WEBVTT 00:00:00.017 --> 00:00:06.277 This is Paul Vershoor with Victor Laman. And Victor was just telling us about 00:00:06.277 --> 00:00:08.097 his theory on consciousness, 00:00:09.217 --> 00:00:15.017 in particular, setting up a contrast between his approach and what's also called global workspace. 00:00:15.257 --> 00:00:19.577 And in some sense, the starting point for you was very much the statement like, 00:00:19.637 --> 00:00:24.277 well, a correlation-based approach towards consciousness is just not going to 00:00:24.277 --> 00:00:26.257 get us there. It's not enough. 00:00:27.037 --> 00:00:28.897 So what's the problem with correlation? 00:00:30.117 --> 00:00:36.197 Well, the problem with correlation is that you have to start out with a definition, 00:00:36.337 --> 00:00:39.557 in this case of consciousness, of which you're sure of. 00:00:39.617 --> 00:00:44.597 And then you can try to find out what that means on the neural side. 00:00:44.777 --> 00:00:48.417 But of course, the real problem with consciousness is that we don't really know 00:00:48.417 --> 00:00:52.497 on the psychological or introspective side what it really is. 00:00:52.617 --> 00:00:54.337 We don't know what we are conscious of. 00:00:54.637 --> 00:00:57.937 We don't know what consciousness really is. We don't know what it's used for. 00:00:57.937 --> 00:01:06.177 Or we have actually no clue of what consciousness really is on the introspective, 00:01:06.177 --> 00:01:07.717 psychological, behavioral side. 00:01:08.057 --> 00:01:15.857 So then, of course, it also doesn't make any sense to just try and find a neural code of that. 00:01:17.197 --> 00:01:22.417 So you mean, as long as we have no satisfying definition, we don't know what 00:01:22.417 --> 00:01:23.337 we're correlating it with. 00:01:23.737 --> 00:01:29.497 Yeah, that's the basic problem. So my stance would be to build a definition 00:01:29.497 --> 00:01:38.277 using neuroscience, so to incorporate neuroscientific findings and neuroscientific theories inside, 00:01:38.637 --> 00:01:42.277 neuroscientific arguments, you might even say, into building, 00:01:42.517 --> 00:01:46.057 well, what you might call a new definition of consciousness, 00:01:46.337 --> 00:01:51.477 which, of course, to some extent incorporates the old ideas we have about consciousness 00:01:51.477 --> 00:01:56.917 from introspection and psychology, But to some extent also overrules or overrides 00:01:56.917 --> 00:02:01.137 those intuitions by things we find out from neuroscience. 00:02:01.977 --> 00:02:06.937 But isn't there a risk that this becomes circular? Because you're saying, 00:02:07.017 --> 00:02:09.917 okay, we don't have a satisfying definition right now. 00:02:11.017 --> 00:02:14.417 So let's try to develop one looking at more detail at neuroscience, 00:02:14.717 --> 00:02:18.197 but it still would imply that you have to have at least an intuition, 00:02:18.877 --> 00:02:22.417 which subset of phenomena you want to look at in order to develop this definition. 00:02:22.737 --> 00:02:26.557 So what's that guideline now that helps you to identify these phenomena? 00:02:27.417 --> 00:02:31.517 Yeah, the intuitions, to some extent, are fine. So, for example, 00:02:31.797 --> 00:02:39.017 it's not problematic to have the intuition that, say, in deep sleep or in coma 00:02:39.017 --> 00:02:43.437 or when you have a fully masked visual stimulus, that in those situations you 00:02:43.437 --> 00:02:45.137 do not have conscious sensations. Right. 00:02:46.211 --> 00:02:51.531 So that's an intuition which works fine. And also at the other extreme end, 00:02:51.611 --> 00:02:55.531 when you have a visual stimulus being presented and someone says, 00:02:55.671 --> 00:02:58.391 yes, I see this visual stimulus and I recognize who's in that picture, 00:02:58.491 --> 00:03:03.211 et cetera, et cetera, there's also no real reason to doubt that in that case 00:03:03.211 --> 00:03:04.491 people have conscious sensations. 00:03:04.491 --> 00:03:10.511 But it's particularly in the middle, in the middle ground, where you go from 00:03:10.511 --> 00:03:14.131 these clearly unconscious situations to these clearly conscious situations, 00:03:14.371 --> 00:03:18.111 where we don't really know whether people are conscious. 00:03:18.231 --> 00:03:20.731 We don't even know whether we self have conscious experiences. 00:03:21.031 --> 00:03:26.851 And that's the situation where you have to extrapolate from these extremes towards 00:03:26.851 --> 00:03:28.691 these situations in the middle. 00:03:28.731 --> 00:03:32.131 But you can only do that properly if you take into account the neuroscience, 00:03:32.511 --> 00:03:35.611 which goes along with it. All right, so you're saying there's like this gray 00:03:35.611 --> 00:03:39.911 zone that has to disentangle, and that's where we have to include more constraints. 00:03:41.371 --> 00:03:45.091 Constraints, of course, also from psychology and introspection, 00:03:45.211 --> 00:03:49.431 but I think even more rigorously constraints from neuroscience. 00:03:49.431 --> 00:03:58.851 To give an example, if we see all the essential characteristics of neuroscientific 00:03:58.851 --> 00:04:03.691 processes which go along with situations where we clearly have a conscious person, 00:04:03.931 --> 00:04:06.111 like when we report having a conscious person. 