Brain correlates of hysteria.

The Tuesday Science section of the New York Times (Sept 26) has an interesting article on hysteria, a fashionable syndrome in the Victorian era which has "disappeared" during this century. Actually the term "conversion disorder" is now used to describe an ill-defined syndrome with no obvious physical cause, usually involving paralysis of a portion of the body or seizures. Sigmund Freud suggested from his case studies that hysteria is something in the psyche or the mind being expressed physically in the body.


The 19th-century French neurologist Jean-Martin Charcot, shown lecturing on hysteria

Peter W. Halligan at Cardiff, co-founder of the journal Cognitive Neuropsychiatry and his colleagues "analyzed the brain function of a woman who was paralyzed on the left side of her body (Cognition, 64, B1-B8, 1997). First they conducted numerous tests to ensure that she had no identifiable organic lesion...When the woman tried to move her “paralyzed leg,” her primary motor cortex was not activated as it should have been; instead her right orbitofrontal and right anterior cingulate cortex, parts of the brain that have been associated with action and emotion, were activated. They reasoned that these emotional areas of the brain were responsible for suppressing movement in her paralyzed leg."






Fig. 1. Relative rCBF (blood flow measured by magnetic resonance imaging) increases associated with movement of the right (good) leg. The figure reveals relative rCBF increases when the normal (right) leg is moved that do not occur when attempts to move the bad (left) leg are made. There is left hemisphere neuronal activation centered on the primary sensory and motor cortex. Additional activation is seen in the left inferior parietal cortex and the right inferior temporal cortex.
Fig. 2. Relative rCBF increases associated with attempted movement of the left (bad) leg. This reveals relative rCBF increases during attempts to move the bad (left) leg that did not occur when the good (right) leg was moved. There is activation in the right anterior cingulate and the right orbito-frontal cortex.

“The patient willed her leg to move,” Dr. Halligan said. “But that act of willing triggered this primitive orbitofrontal area and activated the anterior cingulate to countermand the instruction to move the leg. She was willing it, but the leg would not move.”

"Subsequent studies have bolstered the notion that parts of the brain involved in emotion may be activated inappropriately in patients with conversion disorder and may inhibit the normal functioning of brain circuitry responsible for movement, sensation and sight......Both its persistence and its pervasiveness suggest that hysteria may be derived from an instinctual response to threat. Total shutdown, in the form of paralysis, for example, is not an entirely untoward or unheard of response to an untenable situation. (Think of deer in the headlights.)"

Analogs of human language areas in monkey brains...

A recent article in Nature Neuroscience describes how species-specific calls activate homologs of Broca's (speech generation) and Wernicke's (speech comprehension) areas in the macaque monkey. The authors identified neural systems associated with perceiving species-specific vocalizations in rhesus macaques using positron emission tomography (PET). These vocalizations evoked distinct patterns of brain activity in homologs of the human perisylvian language areas. Rather than resulting from differences in elementary acoustic properties, this activity seemed to reflect higher order auditory processing. Their finding suggests the possibility that the last common ancestor of macaques and humans, which lived 25–30 million years ago, possessed key neural mechanisms that were plausible candidates for exaptation during the evolution of language.


Figure, Broca's area of the human brain (on the right) includes Brodmann's area 44. The macaque brain (on the left, actually smaller than a human brain) has a corresponding area.

Booze inhibits serotonin re-uptake, but not like Prozac does....

