A recent paper by C. Sergent and others has been commented on by R. Kentridge (citations below). They showed that attention to the visual space where a stimulus was, but is now gone, can bring that stimulus into consciousness. This retroperception effect can occur as late as 400 ms after stimulus presentation ends.

Here is the abstract of the Sergent paper:

Is our perceptual experience of a stimulus entirely determined during the early buildup of the sensory representation, within 100 to 150 ms following stimulation? Or can later influences, such as sensory reactivation, still determine whether we become conscious of a stimulus? Late visual reactivation can be experimentally induced by postcueing attention after visual stimulus offset. In a contrary approach from previous work on postcued attention and visual short-term memory, which used multiple item displays, we tested the influence of postcued attention on perception, using a single visual stimulus (Gabor patch) at threshold contrast. We showed that attracting attention to the stimulus location 100 to 400 ms after presentation still drastically improved the viewers’ objective capacity to detect its presence and to discriminate its orientation, along with drastic increase in subjective visibility. This retroperception effect demonstrates that postcued attention can retrospectively trigger the conscious perception of a stimulus that would otherwise have escaped consciousness. It was known that poststimulus events could either suppress consciousness, as in masking, or alter conscious content, as in the flash-lag illusion. Our results show that conscious perception can also be triggered by an external event several hundred ms after stimulus offset, underlining unsuspected temporal flexibility in conscious perception.

The Kentridge commentary concludes:

Although the new study does not directly address underlying mechanisms, the effect must depend on attention acting on some neural trace that persists after the offset of the target. We know that attention modifies the neural response elicited by targets so it is, perhaps, unsurprising that attention can affect neural responses that continue after target offset. Neural activity elicited by transient visual stimuli persists for long periods. What is surprising is that retro-active attention brings otherwise unseen stimulus into consciousness.

Attention plays a role in many theories of consciousness. Both Lamme and Dehaene et al. propose that attention can amplify the neural trace of a stimulus so that it has long-lasting effects spreading from sensory areas of cortex to frontal regions. They accommodate findings that attention can act on stimuli that do not elicit consciousness by suggesting that attention only promotes stimuli to conscious report whose sensory neuronal representation persists through feedback of signals between areas. When attention produces a behavioural effect in the absence of consciousness the strength of neural response is enhanced but no recurrent feedback takes place. … The neural traces that attention acts on in Sergent et al.’s experiments persist for so long that they are likely to depend on feedback of neural signals, so it appears that without attention these recurrent signals do not elicit consciousness, as Dehaene et al. suggest.

The philosopher Ned Block, however, distinguishes between two forms of consciousness: phenomenal consciousness, which corresponds to the experience elicited by a stimulus, and access consciousness, in which the properties of the stimulus become available to cognitive processes. … He explains that ‘‘the strong but still losing coalitions in the back of the head are the neural basis of phenomenal states (so long as they involve recurrent activity)’’. … The contrary position, for example, is that experience of the unreported items is incomplete and so there is no dissociation between experience and cognitive access. For this to occur we need to have, in Block’s own words, ‘‘unconscious representations that are specific enough to do the task with the observed accuracy. the cue is supposed to promote attentional amplification of the cued unconscious specific representation, which, when combined with the conscious generic representation, results in a conscious specific representation of the cued item.’’ That is, of course, exactly what Sergent et al. have found (except that their subjects do not even appear to report a generic representation of the unseen stimulus).

Sergent et al.’s result does not necessarily invalidate the distinction between access and phenomenal consciousness, but it does lend weight to the alternative, and perhaps simpler, position that consciousness is just consciousness.

I suspect that the thalamocortical traffic has a lot to do with sustaining perception of unattended stimuli for some time and the directing of attention to them after the original stimuli have disappeared. There is more going on than feedforward and feedback confined to the neocortex.