00:04:06.111 --> 00:04:15.931 If we see all the key neural ingredients of that situation also happening in 00:04:15.931 --> 00:04:20.471 situations where we have doubts about whether we have conscious sensation, 00:04:20.731 --> 00:04:26.091 then we might conclude on the basis of that neuroscientific evidence alone that 00:04:26.091 --> 00:04:30.251 in those cases we probably have conscious sensation simply because the neural 00:04:30.251 --> 00:04:34.911 mechanisms are so similar in both situations. 00:04:34.911 --> 00:04:42.911 Or at least are similar as long as, with respect to the essential ingredients of consciousness. 00:04:43.711 --> 00:04:47.671 That we have to grant consciousness to situations which intuitively we might 00:04:47.671 --> 00:04:54.111 think we don't have conscious sensations, like in neglect or when we suffer 00:04:54.111 --> 00:04:56.551 from inattentional blindness or attentional blink. 00:04:56.751 --> 00:05:00.391 Typically in situations where attention is removed, there you have, 00:05:00.391 --> 00:05:07.451 This is in particular the situation where you have this gray zone that we don't 00:05:07.451 --> 00:05:09.591 really know whether we have conscious sensations or not. 00:05:09.931 --> 00:05:16.631 Right. So given that, this doesn't explain why you use change blindness as one 00:05:16.631 --> 00:05:19.471 of your paradigms or not. 00:05:20.330 --> 00:05:23.590 Yeah, so we use change blindness to a large extent, 00:05:24.190 --> 00:05:29.930 showing that, on the one hand, if you take the change blindness results per 00:05:29.930 --> 00:05:33.850 se, you have the inclination to think that consciousness is very limited, 00:05:33.910 --> 00:05:37.350 limited only to what you attend to, that you only see a couple of objects at 00:05:37.350 --> 00:05:39.090 the same time, maybe two or three or four. 00:05:39.850 --> 00:05:46.270 Whereas when you do the change blindness experiment in a different way, using the, let's say, 00:05:46.330 --> 00:05:49.130 the iconic memory version of the experiment image where you present a cue in 00:05:49.130 --> 00:05:54.270 between the first image and the second image you will see that there is at least 00:05:54.270 --> 00:05:57.490 evidence that people have a much richer representation somewhere inside their 00:05:57.490 --> 00:06:01.490 heads the only thing is we don't really know whether that is a conscious representation, 00:06:02.130 --> 00:06:07.110 now and in tune trying to find out whether that is a conscious that rich representation 00:06:07.110 --> 00:06:11.590 is a conscious representation you could use neuroscience to try and find out 00:06:11.590 --> 00:06:16.110 whether all the essential potential ingredients for consciousness that you do 00:06:16.110 --> 00:06:20.130 find in situations where consciousness is unequivocal, 00:06:20.310 --> 00:06:27.470 whether you also find those in this rich representation, 00:06:27.910 --> 00:06:34.070 iconic representation, and then conclude, well, apparently, even though it's 00:06:34.070 --> 00:06:37.290 uncertain behaviorally and introspectively whether there's consciousness there, 00:06:37.590 --> 00:06:43.450 while we are sort of forced to conclude based on neuroscience that indeed people 00:06:43.450 --> 00:06:45.250 do have a conscious sensation there, 00:06:45.390 --> 00:06:48.210 and that as a result of that we are forced 00:06:48.210 --> 00:06:55.530 to conclude that consciousness is not limited and only limited to what attention 00:06:55.530 --> 00:07:03.010 is focusing on and limited in respect of that it only holds a few objects but 00:07:03.010 --> 00:07:06.150 that it's It's much richer than indeed you perceive a whole scene all at once. 00:07:06.830 --> 00:07:10.810 Are you not actually posing two questions? On the one hand, it would be like, 00:07:10.850 --> 00:07:16.430 what's the content of memory and under what conditions and which aspects of 00:07:16.430 --> 00:07:18.990 memory are accessible to conscious experience? 00:07:21.033 --> 00:07:25.873 Well, you do the experiments. In the way you do the experiments, 00:07:26.013 --> 00:07:28.773 you are addressing memory. That's correct. 00:07:29.793 --> 00:07:34.393 But, of course, what that tells you is what the content of consciousness is, 00:07:34.913 --> 00:07:39.413 at the moment you look, because it's very difficult to really know what the 00:07:39.413 --> 00:07:44.953 content of consciousness is at the very now, at the moment that you look. 00:07:45.093 --> 00:07:50.353 So the only way to go about that is ask subjects what they saw or when you've 00:07:50.353 --> 00:07:51.213 presented the stimulus. 00:07:51.693 --> 00:07:56.773 And, of course, essentially that's always about memory. But what turns out to 00:07:56.773 --> 00:08:00.953 be the case is that you have different forms of memory of a particular visual scene that you see. 00:08:01.053 --> 00:08:04.053 So you have the working memory, which is limited to a couple of objects, 00:08:04.313 --> 00:08:09.353 and then you have iconic memory, which is much more widespread and contains many more objects. 