Category Archives: attention

What is consciousness?

Consciousness is a word that we can almost point at. When I say it I am fairly sure I don’t have to give a definition – I mean every one experiences consciousness and so they will know what I am talking about. But it is not so. As Inigo Montoya says, “You keep using that word. I do not think it means what you think it means”.

I read in a comment somewhere, long ago, that there were three ways to approach a physical explanation of consciousness: you could claim that as consciousness is not a physical thing, the explanation is impossible; or you could claim that it is physical but too mysterious to explain, the explanation is too hard; or you may claim that it is not what it appears to be and the explanation is obvious – it is not explained but explained away. It has been said that Dennett did this in his book Consciousness Explained – just explained it away.

As I said in a previous post (seeing past the trick) you cannot explain a magic trick as it appears but you can if you don’t believe the trick and look for the sleight of hand or the misdirection. If the subjective, non-physical, experience of a conscious mind is what has to be explained then that is a dead end and will remain a mystery. We have to give up our naïve sense of what consciousness is in order to understand it.

Michael Graziano did a piece in the NewYork Times Sunday Review (here) that portrays consciousness in a useful way.

… I believe a major change in our perspective on consciousness may be necessary, a shift from a credulous and egocentric viewpoint to a skeptical and slightly disconcerting one: namely, that we don’t actually have inner feelings in the way most of us think we do. …

How does the brain go beyond processing information to become subjectively aware of information? The answer is: It doesn’t. The brain has arrived at a conclusion that is not correct. When we introspect and seem to find that ghostly thing — awareness, consciousness, the way green looks or pain feels — our cognitive machinery is accessing internal models and those models are providing information that is wrong. The machinery is computing an elaborate story about a magical-seeming property. And there is no way for the brain to determine through introspection that the story is wrong, because introspection always accesses the same incorrect information. …

But the argument here is that there is no subjective impression; there is only information in a data-processing device. When we look at a red apple, the brain computes information about color. It also computes information about the self and about a (physically incoherent) property of subjective experience. The brain’s cognitive machinery accesses that interlinked information and derives several conclusions: There is a self, a me; there is a red thing nearby; there is such a thing as subjective experience; and I have an experience of that red thing. Cognition is captive to those internal models. Such a brain would inescapably conclude it has subjective experience. …

In the attention schema theory, attention is the physical phenomenon and awareness is the brain’s approximate, slightly incorrect model of it. In neuroscience, attention is a process of enhancing some signals at the expense of others. It’s a way of focusing resources. Attention: a real, mechanistic phenomenon that can be programmed into a computer chip. Awareness: a cartoonish reconstruction of attention that is as physically inaccurate as the brain’s internal model of color.

In this theory, awareness is not an illusion. It’s a caricature. Something — attention — really does exist, and awareness is a distorted accounting of it.”

I have picked out these bits of the argument but it is worth the time to read the original article. He (like philosophers Dennett, Churchland, Metzinger and others) is not explaining consciousness away but looking at what consciousness may actually be. Most scientists working on consciousness are also on this route – they are assuming that consciousness has a physical explanation, looking for evidence and, like Graziano, building theoretical models.

We cannot explain magic but we can explain why some things happen while appearing to be impossible. Look for what really happened and ignore what appeared to happen.

After writing this post but before posting it, I ran across a near perfect example of the problem. A philosopher called Mark Conard has a post called ‘When Science Gets Stupid’ (here). I doubt that he understood Graziano’s piece because he starts right out defining consciousness in exactly the form that it probably isn’t, “to be conscious is to be aware. It’s to have subjective mental states about one’s environment”. He does not refute Graziano’s argument but ignores it. Well, if you start with that as a firm definition, then you have already pre-judged the issue. You cannot explain scientifically ‘subjective mental states’ but possibly you can explain something that appears to be a subjective mental state. I have consciousness, personally, and I call it consciousness, but I very definitely do not feel I have subjective mental states. That is not the explanation I am looking for – I want an explanation of my consciousness not some other definition, subjective mental states, that seems meaningless. What on earth is a subjective mental state?

I found it offensive that Graziano was referred to as “a guy named Michael Graziano”. He is a very well respected scientist. Conrad also down grades Dennett and Churchland by implying that they are not somehow doing philosophy right (not with a capital P). “With it’s methods, science is wonderful, helpful, generates real knowledge about the world; but it’s incapable of investigating lived human experience in all its richness and meaningfulness. That isn’t to say, mind you, that there is no reasoned approach to human experience, no arguments to be made, no evidence to examine. It’s only to say that we need a different methodology–that of Philosophy!”As I had never encountered Conrad before, his pulling rank does not impress me. And his arguments just miss the point entirely. “You keep using that word. I do not think it means what you think it means”.