McGowan comments in Nature Reviews Neuroscience on an article by Daws et. al. in Journal of Neuroscience: This study shows that ethanol inhibits clearance of the neurotransmitter serotonin (5-HT) from the extracellular fluid in the mouse hippocampus, and that, surprisingly, this occurs through a mechanism that is independent of the serotonin transporter (5-HTT) which is inhibited by selective serotonin reuptake inhibitors (SSRIs) such as prozac (fluoxetine) or Paxil (paroxetine). The effect is actually enhanced if the transporter is genetically or pharmacologically inactivated. This study suggests that "blocking the removal of 5-HT underlies, at least in part, the effects of ethanol in the brain. It remains to be determined exactly how ethanol inhibits 5-HT removal from the extracellular fluid. The noradrenaline transporter, which also transports serotonin and is expressed in the hippocampus, is one candidate site of action. However, more work will be required to confirm a role for this transporter in the influence of alcohol on neuronal function and behaviour. These findings could help to explain the positive association between a polymorphism in the promoter region of human 5-HTT, which confers low-expression of 5-HTT, and alcoholism."

Why Christians and Conservatives should accept evolution.

Michael Shermer, in the Oct. issue of Scientific American, gives these arguments for being both a conservative Christian and a Darwinian:
1. EVOLUTION FITS WELL WITH THEOLOGY. What difference does it make when or how God created life (10 thousand or 10 billion years ago?, by natural forces or spoken word?) - All faiths, including Christians, should embrace modern science for what it has done to reveal the magnificence of the divine in a depth and detail unmatched by ancient texts.
2. CREATIONISM IS BAD THEOLOGY. The watchmaker God of intelligent-design creationism make God just a genetic engineer slightly more advanced than we are... this is belittling... an omniscient God must be above such human-like descriptions and constraints.
3. EVOLUTION EXPLAINS ORIGINAL SIN AND THE CHRISTIAN MODEL OF HUMAN NATURE. Like other social primates, we evolved within-group amity and between-group enmity. By nature, then, we are cooperative and competitive, altruistic and selfish, greedy and generous, peaceful and bellicose. Moral codes and a society based on the rule of law are necessary to accentuate the positive and attenuate the negative sides of our evolved nature.
4. EVOLUTION EXPLAINS FAMILY VALUES. In humans and other social mammals brain pathways and hormonal mechanisms have evolved to support attachment and bonding, cooperation and reciprocity, sympathy and empathy, conflict resolution, community concern and reputation anxiety, and response to group social norms. Religious moral codes reflect these evolved moral natures.
5. EVOLUTION EXPLAINS CONSERVATIVE FREE-MARKET ECONOMICS. Charles Darwin's "natural selection" is precisely parallel to Adam Smith's "invisible hand." Darwin showed how complex design and ecological balance were unintended consequences of competition among individual organisms. Smith showed how national wealth and social harmony were unintended consequences of competition among individual people. Nature's economy mirrors society's economy. Both are designed from the bottom up, not the top down.

The Macbeth Effect: washing away your sins.

This work has received some notice, and I thought it worth abstracting the clever experiments involved.

Edited from Zhong et al.: Physical cleansing has been a focal element in religious ceremonies for thousands of years. The prevalence of this practice suggests a psychological association between bodily purity and moral purity. In three studies, the authors explored what they call the "Macbeth effect"—that is, a threat to one's moral purity induces the need to cleanse oneself. In three studies they let this effect reveal itself through an increased mental accessibility of cleansing-related concepts, a greater desire for cleansing products, and a greater likelihood of taking antiseptic wipes.

In the first study they asked participants to recall in detail either an ethical or unethical deed from their past and to describe any feelings or emotions they experienced. Then they engaged in a word completion task in which they converted word fragments into meaningful words. Of the six word fragments, three (W _ _ H, SH _ _ ER, and S _ _ P) could be completed as cleansing-related words (wash, shower, and soap) or as unrelated words (e.g., wish, shaker, and step). Participants who recalled an unethical deed generated more cleansing-related words than those who recalled an ethical deed, suggesting that unethical behavior enhances the accessibility of cleansing-related concepts

