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Martin Arguin discusses the contribution of stereopsis in human visual shape perception that was examined using stimuli with either null, normal, or reversed binocular disparity in an old/new object recognition task.

Image courtesy of interviewee. January 10, 2024

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This video video discusses visual processing in psychology, explaining how raw images captured by photoreceptors in the retina are transformed into meaningful representations for interacting with the environment. This video video complex process involves multiple steps where neurons communicate, and it is noted that visual processing takes almost a tenth of a second, leading to a delay in our perception of the visual world compared to real-time events.

The speaker describes a technique called "random temporal sampling," which involves presenting visual stimuli briefly, allowing researchers to analyze how visibility fluctuates over time. This video video method reveals that visual processing is not static but varies significantly within short timeframes, which is crucial for understanding how we perceive visual information.

Research indicates that our visual functions can fluctuate rapidly, impacting our ability to recognize stimuli. The speaker mentions ongoing studies in areas such as visual word recognition, ADHD, and dementia, highlighting the potential of random temporal sampling to diagnose attentional deficits and detect dementia earlier, facilitating timely interventions.

Ultimately, the speaker aims to connect the temporal features obtained from their research to actual brain activity, emphasizing the importance of understanding the neural mechanisms underlying visual processing and cognition.

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X-TIMESTAMP-MAP:LOCAL=00:00:00.000,MPEGTS=900000

00:00.105 --> 00:04.365
We talk about processing in psychology and perception,

00:04.385 --> 00:06.965
and, we really define it.

00:07.345 --> 00:10.125
But, in, in terms of, visual function,

00:10.125 --> 00:13.485
visual processing is the process by which,

00:14.345 --> 00:17.645
the raw image that this, registered

00:17.645 --> 00:21.965
by our photoreceptors is transformed into a

00:21.965 --> 00:25.365
representation that is useful for our,

00:25.605 --> 00:27.005
interactions with the world.

00:27.225 --> 00:31.125
So it tells us, what things are,

00:31.275 --> 00:35.085
what is the spatial layout of, our environment,

00:35.085 --> 00:39.365
things like that, which are what we need to, you know,

00:39.765 --> 00:41.765
properly interact with, our world.

00:42.475 --> 00:46.005
What is involved in visual processing is actually,

00:46.675 --> 00:51.005
something that occurs in a sequence of, number of steps

00:51.375 --> 00:56.325
where, the image that, initially is registered

00:56.345 --> 01:00.685
by the, the photoreceptors, is, is transmitted,

01:01.465 --> 01:05.765
to, you know, a next step, a next set

01:05.865 --> 01:09.045
of neurons and, and so on.

01:09.045 --> 01:11.205
So that there are, a number of steps like this.

01:11.305 --> 01:15.605
So, in fact, the, the, the,

01:15.745 --> 01:19.485
the point in, our nervous system where,

01:19.485 --> 01:23.245
visual processing occurs is, at the interaction

01:23.245 --> 01:24.365
between neurons.

01:24.865 --> 01:26.605
So at the point where they communicate.

01:27.185 --> 01:32.125
And, in that sense, we, we can, consider, our

01:32.665 --> 01:34.725
visual system as a

01:35.995 --> 01:38.205
very complex communication system.

01:39.065 --> 01:43.565
And at every step of communication between neurons,

01:43.905 --> 01:48.725
there's this opportunity to make the type

01:48.725 --> 01:53.405
of knowledge that we have about the world evolve into this,

01:53.745 --> 01:57.965
more into this complex representation

01:58.825 --> 02:01.845
of, the identity of things,

02:01.865 --> 02:03.925
if it's good for us or not.

02:04.385 --> 02:07.725
Uh, how are, things spatially organized?

02:08.025 --> 02:12.565
So that's, a lot of work, from, you know, this

02:13.455 --> 02:17.205
basic knowledge at, at the retina with which is, you know,

02:17.335 --> 02:20.885
light intensity at a given point, in,

02:20.985 --> 02:22.085
our visual field.

