Visual Attention


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A preview on the research of Lamme et al. (2003) about a possible neuronal basis of visual attention.

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  • Mytoday‘stopicisaboutthe original articlefrom Victor Lamme, andit‘scalled„Whyvisualattentionandawarenessare different“.AlthoughitmightlookasI‘mtheshowmasterhere,theactualwork was donebymyfellowcollegues(1) – Jasper and Martijn.They not onlyhadtoanswereverysingleoneofmyquestions, but also knowthisarticlebyheart.I hopeyourememberthispartwhenwe‘recomingtoyourquestions!
  • Before we start with the article, we’d like to explain some terminology.They were rather difficult to comprehend in the original text,and it is very important to understand how these items behave in the following theories.First of all – many people seem to think that attention and awareness are the same things.That would mean that everything in our attention would also be aware.And that seems to be not the case.Here we have a nice, simple glass.We call it “awareness” - because it behaves just the same.You can fill this glass with liquid from a big bucket(1)…but the glass can only hold a certain amount of water, then it flows over.(2)Then, you can use all sorts of different sources to fill this glass.Whatever it is what flows in, it all gets mixed up to a colorful cocktail.(3)There is only one llimitation for the usage of this item:(4)This glass is a small one. It is not possible to drain the glass in a parallel fashion. Because only one can drink at a time, there are absolutely no straws allowed. (5)The second item I’d like to show you is(6)…this black flashlight.It’s commonly called “Attention”, because it works just the same way.(7)You point the light cone at a certain object in your environment,(8)and it becomes clear and detailled all of a sudden.
  • Ourtoday‘s topic – we‘re now full „in“ - is strongly related with the effect of change blindness.For a long time, scientists had the idea that change blindness would be a problem of attention. This idea seems to have turned out wrong.Change blindness – and, of course, inattentional blindness,have in fact more to do with memory than with attention.To demonstratethis effect, I have built up a little test with an abstract scene.As you look at the point in the center of the scene,you will now see eight blue blocks gathered around the center.To erase your visual buffer follows a short whiteout.Afterwards, the eight blue blocks appear again - together with a white line,which is pointing on one of the blocks.You will have to tell me if the block has rotated or not.OK... Eight Blocks around the center, Whiteout, compare the marked block.Ready?(1)Who thinks the block was rotated?(Count)(2)Indeed, it was rotated.(3)The original results were – as to expect - disappointing.It showed up that participants could solve images with up to four blocks.But, because the important cue comes after the whiteout, every single block had to be stored in working memory.For eight blocks, the capacity of working memory was by far to little to hold the rotation of all blocks in mind.
  • Next experiment, almost the same procedure.Look at the center of the image and memorize the blocks.Yeah - they are a little different this time.Ready?(1) Who thinks that the block was notrotated?OK, that was an easy one.(2)Results seem to be fairly well, as you compare them with the earlier task.Also, the measured capacity of working memory jumped up to eight in this setting.But why?The magic word in this context is Priming!Your attention was pre-focused on exactly the right object,and that helped surviving the whiteout.What happened?(3)You see the white line.The object reaches consciousness.(4)Your consciousness recognizes the meaning of the important line,(5)sends a top-down signal of „Attention“ towards the left block in the visual cortex.The information over the left block is now marked with attention.This is absolutely essential for the next step.Now comes the trick:(6)Position and rotation of the left block are stored in the workingmemory.Here, the block information becomes part of the accessawareness,and can so survive the whiteout.As consciousness then compares the object under attention to the earlier version,it is really easy to see the differences.(Oh, by the way:Don‘t bother rembering all the details, you‘ll get a complete summary after the experiments.)
  • This experiment will be a little harder, although it looks the same.You‘ll see eight blocks around the center, nothing new so far.But the helper line will only be there during the whiteout,so you have to remember all blocks.Ready?(1)And - who saw a rotated block?(2)Great.(3)Here also, results were surprisingly accurate.But this time, synchronization between visual cortex and working memory was not possible.(4)The picture was wiped clear before the marker even appeared,and attention would have marked either all eight blocks – or nothing.(6)There certainly are some people who can store the information of eight blocks at the same time in their working memory.But these people would score in the first experiment just as high as they do now, because working memory is not affected by a short visual whiteout.(7)Much more likely the working memory is empty when the whiteout takes place.There has to be another memory space where objects can be attended – even after the visual buffer is cleared.