The second study investigated whether an implicit threat to moral purity produces a psychological desire for cleansing, through expressed preferences for cleansing products. Participants were told that the experiment was investigating the relationship between handwriting and personality and were asked to hand-copy a short story written in the first person. The story described either an ethical, selfless deed (helping a co-worker) or an unethical act (sabotaging a co-worker). Participants then rated the desirability of various products from 1 (completely undesirable) to 7 (completely desirable). Cleansing products included Dove shower soap, Crest toothpaste, Windex cleaner, Lysol disinfectant, and Tide detergent; other products included Post-it Notes, Nantucket Nectars juice, Energizer batteries, Sony CD cases, and Snickers bars. Copying the unethical story increased the desirability of cleansing products as compared to copying the ethical story, with no differences between conditions for the noncleansing products

In the final study participants described an unethical deed from their past (the same recall task as in the first study). Afterwards, they either cleansed their hands with an antiseptic wipe or not. Then they completed a survey regarding their current emotional state. After completing the survey, participants were asked if they would volunteer without pay for another research study to help out a desperate graduate student. Presumably, participants who had cleansed their hands before being solicited for help would be less motivated to volunteer because the sanitation wipes had already washed away their moral stains and restored a suitable moral self.

As predicted, physical cleansing significantly reduced volunteerism: 74% of those in the not-cleansed condition offered help, whereas only 41% of participants who had a chance to cleanse their hands offered help. Thus, the direct compensatory behavior (i.e., volunteering) dropped by almost 50% when participants had a chance to physically cleanse after recalling an unethical behavior.

Thus, the authors showed that physical cleansing alleviates the upsetting consequences of unethical behavior and reduces threats to one's moral self-image. Daily hygiene routines such as washing hands, as simple and benign as they might seem, can deliver a powerful antidote to threatened morality, enabling people to truly wash away their sins.

Brain Stressed Out? Try this machine.......

In today's mail, a catalog from "The Spiritual Tech" team at Sounds True company in Boulder Co. Any widget you might want to give your brain a tune-up is offered: MINDSPA (Light and Sound Therapy for Brain Enhancement, $200); THE STRESS ERASER (Feel Calm and Relaxed in Minutes Anytime, Anywhere, $300); THE RELAXMATE II (Photo-stimulation therapy for stress relief, $150); THE JOURNEY TO WILD DIVINE AND WISDOM QUEST (a spiritual quest computer game with biofeedback technology, $210...I have to admit I enjoyed playing with this product when it came out). All this in addition to a number of boxed CD sets offering auditory enlightenment.

Even though I'm sympathetic techniques for calming and clearing the old brain (I use some myself), I can't help but crack up and have an immediate "WACKO" reaction to such a glossy slick catalog. So if I buy all of them I'm home free?!

And you thought you had problems....

A treatment for acquired anxiety disorders in humans?

Cai et. al. show in a rodent model that administration of glucocorticoids immediately after reactivation of a contextual fear memory significantly diminishes subsequent recall of that fear memory. Glucocorticoids appear to both decrease fear memory retrieval and also augment consolidation of fear memory extinction.

The experiments used mice with a classical fear conditioning paradigm in which a novel environment is paired with footshock. Re-exposure to the training environment 48 hours later elicited significant fear responses, showing reactivation of a learned association between this environment and the aversive footshock stimulus. If the mice were injected 2 to 5 min after this reactivation with the endogenous stress hormone, corticosterone, they showed decreased contextual fear memory in subsequent tests.

Glucocorticoids have been used in human clinical trials to decrease symptoms of PTSD (post traumatic stress disorder) and phobia. The work of Cai et al. suggest that not only is the particular pharmacologic agent of importance, but that the reactivation of relevant memories, timing of administration relative to reactivation, and number of reactivation trials can have an impact on the desired outcome. The use of mice allows investigation of the underlying receptor subtypes and mechanisms of the glucocorticoid effect on fear memories. This might point to more specific therapy in future human trials that avoid some side effects of general treatment with glucocorticoids.

