The 'connectome' of our cerebral cortex

Hagmann et al. use diffusion mapping techniques to provide some awesome summary graphics of connectivity networks of our cerebral cortex. Regions of the neocortex are linked by a dense network of neural pathways, with several distinct nodes, like airline hubs. Their data:

...provides evidence for the existence of a structural core in human cerebral cortex. This complex of densely connected regions in posterior medial and parietal cortex is both spatially and topologically central within the brain. Its anatomical correspondence with regions of high metabolic activity and with some elements of the human default network suggests that the core may be an important structural basis for shaping large-scale brain dynamics. The availability of single-participant structural and functional connection maps now provides the opportunity to investigate interparticipant connectional variability and to relate it to differences in individual functional connectivity and behavior.

Click on figure to enlarge...

Where Ritalin acts in the brain to focus attention.

An interesting piece of work from Berridge's lab here at the University of Wisconsin shows that the cognition and attention enhancing drug Ritalin (methylphenidate, MPH) fine-tunes the functioning of neurons in the prefrontal cortex (PFC), which is involved in attention, decision-making and impulse control. While it enhances the efflux of the neurotransmitters norepinephrine and dopamine in PFC, it appears to have minimal effects elsewhere.

Only working memory–enhancing doses of MPH increased the responsivity of individual PFC neurons and altered neuronal ensemble responses within the PFC. The effects were not observed outside the PFC (i.e., within somatosensory cortex). In contrast, high-dose MPH profoundly suppressed evoked discharge of PFC neurons. These observations suggest that preferential enhancement of signal processing within the PFC, including alterations in the discharge properties of individual PFC neurons and PFC neuronal ensembles, underlie the behavioral/cognitive actions of low-dose psychostimulants.

Ecocultural basis of cognition

Farmers and fishermen are more holistic than herders. Uskul et al. offer a fascinating study on factors influencing holistic versus more focused perception:

It has been proposed that social interdependence fosters holistic cognition, that is, a tendency to attend to the broad perceptual and cognitive field, rather than to a focal object and its properties, and a tendency to reason in terms of relationships and similarities, rather than rules and categories. This hypothesis has been supported mostly by demonstrations showing that East Asians, who are relatively interdependent, reason and perceive in a more holistic fashion than do Westerners. We examined holistic cognitive tendencies in attention, categorization, and reasoning in three types of communities that belong to the same national, geographic, ethnic, and linguistic regions and yet vary in their degree of social interdependence: farming, fishing, and herding communities in Turkey's eastern Black Sea region. As predicted, members of farming and fishing communities, which emphasize harmonious social interdependence, exhibited greater holistic tendencies than members of herding communities, which emphasize individual decision making and foster social independence. Our findings have implications for how ecocultural factors may have lasting consequences on important aspects of cognition.

Bias at the ballot box.

Berger et al. provide an interesting demonstration of how susceptible a voter's choice is to environmental cues. The two types of study done are described in Tim Lincoln's review of this work in Nature:

The first was an analysis of results from a general election held in Arizona in 2000, the ballot for which included a proposition to raise state sales tax from 5.0% to 5.6%, to increase education spending. Polling stations included churches, schools, community centres and government buildings.

Berger et al. predicted that voting in a school would produce more support for the proposition than voting in other places. Indeed it did, but not by much compared with other documented effects on voter choice such as order on the ballot paper. Nonetheless, the effect persisted through tests for various other confounding factors (for example, the possibility of a consistently different level of voter turnout at school polling locations).

The second study was a carefully run online experiment that also involved a proposed tax increase to fund schools. The 'voting environment' was manipulated by exposing participants to typical images of schools or control images. The upshot was the same, with the school images prompting greater (and apparently unconscious) support for the initiative than, for example, an image of an office.

All in all, the authors conclude that what they call contextual priming of polling location affects how people vote. They reasonably wonder whether such factors could, for example, influence voting in a church on such matters as gay marriage and stem-cell research.