Sergent, C., Wyart, V., Babo-Rebelo, M., Cohen, L., Naccache, L., & Tallon-Baudry, C. (2013). Cueing Attention after the Stimulus Is Gone Can Retrospectively Trigger Conscious Perception Current Biology, 23 (2), 150-155 DOI: 10.1016/j.cub.2012.11.047

Kentridge, R. (2013). Visual Attention: Bringing the Unseen Past into View Current Biology, 23 (2) DOI: 10.1016/j.cub.2012.11.056

A recent paper (citation below) by a Canadian group led by J. Kam has looked at the effects of mind wandering on motor adjustments during a task. Among other interesting results, they indicate that the top-down control of attention is complex and not a single process. Nothing is ever as simple as it first appears.

In their conclusions, they write:

In particular, mind wandering is a phenomenon that spans an extended period of time (i.e., fluctuations of 10–15 s) exceeding a given single event, whereas attentional lapses tend to occur during a much narrower time window capturing the lapse at a single event level. Several recent theoretical and empirical papers have supported and validated these two related models of attention. Specifically, at a theoretical level, Dosenbach and colleagues have suggested there are multiple controlling systems operating at multiple scales of time. Further, in terms of empirical evidence, the findings of Esterman and colleagues suggested the occurrence of two attentional states—one tied to the default mode network (reflective of mind wandering) that is more stable and less error prone in terms of behavioral measures, and a second one tied to the dorsal attention network (reflective of attentional lapses) that requires more effortful processing. That the effects of mind wandering appear to parallel effects of attentional lapses actually lends support to the notion that task-related attention (or mind wandering) and selective attention (or attentional lapses) may exert similar forms of top–down attentional control on other neurocognitive processes. In the case of attentional control of sensory response, it has been suggested that there are at least two distinct control systems operating in parallel—one associated with rapid shifts of selective visual attention and another one associated with slower fluctuations in task-related attention . In the case of behavioral control, that Weissman and colleagues have demonstrated that attentional lapses impair goal-directed behavior and are associated with reduced pre-stimulus activation in the anterior cingulate cortex and that we found impaired adjustment of behavioral control are consistent with the idea that varying attentional control systems appear to have similar impact on various neurocognitive processes. Taken together, mind wandering and attentional lapses do appear to be related conceptually, but future work needs to be done to disentangle the overlaying attentional influences linked to dissociable neural systems.

Here is the abstract:

Mind wandering episodes have been construed as periods of “stimulus-independent” thought, where our minds are decoupled from the external sensory environment. In two experiments, we used behavioral and event-related potential (ERP) measures to determine whether mind wandering episodes can also be considered as periods of “response-independent” thought, with our minds disengaged from adjusting our behavioral outputs. In the first experiment, participants performed a motor tracking task and were occasionally prompted to report whether their attention was “on-task” or “mind wandering.” We found greater tracking error in periods prior to mind wandering vs. on-task reports. To ascertain whether this finding was due to attenuation in visual perception per se vs. a disruptive effect of mind wandering on performance monitoring, we conducted a second experiment in which participants completed a time-estimation task. They were given feedback on the accuracy of their estimations while we recorded their EEG, and were also occasionally asked to report their attention state. We found that the sensitivity of behavior and the P3 ERP component to feedback signals were significantly reduced just prior to mind wandering vs. on-task attentional reports. Moreover, these effects co-occurred with decreases in the error-related negativity elicited by feedback signals (fERN), a direct measure of behavioral feedback assessment in cortex. Our findings suggest that the functional consequences of mind wandering are not limited to just the processing of incoming stimulation per se, but extend as well to the control and adjustment of behavior.

Kam, J., Dao, E., Blinn, P., Krigolson, O., Boyd, L., & Handy, T. (2012). Mind wandering and motor control: off-task thinking disrupts the online adjustment of behavior Frontiers in Human Neuroscience, 6 DOI: 10.3389/fnhum.2012.00329

ScienceDaily reports (here) on a paper by Niebergall, Khayat, Treue and Martinez-Trujillo, Multifocal Attention Filters Targets from Distracters within and beyond MT Neurons’ Receptive Field Boundaries.

What they show is the ability to split the ‘attentional spotlight’ in order to attend to multiple visual object without processing other objects between the objects of interest.

When we pay attention to an object, neurons responsible for this location in our field of view are more active then when they process unattended objects. But quite often we want to pay attention to multiple objects in different spatial positions, with interspersed irrelevant objects.