00:08:11.313 --> 00:08:15.413 And these two sorts of memory are remnants of the two different representations 00:08:15.413 --> 00:08:20.253 that you had while you were viewing the scene, While you were viewing the scene, 00:08:20.393 --> 00:08:25.733 you probably also had a focused representation, 00:08:26.493 --> 00:08:30.653 attention being focused on 00:08:30.653 --> 00:08:36.393 a few objects which you could cognitively manipulate and things like that. 00:08:36.533 --> 00:08:41.373 But at the same time, you also had a much richer representation containing many 00:08:41.373 --> 00:08:47.013 more objects which you were not attending to and which you could not cognitively 00:08:47.013 --> 00:08:51.513 manipulate and which is linked to this iconic memory trace. 00:08:51.673 --> 00:08:55.513 So the memory traces tell you something about the representation that exists 00:08:55.513 --> 00:08:58.913 at the moment that you look, which is, of course, the real question. 00:09:01.493 --> 00:09:06.193 But in the case of change blindness, there might be, let's say, 00:09:06.213 --> 00:09:09.933 at some level that change blindness becomes almost trivial. 00:09:10.253 --> 00:09:14.893 I mean, there are, let's say, given that perception means that you have to compress, 00:09:14.893 --> 00:09:18.733 You have to throw away, if you want, signals to get to a percept. 00:09:20.273 --> 00:09:26.653 So in that process, of course, there will be, let's say, pieces of information, 00:09:26.953 --> 00:09:32.453 objects disappearing from memory, possibly, or from consciousness, 00:09:32.573 --> 00:09:37.713 because it's also a necessary ingredient of just being able to perceive the world at all. 00:09:37.713 --> 00:09:44.073 So, from that perspective, you could argue, well, it's not a big surprise that 00:09:44.073 --> 00:09:48.013 it is a finite set, both iconic memory, 00:09:48.213 --> 00:09:53.393 but also then, let's say, your working memory for visual processing would be finite. 00:09:53.693 --> 00:10:01.553 So, why then can this paradigm give you an additional insight into this interaction 00:10:01.553 --> 00:10:04.333 between perception, attention, and consciousness? 00:10:07.899 --> 00:10:14.739 Well, obviously, whenever you go from a physical stimulus falling on your retina 00:10:14.739 --> 00:10:19.339 to representation in consciousness, there's some sort of compression going on 00:10:19.339 --> 00:10:20.939 and some sort of interpretation of this. 00:10:21.079 --> 00:10:25.259 You have things like visual illusions, which tell you that whatever is physically 00:10:25.259 --> 00:10:32.439 out there is not translated in a direct way into your conscious percepts. 00:10:32.439 --> 00:10:36.999 There's some things like memory and previous experience and all that thing going on. 00:10:38.619 --> 00:10:45.039 But regardless of that, what remains is that apparently in that transition from 00:10:45.039 --> 00:10:49.039 the physical stimulus to these mental representations, 00:10:49.599 --> 00:10:55.399 you have, well, so to say, different representations, different stages. 00:10:55.399 --> 00:10:59.319 You have a representation which is rich and detailed, which contains more or 00:10:59.319 --> 00:11:03.179 less the whole scene, albeit in an interpreted fashion. 00:11:03.539 --> 00:11:09.599 And then you have a representation which is related to the focus of attention, which is more limited. 00:11:10.159 --> 00:11:14.799 So you have these different representations all sitting there at the same time inside your mind. 00:11:15.039 --> 00:11:17.779 And the real unanswerable question, at 00:11:17.779 --> 00:11:20.519 least unanswerable from an introspective and behavioral point of view 00:11:20.519 --> 00:11:24.099 is which of these representations is is the 00:11:24.099 --> 00:11:26.779 conscious one that's the real that's the 00:11:26.779 --> 00:11:29.679 real problem and that's the thing which we cannot answer from 00:11:29.679 --> 00:11:36.359 introspection or behavior right so now there you um to answer now that question 00:11:36.359 --> 00:11:44.139 you you also are introducing a a fairly a specific uh picture on how perception 00:11:44.139 --> 00:11:47.279 visual perception would work right according to a number of stages. 00:11:47.919 --> 00:11:53.019 So what are these stages exactly and on the ground of what did you distinguish them? 00:11:54.404 --> 00:11:58.624 Okay, so whenever a visual stimulus is presented to our eyes, 00:11:59.664 --> 00:12:02.824 basically we go through four stages of cortical processing. 00:12:03.824 --> 00:12:11.984 First you have, let's say, a fairly shallow processing, feed-forward processing 00:12:11.984 --> 00:12:16.284 by early visual areas and maybe a couple of more high-level visual areas. 00:12:17.244 --> 00:12:21.864 And then following that, if a stimulus is attended, you will have this feed-forward 00:12:21.864 --> 00:12:26.384 processing penetrating all the way up to higher visual areas, 00:12:26.584 --> 00:12:28.364 motor areas, prefrontal cortex, etc. 00:12:28.624 --> 00:12:34.304 So those are the first two stages which are sort of automatically executed. 00:12:35.384 --> 00:12:41.684 Feed-forward processing either in the shallow or in a more extensive deep fashion, 00:12:41.904 --> 00:12:42.884 depending on the tension. 00:12:43.544 --> 00:12:47.064 And then after that you have what I call stages three and four where you have 00:12:47.064 --> 00:12:51.384 recurrent processing, which means higher level areas feeding back into lower 00:12:51.384 --> 00:12:55.244 areas and then engaging in reentrant or recurrent processing. 