But here's a thought. In the event of science spending being on the political agenda, why not offer the lab as a polling station? But maybe dim that fluorescent lighting, and persuade all those bearded fellows in white coats to take the day off — or not, as the case may be.

Best visual illusion of the year

Check out the Best Visual Illusion of the Year contest.....

Anticipating the Future to ‘See’ the Present

The title of this post is also the title of an article by Benedict Carey that describes works supporting the idea that the brain uses a bag of ad hoc tricks to build a streaming model of the world. Because it takes the brain at least a tenth of a second to model visual information, it is always working with old information. The argument is that the brain has evolved to meet this problem by projecting or guessing a split second into the future when it perceives motion. By modeling the future during movement, it is “seeing” the present. These two illusions illustrate the process:

Leaning toward the image makes it appear as if it is bulging.

The radiating lines trick the brain into perceiving motion forward, so the center appears to bulge.

Body odors - brain processing different from similar common odors

Here is an edited paste-up of text and abstract from Lundström et al.

Humans are highly accurate at identifying individuals based solely on their body odors, being able to use signals conveyed in body odor to make accurate kin–nonkin judgments, and to detect minute differences in genetic composition of unknown individuals. While visual and auditory stimuli of high social and ecological importance are processed in the brain by specialized neuronal networks, such specialized processing has not yet been demonstrated for olfactory stimuli. The authors used positron emission tomography to ask whether the central processing of body odors differs from perceptually similar non-body odors as women smelled odors collected from friends and non-friends who had slept for seven nights with tight cotton t-shirts with cotton nursing pads sewn into the underarm area. Body odors activated a network consisting of the posterior cingulate cortex, occipital gyrus, angular gyrus, and the anterior cingulate cortex, none of which is believed to be related to olfactory processing. However, together they form an interesting pattern. Posterior cingulate cortex is known to be active in response to emotional stimuli, whereas the anterior cingulate cortex is believed to regulate attentional efforts. This suggests processing of body odors is similar to what previously has been demonstrated for highly emotional stimuli, such as visual images of snakes, where the posterior cingulate cortex works in concert with the anterior cingulate cortex. A separation in the processing of odors based on their source was observed. Smelling a friend's body odor activated regions previously seen for familiar stimuli, whereas smelling a stranger activated amygdala and insular regions akin to what has previously been demonstrated for fearful stimuli.

The data provide evidence that social olfactory stimuli of high ecological relevance are processed by specialized neuronal networks, just as has been demonstrated for auditory and visual stimuli.

What and Where pathways in auditory brain

The visual cortex has parallel processing streams that deal mainly either with the location of an image (the dorsal stream) or its identity (the ventral stream). It now appears that auditory cortex (in cats) has similar parallel processing of the location and identity of sounds. Here is the abstract from Lomber and Malhotra and a graphic from the summary by Sumner and Moore.

Studies of cortical connections or neuronal function in different cerebral areas support the hypothesis that parallel cortical processing streams, similar to those identified in visual cortex, may exist in the auditory system. However, this model has not yet been behaviorally tested. We used reversible cooling deactivation to investigate whether the individual regions in cat nonprimary auditory cortex that are responsible for processing the pattern of an acoustic stimulus or localizing a sound in space could be doubly dissociated in the same animal. We found that bilateral deactivation of the posterior auditory field resulted in deficits in a sound-localization task, whereas bilateral deactivation of the anterior auditory field resulted in deficits in a pattern-discrimination task, but not vice versa. These findings support a model of cortical organization that proposes that identifying an acoustic stimulus ('what') and its spatial location ('where') are processed in separate streams in auditory cortex.

Legend: The effects of cooling posterior and anterior regions of auditory cortex are doubly disassociated, with anterior regions being important for discriminating between sounds and posterior parts being important for localizing them.