There are three theories of how this is done: either the focus is ‘zoomed out’ to cover all relevant objects even if this includes irrelevant ones; or, the focus is split into more than one focus; or, the focus switches back and forth between relevant objects.

In order to explain how such a complex ability is achieved, the neuroscientists measured the activity of individual neurons in areas of the brain involved in vision. They studied two rhesus macaques, which were trained in a visual attention task. The monkeys had learned to pay attention to two relevant objects on a screen, with an irrelevant object between them. The experiment showed, that the macaques’ neurons responded strongly to the two attended objects with only a weak response to the irrelevant stimulus in the middle. So the brain is able to spatially split visual attention and ignore the areas in between.

Here is the paper’s abstract:

Visual attention has been classically described as a spotlight that enhances the processing of a behaviorally relevant object. However, in many situations, humans and animals must simultaneously attend to several relevant objects separated by distracters. To account for this ability, various models of attention have been proposed including splitting of the attentional spotlight into multiple foci, zooming of the spotlight over a region of space, and switching of the spotlight among objects. We investigated this controversial issue by recording neuronal activity in visual area MT of two macaques while they attended to two translating objects that circumvented a third distracter object located inside the neurons’ receptive field. We found that when the attended objects passed through or nearby the receptive field, neuronal responses to the distracter were either decreased or remained unaltered. These results demonstrate that attention can split into multiple spotlights corresponding to relevant objects while filtering out interspersed distracters.

I have posted on this before (here and here) but I am going to again, prompted by Tallon-Baudry’s talk at the Turing 2012 Consciousness Event (video). The experimental detail covered in the talk is from a paper with Wyart and Dehaene (citation below). She reviewed this area of research recently (citation below). Abstract:

Consciousness, as described in the experimental literature, is a multi-faceted phenomenon, that impinges on other well-studied concepts such as attention and control. Do consciousness and attention refer to different aspects of the same core phenomenon, or do they correspond to distinct functions? One possibility to address this question is to examine the neural mechanisms underlying consciousness and attention. If consciousness and attention pertain to the same concept, they should rely on shared neural mechanisms. Conversely, if their underlying mechanisms are distinct, then consciousness and attention should be considered as distinct entities. This paper therefore reviews neurophysiological facts arguing in favor or against a tight relationship between consciousness and attention. Three neural mechanisms that have been associated with both attention and consciousness are examined (neural amplification, involvement of the fronto-parietal network, and oscillatory synchrony), to conclude that the commonalities between attention and consciousness at the neural level may have been overestimated. Last but not least, experiments in which both attention and consciousness were probed at the neural level point toward a dissociation between the two concepts. It therefore appears from this review that consciousness and attention rely on distinct neural properties, although they can interact at the behavioral level. It is proposed that a “cumulative influence model,” in which attention and consciousness correspond to distinct neural mechanisms feeding a single decisional process leading to behavior, fits best with available neural and behavioral data. In this view, consciousness should not be considered as a top-level executive function but should rather be defined by its experiential properties.

She outlines three ways of relating consciousness and attention.

Gateway hypothesis: attention and consciousness reflect related concepts, much as temperature and heat. The idea that attention acts as a gateway for consciousness has been formalized in influential theories of consciousness: those events that enter consciousness are those that have been selected and amplified by attention.

Reverse dependence hypothesis: alternatively, whether a stimulus has been detected or not at the neural level could trigger different attentional mechanisms.

Cumulative influence hypothesis: attention and consciousness would be implemented by distinct neural mechanisms, but would both influence, although with different weights, the final report of the subject on the presence or absence of a stimulus. This hypothesis postulates the existence of a decision variable that would accumulate mainly consciousness-related neural activity, but also, to a lesser extent, attention-related neural activity. Behavioral reports based on this decision variable could therefore show an interaction between attention and consciousness, whereas neural variables could be related solely to attention and consciousness.

