03/07/2011 by admin.

When I was first learning to identify things through a microscope, it seemed an impossible task. There was a sea of variously shaped and coloured splauches and each one had to be examined with respect to a long set of specification that had to be memorized. But I discovered after a few of these learning tasks that what was difficult at first became extremely easy. I would just look generally at the microscope field and the cells I was searching for just popped out of the background. A similar thing happened when I was first visiting African game parks. At first I would be scanning the vista with binoculars and taking a long time to spot any animal that was visible. After a while I just looked without binoculars and saw animals, dozens of them. I needed the binoculars to identify them sometimes or to see what they were doing but for finding them in the first place – better just to relax and look. I have often wondered how we learn these search tricks.

There is a recent paper by Hussain, Sekuler and Bennett, Superior Identification of Familiar Visual Patterns a Year After Learning. I do not have access to the paper but the ScienceDaily posting is (here) The paper seems to be about this ability. Here is the abstract:

Practice improves visual performance on simple tasks in which stimuli vary along one dimension. Such learning frequently is stimulus-specific and enduring, and has been associated with plasticity in striate cortex. It is unclear if similar lasting effects occur for naturalistic patterns that vary on multiple dimensions. We measured perceptual learning in identification tasks that used faces and textures, stimuli that engage multiple stages in visual processing. Performance improved significantly across 2 consecutive days of practice. More important, the effects of practice were remarkably stable across time: Improvements were maintained approximately 1 year later, and both the relative difficulty of identifying individual stimuli and individual differences in performance were essentially constant across sessions. Finally, the effects of practice were largely stimulus-specific. Our results suggest that the characteristics of perceptual learning are similar across a spectrum of stimulus complexities.

These were not straight forward images.

Over the course of two consecutive days, participants were asked to identify a specific face or pattern from a larger group of images. The task was challenging because images were degraded — faces were cropped, for example — and shown very briefly. Participants had difficulty identifying the correct images in the early stages, but accuracy rates steadily climbed with practice.

There are some important differences between this type of memory and usual episodic memory. This is a ‘how to’ memory, like riding a bike; they are memories of how to find and identify x where no two x are the same. These memories are formed and held differently and do not suffer the modification and weakening over time that memories of events do. They are not fact or semantic memories either. I am sure I can identify quickly cell types that I learned 50 years ago but I am not sure I would remember their names or facts about them. Facts and names are getting hazy. Even some of the animal names have become a little faint.

These particular how-to-perceive memories (unlike riding a bicycle) have a very conscious affect. We see the objects of our search pop out clearly from the surroundings. This must be a product of attention swinging to them as soon as they are identified.

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09/06/2011 by admin.

Unconscious pop-out: Attentional capture by unseen feature singletons only when top-down attention is available, is the title of a paper about to be published. When the paper appears it will likely be unavailable to me, but if I can read it, I will post again with more detail. Here is most of the press release:

Paying attention to something and being aware of it seem like the same thing -they both involve somehow knowing the thing is there. However, a new study, which will be published in an upcoming issue of Psychological Science, a journal of the Association for Psychological Science, finds that these are actually separate; your brain can pay attention to something without you being aware that it’s there.

“We wanted to ask, can things attract your attention even when you don’t see them at all?” says Po-Jang Hsieh, co-author… Usually, when people pay attention to something, they also become aware of it; in fact, many psychologists assume these two concepts are inextricably linked. But more evidence has suggested that’s not the case.

To test this, Hsieh and his colleagues came up with an experiment that used the phenomenon called “visual pop-out.” They set each participant up with a display that showed a different video to each eye. One eye was shown colorful, shifting patterns; all awareness went to that eye, because that’s the way the brain works. The other eye was shown a pattern of shapes that didn’t move. Most were green, but one was red. Then subjects were tested to see what part of the screen their attention had gone to. The researchers found that people’s attention went to that red shape – even though they had no idea they’d seen it at all.

In another experiment, the researchers found that if people were distracted with a demanding task, the red shape didn’t attract attention unconsciously anymore. … “We need to be able to direct attention to objects of potential interest even before we have become aware of those objects,” he says.

What appears to be the gist of the paper is that bottom-up, perception driven, and top-down, task driven, attention can be ‘active’ at the same time; the bottom-up, in this case, determining what reaches awareness and the top-down being independent of awareness. It has been a question in my mind for some time – is attention an integral part of consciousness or just part of its preparation (like perception). This work seems to imply the later, that attention and consciousness are separate processes which interact.

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28/04/2011 by admin.