Innate Imitation of Facial Expressions by Newborn Monkeys

Almost 30 years ago, Meltzoff and coworkers reported that 2- to 3-wk-old human infants responded with corresponding matching behaviors to specific human facial gestures, such as mouth opening, tongue protrusion, and lip protrusion. We are born with a computational model that transforms visual information into motor commands, a phenomenal connection between self and others exists from birth. This innate link brings us experientially into a world of others. There seems to be a clear evolutionary rationale for this: in highly social primates the imitation of affiliative and other facial gestures could be a basis of bonding to caretakers and fine tuning complex social interactions. (See my Feb. 10 post on the mirror system of neurons that might underlie this behavior).

The evolutionary origins of this mirroring behavior may extend further back that we have thought. The capacity of neonates to imitate adult facial movements has been thought to be limited to humans and perhaps the ape lineage. Now Ferrari et al report the behavioral responses of infant rhesus macaques (Macaca mulatta) to human facial and hand gestures: lip smacking, tongue protrusion, mouth opening, hand opening, and opening and closing of eyes.

Here are pictures they provide of monkey infants tested 1-3 days after birth, imitating mouth opening and tongue protrusion. By day 7 the imitation behavior had largely disappeared, unlike human and chimpanzee behaviors. This might be because these monkeys mature very rapidly, and by one week may already be leaving their mothers for short periods of time.

The Mind Games of Neuroeconomics

The Sept. 18 issue of the The New Yorker has an engaging article by John Cassidy that reviews collaborative work by economists and neuroscientists studying how multiple systems in the brain balance competitions between emotion and reason in making economic decisions. By now a substantial list of irrational economic behaviors have been documented that frequently make the rational Homo economicus of mathematical economics irrelevant. The rational-actor framework doesn't fit with stock-market bubbles, drug addiction, and compulsive shopping. Behavorial economists now examine brain activity during risk aversion scenarios, trust in fairness games, choosing between immediate and delayed rewards. One concept that has emerged is "asymmetric paternalism" a new political philosophy based on the idea of saving people from the vagaries of their limbic regions. One example would be retirement planning. Because company 401(k) retirement plans are often optional, many people fail to join them. The lure of spending money on short term goals is too great, even given the greater longer term return of money put in a retirement plan. In companies that automatically include their employees in such a plan unless they opt out, enrollment rates are sharply higher.

Culture Shapes Arithmetic in the Brain

A collaborative study by Chinese and American authors has suggested that our mother tongue might influence the development of the brain circuits involved in processing numbers and arithmetic. They used Arabic digits (a symbol system shared by both languages, rather than phonological or orthographic symbols) to present simple problems (as in 3 + 4 = ?). Using functional MRI, they demonstrated a differential cortical representation of numbers between native Chinese and English speakers (NCS and NES). Contrasting to native English speakers, who largely employ a language process that relies on the left perisylvian cortices for mental calculation such as a simple addition task, native Chinese speakers, instead, engage a visuo-premotor association network for the same task.

"Remarkable differences between NES and NCS were found during the condition of Number representation, especially in the left hemisphere ( B and D). The activation in NES is greater in the left SMA, Broca area, and Wernicke area (Wn), compared with the corresponding areas in NCS. Meanwhile, the occipito-parietal pathway, sensorimotor areas (including the cerebellum), as well as the frontal cortex, show a similar level of activation for both NCS and NES during the Number condition, which is congruent with the suggestion that the classical number-processing model involves verbal, analogue, and visual components. Importantly, much larger brain activation was found at a region in-between BA6, BA8, and BA9 in NCS. We termed this region as a premotor association area (PMA), which has been previously associated with visuo-spatial processing and various functions more closely related to cognitive than to motor processes in humans and nonhuman primates as well."

The authors note that, in addition to mother tongue, it is possible that different teaching methods across cultures, or variations in genetic disposition, could also prime the brains of Chinese and English speakers to solve mathematical equations in different ways.