02:22.865 --> 02:27.005
And, to be able to perform this sort of magic,

02:27.715 --> 02:31.125
lots of, communication steps between neurons

02:31.705 --> 02:36.245
and, you need, this, nerve signal,

02:36.385 --> 02:39.045
neural signal to, travel,

02:39.115 --> 02:40.605
from one point to the next.

02:41.185 --> 02:43.045
And all this takes time.

02:43.585 --> 02:48.485
And, so, actually, just in terms of,

02:48.785 --> 02:53.565
the time it takes to communicate, the,

02:53.855 --> 02:56.605
input from the retina into our cortex,

02:56.715 --> 02:59.045
just the primary visual cortex,

02:59.385 --> 03:02.005
it takes a bit less than a 10th of a second.

03:02.745 --> 03:07.485
Uh, so, that means, actually that, our

03:08.345 --> 03:11.645
cortex, our knowledge of the visual world is always late

03:12.385 --> 03:16.605
in comparison to, what is, going on in front of us.

03:17.705 --> 03:22.245
And, what, what, what, we are doing is actually,

03:22.825 --> 03:26.165
trying to use this,

03:26.805 --> 03:31.605
temporal aspect in which, visual processing occurs,

03:31.605 --> 03:36.525
to, gain knowledge about the visual function.

03:37.185 --> 03:40.885
And, so, in, in the last few years,

03:40.955 --> 03:43.085
I've developed this technique, which is,

03:43.085 --> 03:46.765
random temporal sampling, through which,

03:46.765 --> 03:50.845
what we are doing is, to present,

03:50.905 --> 03:52.725
visual stimulus briefly.

03:53.545 --> 03:56.085
And, that a participant has

03:56.105 --> 03:59.845
to perform a task on the stimulus in question, say,

03:59.905 --> 04:04.365
to identify it or say if it's, the meaning or whatever.

04:05.265 --> 04:09.285
And, during the exposure duration, what we do is

04:09.305 --> 04:14.005
to have, the visibility of the stimulus,

04:14.155 --> 04:15.805
vary randomly through time.

04:16.545 --> 04:20.525
And, by a**l, analyzing, the relation between,

04:20.865 --> 04:22.045
performances

04:22.385 --> 04:25.685
and those temporal samples that,

04:25.935 --> 04:30.885
we're obtaining on every trial, then, we are able to

04:32.125 --> 04:35.605
derive, some knowledge about,

04:36.545 --> 04:39.245
how visual processing unfolds through time.

04:40.105 --> 04:44.645
So, that's, largely, what we're,

04:44.665 --> 04:45.725
doing these days.

04:46.025 --> 04:50.245
One basic thing, which is very counterintuitive is, is that,

04:50.545 --> 04:54.805
our visual function fluctuates through time in a very,

04:54.985 --> 04:56.205
short timeframe.

04:56.785 --> 04:58.485
So, for instance,

04:58.665 --> 05:03.245
the exposure durations we typically use are, of,

05:03.425 --> 05:04.525
200 milliseconds.

05:04.525 --> 05:06.965
That's one fifth of a second. That's very fast.

05:07.945 --> 05:11.725
And, throughout this duration, we, can identify

05:12.385 --> 05:16.935
points in time where, we're very capable

05:17.435 --> 05:20.615
of, acquiring, visual information.

05:20.675 --> 05:23.015
But there are other points in time where,

05:23.995 --> 05:25.255
you know, we're just hopeless.

05:25.445 --> 05:28.415
What I think, and, and which is the actual,

05:29.295 --> 05:32.775
actually the inspiration for random temporal sampling,

05:33.195 --> 05:35.375
is that,

05:35.675 --> 05:40.215
the way our nervous system is, doing its job

05:40.515 --> 05:43.215
of, say, vision

05:43.475 --> 05:48.335
or whatever else is, through, mechanisms

05:48.335 --> 05:52.775
where, groups of neurons, temp,

05:52.965 --> 05:55.095
temporarily linked with each other,

05:55.675 --> 05:59.925
and, produce, bursts of,

06:00.465 --> 06:04.645
firing, which are, which oscillate through time,

06:04.705 --> 06:06.165
for a, a brief period of time.