Now that fMRI can be presented to subjects in nearly real-time feedback it is possible to directly observe the result of subjective mental experience on neural activity (or vice versa). This is another way to look at consciousness. Kalina Christoff and group have a recent paper (see citation) on feedback regulation of the rostrolateral prefrontal cortex (RLPRC), an area associated with awareness of meta-cognition or control of introspection. Here is the abstract:

Recent real-time fMRI (rt-fMRI) training studies have demonstrated that subjects can achieve improved control over localized brain regions by using real-time feedback about the level of fMRI signal in these regions. It has remained unknown, however, whether subjects can gain control over anterior prefrontal cortex (PFC) regions that support some of the most complex forms of human thought. In this study, we used rt-fMRI training to examine whether subjects can learn to regulate the rostrolateral prefrontal cortex (RLPFC), or the lateral part of the anterior PFC, by using a meta-cognitive awareness strategy. We show that individuals can achieve improved regulation over the level of fMRI signal in their RLPFC by turning attention towards or away from their own thoughts. The ability to achieve improved modulation was contingent on observing veridical real-time feedback about the level of RLPFC activity during training; a sham-feedback control group demonstrated no improvement in modulation ability and neither did control subjects who received no rt- fMRI feedback but underwent otherwise identical training. Prior to training, meta-cognitive awareness was associated with recruitment of anterior PFC subregions, including both RLPFC and medial PFC, as well as a number of other midline and posterior cortical regions. Following training, however, regulation improvement was specific to RLPFC and was not observed in other frontal, midline, or parietal cortical regions. These results demonstrate the feasibility of acquiring control over high-level prefrontal regions through rt-fMRI training and offer a novel view into the correspondence between observable neuroscientific measures and highly subjective mental states.

Previous studies have suggested the RLPFC’s role is to monitor, coordinate, integrate and evaluate the products of of higher level stages of cognitive processing. Subjects used observation of their own thoughts to increase RLPFC activity and they used external sensory and bodily sensations to decrease the activity. With real time feedback they significantly increased their ability to control the level of activity in the RLPFC. Controls attempted the same effects without any feedback or with sham feedback and did not achieve significant changes. However, trained mediators achieve similar (not identical) effects.

While previous rt-fMRI feedback training studies have shown that subjects could learn to regulate activation with the sensorimotor contex by imagining hand movements, the insula by recalling personal affectively charged events, the anterior cingulate by attending to and away from the painful properties of a stimulus, and the inferior frontal gyrus through the use of various strategies involving sub-vocal speech, here we show that subjects can use an abstract mental process such as metacognitive awareness of one’s own thoughts to regulate activation levels in one of the highest-order cortical association regions.

This is a very powerful tool. It is a fairly probable guess that what the subjects are doing is steering attention – the focus of conscious attention. We will hear much more from this experimental setup in the future and it will shine a light on consciousness.

McCaig, R., Dixon, M., Keramatian, K., Liu, I., & Christoff, K. (2011). Improved modulation of rostrolateral prefrontal cortex using real-time fMRI training and meta-cognitive awareness NeuroImage, 55 (3), 1298-1305 DOI: 10.1016/j.neuroimage.2010.12.016

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07/04/2011 by admin.

Here is the abstract of a paper by A. Shackman, J. Maxwell, B. McMenamin, L. Greischar and R. Davidson in The Journal of Neuroscience, Jan 2011, Stress Potentiates Early and Attenuates Late Stages of Visual Processing. The whole paper is not freely available unfortunately.

Stress can fundamentally alter neural responses to incoming information. Recent research suggests that stress and anxiety shift the balance of attention away from a task-directed mode, governed by prefrontal cortex, to a sensory-vigilance mode, governed by the amygdala and other threat-sensitive regions. A key untested prediction of this framework is that stress exerts dissociable effects on different stages of information processing. This study exploited the temporal resolution afforded by event-related potentials to disentangle the impact of stress on vigilance, indexed by early perceptual activity, from its impact on task-directed cognition, indexed by later postperceptual activity in humans. Results indicated that threat of shock amplified stress, measured using retrospective ratings and concurrent facial electromyography. Stress also double-dissociated early sensory-specific processing from later task-directed processing of emotionally neutral stimuli: stress amplified N1 (184–236 ms) and attenuated P3 (316–488 ms) activity. This demonstrates that stress can have strikingly different consequences at different processing stages. Consistent with recent suggestions, stress amplified earlier extrastriate activity in a manner consistent with vigilance for threat (N1), but disrupted later activity associated with the evaluation of task-relevant information (P3). These results provide a novel basis for understanding how stress can modulate information processing in everyday life and stress-sensitive disorders.