00:12:55.584 --> 00:13:00.644 And then also you can have these reentrant processes being either of a shallow 00:13:00.644 --> 00:13:04.884 nature in the sense that they only involve, for example, a few visual areas 00:13:04.884 --> 00:13:08.544 or that they grow more widespread when attention is allocated, 00:13:09.244 --> 00:13:12.044 to the stimuli that evoke these processes. 00:13:13.724 --> 00:13:18.124 But the reentrant interactions also include frontal parietal cortex and you 00:13:18.124 --> 00:13:24.304 have what others would typically call global workspace ignition amplification. 00:13:25.606 --> 00:13:31.186 Okay, so it's an incrementally more complex circuit we're looking at. Yeah, exactly. 00:13:31.486 --> 00:13:35.726 Also bringing in more and more top-down information, higher-level cognitive information. 00:13:37.526 --> 00:13:42.266 Well, I wouldn't put it that way, because already in the feed-forward activation, 00:13:42.406 --> 00:13:46.526 you can reach high-level areas like the prefrontal cortex. 00:13:46.766 --> 00:13:51.326 And we have done some experiments showing that when you have this feed-forward 00:13:51.326 --> 00:13:57.106 activation of prefrontal cortex, that may activate cognitive functions like 00:13:57.106 --> 00:14:00.926 inhibitory control or attention and things like that. 00:14:01.826 --> 00:14:07.426 Which tells you that these feed-forward activations, which we think on the basis 00:14:07.426 --> 00:14:08.226 of all kinds of experiments, 00:14:09.086 --> 00:14:12.666 are not generating any conscious sensations, that these feed-forward activations 00:14:12.666 --> 00:14:16.986 may still activate all sorts of cognitive functions like attention or cognitive 00:14:16.986 --> 00:14:19.346 control, but nevertheless are unconscious. 00:14:19.826 --> 00:14:24.046 And of course, similarly, you can have recurrent interactions interactions, 00:14:24.206 --> 00:14:31.206 which are either penetrating deeply or not, and that means that you would have 00:14:31.206 --> 00:14:34.446 conscious versions of either attention or cognitive control, 00:14:34.726 --> 00:14:41.826 meaning that in this view consciousness and attention or consciousness and cognitive 00:14:41.826 --> 00:14:45.366 control or any other cognitive function are essentially orthogonal, 00:14:45.746 --> 00:14:50.086 meaning that you can have both unconscious attention and conscious attention, 00:14:50.306 --> 00:14:53.086 that you can have both unconscious cognitive control and conscious is 00:14:53.086 --> 00:14:56.626 conflict control but then in these these four phases 00:14:56.626 --> 00:15:00.406 of processing what's the minimal configuration that 00:15:00.406 --> 00:15:07.166 could give me a conscious percept yeah so i think the the evidence points to 00:15:07.166 --> 00:15:12.086 the idea that the minimal configuration you need for having a conscious percept 00:15:12.086 --> 00:15:19.086 is that you need to have re-entrant recurrent interactions so stages one and two which are. 00:15:20.026 --> 00:15:27.026 Are entirely feed forward, even though a stage two process may reach prefrontal 00:15:27.026 --> 00:15:31.006 areas, high level areas, that still will be an unconscious process in the sense 00:15:31.006 --> 00:15:33.246 that it's not accompanied by any conscious sensation. 00:15:33.586 --> 00:15:38.346 It's only when you go to stage three where you have reentrant interactions or 00:15:38.346 --> 00:15:40.926 to stage four where you have widespread reentrant interactions, 00:15:41.146 --> 00:15:44.806 including frontal parietal network, that you have conscious sensations. 00:15:44.946 --> 00:15:46.926 That's the idea I'm pushing for. 00:15:48.283 --> 00:15:52.203 But this seems to be a more necessary condition for consciousness, 00:15:52.443 --> 00:15:53.523 and not a sufficient one. 00:15:54.403 --> 00:16:02.063 Yeah, this whole necessary versus sufficient argument is not getting us anywhere 00:16:02.063 --> 00:16:07.123 in the sense that you could always say that something is either necessary or 00:16:07.123 --> 00:16:09.123 sufficient or not necessary or not sufficient. 00:16:09.643 --> 00:16:17.463 What I'm trying to argue is that whenever you have random interactions, 00:16:17.783 --> 00:16:19.103 you have a conscious sensation. 00:16:19.483 --> 00:16:24.163 The only thing is that when these re-entrant interactions are limited to early 00:16:24.163 --> 00:16:28.583 visual errors, you will have a visual sensation which is not linked to cognition, 00:16:28.823 --> 00:16:32.283 not linked to reportability, so you cannot report it to the outside world, 00:16:32.423 --> 00:16:33.903 you cannot store it in working memory, etc. 00:16:34.123 --> 00:16:36.263 But you will still have a conscious sensation. 00:16:37.323 --> 00:16:44.223 And of course, when these re-entrant interactions grow more widespread to stage 00:16:44.223 --> 00:16:47.923 four, when they they incorporate frontal parietal, 00:16:48.463 --> 00:16:52.503 network, then you will have a conscious sensation which is also reportable, 00:16:52.583 --> 00:16:56.403 which you can cognitively manipulate, which you can attend to, etc. 00:16:57.023 --> 00:17:01.903 Okay, so it means on the one extreme we can say, well, you don't necessarily 00:17:01.903 --> 00:17:05.723 need a pure frontal engagement to have a conscious experience, right? 00:17:05.743 --> 00:17:08.123 This is one consequence of what you're saying. 00:17:08.423 --> 00:17:10.743 Yeah, that's certainly one of the important consequences. 