Remembering visual images

There is an interesting recent paper (see citation) on visual memory. The researchers’ intent is to map and areas and causal directions between them for a particular process in healthy individuals so that sufferers showing lost of that process can be studied in the same way and the areas/connections which are faulty identified. In this study they were looking at encoding of vision for memory.

40 healthy subjects were examined. “… participants were presented with stimuli that represented a balanced mixture of indoor (50%) and outdoor (50%) scenes that included both images of inanimate objects as well as pictures of people and faces with neutral expressions. Attention to the task was monitored by asking participants to indicate whether the scene was indoor or outdoor using a button

box held in the right hand. Participants were also instructed to memorize all scenes for later memory testing. During the control condition, participants viewed pairs of scrambled images and were asked to indicate using the same button box whether both images in each pair were the same or not (50% of pairs contained the same images). Use of the control condition allowed for subtraction of visuo-perceptual, decision-making, and motor aspects of the task, with a goal of improved isolation of the memory encoding aspect of the active condition.” All the subjects performed well on both tasks and on later recognition of the scene they were asked to remember. “Thirty-two ICA components were identified. Of these, 10 were determined to be task-related (i.e., not representing noise or components related to the control condition) and were included in further analyses and model generation. Each retained component was attributed to a particular network based on previously published data. ” Granger causality analysis was carried out on each pair of the 10 components.

Here is the resulting picture:visual plan

The authors give a description of the many functions that have been attributed to their 10 areas (independent components) which is interesting reading. But not very significant because the areas are on the large size and because it is reasonable to argue from a specific function to an active area but not from an active area to a specific function. The information does have a bearing on some theories and models. The fact that this work does not itself produce a model does not make it less useful in studying abnormal visual memory encoding.

The involvement of the ‘what’ visual stream rather than the stream used for motor actions is expected, as is the involvement of working memory. There is clearly a major importance of attention in this process. The involvement of language/concepts is interesting. “Episodic memory is defined as the ability to consciously recall dated information and spatiotemporal relations from previous experiences, while semantic memory consists of stored information about features and attributes that define concepts. The visual encoding of a scene in order to remember and recognize it later (i.e., visual memory encoding) engages both episodic and semantic memory, and an efficient retrieval system is needed for later recall.” The data is likely to be useful in evaluating theoretical ideas. The author mention support for the hemispheric encoding/retrieval asymmetry model.

The abstract:

Memory encoding engages multiple concurrent and sequential processes. While the individual processes involved in successful encoding have been examined in many studies, a sequence of events and the importance of modules associated with memory encoding has not been established. For this reason, we sought to perform a comprehensive examination of the network for memory encoding using data driven methods and to determine the directionality of the information flow in order to build a viable model of visual memory encoding. Forty healthy controls ages 19–59 performed a visual scene encoding task. FMRI data were preprocessed using SPM8 and then processed using independent component analysis (ICA) with the reliability of the identified components confirmed using ICASSO as implemented in GIFT. The directionality of the information flow was examined using Granger causality analyses (GCA). All participants performed the fMRI task well above the chance level (.90% correct on both active and control conditions) and the post-fMRI testing recall revealed correct memory encoding at 86.3365.83%. ICA identified involvement of components of five different networks in the process of memory encoding, and the GCA allowed for the directionality of the information flow to be assessed, from visual cortex via ventral stream to the attention network and then to the default mode network (DMN). Two additional networks involved in this process were the cerebellar and the auditory-insular network. This study provides evidence that successful visual memory encoding is dependent on multiple modules that are part of other networks that are only indirectly related to the main process. This model may help to identify the node(s) of the network that are affected by a specific disease processes and explain the presence of memory encoding difficulties in patients in whom focal or global network dysfunction exists. ”
ResearchBlogging.org

Nenert, R., Allendorfer, J., & Szaflarski, J. (2014). A Model for Visual Memory Encoding PLoS ONE, 9 (10) DOI: 10.1371/journal.pone.0107761

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Distractions

 

What happens when you overcome distraction and remain focused. The brain can retain its concentration. How? Science Daily (here) reports on a paper by Jacobs and Nieder in Neuron, which shows that one part of the brain ignores the distraction completely while another attends to it very briefly and then returns to the memory task at hand.

Science Daily says, “The monkeys had to remember the number of dots in an image and reproduce the knowledge a moment later. While they were taking in the information, a distraction was introduced, showing a different number of dots. And even though the monkeys were mostly able to ignore the distraction, their concentration was disturbed and their memory performance suffered.

Measurements of the electrical activity of nerve cells in two key areas of the brain showed a surprising result: nerve cells in the prefrontal cortex signaled the distraction while it was being presented, but immediately restored the remembered information (the number of dots) once the distraction was switched off. In contrast, nerve cells in the parietal cortex were unimpressed by the distraction and reliably transmitted the information about the correct number of dots.”