When involved in a task, the prefrontal cortex steers attention. Only surprising sensory input will usually overcome the task oriented focus of attention. It seems that stress overturns this situation and makes non-surprising sensory input override tasks in steering attention. This is probably important for the avoidance of danger – the environment requires careful monitoring. But I suppose this is part of why being upset can make it so hard to concentrate on what I’m trying to get done.

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21/02/2011 by admin.

The default mode network is not as simple as it seemed. There are probably several configurations. A recent paper (by D Stawarczyk and others) has looked at the difference between the default network when the subject is not attending to a task and when the subject is ignoring sensory stimulating from the outside world.

Here is the abstract:

The default mode network (DMN) is a set of brain regions that consistently shows higher activity at rest compared to tasks requiring sustained focused attention toward externally presented stimuli. The cognitive processes that the DMN possibly underlies remain a matter of debate. It has alternately been proposed that DMN activity reflects unfocused attention toward external stimuli or the occurrence of internally generated thoughts. The present study aimed at clarifying this issue by investigating the neural correlates of the various kinds of conscious experiences that can occur during task performance.

Four classes of conscious experiences (i.e., being fully focused on the task, distractions by irrelevant sensations/perceptions, interfering thoughts related to the appraisal of the task, and mind-wandering) that varied along two dimensions (‘‘task- relatedness’’ and ‘‘stimulus-dependency’’) were sampled using thought-probes while the participants performed a go/no-go task. Analyses performed on the intervals preceding each probe according to the reported subjective experience revealed that both dimensions are relevant to explain activity in several regions of the DMN, namely the medial prefrontal cortex, posterior cingulate cortex/precuneus, and posterior inferior parietal lobe. Notably, an additive effect of the two dimensions was demonstrated for midline DMN regions. On the other hand, lateral temporal regions (also part of the DMN) were specifically related to stimulus-independent reports. These results suggest that midline DMN regions underlie cognitive processes that are active during both internal thoughts and external unfocused attention. They also strengthen the view that the DMN can be fractionated into different subcomponents and reveal the necessity to consider both the stimulus- dependent and the task-related dimensions of conscious experiences when studying the possible functional roles of the DMN.

The digits between 1 and 9 were shown at the center of a screen. Subjects were asked to be as quick and accurate as possible in responding to each number except if the number was 3. Series of stimuli were followed by a thought-probe which interrupted the task. For each probe, subjects were asked to characterize the conscious experience they has in the few trials prior to the probe. They were given four possible responses: on-task, task-related interferences, external distractions, mind-wandering. In total the responses were respectively 32, 22, 26, 21%. Subjects had training trials, and trials in and out of a scanner. This is an interesting blend of high-tech fMRI scanning, cognitive computer screen and keyboard experimentation and reporting of conscious thoughts.

I think it may be too early to label the default network as having one, two of even four or five functions. I assume that there are various network configurations for various tasks and likewise various configurations for various ‘resting’ or default conditions. The worry-wart that is stewing over some imagined problem is likely to have a very different mind-wandering configuration to the person anticipating their up-coming vacation. I look forward to examinations of the default network for years to come.

Stawarczyk, D., Majerus, S., Maquet, P., & D’Argembeau, A. (2011). Neural Correlates of Ongoing Conscious Experience: Both Task-Unrelatedness and Stimulus-Independence Are Related to Default Network Activity PLoS ONE, 6 (2) DOI: 10.1371/journal.pone.0016997

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09/09/2010 by admin.

According to Victor Lamme, the reason that the study of consciousness is so difficult is that it gives priority to introspection and behaviour so, as a result, we are fooled into thinking that we know what we are conscious of. By adding evidence from neuroscience into the mix, he hopes to understand consciousness. He looks at the components of what we call consciousness and teases them apart: the phenomenal experience, the behavioural control, the access to the experience/ability to report it, the working memory, the attention focus. Then he asks what neural events match which aspects of consciousness.

Vision is the sense that Lamme uses to explain his model. The first cut is made between the iconic memory and working memory. The iconic image has more detail, is short-lived and overwritten by a change of scene, is not useful to cognition; while the working memory image has limited detail, can last for some time and is not overwritten by new events, is useful to cognition. The parts of the iconic image that become part of the working memory are those few which are attended to – so this cut can also be seen as consciousness with attention verses consciousness without attention.