MRI Detection of Brain Awareness in the Vegetative State

A fascinating report by Owen et al in Science documents one case in which a woman, completely unresponsive and diagnosed as being in a vegetative state, showed responses in her language and motor brain areas that were indistinguishable from normal. From a review by Miller: "Five months after an auto accident, she was unresponsive, unable to communicate, and met the clinical criteria for vegetative state. However, fMRI scans showed that language-processing regions of her brain became active when words were spoken to her but not when she was exposed to nonspeech sounds. Sentences containing ambiguous words such as "creek/creak" activated additional language regions, as they do in healthy people. These findings indicated that she retained some ability to process language... In another test, the researchers instructed the woman to picture herself playing tennis or walking through her house. In healthy people, imagining each activity activates a different set of brain areas involved in planning movements. The patient's fMRI scans showed an identical pattern--clear evidence, Owen and colleagues say, that she made a conscious decision to follow their instructions."

"Although some researchers aren't convinced Owen's team has cinched the case for consciousness in this woman, most agree that the fMRI scans reveal evidence of cognition that could not have been anticipated from standard MRI scans....Owen hopes to build on this work to develop a battery of fMRI tests for measuring cognitive functions in brain-damaged patients who are unable to communicate. He says this approach might someday be used to customize a patient's rehabilitation. For instance, if a patient's fMRI scans revealed an incapacitated visual system but a working auditory system, therapists could employ speech and sound."

Fatherhood changes the prefrontal cortex.

Like human fathers, male marmosets help raise their young. Neuroimaging studies show that stimuli related to one's own child activate the anterior paracingulate and orbitofrontal areas of the prefrontal cortex (PFC). The PFC shows structural plasticity in adulthood and contains receptors for several neuropeptides implicated in parental behavior, such as vasopressin, oxytocin and prolactin. Kozorovitskiy et al now report in Nature Neuroscience that first-time and experienced marmoset fathers have enhanced density of dendritic spines on pyramidal neurons in prefrontal cortex as compared to non-fathers. In parallel, the abundance of vasopressin V1a receptors and the proportion of V1a receptor–labeled dendritic spines increase. How this links to function and behavior is not known, and it would be interesting to see if similar changes are seen in the brains of nonparental caregivers (since marmosets breed cooperatively).

Left) Marmoset father carrying infants. Right) Pyramidal neuron of a marmoset father, with close-up views of apical (a) and basal (b) dendrites.

God on the Brain

The Economist has a nice review and critical discussion of work by Mario Beauregard and collaborators at the Univ. of Montreal doing fMRI imaging of the brains of Carmelite nuns as they recall experiences of mystical union (by definition such experiences can not be summoned at will). The idea is based on the fact that imagining an experience usually activates the same brain regions that are active when the experience is actually taking place. Not surprisingly, there is no "God spot" in the brain, and activity in a number of brain regions, notably emotional areas, correlates with the recall of union. From their abstract in Neuroscience Letters (Volume 405, Issue 3 , 25 September 2006): "The brain activity of Carmelite nuns was measured while they were subjectively in a state of union with God. This state was associated with significant loci of activation in the right medial orbitofrontal cortex, right middle temporal cortex, right inferior and superior parietal lobules, right caudate, left medial prefrontal cortex, left anterior cingulate cortex, left inferior parietal lobule, left insula, left caudate, and left brainstem. Other loci of activation were seen in the extra-striate visual cortex. These results suggest that mystical experiences are mediated by several brain regions and systems."

Brain imaging has been to used to study a number of other altered states of consciousness, such as the phantom limb phenomenon and out of body experiences. Brain damage in the region of junction of the temporal and parietal lobes can alter perception of personal and extrapersonal space, and other studies have shown the changes in activation in this region correlates with meditative experiences of sensing sensing a greater interconnectedness of things, and dissolution of self into some larger entity.

The central role of "construals" in determining performance... the power of brief interventions

An article in the Sept. 1 issue of Science by Cohen et. al. and an accompanying review by Wilson point out the power of brief interventions that change people's self- and social perceptions.