Meeting George Bush versus Meeting Cinderella

The rest of the title of this article by von Cramon and Schubotz is "The Neural Response When Telling Apart What is Real from What is Fictional in the Context of Our Reality." Our ability to distinguish fact from fiction emerges early during our development, and by the age of 5, we not only differentiate reality from fiction but can also distinguish between different fictional worlds. The neural correlates underlying this ability are unknown. The authors obtain fMRI images showing significant difference in brain activity while processing real versus fictional conditions. The graphic is from the paper just to include a pretty picture, I'll spare you the details, because they really don't add all that much to the bottom line:

The processing of real and fictional scenarios activated a common set of regions including medial-temporal lobe structures. When the scenarios involved real people, brain regions associated with episodic memory retrieval and self-referential thinking, the anterior prefrontal cortex and the precuneus/posterior cingulate, were more active. In contrast, areas along the left lateral inferior frontal gyrus (shown in the graphic), associated with semantic memory retrieval, were implicated for scenarios with fictional characters. This implies that there is a fine distinction in the manner in which conceptual information concerning real persons in contrast to fictional characters is represented. In general terms, the findings suggest that fiction relative to reality tends to be represented in more factual terms, whereas our representations of reality relative to fiction are colored by personal subjectivity. What modulates our understanding of the relative difference between reality and fiction seems to be whether such character-type information is coded in self-relevant terms or not.

The authors note their agreement with the statement of William James: "In the relative sense, then, the sense in which we contrast reality with simple unreality, ... reality means simply relation to our emotional and active life

Older adults have a broader attention span

An article by Reistad-Long describes studies suggesting that a broader attention span may enable older adults to ultimately know more about a situation and the indirect message of what’s going on than their younger peers. For example, older people take longer to read passages that are interrupted with unexpected words or phrases, but are more likely to be successful at answering questions for which the out-of-place words might be answers. This might yield advantages in the real world, where it is not always clear what information is important, or will become important. Maybe we think of older people as wiser because they take in more information from a situation, and are able to combine it with a comparatively greater store of general knowledge.

Brain imaging of belief, disbelief, and uncertainty

A fascinating fMRI study by Sam Harris and colleagues has used functional magnetic resonance imaging (fMRI) to study the brains of 14 adults while they judged written statements to be true (belief), false (disbelief), or undecidable (uncertainty). (Yes, this is the same Sam Harris who wrote "The End of Faith" and "Letter to a Christian Nation."). To characterize belief, disbelief, and uncertainty in a content-independent manner, they included statements from a wide range of categories: autobiographical, mathematical, geographical, religious, ethical, semantic, and factual. They show that belief, disbelief, and uncertainty are mediated primarily by regions in the medial PFC, the anterior insula, the superior parietal lobule, and the caudate. The acceptance and rejection of propositional truth-claims appear to be governed, in part, by the same regions that judge the pleasantness of tastes and odors.

...the final acceptance of a statement as true or its rejection as false appears to rely on more primitive, hedonic processing in the medial prefrontal cortex and the anterior insula. Truth may be beauty, and beauty truth, in more than a metaphorical sense, and false propositions may actually disgust us.
...When compared with both belief and uncertainty, disbelief was associated in our study with bilateral activation of the anterior insula..., a primary region for the sensation of taste. The anterior insula has been regularly linked to pain perception and even to the perception of pain in others. This region, together with left frontal operculum (also active in the contrast disbelief - belief), appears to mediate negatively valenced feelings such as disgust. Studies of olfaction have shown that the left frontal operculum is engaged when subjects are required to make active judgments about the unpleasantness of odors. Thus, regions that have been regularly implicated in the hedonic appraisal of stimuli, often negative, appeared in our study to respond preferentially when subjects rejected written statements as false. Our results appear to make sense of the emotional tone of disbelief, placing it on a continuum with other modes of stimulus appraisal and rejection.
...Several psychological studies appear to support Spinoza’s conjecture that the mere comprehension of a statement entails the tacit acceptance of its being true, whereas disbelief requires a subsequent process of rejection...Understanding a proposition may be analogous to perceiving an object in physical space: We seem to accept appearances as reality until they prove otherwise...subjects assessed true statements as believable faster than they judged them as unbelievable or undecidable. Further, because the brain appears to process false or uncertain statements in regions linked to pain and disgust, especially in judging tastes and odors, this study gives new meaning to a claim passing the “taste test” or the “smell test.”