06:06.305 --> 06:09.245
So we, you have this, you know, bunch of neurons

06:09.245 --> 06:13.565
that are at, you know, pro producing, nerve impulses at,

06:13.625 --> 06:16.125
a given frequency altogether.

06:16.905 --> 06:18.725
And this lasts for a bit of time.

06:19.225 --> 06:22.605
And then, you know, another group of neuron,

06:22.615 --> 06:24.685
takes over and, and,

06:24.685 --> 06:27.805
and actually you may have, many different groups

06:27.905 --> 06:32.645
of such neurons, that, are active together.

06:33.865 --> 06:38.085
And, if, you have this,

06:38.665 --> 06:41.005
you know,

06:41.125 --> 06:44.765
temporal oscillations in the basic mechanisms

06:44.765 --> 06:47.645
that under light vision, then that should mean

06:47.715 --> 06:51.365
that our visual function oscillates through time as well.

06:51.945 --> 06:54.885
So that's the, the logic that brought me to,

06:55.665 --> 06:57.165
temporal sampling.

06:57.905 --> 07:02.765
And, so far, it, it's, proving to be accurate that,

07:03.145 --> 07:07.485
we, we find, these, fluctuations of,

07:07.615 --> 07:09.645
perceptual capacity through time.

07:10.145 --> 07:13.605
It, it's, it's a very exciting, a very exciting tool

07:13.605 --> 07:18.365
because, with that, we can,

07:19.045 --> 07:23.285
actually use this feature of visual processing to,

07:23.925 --> 07:27.925
investigate other aspects of visual processing, such as,

07:29.465 --> 07:32.725
you know, the, the nature of the features that,

07:33.105 --> 07:36.605
we are using for visual recognition,

07:36.715 --> 07:40.285
whether this is the same when we recognize faces

07:40.505 --> 07:44.045
or recognize words, you know, there, there are,

07:44.795 --> 07:47.005
it's like a magic wand, actually.

07:47.855 --> 07:52.365
There are many ways in which, we can apply, the,

07:52.595 --> 07:53.685
this, this method.

07:54.345 --> 07:58.045
And, one, which is very exciting, which,

07:58.215 --> 08:02.365
we're we, we just sent off, for publication is,

08:02.435 --> 08:06.965
regarding, visual word recognition, which we know,

08:07.545 --> 08:09.205
is based,

08:09.945 --> 08:13.045
in large part on our capacity to

08:13.765 --> 08:15.045
identify individual letters.

08:16.225 --> 08:20.645
And, what we, demonstrate through this analysis

08:20.645 --> 08:24.805
of the temporal features of processing is that,

08:25.265 --> 08:30.045
we actually have, distinct visual mechanisms

08:30.045 --> 08:33.245
that, process each individual letter in a word.

08:33.905 --> 08:36.925
Uh, and, some of them are interested in

08:38.045 --> 08:39.925
identifying the letter in question,

08:40.665 --> 08:44.925
but others are interested in linking, this letter

08:45.025 --> 08:46.525
to other letters in the word.

08:47.265 --> 08:52.005
So, you have this, these two levels of,

08:52.225 --> 08:54.445
of the process,

08:54.785 --> 08:57.685
Uh, examining the, the letters in a word.

08:58.345 --> 09:02.645
And, actually it's, you know, when you consider it,

09:02.645 --> 09:04.725
it's very nice to have both

09:04.725 --> 09:09.525
because, you know, we, we need, we know we need

09:09.525 --> 09:13.245
to identify the letters, but, we want to do it fast

09:13.625 --> 09:15.325
and, do it very effectively.

09:15.425 --> 09:20.165
So having those mechanism of that put letters together,

09:20.305 --> 09:22.805
is, is a very nice thing to have.

09:22.995 --> 09:26.085
Also, there's one thing which I would like to mention.