Intuition favours the gateway model but Tallon-Baudry puts forward evidence for the cumulative model but looking for connections (or lack of connections) in the neural correlates of attention and consciousness. If they have no joint neural correlates then how can they influence one another. The obvious overlaps are neural amplification, involvement of the fronto-parietal network, and oscillatory synchrony; none of these appear solid.

To summarize, attention does operate in sensory regions, but neural amplification by attention appears functionally distinct from the neural amplification related to consciousness: attention does not shorten response latencies, as more contrasted objects would, attention-related and consciousness- related neural activities in retinotopic areas can be dissociated . There is growing evidence that events that do not reach consciousness nevertheless activate parietal and frontal regions, suggesting that they are not sufficient for consciousness to emerge. Because frontal regions are not always activated, one can even wonder whether they are necessary. An alternative possibility is that they reflect a consequence of consciousness, rather than a cause. Last, oscillatory synchrony is not associated exclusively with a single process, be it feature binding, memory and learning, attention, or consciousness, but should rather be considered as a generic mechanism governing neural interactions .

Tallon-Baudry points out a few of the weaknesses of the cummulative model (the place of decisional bias, the dangers of fMRI data, the other types of attention besides spatial) but insists that to the present it best fits the evidence.

Even if the cumulative influence hypothesis has its limitations, it is so far the model that fits best with experimental data. Interestingly this model points toward the existence of a sensory neural activity related to consciousness, uncontaminated by other cognitive processes such as attention. Such an activity could potentially be very close to the immediate subjective experience of the subject. This is reminiscent of the idea of phenomenal awareness, that could be distinct from cognitive access.

V. Wyart, S. Dehaene, & C. Tallon-Baudry (2012). Early dissociation between neural signatures of endogenous spatial attention and perceptual awareness during visual masking Frontiers in Human Neuroscience DOI: 10.3389/fnhum.2012.00016

Catherine Tallon-Baudry (2012). On the neural mechanisms subserving consciousness and attention Frontiers in Psychology DOI: 10.3389/fpsyg.2011.00397

There is an idea that EB Bolles argued for in his blog, Babel’s Dawn (here), and his book by the same name. It is that words are in effect pointers than force the listener’s attention to a topic or element of a topic. So if I say ‘flag’ and there is a flag near by, your attention will shift to that flag, and, if there is no flag in sight, your attention with shift to the concept of flag in your mind. The shift would be automatic. Words steer attention and force it to find what matches the word; the meaning of a word is the collection of concepts that it can force into attention. This idea depends on whether attention can be steered and the usual example used the illustrate the effect is the way we follow a pointing finger or another person’ gaze.

A recent paper (see citation) confirms that both gaze and arrows can steer attention. Here is what they did:

…we aimed at testing a strong definition of resistance to suppression for orienting of attention elicited by these two cues. In five experiments, participants were informed with 100% certainty about the future location of a target they had to react to by presentation of either a direction word at the beginning of each trial or instructions at the beginning of each block. Gaze and arrows were presented before the target as uninformative distractors irrelevant for the task. The results showed similar patterns for gaze and arrows—namely, an interference effect when the distractors were incongruent with the upcoming target location. This suggests that the orienting of attention mediated by gaze and arrows can be considered as strongly automatic.

The finding that the information conveyed by distractors interfered with the task indicates that orienting of attention mediated by both gaze and arrows resists suppression and can be defined as strongly automatic. Indeed, even though participants were informed with 100% certainty about the upcoming target location, and, thus, they were motivated to voluntarily attend to that location, results showed that they could not ignore the information conveyed by the distractors.

The authors do not seem to view the arrow as a stand-in for pointing and therefore likely to be a similar cue to gaze – one that we are innately supplied with. My opinion is that it is likely to be closely related to pointing. Humans and some animals do follow pointing at an early age.

However, it is important to point out that the similar behavioural effect obtained for gaze and arrows—namely, the elicitation of an automatic attention shift—does not necessarily imply that the underlying processes are the same for these two cue types. Indeed, arrows are able to elicit an automatic attention shift probably because they are a well-learned symbol, which conveys a strong spatial information that is reinforced every day, for instance by means of road signs. On the contrary, gaze is likely to trigger an automatic attention orienting because it may represent a special cue characterized by a strong biological significance given its relevance in everyday life, and, for such reasons, humans would have developed a reflexive attention shift in response to the view of an averted gaze that would also be supported by a dedicated neural circuit. Moreover, the presence of gaze-mediated orienting of attention in both new-borns as young as 2 days old and several species of nonhuman primates suggests that this phenomenon can be defined as innate, thus reinforcing the special nature of gaze as compared to other cue types.