Rapid orienting to positive, as well as negative, emotional stimuli.

Most of the work on how emotions focus our attention has focused on negative stimuli (snakes, angry faces, etc.) Brosch et al. use ERP measurement to note that our attention also can very reliably be captured by positive nurturance stimuli such as baby faces. The results confirm that biological relevance, and not exclusively fear, produces an automatic spatial orienting toward the location of a stimulus. From the paper:

...we recorded event-related potentials from 20 subjects performing a dot-probe task in which the cues were fear-inducing and nurturance-inducing stimuli (i.e., anger faces and baby faces). Highly similar validity modulation was found for the P1 time-locked to target onset, indicating early attentional capture by both positive and negative emotional stimuli. Topographic segmentation analysis and source localization indicate that the same amplification process is involved whether attention orienting is triggered by negative, fear-relevant stimuli or positive, nurturance-relevant stimuli.

Illustration of the experimental sequence. Each trial started with a fixation cross. Then the cue, consisting of two images presented on the left and right sides of the screen, was presented briefly. One of the two pictures was an emotional face, and the other was a neutral face. Following offset of the face pair, the fixation cross was presented randomly for 100, 150, 200, 250, or 300 ms. Afterward, the target, a triangle pointing upward or downward, appeared for 150 ms in the location of one of the previously presented faces. In a valid trial, the triangle was in the location of the emotional image; in an invalid trial, the triangle was in the location of the neutral image. Some participants were required to respond if the triangle pointed upward, and the others were required to respond if the stimulus pointed downward. SOA = stimulus onset asynchrony.

Our facial touch sensitivity - enhanced by viewing a touch.

Studies have shown that observing touch on another person's body activates brain regions involved in tactile perception, even when the observer's body is not directly stimulated. Previous work has shown that in some synaesthetes, this effect induces a sensation of being touched. Serino et al. show in nonsynaesthetes, that

..when observers see a face being touched by hands, rather than a face being merely approached by hands, their detection of subthreshold tactile stimuli on their own faces is enhanced. This effect is specific to observing touch on a body part, and is not found for touch on a nonbodily stimulus, namely, a picture of a house...Thus, observing touch can activate the tactile system, and if perceptual thresholds are manipulated, such activation can result in a behavioral effect in nonsynaesthetes.The effect is maximum if the observed body matches the observer's body.

Figure - Visual stimuli used in the tactile confrontation task. In blocked trials, subjects viewed an image of their own face, another person's face, or a house. In each trial, the finger on the bottom left, the finger on the bottom right, or both fingers moved toward the target; in the touch condition, the finger (or fingers) actually touched the target, and in the no-touch condition, the finger (or fingers) reached a position 5 cm away from the target.

Think of when you might have watched a romantic touch in a movie, sitting next to someone you wished would stroke you.....

Personality dominance: reflection in brain imaging and spatial attention

Here are two different takes, from the Journals Neuron and Psychological Science on correlates of human dominance hierarchies:
In the Neuron article, Zink et al. monitor the brain activity patters of gamers that form in response to status cues. They set artificial hierarchies by assigning 72 volunteers a skill rank in a computer game that flagged onscreen opponents as superior or inferior players. But the opponents were really computers, and the games and ranks were rigged so that status was only perceived. One finding was that brain regions associated with emotion or pain become busier when gamers are losing to inferior opponents. From their abstract:

....In both stable and unstable social hierarchies, viewing a superior individual differentially engaged perceptual-attentional, saliency, and cognitive systems, notably dorsolateral prefrontal cortex. In the unstable hierarchy setting, additional regions related to emotional processing (amygdala), social cognition (medial prefrontal cortex), and behavioral readiness were recruited...social hierarchical consequences of performance were neurally dissociable and of comparable salience to monetary reward, providing a neural basis for the high motivational value of status...results identify neural mechanisms that may mediate the enormous influence of social status on human behavior and health.