09:26.625 --> 09:30.565
Uh, you, you talk about, applications with,

09:31.135 --> 09:32.445
cases of brain damage.

09:33.065 --> 09:36.485
And, there are studies we're doing,

09:36.595 --> 09:40.925
that are relevant, one of which is,

09:41.085 --> 09:45.205
pertains to, A DHD, you know, this attentional deficit

09:45.435 --> 09:46.725
that people have.

09:47.345 --> 09:50.245
And, what we find is that, the,

09:50.385 --> 09:53.765
the temporal features of processing are very different

09:54.385 --> 09:56.645
in persons with A DHD

09:56.865 --> 10:00.085
and, persons with normal development.

10:00.585 --> 10:05.445
And now we're, looking at, future studies where,

10:05.855 --> 10:10.005
we're interested in, finding out if,

10:10.005 --> 10:14.285
temporal sampling might be a good way to diagnose,

10:14.485 --> 10:19.365
A DHD, which, would be highly convenient,

10:19.705 --> 10:23.725
in, in terms of the, the, the facility of accessing to,

10:24.105 --> 10:25.925
such a diagnostic tool.

10:26.705 --> 10:29.685
And, another project we have is,

10:29.985 --> 10:34.005
one interested in the, early detection of dementias,

10:34.865 --> 10:37.005
which is a big issue.

10:37.425 --> 10:41.045
Uh, we want, you know, to be able to, detect,

10:41.045 --> 10:43.725
the development of dementia, as early

10:43.905 --> 10:47.725
as we can in persons, not because it's a good news, but

10:47.725 --> 10:52.605
because we can, do interventions

10:53.185 --> 10:56.405
to, prevent, further deterioration

10:56.745 --> 11:00.205
and, you know, structuring the environment.

11:00.305 --> 11:02.485
And there are, there are many things that can be done

11:03.305 --> 11:07.365
and, which, perhaps may be very costly,

11:07.425 --> 11:11.485
but, it's, you know, nothing compared to the cost of

11:12.085 --> 11:14.165
a person that is really deteriorated

11:14.305 --> 11:16.845
and, can't, work for themselves.

11:17.265 --> 11:20.925
So, we we're trying to, well look at,

11:21.155 --> 11:25.765
many different ways in which, we, we can,

11:26.115 --> 11:28.445
make this pay, you know, the, the disability

11:28.515 --> 11:30.405
that we have now to,

11:30.595 --> 11:34.325
determine the future temporal features of, processing.

11:34.745 --> 11:39.205
And, it's, it's been so fruitful so far.

11:40.505 --> 11:45.485
One thing we're doing now is to try to exploit,

11:45.825 --> 11:47.725
the, the potential of,

11:47.725 --> 11:49.685
temporal sampling as much as we can.

11:50.225 --> 11:52.725
Uh, it, it took quite a while to develop.

11:53.625 --> 11:58.205
And, well, you know,

11:58.425 --> 12:01.845
if you're taken at doing that kind of thing, well,

12:01.905 --> 12:03.485
you can do other stuff.

12:04.105 --> 12:08.685
And, so, well, I, I haven't published as much

12:08.705 --> 12:12.685
as I would have otherwise, had I not worked on,

12:12.865 --> 12:14.005
this development.

12:14.105 --> 12:16.325
So now I, I'm trying to make it pay.

12:16.785 --> 12:20.005
Uh, and, so we have, you know, various,

12:20.005 --> 12:23.925
different projects that, we, we are working on,

12:24.945 --> 12:26.245
to, exploit this.

12:26.385 --> 12:31.085
Uh, some are interested, as I mentioned, in,

12:31.605 --> 12:35.885
aging and A DHD, others in, autism.

12:36.625 --> 12:40.805
Uh, we are looking also at, interocular processing in,

12:40.805 --> 12:41.885
amblyopia.