Consciousness is then divided into stages using the neural events associated with consciousness. These events are the fast feedforward sweep (FFS) and the recurrent processing (RP). In the FFS, information flows from the visual cortex forward through the dorsal and ventral paths to the motor and frontal cortex area. This sweep starts with purely visual processing and ends with motor and executive processing. In RP, information flows out horizontally in each area and flows back to lower levels, as far back as the original visual cortex. In other words, there is a bottom-up stream followed by a sidewise and top-down spread.

Lamme’s stages are:

Stage 1 – Superficial processing during the FFS. Processing stops at the visual areas if a stimulus is not attended to and is also quickly overwritten by a masking image.

Stage 2 – Deep processing during the FFS. If stimulus is attended to but is quickly overwritten the result is that processing reaches the prefrontal and motor areas but remains unconscious.

Stage 3 – Superficial processing with RP. If the stimulus is not masked and has time to evoke RP but is not attended to or is neglected (inattentional blindness, change blindness, attentional blink), the FFS does not travel far but is followed by RP in the area it has managed to reach.

Stage 4 – Deep or widespread RP. If the stimulus has time for the FFS to travel fully forward and is attended to, the RP will span all levels from original visual to executive areas. This consciousness can be reported.

With this four stage model, Lamme labels Stages 1 & 2 as not having consciousness, Stage 3 as iconic representation and Stage 4 as working memory representation. The travel of the FFS forward is associated with attention and the spread of RP is associated with phenomenality.

Lamme argues that the inclusion of neuroscientific evidence is important.

“My main objection is against a form of cognitive psychology where mental constructs are taken as undeniable truths to which neuroscience has to be fitted. I would argue that in the study of consciousness, there are no undeniable truths.

That is the standard approach in science. Intuition told us the sun revolves around the earth, while in fact it is the other way around. Intuition dictated creation, where evolution is the counterintuitive scientific answer. To make scientific headway in our science of consciousness, we need to acknowledge that our intuitions may be wrong and need to be set aside. The upshot is that – finally – we may start solving the questions that have been bothering us for the ages.”

What a breathe of fresh air to have introspection taken off its pedestal!

I have my own list of what explanations of consciousness should address and Lamme touches most of them. My disappointment is the sparse mentions of the role of the thalamus and the nature of synchronous activity as well as the lack of a mention of the apparent projection into the near future of the representation of moving objects.

 
Lamme, V. (2010). How neuroscience will change our view on consciousness Cognitive Neuroscience, 1 (3), 204-220 DOI: 10.1080/17588921003731586

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03/05/2010 by admin.

ScienceDaily has an item (here) reporting on a paper, “Out of Mind, Out of Sight: Eye Blinking as Indicator and Embodiment of Mind Wandering” by D. Smilek and group in Psychological Science.

When your mind wanders, you’re not paying attention to what’s going in front of you. A new study suggests that it’s not just the mind, it’s the body, too; when subjects’ minds wandered, they blinked more, setting up a tiny physical barrier between themselves and the outside world….

… participants blinked more when their minds were wandering than when they were on task. …”What we suggest is that when you start to mind-wander, you start to gate the information even at the sensory endings — you basically close your eyelid so there’s less information coming into the brain,” says Smilek.

This is part of a shift in how scientists are thinking about the mind, he says. Psychologists are realizing that “you can’t think about these mental processes, like attention, separately from the fact that the individual’s brain is in a body, and the body’s acting in the world.” The mind doesn’t ignore the world all by itself; the eyelids help.

I suspect that the process that turns down the volume of auditory signals (for instance when we ourselves are speaking) may also be at work in this situation. As attention focus is the result of both a top-down and a bottom-up control, in order for the top-down to have more control, it may have to interfere with normal perception and bottom-up signals.

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30/04/2010 by admin.

A good post in Frontal Cortex (here) talked about enculturation and how that inhibits new ideas, how we just don’t notice what it would be uncomfortable to notice because it would break our rules.

….There was a squirt of blood to the anterior cingulate cortex, a collar of tissue located in the center of the brain. The ACC is typically associated with the perception of errors and contradictions — neuroscientists often refer to it as part of the “Oh shit!” circuit — so it makes sense that it would be turned on when we watch a video of something that seems wrong….But there’s another region of the brain that can be activated as we go about editing reality. It’s called the dorsolateral prefrontal cortex, or DLPFC. It’s located just behind the forehead and is one of the last brain areas to develop in young adults. It plays a crucial role in suppressing so-called unwanted representations, getting rid of those thoughts that don’t square with our preconceptions.