You may... "undoubtedly be surprised, or even incredulous, that a 15-min intervention can reduce the racial achievement gap by 40%. Yet this is precisely what Cohen et al. .... African American seventh graders randomly assigned to write about their most important values achieved significantly better end-of-semester grades than students in a control condition. How can this be?"

The table shows the result of this and similar studies (click to enlarge):

Legend: Brief theory-based interventions improved students' grades [increases shown on a four-point grade point average (GPA) scale, relative to randomly assigned control groups].

"The Cohen et al. study and the others like it illustrate key social psychological points. It can be as important to change people's "construals"--their interpretations of the social world and their place in it--as it is to change the objective environment....It is not clear why students in the Cohen et al. sample failed to self-affirm on their own. Why did it take an in-class essay to focus students' attention on values that were important to them? Issues of generalizability also arise, such as whether the self-affirmation exercise would work with younger age groups."

Seligman's Happiness Regimen...

An article in the August issue of Discover Magazine discusses whether we can train ourselves to be happy. Classes are now taught on obtaining happiness, and utilize such exercises as writing and reciting a "gratitude" letter to a friend and jotting down three happy events of each day every night for a week. Instead of trying to figure out why you are sad, the emphasis is on training the mind to focus on the past as being very positive.


credit: Discover Magazine

The article focuses on an interview with Martin Seligman, who coined the term positive psychology in 1998 when he was president of the American Psychological Association. The association's official journal devoted its entire January 2000 issue to the subject. Some 350 psychologists from 23 countries attended the seventh annual Positive Psychology International Summit last October; as evidence of the movement's mainstream credentials, the next one, this fall, is cosponsored by Toyota. You can now subscribe to the Journal of Happiness Studies and buy one of Seligman's best-selling books, like Authentic Happiness or Learned Optimism.

...Happiness is a surprisingly contentious subject, and at least some psychologists argue that "think positive" exhortations should be left to pop purveyors like Norman Vincent Peale and Tony Robbins. "We live in a culture that already expects you to be happy all the time. I call it the tyranny of the positive attitude," grouses Barbara Held, professor of psychology at Bowdoin College and the author of Stop Smiling, Start Kvetching. In Held's view, having the positive psychology movement throw its weight behind that cultural bias serves up a double whammy: People who feel bad must now shoulder the added weight of feeling defective for feeling bad. "People say we are trying to tell people what kind of lives to lead," Seligman responds. "But I'm old-fashioned about science. I think science needs to be descriptive. I am just trying to describe." He wants to leave the choice of whether to follow to others.

You might enjoy having a look at the the Positive Psychology Center and Authentic Happiness wesites.

The Expert Mind

I've been meaning to mention an interesting article in the August issue of Scientific American, by Philip Ross, on how people become experts in different fields of accomplishment.

Some clips ard paraphrase from that article: Some of the most clear research on expertise has studied skill at chess, which can be clearly measured. What emerges is that the expert relies not so much on an intrinsically stronger power of analysis as on a store of structured knowledge. Similar results have been demonstrated in bridge players (who can remember cards played in many games), computer programmers (who can reconstruct masses of computer code) and musicians (who can recall long snatches of music). Ability in one area tends not to transfer to another. American psychologist Edward Thorndike first noted this lack of transference over a century ago, when he showed that the study of Latin, for instance, did not improve command of English and that geometric proofs do not teach the use of logic in daily life.


Figure from Amidzic et al. (2001) Brain activity in chess masters is different from the pattern observed in novices. Relationship between chess-playing skill (Elo rating scale) and the relative share of dipoles located in medial temporal lobe structures (black) and in the frontal and parietal cortices (red). In weaker players more activfity occurred in the brain's medial temporal lobe than in the frontal and parietal cortices, which suggests that the amateurs were analyzing unusual new moves. In gradmasters, however, the frontal and parietal cortices were more active, indicating that they were retrieving information from long term memory.