12:42.465 --> 12:46.125
Uh, so, you know, ma many different ways in which, we,

12:46.125 --> 12:48.445
we can use, the, the method

12:49.305 --> 12:54.245
and, what is going to be, very next,

12:54.355 --> 12:58.925
important next step will be, to examine how,

13:00.095 --> 13:05.045
those features that we, obtain from the technique,

13:05.425 --> 13:08.405
map onto the actual brain activity.

13:08.405 --> 13:09.845
Because,

13:10.655 --> 13:13.765
right now we are not measuring brain activity directly.

13:13.825 --> 13:15.325
We are measuring, you know,

13:15.635 --> 13:18.325
what emanates from brain activity.

13:19.145 --> 13:23.965
And, so what, what, we, are, what,

13:23.995 --> 13:27.565
what, what I want to look at next is, is go, is going to be,

13:27.985 --> 13:32.525
how, this relates those temporal features

13:32.525 --> 13:36.085
that we extract, how they relate to, the,

13:36.145 --> 13:37.965
the electrical activity of the brain.

13:38.665 --> 13:41.565
And, so that's going to be,

13:42.595 --> 13:44.125
very powerful stuff.

13:44.425 --> 13:45.725
Uh, I expect also.

00:00 - We talk about processing in psychology and perception, and, we really define it. But, in, in terms of, visual function, visual processing is the process by which, the raw image that this, registered by our photoreceptors is transformed into a

00:21 - representation that is useful for our, interactions with the world. So it tells us, what things are, what is the spatial layout of, our environment, things like that, which are what we need to, you know, properly interact with, our world. What is involved in visual processing is actually, something that occurs in a sequence of, number of steps where, the image that, initially is registered by the, the photoreceptors, is, is transmitted,

01:01 - to, you know, a next step, a next set of neurons and, and so on. So that there are, a number of steps like this. So, in fact, the, the, the, the point in, our nervous system where, visual processing occurs is, at the interaction between neurons. So at the point where they communicate. And, in that sense, we, we can, consider, our visual system as a

01:35 - very complex communication system. And at every step of communication between neurons, there's this opportunity to make the type of knowledge that we have about the world evolve into this, more into this complex representation of, the identity of things, if it's good for us or not. how are, things spatially organized? So that's, a lot of work, from, you know, this basic knowledge at, at the retina with which is, you know,

02:17 - light intensity at a given point, in, our visual field. And, to be able to perform this sort of magic, lots of, communication steps between neurons and, you need, this, nerve signal, neural signal to, travel, from one point to the next. And all this takes time. And, so, actually, just in terms of, the time it takes to communicate, the,

02:53 - input from the retina into our cortex, just the primary visual cortex, it takes a bit less than a 10th of a second. so, that means, actually that, our cortex, our knowledge of the visual world is always late in comparison to, what is, going on in front of us. And, what, what, what, we are doing is actually, trying to use this, temporal aspect in which, visual processing occurs, to, gain knowledge about the visual function.

03:37 - And, so, in, in the last few years, I've developed this technique, which is, random temporal sampling, through which, what we are doing is, to present, visual stimulus briefly. And, that a participant has to perform a task on the stimulus in question, say, to identify it or say if it's, the meaning or whatever. And, during the exposure duration, what we do is to have, the visibility of the stimulus,

04:14 - vary randomly through time. And, by a**l, analyzing, the relation between, performances and those temporal samples that, we're obtaining on every trial, then, we are able to derive, some knowledge about, how visual processing unfolds through time. So, that's, largely, what we're, doing these days. One basic thing, which is very counterintuitive is, is that,

04:50 - our visual function fluctuates through time in a very, short timeframe. So, for instance, the exposure durations we typically use are, of, 200 milliseconds. That's one fifth of a second. That's very fast. And, throughout this duration, we, can identify points in time where, we're very capable of, acquiring, visual information. But there are other points in time where,

05:23 - you know, we're just hopeless. What I think, and, and which is the actual, actually the inspiration for random temporal sampling, is that, the way our nervous system is, doing its job of, say, vision or whatever else is, through, mechanisms where, groups of neurons, temp, temporarily linked with each other, and, produce, bursts of,

06:00 - firing, which are, which oscillate through time, for a, a brief period of time. So we, you have this, you know, bunch of neurons that are at, you know, pro producing, nerve impulses at, a given frequency altogether. And this lasts for a bit of time. And then, you know, another group of neuron, takes over and, and, and actually you may have, many different groups of such neurons, that, are active together.