The paper’s highlights and summary were:

  • Prefrontal suppression of distractors is not required to filter interfering stimuli
  • Distractors can be bypassed by storing and retrieving target information
  • Frontal and parietal cortex assume complementary functions to control working memory

Prefrontal cortex (PFC) and posterior parietal cortex are important for maintaining behaviorally relevant information in working memory. Here, we challenge the commonly held view that suppression of distractors by PFC neurons is the main mechanism underlying the filtering of task-irrelevant information. We recorded single-unit activity from PFC and the ventral intraparietal area (VIP) of monkeys trained to resist distracting stimuli in a delayed-match-to-numerosity task. Surprisingly, PFC neurons preferentially encoded distractors during their presentation. Shortly after this interference, however, PFC neurons restored target information, which predicted correct behavioral decisions. In contrast, most VIP neurons only encoded target numerosities throughout the trial. Representation of target information in VIP was the earliest and most reliable neuronal correlate of behavior. Our data suggest that distracting stimuli can be bypassed by storing and retrieving target information, emphasizing active maintenance processes during working memory with complementary functions for frontal and parietal cortex in controlling memory content.

It is interesting that this as not what the researchers expected to find. “The researchers were surprised by the two brain areas’ difference in sensitivity to distraction. “We had assumed that the prefrontal cortex is able to filter out all kinds of distractions, while the parietal cortex was considered more vulnerable to disturbances,” says Professor Nieder. “We will have to rethink that. The memory-storage tasks and the strategies of each brain area are distributed differently from what we expected.””

But I’m sure they found it made sense after thinking about it. We can look at it this way: the ventral intrapariental area is involved with the task, concentrating on the task and little else (bottom-up). The prefrontal cortex on the other hand is involved in somewhat higher level executive operations (top-down). It looks at what is happening, and as it is those researchers trying to distract me, I ignore it and carry on with the task. If on the other hand it is a big machine about to hit me, I will not ignore it and stop the silly dot test while getting out of the way. Something has to be a look-out, take note of things that are happening and decide whether to ignore distractions.

 

The awareness trick

 

The hard question of consciousness may not be that hard, if one doesn’t give up too soon. Consider magic – the magician does a magic trick and we see the magic but we do not believe it is supernatural. Why? Because magicians in fear of their lives long ago convinced their audiences that it was a trick. They would not reveal how the trick was done but assured us – really, really, it is a trick, we are not dangerous, no supernatural magic here. Let’s consider the idea that consciousness is not supernatural magic but a trick. We don’t know how the trick is done but we know it is a trick. If that is so, than it can be understood with effort (and not throwing up our hands and saying ‘too hard’). Somehow an information processing organ produces our consciousness and we just have to figure out how.

This seems to be the route taken by Michael Graziano – assume consciousness is understandable and try to understand it. He concentrates on awareness – how is awareness produced. He goes straight for the hard question.

He reasons that the brain must have a way to deal with other’s actions – understand and predict them. Our brains use a model of what someone’s actions imply about their future actions. We attribute to others a mechanism that includes entities like intentions, preferences, and in particular for Graziano’s understanding, we attribute awareness to others. We take the trouble to figure out and remember what others are aware of and what they are not aware of. It is important if you are a predator to calculate what your prey is aware of and if you are the potential victim to calculate what your predator is aware of. It is extremely important in social animals for cooperating with others. So we have this (possibly hypothetical) attribute, awareness, that we keep track of in other people and animals. We even have a good idea of where in the brain much of this calculation goes on: the temporoparietal junction (TPJ) and the superior temporal sulcus (STS). Experiments have linked these areas with ‘social attribution’ of various attributes to the internal processing of others. In other words they create a ‘mind’ for the other animal and use it to predict the other’s actions; these areas do the theory-of-mind calculations and they track the awareness in others.

But here is the interesting part – the areas also seems to do similar theory-of-mind calculation about ourselves. When the TPJ and STS are damaged, the awareness of patients is affected and they lose awareness of one side of space. Experimentally people have been shown to have vision on the ‘blind side’, to avoid obstacles on that side and to be aware in memory if they are asked to turn around and look the opposite way. Then they are aware of what they could not see before and not aware of what they did see. These areas are involved in producing the phenomenon of awareness.

One way of saying this is that we have evolved a process that creates a ‘mind’ for another animal and we use that ‘mind’ to understand and predict the animal but we also use it to understand and predict ourselves by creating our ‘mind’.