  • Theanswer to this problem is a second form of awareness,(1)the so called “Phenomenal awareness”.- more neurological basisIt’s a huge glass and can hold a great amount of information.(2)but it has a big hole in it and objects are leaking out quickly.So – if consciousness plans to work with these chunks, it has to use the stable container of Access Awareness.In contrast to all the other areas – (3)V1, V2, V3, fusiform gyrus and so on –the region of Phenomenal Awareness is the first one that can be reached(4)by attention.Try for yourself:Do you know the wave length of this color?(5)You can look as hard as you want. Your retina cells could calculate that easily – but there is simply no way to put attention to your retina.Or, another example. Do you know if our docent has a wider eye distance than your mother?(6)Your fusiform gyrus would have that information available, if you could only ask it!As you probably see, certain visual areas cannot be reached from conscious attention.Because of these findings, it is suggested that phenomenal awareness is always incomplete.(7)Phenomenal awareness is basically one big bucket(8)where all encoded objects are stored.Now, how is decided which object is the chosen one for access awareness?In this case, it’s easy.Our consciousness knew that it had to look for an important short line.(9)When this line was recognized in the phenomenal awareness,(10)the attention was shifted to the left block before it can leak through the hole,(11)and the block information was stored in the access awareness. From here, the comparison can begin once again.If you wonder why we keep mixing up memories and awareness:Research about the neurological basis of awareness showed that(12)Access awareness is probably also known as working memory(13)and Phenomenal awareness seems to use some parts of iconic memory.The author of the original article suggest only to use the “awareness” terms for short processes.So could “memory” be associated with changes in long-term memory – because these are the only changes which happen on a level of pure structure.
  • Now is a white line pointing towards a pink block a fairly specialized task.(1)Usually, the selection of attention is coupled with a complex environment.It is even possible that your visual attention lies on a completely different (2) object compared to your consciousness – and you will not be aware of anything in your field of view.(3)As you are sitting on a desk and your mind is anywhere but at the object right in front of you,your visual attention can be fully directed on a cup of coffee and you still won’t be aware of it.Attention is thus neccesary for awareness, but does not always lead to it!(4)„My coffee? Oh – right. I‘m afraid it‘s cold already.“After all, you can summarize these findings into a model of selection.(5)At the lowest level, a great amount of information flows trough the input channels.This input is then pre-filtered through the information channels – for example, the visual cortex.Some elements are filtered out here and can never reach the stage of awareness.(6)For example, the comparison of face features earlier.(7)In the next stage, information flows into the bucket of Phenomenal Awareness.This is – as we already know - the first time, where attention can set the priority of objects.By the way: This is a general model, and that’s why an “object” can be every chunk of mind.It can be a sound, smell, a picture or a pain – basically everything sensory.Firstwhen the attention is directed on a certain object in the phenomenal awareness,(8)it is possible for consciousness to recognize its meaning and work further with it.This attentional selection is (9) influenced by a couple of effects:(10) At first, your previous experience plays an important role. Coffee makers, for example, will look at a cup of coffee with much more attention than anybody else.(11) Next, your recent memories form an important way for attentional selection. If you just saw the pink block, you know what I mean.(12) Finally, your genetic background has a certain influence on your selection process. One can imagine that cats attend the sight of a mouse quite differently than a human. And when it‘s coming to the presence of a cat, the difference of attention between mice and human is even bigger.All these different effects together form a special form of attention:Endogenous Attention. It is a sort of general pre-selection to some certain items in your environment.(13)That can happen through anticipation (for example, as you expect to get hurt by a hot cup of coffee)or based on your actual needs and goals.Likewise you would be more likely to be aware of expensive cars on the road if you just won in the lottery.