06:33 - And, if, you have this, you know, temporal oscillations in the basic mechanisms that under light vision, then that should mean that our visual function oscillates through time as well. So that's the, the logic that brought me to, temporal sampling. And, so far, it, it's, proving to be accurate that, we, we find, these, fluctuations of, perceptual capacity through time.

07:10 - It, it's, it's a very exciting, a very exciting tool because, with that, we can, actually use this feature of visual processing to, investigate other aspects of visual processing, such as, you know, the, the nature of the features that, we are using for visual recognition, whether this is the same when we recognize faces or recognize words, you know, there, there are, it's like a magic wand, actually. There are many ways in which, we can apply, the,

07:52 - this, this method. And, one, which is very exciting, which, we're we, we just sent off, for publication is, regarding, visual word recognition, which we know, is based, in large part on our capacity to identify individual letters. And, what we, demonstrate through this analysis of the temporal features of processing is that, we actually have, distinct visual mechanisms

08:30 - that, process each individual letter in a word. and, some of them are interested in identifying the letter in question, but others are interested in linking, this letter to other letters in the word. So, you have this, these two levels of, of the process, examining the, the letters in a word. And, actually it's, you know, when you consider it, it's very nice to have both

09:04 - because, you know, we, we need, we know we need to identify the letters, but, we want to do it fast and, do it very effectively. So having those mechanism of that put letters together, is, is a very nice thing to have. Also, there's one thing which I would like to mention. you, you talk about, applications with, cases of brain damage. And, there are studies we're doing, that are relevant, one of which is,

09:41 - pertains to, A DHD, you know, this attentional deficit that people have. And, what we find is that, the, the temporal features of processing are very different in persons with A DHD and, persons with normal development. And now we're, looking at, future studies where, we're interested in, finding out if, temporal sampling might be a good way to diagnose, A DHD, which, would be highly convenient,

10:19 - in, in terms of the, the, the facility of accessing to, such a diagnostic tool. And, another project we have is, one interested in the, early detection of dementias, which is a big issue. we want, you know, to be able to, detect, the development of dementia, as early as we can in persons, not because it's a good news, but because we can, do interventions to, prevent, further deterioration

10:56 - and, you know, structuring the environment. And there are, there are many things that can be done and, which, perhaps may be very costly, but, it's, you know, nothing compared to the cost of a person that is really deteriorated and, can't, work for themselves. So, we we're trying to, well look at, many different ways in which, we, we can, make this pay, you know, the, the disability that we have now to,

11:30 - determine the future temporal features of, processing. And, it's, it's been so fruitful so far. One thing we're doing now is to try to exploit, the, the potential of, temporal sampling as much as we can. it, it took quite a while to develop. And, well, you know, if you're taken at doing that kind of thing, well, you can do other stuff. And, so, well, I, I haven't published as much

12:08 - as I would have otherwise, had I not worked on, this development. So now I, I'm trying to make it pay. and, so we have, you know, various, different projects that, we, we are working on, to, exploit this. some are interested, as I mentioned, in, aging and A DHD, others in, autism. we are looking also at, interocular processing in, amblyopia.

12:42 - so, you know, ma many different ways in which, we, we can use, the, the method and, what is going to be, very next, important next step will be, to examine how, those features that we, obtain from the technique, map onto the actual brain activity. Because, right now we are not measuring brain activity directly. We are measuring, you know, what emanates from brain activity.

13:19 - And, so what, what, we, are, what, what, what I want to look at next is, is go, is going to be, how, this relates those temporal features that we extract, how they relate to, the, the electrical activity of the brain. And, so that's going to be, very powerful stuff. I expect also.

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