that actually is

expressed by algae that actually is light-sensitive but it couples directly

light-sensitive but it couples directly

light-sensitive but it couples directly to an ion channel making it easier to

to an ion channel making it easier to

to an ion channel making it easier to kind of express potentially in neurons

kind of express potentially in neurons

kind of express potentially in neurons and they managed to express these things

and they managed to express these things

and they managed to express these things in neurons rendering them controllable

in neurons rendering them controllable

in neurons rendering them controllable with light and this has brought about a

with light and this has brought about a

with light and this has brought about a real revolution in neuroscience because

real revolution in neuroscience because

real revolution in neuroscience because it allows us to go beyond

it allows us to go beyond

it allows us to go beyond just identifying correlations between

just identifying correlations between

just identifying correlations between signals we observed in the brain and

signals we observed in the brain and

signals we observed in the brain and particularly havior x’ were interested

particularly havior x’ were interested

particularly havior x’ were interested in or particular brain functions and

in or particular brain functions and

in or particular brain functions and actually inject in signals into

actually inject in signals into

actually inject in signals into particular genetically targeted cells

particular genetically targeted cells

particular genetically targeted cells during behavior and so that’s what

during behavior and so that’s what

during behavior and so that’s what that’s what these guys did in their

that’s what these guys did in their

that’s what these guys did in their experiments they induced dopamine

experiments they induced dopamine

experiments they induced dopamine neurons to express these light-sensitive

neurons to express these light-sensitive

neurons to express these light-sensitive opsins and then they inserted a little

opsins and then they inserted a little

opsins and then they inserted a little glass fiber right above the dopamine

glass fiber right above the dopamine

glass fiber right above the dopamine neurons and then randomly throughout

neurons and then randomly throughout

neurons and then randomly throughout these behavioral sessions they would

these behavioral sessions they would

these behavioral sessions they would illuminate these cells to either

illuminate these cells to either

illuminate these cells to either activate or inhibit their activity and

activate or inhibit their activity and

activate or inhibit their activity and what they found was indeed when they

what they found was indeed when they

what they found was indeed when they activated dopamine neurons they were

activated dopamine neurons they were

activated dopamine neurons they were able to apparently slow animals

able to apparently slow animals

able to apparently slow animals timekeeping consistent with the

timekeeping consistent with the

timekeeping consistent with the observations they had made in the

observations they had made in the

observations they had made in the previous experiment and conversely when

previous experiment and conversely when

previous experiment and conversely when they inhibited these neurons both though

they inhibited these neurons both though

they inhibited these neurons both though the effect was a little bit more modest

the effect was a little bit more modest

the effect was a little bit more modest they caused the animal to apparently

they caused the animal to apparently

they caused the animal to apparently speed up its timekeeping they showed a

speed up its timekeeping they showed a

speed up its timekeeping they showed a tendency to overestimate duration so

tendency to overestimate duration so

tendency to overestimate duration so dopamine neuron activation slows and

dopamine neuron activation slows and

dopamine neuron activation slows and inhibition seems to speed timekeeping

inhibition seems to speed timekeeping

inhibition seems to speed timekeeping and so I want to step back now and ask a

and so I want to step back now and ask a

and so I want to step back now and ask a more general question which is which is

Why is time so variable? | Joe Paton | TEDxISTAlameda

Be First to Comment

Leave a Reply Cancel reply