It is not easy to see how communication is possible unless there is some sort of ‘steering attention to x’ mechanism so that one brain could influence the events in another brain. That is after all what communication is. Studying the control of attention is important to many aspects of neuroscience (preception, consciousness, communication at least).

Galfano G., Dalmaso M., Marzoli D., Pavan G., Coricelli C., & Castelli L. (2012). Eye gaze cannot be ignored (but neither can arrows) The Quarterly Journal of Experimental Psychology

If we look at how communication works we find that words and phrases have a great influence on attention. They bring into the consciousness of the listener the concepts that are uttered. This is what meaning is – the concepts that a word or phrase can steer attention towards. This is what communication is – the sharing of attention by two (or more) brains on a sequence of concepts.

So it is not surprising that it is useful to talk to oneself. What we are doing when we self-talk is to steer our consciousness. In recent paper (see citation below), Lupyan and Swingley look at how self-directed speech affects searching. Here is part of their conclusions:

In this work, we examined effects of self-directed speech on performance on a simple visual task. Speaking the name of the object for which one was searching affected performance on the visual search task relative to intermixed trials on which participants read the word but did not actually speak it before or during search. The effect of speaking depended strongly on the characteristics of the target item. Search was improved for the most familiar and prototypical items - those for which speaking the name is hypothesized to evoke the visual representation that best matches the visual characteristics of the target item. Search was unaffected or impaired as the discrepancy between the name and target - measured by measures of familiarity and imagery concordance - was increased.

Facilitation due to speaking also became larger with repeated exposures to the target items. Arguably this occurred because multiple exposures strengthened the associations between the label (e.g., “elephant”) and the visual exemplar (a given picture of an elephant). The idea that saying a category name activates a more prototypical representation of the category is also supported by the finding that speaking the name actually hurts performance for items with low within-category similarity. One implication is that repeating the word “knife” may, for example, help an airport baggage screener spot typical knives, but actually make it more difficult to find less prototypical knives.

On our view, the reason speaking the target name affects visual search performance is that speaking its name helps to activate and/or keep active visual (as well as nonvisual) features that are diagnostic of the object’s category, facilitating the processing of objects with representations overlapping those activated by the label. This activation of visual features occurs during silent reading as well. Indeed, it is what allows fore-knowledge of the target to guide search. Self-directed speech, as implemented in the present studies, is hypothesized to further enhance this process.

This idea of controlling attention is also shown when people try to keep some piece of information in working memory by repeating it, when they encourage themselves to do something difficult or scaring, when they are learning (or planning) a complex sequence of actions. Searching is not the only activity that benefits from a little talking to yourself.

Lupyan, G., & Swingley, D. (2011). Self-directed speech affects visual search performance The Quarterly Journal of Experimental Psychology, 1-18 DOI: 10.1080/17470218.2011.647039

I have been interested in communication for many years. Not written stuff but oral speech and accompanying non-verbal communication. How is it that we manage a link, a synchrony, a shared perception between two minds.

A recent blog posting in the Scientific American has some interesting things to say about movies, similar to what has been said about stage magic. There are ways to affect the audience and are skilled practitioners of these arts. Here is the link to Maria Konninova’s posting, The Innate Irresistibility of Film.

Of course we start out with a perceptual slight of hand. The movie is discrete frames but we see it as a continuous. This is because the frames per second is close to the natural ‘frames’ of consciousness which is also discrete. Konninova also mentions the control of blinks, eye movements and event breaks.

… researchers are finally beginning to understand what it is that makes the present-day film experience so binding on a profound level - and why it’s often difficult for older movies to keep up. It seems that filmmakers have over the years perfected the way to best capture - and keep - viewers’ attention. Through trial, error, and instinct, Hollywood has figured out how best to cater to the natural dynamic of our attention and how to capitalize on our naïve assumptions about the continuity of space, time, and action.