  • There are basically three possibilites to get attention for one object.One is (1) Priming.If you think at one concept, the neural paths are already firing at a higher base frequency, and related concepts are more likely to appear in your mind.The other one is (2) endogenous attention – anticipation, needs and goals.And the last one is (3) exogenous attention – or simply (4) Salience.Salient objects are quite powerful to draw the attention to themselves.They all are in some form extreme – for example, very bright or moving fast, or just making a loud noise.What happened when you saw this last picture?We’ll take a look at your brain in slow-motion.(5)Let’s say your eye saw two objects at this moment.(6)40 miliseconds, and they’ve reached the primary visual cortex.Just a short time after this, the input is encoded as cup of coffee - and a hamburger.(7)The activated neurons for both objects fill large areas of the visual cortex,and this activation tries to expand towards the frontal areas.(8)This wave of neural activation is called feedforward sweep:- it is a bottom-up signal it works fast and completely automatic and it prepares Both objects will now try to reach the frontoparietal region and get a response from there.(9)But this region can only respond to one of the two signals –and this is where attentional selection comes into play.The initial signal of the hamburger was more salient and powerful.So you could expect it would win the race,(10)synchronize with the frontal signal and produce something called Recurrent Processing.(11)But, attentional selection is influenced by more effects than by signal strength.First of all, you probably aren’t hungry, but need some caffeeine.From the side of endogenous attention (needs and goals),that’s one point for the coffee and one against the hamburger.(12)Then, you saw this cup of coffee already three times before.It’s not in your long term memory yet, but there should be a good amount of priming.Priming is probably the strongest influence of attention, and leads to a better, deeper and faster signal processing.And after the consideration of several other effects, it might be that the coffee might win the attentional selection.(13)Of course, the early visual areas can now start recurrent processing with the areas of higher consciousness and hold this connection for several seconds.If all the arrows seem a little weird now, don’t give up. Here’s the finish line:This sychronisation effect called Recurrent Processing seems to be what makes out access awareness.(14)So instead, you could just say: throw this cup of coffee into the glass.And, as you look at the white signals trying to connect to the frontal areas:(15)You can as well call these trials Phenomenal awareness. 
  • We are almost finished, let me just summarize everything.While the neuron activation spreads during the Feedforward Sweep (1)occurs a phenomenal awareness of all encoded objects.Then, Attentional Selection chooses from all signals which reach the higher brain regions.Here, all sorts of different effect influence the choice – but the object is still unconscious!First when Recurrent Processing has connected the two brain areas,our consciousness can see the chosen object.Interesting facts:- Not only Access Awareness, but also Phenomenal Awareness builds up long-term memories.That means that the iconic memory has stored thousands of pictures – probably even some images your consciousness never saw! If you erase the original image in V1, right after the Feedforward Sweep begins – the activation wave can get really far, although there is nothing left to synchronize. Traces of such a „fake“ Feedforward Sweep can even be found as far away as in the motor cortex. If you put an animal under anesthesia, Feedforward Sweep in the brain is still working, just as before. Only, all synchronization trials from the different areas are unsuccesful. Recurrent Processing is strongly surpressed under anesthesia – especially in these areas, where perception is usually organized.
  • Visual Attention

    1. 1. Change Blindness<br />Terminology<br />Awareness<br />Selection<br />Neuro<br />Visual Attention and Awareness<br />...and why they‘re different<br />12-09-2008<br />Martijn Oude Voshaar<br />Dominic Portain<br />Jasper Smit<br />
    2. 2. Basic Terminology<br />Change Blindness<br />Terminology<br />Awareness<br />Selection<br />Neuro<br />„Attention“<br />„Awareness“<br />
    3. 3. Change Blindness<br />Change Blindness<br />Terminology<br />Awareness<br />Selection<br />Neuro<br />
    4. 4. Change Blindness<br />Change Blindness<br />Terminology<br />Awareness<br />Selection<br />Neuro<br />Frontoparietal<br />Cortex<br />Access Awareness<br />Visual Cortex<br />
    5. 5. Change Blindness<br />Terminology<br />Awareness<br />Selection<br />Neuro<br />Change Blindness<br />
    6. 6. Path of Awareness<br />ChangeBlindness<br />Terminology<br />Awareness<br />Selection<br />Neuro<br />Frontoparietal<br />Cortex<br />Phenomenal Awareness<br />Iconic Memory<br />Access Awareness<br />Visual Cortex<br />Working Memory<br />
    7. 7. Selection processes<br />Change Blindness<br />Terminology<br />Awareness<br />Selection<br />Neuro<br />Conscious Report<br />not available<br />Frontoparietal Cortex<br />Attended<br />Unat-tended<br />lost<br />Attentional Selection<br />Conscious<br />Uncon-scious<br />Phenomenal Awareness<br />Sensory Input<br />Access Awareness<br />
    8. 8. Neuronal activity<br />Change Blindness<br />Terminology<br />Awareness<br />Selection<br />Neuro<br />feedforward sweep<br />parietal<br />Fronto-parietal<br />Cortex<br />Priming<br />recurrent processing<br />frontal<br />occipital<br />Endogenous Attention<br />temporal<br />Exogenous Attention<br />Salience<br />
    9. 9. Conclusions<br />Change Blindness<br />Terminology<br />Awareness<br />Selection<br />Neuro<br />feedforward sweep<br />recurrent processing<br />Phenomenal Awareness<br />Attentional Selection<br />Access Awareness<br />60-80 ms<br />100-150 ms<br />200-300 ms<br />