Graziano says, “The conjunction of these two previous findings suggests that awareness is a computed feature constructed by an expert system in the brain. The feature of awareness can be attributed to other people in the context of social perception. It can also be attributed to oneself, in effect creating one’s own awareness.” But how is this creation done? He proposes that awareness is a model of attention. To say that someone is aware of something is to say that they are attending to it – it has their attention. So our conscious awareness at any moment is the current attention model/schema that the brain has constructed. “One’s own awareness is a schematized model of one’s own attention.” And because it is a model it is approximate and simplified – not a complete and accurate version of attention but a model. We can attend, on occasion, to things we are not aware of. Like our model of the world and our model of our bodies, we cannot rely on completeness or accuracy. Models/schema are not the real thing – they are not the world, not our bodies and not our information processing organs or brains. Consciousness/awareness/mind is a useful fiction based on attention in the brain.

Anyway, that is what Graziano’s ‘Attention Schema Theory’ looks like. It seems a good start to solving the hard question. The material is from a podcast http://brainsciencepodcast.com/bsp/108-graziano .

 

The pulvinar and attention

The streetlight effect is a type of observational bias where people only look for whatever they are searching for by looking where it is easiest. The parable is told several ways but includes the following details: A policeman sees a drunk man searching for something under a streetlight and asks what the drunk has lost. He says he lost his keys and they both look under the streetlight together. After a few minutes the policeman asks if he is sure he lost them here, and the drunk replies, no, that he lost them in the park. The policeman asks why he is searching here, and the drunk replies, “this is where the light is.” This is how Wikipedia tells how this old joke gave the streetlight effect its name. The effect seems to me to be common in neuroscience. Many researchers seem to ignore the thalamus and concentrate only on the cortex when trying to understand perception, consciousness, attention, and working memory. Just because it is easier to look only at activity in the cortex does not mean that everything happens there.

 

Part of the thalamus, the pulvinar, has been shown to be involved in attention, especially visual attention. A recent paper (see citation) examines the pulvinar’s role in maintaining attention. This is another bit of evidence pointing to the importance of thalamus-cortex interaction in the areas of perception, consciousness and attention.

 

Attention is marked by synchronous firing in a number of cortical areas that represent the visual item being held in attention. “Simultaneous neural recordings from two cortical areas have suggested that this selective routing depends on the degree of synchrony between neuronal groups in each cortical area . However, it is unclear how different cortical areas synchronize their activity. Although direct interaction between two cortical areas may give rise to their synchrony, an alternative possibility is that a third area, connected to both of them, mediates cortical synchronization…We therefore hypothesized that the pulvinar increases synchrony between sequential processing stages across the visual cortex during selective attention. ”

 

The experimental setup was a screen on which appeared a short cue as to where a trigger was going to appear. The monkey had to hold this cued location in mind during a delay before the trigger appeared. The monkey was to react to the type of trigger and not be distracted by other similar images in other locations. The activity in various brain regions could be examined before, during and after the attention that was forced by the delay between cue and trigger. The activity in three areas was followed: two regions along the ventral visual pathway that are synchronous during visual attention and an area of the pulvinar that was in two-way interaction with both these visual areas. The ventral stream is the ‘what’ visual stream that is involved in object recognition, episodic memory and consciousness (as opposed to the ‘where’ dorsal stream involved in motor control and is largely unconscious). During the attention period these areas had increased activity and were synchronized in the alpha and gamma bands. Further, using conditional Granger causality calculations, it was the pulvinar that was influencing the two visual cortex areas rather than the other way around and rather than the two visual areas influencing each other. This pulvinar driving was only seen during the attention period.

 

The hypothesis, that the pulvinar nucleus of the thalamus maintains attention by increasing “the synchrony between sequential processing stages across the visual cortex”, has some strong corroborating evidence now. Here is the paper’s abstract:

 

Selective attention mechanisms route behaviorally relevant information through large-scale cortical networks. Although evidence suggests that populations of cortical neurons synchronize their activity to preferentially transmit information about attentional priorities, it is unclear how cortical synchrony across a network is accomplished. Based on its anatomical connectivity with the cortex, we hypothesized that the pulvinar, a thalamic nucleus, regulates cortical synchrony. We mapped pulvino-cortical networks within the visual system, using diffusion tensor imaging, and simultaneously recorded spikes and field potentials from these interconnected network sites in monkeys performing a visuospatial attention task. The pulvinar synchronized activity between interconnected cortical areas according to attentional allocation, suggesting a critical role for the thalamus not only in attentional selection but more generally in regulating information transmission across the visual cortex.

 

ResearchBlogging.org

Saalmann, Y., Pinsk, M., Wang, L., Li, X., & Kastner, S. (2012). The Pulvinar Regulates Information Transmission Between Cortical Areas Based on Attention Demands Science, 337 (6095), 753-756 DOI: 10.1126/science.1223082

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