The article in Psychological Science deals with our tendency to represent dominance in vertical terms. This tendency is apparent in linguistic metaphor, anthropological data, sociological data, and scientific theories of personality dominance. The ubiquity of such mappings is consistent with the central postulate of the metaphor-representation perspective: that people must draw from the perceptual domain, as reflected in common metaphors, when attempting to represent abstract concepts such as dominance or power. Moeller et al. examine whether dominant personality correlates with performance on vertical versus horizontal discriminations.

Previous research has shown that dominant individuals frequently think in terms of dominance hierarchies, which typically invoke vertical metaphor (e.g., "upper" vs. "lower" class). Accordingly, we predicted that in spatial attention paradigms, such individuals would systematically favor the vertical dimension of space more than individuals low in dominance. This prediction was supported by two studies (total N = 96), which provided three tests involving two different spatial attention paradigms. In all cases, analyses controlling for speed of response to horizontal spatial probes revealed that more dominant individuals were faster than less dominant individuals to respond to probes along the vertical dimension of space. Such data support the metaphor-representation perspective, according to which people think in metaphoric terms, even in on-line processing tasks. These results have implications for understanding dominance and also indicate that conceptual metaphor is relevant to understanding the cognitive-processing basis of personality.

Our brains can choose our actions 10 sec before awareness

Here is an elegant update from Soon et al. of the continuing story that started with Libet's original observation that supplementary motor area (SMA) becomes active before our subjective sense of consciously willing an action. This work ignited a a long controversy as to whether subjectively 'free' decisions are determined by brain activity ahead of time. These new results go substantially further than those of previous studies by showing that the earliest predictive information is encoded in specific regions of frontopolar and parietal cortex, up to 10 seconds before it enters awareness (and not in SMA), presumably reflecting the operation of a network of high-level control areas that begin to prepare an upcoming decision. This preparatory time period in high-level control regions is considerably longer than that reported previously for motor-related brain regions.


Figure (click to enlarge) Color-coded brain areas show regions where the specific outcome of a motor decision could be decoded before (bottom, green) and after (top, red) it had been made. The graphs separately depict for each time point the accuracy with which the subject's free choice to press the left or right button could be decoded from the spatial pattern of brain activity in that region (solid line, left axis; filled symbols, significant at P < 0.05; open symbols, not significant; error bars, s.e.m.; chance level is 50%). As might be expected, the decoding accuracy was higher in cortical areas involved in the motor execution of the response than in areas shaping the upcoming decision before it reaches awareness (note the difference in scale). The vertical red line shows the earliest time at which the subjects became aware of their choices. The dashed (right) vertical line in each graph shows the onset of the next trial. The inset in the bottom left shows the representative spatial pattern of preference of the most discriminative searchlight position in frontopolar cortex for one subject (ant, anterior; sup, superior)

An integrated view of our subjective energies.

I recently attended the Wisconsin Symposium on Emotion (Now in its 14th year). Its topic was "Emotion, Consciousness and Psychopathology." I want to mention the talk given by A.D.(Bud) Craig, which was a real tour de force, the kind of science I feel I can integrate with my own personal experience. Its title was "How do you feel? The neurobiological basis for human awareness of feelings from the body." I have referenced Craig's work in previous posts, also check here. Here are PDFs of his two recent review articles in Trends in Cognitive Science (2005) and Nature Reviews Neuroscience (2002) which I recommend.

His view is that in our nervous systems, there is a fundamental bilateral partitioning or separation, from basic spinal cord and brain stem homeostatic systems to our highest prefrontal lobe functions, in which the right side spends energy and the left side brings it in. This reflects the relative activities of the sympathetic versus parasympathetic nervous systems. (enter 'parasympathetic' in the google search box in the left column to see some previous mindblog posts on autonomic regulation of chilling out versus getting excited).