00:17:12.283 --> 00:17:15.883 That's the upper bound, if you want, but now at the lower bound, 00:17:16.463 --> 00:17:19.543 Maybe their things are a bit more fuzzy because sometimes I would argue, 00:17:19.603 --> 00:17:23.943 well, a red level of a primary visual area, I will have dense recurrent interactions 00:17:23.943 --> 00:17:28.463 locally to the area and with thalamus and so on. So I have recurrence. 00:17:29.583 --> 00:17:33.843 However, if I would only stimulate V1, as also some studies have shown, 00:17:34.023 --> 00:17:37.643 I would not necessarily consciously experience that stimulus. 00:17:37.643 --> 00:17:44.183 So, it seems that this recurrence of a certain, of a minimal recurrence of a 00:17:44.183 --> 00:17:48.263 certain kind must be present to then lead to a conscious experience. 00:17:48.423 --> 00:17:50.963 So, what's that minimal requirement on recurrence? 00:17:52.103 --> 00:17:58.023 Yeah, there's probably some minimal requirement which we need to add to that, 00:17:58.043 --> 00:18:00.003 if you like, definition of consciousness. 00:18:01.483 --> 00:18:04.803 I'm not entirely sure what it should be. Maybe it has something to do with the 00:18:04.803 --> 00:18:10.223 amount of complexity of the interactions, you know, a lot of Tononi and people 00:18:10.223 --> 00:18:12.343 and proposals like that. 00:18:16.434 --> 00:18:23.794 If you would ask me, basically, I would say that, you know, whenever you have 00:18:23.794 --> 00:18:27.474 reentrant interactions between visual areas, you have some sort of visual percept. 00:18:27.734 --> 00:18:30.774 Of course, it might be a very primitive visual percept, like, 00:18:30.794 --> 00:18:35.734 you know, only seeing a glimmering of light without any cognition added to it, 00:18:35.794 --> 00:18:39.654 without you really knowing what the object is, without you, you know, 00:18:39.654 --> 00:18:44.314 erupt from any normal sense of vision that you would normally have. 00:18:44.314 --> 00:18:47.054 But still it would be a conscious percept you know and the 00:18:47.054 --> 00:18:50.334 only thing that is added when you when when these 00:18:50.334 --> 00:18:53.254 re-entrant interactions incorporate more visual areas 00:18:53.254 --> 00:18:56.394 let's say object selective areas or face selective areas or 00:18:56.394 --> 00:19:03.094 motion selective areas what you add are more layers in terms of well essentially 00:19:03.094 --> 00:19:09.594 how beautiful the the the visual sensation is you know we see you add colors 00:19:09.594 --> 00:19:14.834 you add motion you add you add you add shape you add whether it's a face or not and stuff like that. 00:19:14.974 --> 00:19:21.654 So all this gets added to the visual percept, but that doesn't make it a more 00:19:21.654 --> 00:19:23.154 conscious visual percept. 00:19:23.234 --> 00:19:25.214 It only makes it a ritual visual percept. 00:19:25.374 --> 00:19:28.454 But in every case, it's a conscious visual percept. 00:19:29.730 --> 00:19:33.190 The only thing is that when the recurrent iterations are very localized, 00:19:33.490 --> 00:19:37.430 it's a fairly poor and sorry visual percept. 00:19:37.530 --> 00:19:41.170 And in the other case, it's a rich and very beautiful one. Okay. 00:19:41.590 --> 00:19:45.610 Now, in the data that you described, though, there was another aspect that came 00:19:45.610 --> 00:19:51.370 to the foreground where you had these unconsciously perceived faces that you masked out. 00:19:51.950 --> 00:19:55.110 Remember, you had these… You generated crosses from everything, 00:19:55.210 --> 00:19:59.030 but actually, subconsciously, a face might have been detected. 00:20:00.670 --> 00:20:05.790 When you looked at that data, it looked like the main distinguishing factor 00:20:05.790 --> 00:20:09.390 was whether there was sustained activity or not. 00:20:09.610 --> 00:20:14.750 That's true. So would you accept that as a second parameter where you could 00:20:14.750 --> 00:20:20.370 say, well, maybe to become a consciously perceived stimulus, 00:20:20.750 --> 00:20:27.010 I have to trigger sufficiently sustained activity to engage these recurrent 00:20:27.010 --> 00:20:27.790 circuits sufficiently, 00:20:28.210 --> 00:20:34.130 possibly even including frontal circuits, to construct the experience. Would you buy that? 00:20:35.970 --> 00:20:38.770 Well, the short answer is no. 00:20:38.770 --> 00:20:44.390 No, simply because, you know, experimentally, it's, of course, 00:20:44.410 --> 00:20:48.950 very difficult to tease apart sustained activity and reentered or recurrent 00:20:48.950 --> 00:20:52.270 activity because you cannot have recurrent activity without it being sustained. 00:20:52.850 --> 00:20:56.030 Well, you might have sustained activity without it being recurrent, 00:20:56.050 --> 00:20:59.590 but at least the other way around, it's very difficult to tease those two apart. 00:21:00.710 --> 00:21:05.030 So you might argue, well, maybe it's just about the activity being sustained, 00:21:05.170 --> 00:21:06.690 which is generating the conscious percept. 00:21:06.950 --> 00:21:12.190 The only problem I have with that is that, you know, it doesn't explain anything to me. 00:21:12.230 --> 00:21:17.970 Why would neural activity that's more sustained give you a conscious sensation, whereas. 00:21:20.131 --> 00:21:22.651 Activity that is less sustained would not give you a concept. 