… blink synchronicity: if we see someone blink, we’ll likely blink right along with him. Film editor Walter Murch noticed that very thing when he was editing Francis Ford Coppola’s The Conversation. When Gene Hackman blinked, there went Murch’s eyes—and that’s precisely where he wanted to place the film cut. Cut at the blinks, and more likely than not, the viewers will perceive the action as continuous. The cut itself will go unnoticed. … People who view the same film tend to synchronize their blinks – and that synchronization reflects the editing of the story. …

When people watch a movie, their eyes tend to follow similar patterns. Even if a scene has no actors, it remains likely that gaze focus will follow the same trajectory between different viewers. And it’s not just the gaze: each viewer’s brain may actually be reacting in similar fashion as well.

In one study, individuals watched the first 30 minutes of The Good, The Bad and the Ugly while their brains were scanned by fMRI. Researchers found that 45% of neocortical activity—including areas implicated in vision, hearing, emotion, language, and multisensory integration—was quite similar for each viewer. That’s almost half the activity of that part of our brain that coordinates our higher cognitive functions. Impressive indeed.

… When people viewed The Red Balloon in a scanner and then divided the film into events, cuts that coincided with significant changes in action predictably activated dorsal frontal and medial temporal areas of the brain—associated with attentional control and motion processing, respectively—in a similar fashion for each viewer.

In the same way that we could learn much about attention from magicians, we could learn much about consciousness from movie editors. Back to the subject of communication, we can also learn from ordinary conversations. It seems that people who are busy talking seem to get on the same wave length. They synchronize their movements and posture, they get a rhythm going in the speech, their mimic each other’s face expressions, they blink together. Hey, they are coordinating their consciousness.

Christopher Bergland (here) believes that we think in a different way when we exercise.

Anyone who exercises regularly knows that your thinking process changes when you are walking, jogging, biking, swimming, riding the elliptical trainer, etc. New ideas tend to bubble up and crystallize when you are inside the aerobic zone. You are able to connect the dots and problem solve with a cognitive flexibility that you don’t have when you are sitting at your desk. This is a universal phenomenon, but one that neuroscientists are just beginning to understand. … Creativity is the ability to bring together disparate ideas in new and useful combinations. What is happening to the electrical, chemical and architectural environment of our brains when we exercise that stimulates our imagination and makes us more creative? What is the parallel between the waking dream state induced by exercise and the REM dream state experienced during sleep? Although these questions remain enigmatic, neuroscientists have identified that the non-thinking ‘default state‘ of consciousness is key to creative thinking. … Sweat is like WD-40 for your mind-–it lubricates the rusty hinges of your brain and makes your thinking more fluid. Exercise allows your conscious mind to access fresh ideas that are buried in the subconscious. Every thought that you have is a unique tapestry of millions of neurons locking together in a specific pattern-this is called an engram. If you do not ‘unclamp’ during the day, you get locked into a loop of rut-like thinking. If for any reason you are unable to do aerobic activity, focused meditation is also an excellent way to create a default state.

The piece has quotes from a number of writers and runners such as:

Ralph Waldo Emerson said of Thoreau: “The length of his walk uniformly made the length of his writing. If shut up in the house, he did not write at all.”

I find this idea intriguing. There is no reason why the rhythm and effort of running (or even walking) would not affect both cognition and consciousness. There might even be some chemistry there. But also the ‘default network’ angle is interesting. If the motor part of the brain is busy and, because of moving, we cannot override the control of sensory input – then there cannot be a ‘task’ control of attention. It would be, or be like, the default network being in control.

A totally opposite but somehow the similar effect is my old trick of sitting still in the dark and silence to think. What would be the difference between: the motor and sensory parts of the brain working automatically and therefore leaving the rest of the brain free to mull; and, a sort of imposed sensory deprivation and motor inactivity letting the brain mull? Maybe or maybe not. I mention this for those of you who are like me and too old and sore to ever run again.