When physics students saw the Aristotelian video with the aberrant balls, their DLPFCs kicked into gear and they quickly deleted the image from their consciousness. In most contexts, this act of editing is an essential cognitive skill. (When the DLPFC is damaged, people often struggle to pay attention, since they can’t filter out irrelevant stimuli.) However, when it comes to noticing anomalies, an efficient prefrontal cortex can actually be a serious liability. The DLPFC is constantly censoring the world, erasing facts from our experience. If the ACC is the “Oh shit!” circuit, the DLPFC is the Delete key. When the ACC and DLPFC “turn on together, people aren’t just noticing that something doesn’t look right,” Dunbar says. “They’re also inhibiting that information.”

This is a top-down erasing of sensory data. We have to process the image to understand what it is, then conclude that it is ‘impossible’, then eliminate the offending part from the image, all before the image is rendered conscious and we are aware of it. No spam in the conscious in-box – it makes life easier.

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03/04/2010 by admin.

Science Daily reports (here) on a paper in Nature Neuroscience, A central role for the lateral prefrontal cortex in goal-directed and stimulus-driven attention, by C. Asplund and group. They investigated being made temporarily blind by surprises.

“The simple example of having your reading interrupted by a fire alarm illustrates a fundamental aspect of attention: what ultimately reaches our awareness and guides our behavior depends on the interaction between goal-directed and stimulus-driven attention. For coherent behavior to emerge, you need these two forms of attention to be coordinated… We found a brain area, the inferior frontal junction, that may play a primary role in coordinating these two forms of attention.”

… the research team asked individuals to detect the letter “X” in a stream of letters appearing on a screen while their brain activity was being monitored using functional magnetic resonance imaging, or fMRI. Occasionally, an image of a face would unexpectedly interrupt the stream. The surprise caused the subject to completely miss the “X” the first couple of times, despite the fact they were staring directly at the part of the screen on which it appeared. They were eventually able to identify it as successfully as when there was no surprise. …the inferior frontal junction, a region of the lateral prefrontal cortex, was involved in both the original task and in the reaction to the surprise.

“What we think might be happening is that this brain area is coordinating different attention systems — it has a response both when you are controlling your attention and when you feel as though your attention is jerked away.”

“What we show is the dark side or negative impact of the orienting response. We found it blinds you to other events that can occur soon after the presentation of the surprise stimulus.,” The researchers hypothesize that we may be temporarily blinded by surprise because the surprise stimulus and subsequent response occupies so much of our processing ability. “The idea is that we can’t attend to everything at once. It seems that the inferior frontal junction is involved in this limitation in attention.”

The new research supports previous work by Marois’ laboratory that found the interior frontal junction plays the role of an attentional bottleneck — limiting our ability to multitask and attend to many things at once.

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31/03/2010 by admin.

When we are looking at consciousness, we are also looking at altered states of consciousness. One of the most common altered state is the result of consuming alcohol. Psyblog has an interesting look at the effects of alcohol (here) especially its effect on attention. Here is part of the posting.

According to a growing body of evidence collected over the last three or more decades, people’s Jekyll and Hyde behaviour while drinking can be understood by a simple idea which has some intriguing ramifications.

The alcohol myopia model says that drink makes our attentional system short-sighted and the more we drink, the more short-sighted it becomes. With more alcohol our brains become less and less able to process peripheral cues and more focused on what is right in front of us. It’s this balance between what is right in front of us and what we don’t notice around the edges that determines how alcohol affects us in different situations.

Here are a few effects which imbibers will recognise immediately:

• An ego boost: when people drink, they often feel better about themselves. This may be because the attentional short-sightedness induced by alcohol makes all our shortcomings float away and so we feel closer to our ideal selves. This is probably one of the reasons it is so potentially addictive, it is self-actualisation in bottle form.

• Real worries can get worse: if we’ve had a bad day and we sit quietly with a drink, alcohol can make it worse because all the peripheral cues which are potential distractors are cut out and all we see are our problems.

• Pleasure in the moment: the flip-side of this attentional focus is that if, while drinking, we are doing something enjoyable, we find it easier to ignore any nagging doubts or stray worries wandering through our minds. We can be totally in the moment listening to music, watching sports or talking with a good friend.

• In the zone: it’s even possible that for some types of task it may increase performance as we let go of our insecurities. Perhaps that’s why so many writers wrote with a glass of whisky at their side.

Tentatively, I think consciousness is essentially no more than a model of reality, a focus of attention and a working memory operating together. Of course, this may sound simple, but it isn’t – there are many processes that each could be and many ways they could interact.

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