00:21:22.751 --> 00:21:23.911 That doesn't make any sense to me. 00:21:24.171 --> 00:21:27.851 Well, on the other hand, the difference between recurrent and feed-forward processing 00:21:27.851 --> 00:21:32.491 is so fundamental in the sense that recurrent activity will give you the integration 00:21:32.491 --> 00:21:35.811 of information over different areas of the brain. 00:21:36.891 --> 00:21:42.771 As I've proposed in the talk, it might also give you things like more synaptic 00:21:42.771 --> 00:21:44.091 plasticity being engaged. 00:21:45.091 --> 00:21:48.511 There are many fundamental differences between recurrent activity, 00:21:48.871 --> 00:21:52.311 it will give you a higher complexity of the neural networks that are involved. 00:21:52.671 --> 00:21:56.291 But there are so many fundamental differences between recurrent activity and 00:21:56.291 --> 00:22:02.211 feedforward activity that I find some explanation in that being the difference 00:22:02.211 --> 00:22:03.931 between conscious and unconscious processing, 00:22:04.391 --> 00:22:09.771 which I totally do not find in short versus sustained activity. 00:22:10.331 --> 00:22:15.891 But imagine I would be a global workspace person. Then in some sense, 00:22:15.891 --> 00:22:17.931 I would agree with you on recurrent connectivity. 00:22:18.291 --> 00:22:25.111 I would say, no, I have highly complex and differentiated and integrated global 00:22:25.111 --> 00:22:27.751 interactions in these networks. 00:22:27.991 --> 00:22:31.551 And then I could argue, and I need at the input side of that, 00:22:31.671 --> 00:22:36.931 I need an activity of a certain duration to drive this global workspace sufficiently. 00:22:37.271 --> 00:22:41.151 So if I have one of these masking tasks, so the stimulus gets suppressed, 00:22:41.471 --> 00:22:45.551 I cannot drive the global workspace circuitry sufficiently. So therefore, 00:22:45.791 --> 00:22:48.051 a conscious percept cannot emerge. 00:22:48.351 --> 00:22:52.111 While if I have a more sustained activity, I can drive the global workspace 00:22:52.111 --> 00:22:54.911 and develop the consciously experienced percept. 00:22:55.351 --> 00:22:57.791 But what would be wrong with that argument? 00:22:58.451 --> 00:22:59.471 Well, of course, no. 00:23:00.761 --> 00:23:04.341 What you're saying now is that the conscious percept is not coming from the 00:23:04.341 --> 00:23:08.841 sustained activity itself, but from the sustained activity driving something 00:23:08.841 --> 00:23:10.941 else, in this case, global workspace activation. 00:23:12.221 --> 00:23:15.981 So essentially what you're saying is that the conscious sensation comes from 00:23:15.981 --> 00:23:17.021 the global workspace activation. 00:23:18.001 --> 00:23:21.061 But the necessary requirement of that is sustained activity. 00:23:24.161 --> 00:23:33.621 Well, what I've tried to point out in the presentation is that, 00:23:33.761 --> 00:23:38.921 of course, you could hold the case that you only have constant sensation whenever 00:23:38.921 --> 00:23:40.541 there's global workspace activity, 00:23:40.821 --> 00:23:45.821 but there are a number of theoretical, scientific, and other problems with that, 00:23:45.821 --> 00:23:53.881 such as that you know this entails that for some reason it's prefrontal cortex, 00:23:55.821 --> 00:23:59.501 activity which is important for consciousness which doesn't seem to have any 00:23:59.501 --> 00:24:04.421 explanatory power it's there's of course lots of evidence that you can have 00:24:04.421 --> 00:24:09.221 prefrontal cortex activation without you having any conscious sensation so again 00:24:09.221 --> 00:24:14.841 there's no real reason to assume that you have that you need to have prefrontal cortex activation, 00:24:15.961 --> 00:24:18.821 for generating consciousness, or the other way around. 00:24:18.901 --> 00:24:23.121 You can have prefrontal cortex activation without you clearly having any conscious sensation. 00:24:23.921 --> 00:24:29.081 When you assume the global workspace activation to be essential for consciousness, 00:24:29.301 --> 00:24:32.881 you always conflate consciousness with attention, you conflate consciousness 00:24:32.881 --> 00:24:36.941 with cognitive control, and also you're not capable of dissociating consciousness 00:24:36.941 --> 00:24:38.601 from a report about consciousness. 00:24:38.861 --> 00:24:42.241 So there are lots of reasons why consciousness. 00:24:43.549 --> 00:24:47.249 Saying that global workspace activation is the essential thing that you need 00:24:47.249 --> 00:24:50.349 for having a conscious sensation, from a scientific point of view, 00:24:50.389 --> 00:24:52.009 seems, well, misguided. 00:24:52.669 --> 00:24:57.209 So that's an important part of your story, where you're saying, 00:24:57.289 --> 00:25:02.449 well, global workspace is one view on conscious experience, and I disagree with 00:25:02.449 --> 00:25:05.929 this view for a number of reasons that you now just summarized. 