The right and left insula appear to be central in processing feelings, all the way from basic (interoceptive) body sensing (posterior insula) up through subjective feelings, disgust, trust, anger, social hurt, empathic happiness, lust, pain, etc. All of these are homeostatic emotional currency that help regular body balance all the way from from blood pressure, glucose, heart rate, salt regulation, up through social self image. Here is a graphic from his 2005 article that shows the central role of the left and right anterior insula (which act as the sensory cortex of limbic system) in receiving information about body state and feeling from sympathetic and parasympathetic input and then interacting with anterior cingulate (the motor cortex of the limbic system) and frontal cortex. (click to enlarge):


Positive emotions (pleasant music, maternal emotions) correlate with enhanced left parasympathic, left anterior insula, left anterior cingulate and left frontal activation, while negative emotions (anger, fear, etc.) enhance activation of the corresponding structures on the right side.

Some very simple manipulations can stroke the relative activation of these two systems. Slowing one's breathing, as usually happens during meditation dials up the left anterior insula system, while breathing more rapidly increases anxiety and right anterior insula activity. In fact, giving instruction to a subject to breathe more slowly or more rapidly can change their emotional reaction to stimuli. In one experiment mentioned by Craig, a picture of a baby seal elicited warm nuturing emotions when breathing was slowed, but when breathing was increased, subjects were more likely to suspect the seal might attack or bite them! Experiments are now being attempted to measure whether oxytocin (the affiliative, trusting hormone) correlate with left insular activation while right insula activation correlates with cortisone (the stress hormone) release.

This sort of global description fascinates me, because it instructs us in how integrated a package we are, and how attention to some of the basement details of our daily life (such as breathing) can fundamentally alter our mood and temperament.

Attention regulation in meditation

From the Laboratory of Affective Neuroscience at the Univ. of Wisc. in Madison, Lutz, Davidson and collegues offer a review in Trends in Cognitive Science (PDF here) of studies of the effects on attention and emotion processes of two broad categories of meditation: focused attention and open monitoring.

More on language and perception...

Christine Kenneally writes a nice summary of current work on how language can nudge our perception. One interesting result demonstrates that labeling different categories enhances one's ability to discriminate between them. She discusses the work of Boroditsky mentioned in my Feb. 22 post, and work showing that in giving us symbols for spatial patterns, spatial language helps us carve up the world in specific ways. It appears that the ability to count is necessary to deal with large, specific numbers. And the only way to count past a certain point is with language.

Space versus body based number representation

Here is a fascinating bit of work from Brozzoli et al. showing how our touch perception can reveal the dominance of spatial over digital representation of numbers.

We learn counting on our fingers, and the digital representation of numbers we develop is still present in adulthood. Such an anatomy–magnitude association establishes tight functional correspondences between fingers and numbers. However, it has long been known that small-to-large magnitude information is arranged left-to-right along a mental number line. Here, we investigated touch perception to disambiguate whether number representation is embodied on the hand ("1" = thumb; "5" = little finger) or disembodied in the extrapersonal space ("1" = left; "5" = right). We directly contrasted these number representations in two experiments using a single centrally located effector (the foot) and a simple postural manipulation of the hand (palm-up vs. palm-down). We show that visual presentation of a number ("1" or "5") shifts attention cross-modally, modulating the detection of tactile stimuli delivered on the little finger or thumb. With the hand resting palm-down, subjects perform better when reporting tactile stimuli delivered to the little finger after presentation of number "5" than number "1." Crucially, this pattern reverses (better performance after number "1" than "5") when the hand is in a palm-up posture, in which the position of the fingers in external space, but not their relative anatomical position, is reversed. The human brain can thus use either space- or body-based representation of numbers, but in case of competition, the former dominates the latter, showing the stronger role played by the mental number line organization.

What do you see and not see?

Here is an update of a well known demonstration that I have used in my lectures (and in my "I-Illusion" web-lecture at dericbownds.net) - on what happens when you focus your attention.