00:25:05.989 --> 00:25:11.469 And my alternative proposal is the one of recurrent interaction of some kind. 00:25:11.469 --> 00:25:14.389 So um but but 00:25:14.389 --> 00:25:17.169 to what extent is your proposal not 00:25:17.169 --> 00:25:20.869 also consistent with a possible alternative interpretation 00:25:20.869 --> 00:25:23.949 of a global workspace because i could argue well these systems 00:25:23.949 --> 00:25:29.689 you point your finger to are like uh still global workspaces but at a smaller 00:25:29.689 --> 00:25:36.749 scale yeah not necessarily inconsistent yeah okay but of course if you know 00:25:36.749 --> 00:25:41.549 if i if i discuss this with uh the real proponents of global workspace theory, 00:25:42.509 --> 00:25:51.769 they explicitly excluded the possibility of global workspaces being possible at a more local scale. 00:25:51.949 --> 00:25:55.229 Because indeed, you're right. If you would acknowledge that you can have global 00:25:55.229 --> 00:25:57.909 workspace on a more local scale, let's say only visual cortex, 00:25:58.129 --> 00:26:01.589 then of course it's totally similar to what I'm saying. 00:26:02.429 --> 00:26:09.829 But for some reason, which by the way is a total mystery to me, uh. 00:26:11.735 --> 00:26:15.975 Essential tenet of global workspace theory as it has been put forward in the 00:26:15.975 --> 00:26:21.315 last couple of years is that it requires the global broadcasting of information 00:26:21.315 --> 00:26:25.295 via these prefrontal parietal networks throughout the whole brain, 00:26:25.395 --> 00:26:26.995 which is essentially different. 00:26:27.255 --> 00:26:31.035 But that seems to be the sticky point, right? There's much more debate on whether 00:26:31.035 --> 00:26:36.815 this frontal parietal network is a necessary ingredient of consciousness or sufficient even or not. 00:26:36.815 --> 00:26:40.575 Because if you would leave out this component, you would happily agree on some 00:26:40.575 --> 00:26:43.755 sort of adapted version of what you might call a workspace. 00:26:44.635 --> 00:26:49.575 Sure. I wouldn't see any reason for calling it a workspace, though. 00:26:49.695 --> 00:26:58.675 But, you know, scientists more easily use each other's toothbrush than each other's term. 00:26:59.655 --> 00:27:06.535 But aside from that, yeah, why not? Okay. So from now on, you talk about the visual workspace. 00:27:08.855 --> 00:27:11.795 Okay but then the other the other thing before 00:27:11.795 --> 00:27:14.935 getting to the to the conclusions here um what i 00:27:14.935 --> 00:27:18.395 found very interesting is that you also really started to to to push this notion 00:27:18.395 --> 00:27:24.035 of feed forward and recurrent down to to to to uh the neural substrate to the 00:27:24.035 --> 00:27:28.975 level of actually receptor types and so on yeah so so can you maybe explain 00:27:28.975 --> 00:27:32.875 that a little bit yeah so let's say from From a theoretical point of view, 00:27:32.935 --> 00:27:40.195 we had the, well, let's say hunch that there might be differences in the molecular 00:27:40.195 --> 00:27:44.495 machinery that is used for feed-forward processing as opposed to recurrent processing. 00:27:44.755 --> 00:27:48.495 And in particular, that recurrent processing, you know, because it satisfies 00:27:48.495 --> 00:27:53.175 the HEP rule and stuff like that, would be more prone to induce processes related 00:27:53.175 --> 00:27:56.475 to synaptic plasticity and MDA receptor activation and stuff like that. 00:27:56.475 --> 00:28:03.755 So, we did some experiments to sort of verify this hunch, and indeed we found 00:28:03.755 --> 00:28:05.495 that in monkey visual cortex. 00:28:05.835 --> 00:28:16.115 The recurrent signals are almost abolished when you apply NMDA receptor blockers 00:28:16.115 --> 00:28:20.015 like APV, while the feedforward signal is not. 00:28:20.015 --> 00:28:23.375 And conversely, you can block the feed-forward signal by an empire receptor 00:28:23.375 --> 00:28:28.935 blocker like CNQX, which doesn't interfere that much with the recurrent signals. 00:28:29.235 --> 00:28:34.055 So indeed, pointing out that there might be different synaptic mechanisms related 00:28:34.055 --> 00:28:36.035 to feed-forward and recurrent processing. 00:28:36.035 --> 00:28:45.295 And that triggered the idea that maybe recurrent processing is much more related 00:28:45.295 --> 00:28:50.755 to inducing synaptic plasticity, learning, in other words, changing your brain. 00:28:50.755 --> 00:28:57.315 And then of course you know ultimately this could imply that the difference 00:28:57.315 --> 00:29:01.175 between conscious and unconscious processing is that conscious processing changes 00:29:01.175 --> 00:29:05.175 your brain because it induces synaptic plasticity whereas unconscious processing 00:29:05.175 --> 00:29:10.335 does not change your brain which at least to me gives sort of a fundamental answer. 00:29:11.214 --> 00:29:14.014 Hunch or intuition about what consciousness is 00:29:14.014 --> 00:29:16.794 really about and what and what the difference is what the real 00:29:16.794 --> 00:29:20.434 difference is between conscious and unconscious processing but but 00:29:20.434 --> 00:29:24.394 would you be willing to to really say like well and necessary condition 00:29:24.394 --> 00:29:27.854 for learning in the brain is is consciousness 00:29:27.854 --> 00:29:30.534 yeah so uh you know 00:29:30.534 --> 00:29:33.634 let's say a funny prediction of 00:29:33.634 --> 00:29:36.794 that idea would be that there's no such thing as unconscious learning 00:29:36.794 --> 00:29:40.174 uh which you know is already contradicted 00:29:40.174 --> 00:29:42.994 by the existing literature well actually if 00:29:42.994 --> 00:29:46.154 you look at it closely it's not because all the instances of unconscious 00:29:46.154 --> 00:29:49.594 learning that i've come across are mostly about 00:29:49.594 --> 00:29:52.654 what i would call inattentional learning which is something else 00:29:52.654 --> 00:29:56.874 entirely uh so all the 00:29:56.874 --> 00:29:59.754 instances where you find so-called unconscious learning are 00:29:59.754 --> 00:30:03.274 in fact instances where uh you might 00:30:03.274 --> 00:30:06.094 well you you can fairly well assume that 00:30:06.094 --> 00:30:08.814 you still have these re-entrant processes going on on 00:30:08.814 --> 00:30:11.714 a local scale although not at a global scale 00:30:11.714 --> 00:30:15.294 so that indeed people are not able to report about these stimuli devoted to 00:30:15.294 --> 00:30:24.194 learning but for example unconscious learning has never in my mind at least 00:30:24.194 --> 00:30:25.894 been convincingly shown in 00:30:25.894 --> 00:30:30.554 cases where you can really be sure that there is not that there is no uh. 00:30:31.254 --> 00:30:34.834 Recurrent processing going on like for example when you have a fully masked 00:30:34.834 --> 00:30:38.974 visual stimulus which is only evoked feedforward processing, 00:30:39.294 --> 00:30:42.754 you will never find any learning related to such a fully masked stimulus. 00:30:43.014 --> 00:30:47.814 It's only in cases where you rather manipulate attentional reportability where 00:30:47.814 --> 00:30:51.114 you find so-called unconscious learning. 00:30:51.294 --> 00:30:55.954 How about motor learning, like in conditioning or forms of learning dependent on the cerebellum? 00:30:57.294 --> 00:31:00.874 I'm not an expert on that, so I'm going to take the 15 minutes. 00:31:00.874 --> 00:31:03.234 They exist, I'm telling you. 00:31:04.994 --> 00:31:09.894 Oh, you know, the cerebellum, that was already pointed out, of course, in various talks. 00:31:11.054 --> 00:31:16.994 The cerebellum is a very strange system in the sense that even though you might 00:31:16.994 --> 00:31:20.094 have recurrence there, there's still no... it's probably not associated with 00:31:20.094 --> 00:31:22.094 conscious experiences. And it's... 00:31:24.402 --> 00:31:29.402 I have nothing to say about the state of health. Yeah, it's too scary, you know? 00:31:29.622 --> 00:31:33.702 Yeah. So to conclude, I have two questions for you. 00:31:33.782 --> 00:31:41.102 On the one hand, you went on this trajectory actually being very closely to 00:31:41.102 --> 00:31:44.562 the data, physiologists, getting data in monkey and other animals. 00:31:45.122 --> 00:31:48.982 And now you're moving more to these really challenging questions in this domain of consciousness. 00:31:48.982 --> 00:31:52.202 And given that experience what's what's 00:31:52.202 --> 00:31:55.022 the the victor lama law you think we should all adhere to in 00:31:55.022 --> 00:31:57.962 our study of the brain and consciousness well i 00:31:57.962 --> 00:32:05.802 think there are two laws uh the first law is that you you cannot know what either 00:32:05.802 --> 00:32:10.862 someone else or yourself is conscious of uh at any particular moment in time 00:32:10.862 --> 00:32:15.442 you simply don't know what the content of consciousness is and of course the 00:32:15.462 --> 00:32:20.182 upshot of that is that it's useless trying to find neural correlates of consciousness. 00:32:22.142 --> 00:32:26.802 And I would say the second law is, sort of following from that, 00:32:26.842 --> 00:32:33.682 of course, that we don't need neural correlates, but we need neural arguments 00:32:33.682 --> 00:32:36.182 to tell us what consciousness really is. 00:32:36.442 --> 00:32:40.682 And if I put all the neural arguments together, together, of course, 00:32:40.682 --> 00:32:43.862 with psychological insights and introspective insights. 00:32:45.422 --> 00:32:51.402 I have the strong idea that the fundamental ingredient for consciousness is recurrence. 00:32:52.842 --> 00:32:57.502 So now, if five years from now, I go up to Amsterdam and I'm going to find you, 00:32:57.522 --> 00:33:00.782 chase you down and ask you like, okay, Victor, five years back, 00:33:00.842 --> 00:33:03.822 you made this prediction, I'm going to check with you whether it was right or wrong. 00:33:04.142 --> 00:33:08.042 What's this one prediction you were willing to stick your neck out for today? 00:33:09.122 --> 00:33:12.022 Day oh well one of the predictions would be 00:33:12.022 --> 00:33:15.042 like the things we discussed about learning 00:33:15.042 --> 00:33:17.962 uh this is this is something i 00:33:17.962 --> 00:33:22.482 i i really like very much because you know the link between reentrant connections 00:33:22.482 --> 00:33:28.122 and and mda receptor activation uh that's really putting some sort of fundamental 00:33:28.122 --> 00:33:36.242 ground under this whole idea of what consciousness is about so uh i think we at At that point, 00:33:36.262 --> 00:33:39.362 we will have proven that there's no such thing as really unconscious learning 00:33:39.362 --> 00:33:40.642 and that you, for example, 00:33:40.842 --> 00:33:48.302 that you only get, say, visual learning from inattention paradigms and not from 00:33:48.302 --> 00:33:51.022 really, well, and not from masking paradigms, for example. 00:33:51.322 --> 00:33:55.042 Wonderful. Victor Lowe, thank you very much for this interview. Well, you're welcome.