It takes enormous effort to build these structures in the mind. Herbert Simon coined a psychological law of his own, the 10-year rule, which states that it takes approximately a decade of heavy labor to master any field. Even child prodigies, such as Gauss in mathematics, Mozart in music and Bobby Fischer in chess, must have made an equivalent effort, perhaps by starting earlier and working harder than others. K.A. Ericsson argues that what matters is not experience per se but "effortful study," which entails continually tackling challenges that lie just beyond one's competence...Having reached an acceptable performance--for instance, keeping up with one's golf buddies or passing a driver's exam--most people relax. Their performance then becomes automatic and therefore impervious to further improvement. In contrast, experts-in-training keep the lid of their mind's box open all the time, so that they can inspect, criticize and augment its contents and thereby approach the standard set by leaders in their fields...

At this point, many skeptics will finally lose patience. Surely, they will say, it takes more to get to Carnegie Hall than practice, practice, practice. Yet this belief in the importance of innate talent, strongest perhaps among the experts themselves and their trainers, is strangely lacking in hard evidence to substantiate it...motivation appears to be a more important factor than innate ability in the development of expertise. It is no accident that in music, chess and sports--all domains in which expertise is defined by competitive performance rather than academic credentialing--professionalism has been emerging at ever younger ages, under the ministrations of increasingly dedicated parents and even extended families.

Neural operations that give rise to a unitary sense of self.

An interesting article by Moran et. al. in Journal of Cognitive Neuroscience: They examined whether the cognitive and affective components of self-reflection can be dissociated using functional magnetic resonance imaging. Using a simple paradigm in which subjects judged the personal relevance of personality characteristics that were either favorable (e.g., "honest") or unfavorable (e.g., "lazy"), they found that distinct neural circuits in adjacent regions of the prefrontal cortex subserve cognitive and emotional aspects of self-reflection. The medial prefrontal cortex responded only to material that was self-descriptive, and this did not differ as a function of the valence of the trait. When material was judged to be self-relevant, the valence of the material was resolved in an adjacent region of ventral anterior cingulate.


Figure Legend: Whole-brain ANOVA analysis revealed a main effect of self-relevance (top left) in the medial prefrontal cortex (MPFC) and posterior cingulate cortex (pCC), a main effect of valence (top right) in the ventral anterior cingulate cortex (vACC), and a self-relevance by valence interaction (bottom left) in the vACC, the dorsal anterior cingulate cortex (dACC), and the supplementary motor area (SMA). To qualitatively identify whether brain regions identified in the ANOVA analysis showed a strong bias toward one of the two main effects, a self-relevance/valence sensitivity measure (F ratio) was computed on a voxel-by-voxel basis by dividing the self-relevance F score for each voxel by the valence F score. Voxels that did not yield a significant main effect of either self-relevance or valence were excluded from further analysis to avoid spurious F ratio effects. To facilitate visualization of this sensitivity measure, F ratios were transformed to a logarithmic scale. Voxels that were more sensitive to trait valence yielded negative values (blue color scale), whereas voxels that were more sensitive to self-relevance yielded positive values (yellow color scale). Voxels at the tail end of the color scales were those voxels that exhibited the greatest bias toward trait valence and self-relevance, respectively. Voxels in the MPFC (BA 10) and two regions of the pCC (BA 29/30 and BA 23) demonstrated greater sensitivity to self-relevance, whereas voxels in the vACC (BA 25) demonstrated greater sensitivity to trait valence.

Avoiding Punishment is its Own Reward...

Work by Kim et al employs functional imaging to suggest a similar role for the human medial orbitofrontal cortex in processing the receipt of a reward and the successful avoidance of an aversive outcome.


Figure: Medial OFC showing a significant increase in activity after avoidance of an aversive outcome as well as after obtaining reward. No other brain areas showed significant effects at p < 0.001.

These results are compatible with the possibility that activity in the medial OFC during avoidance reflects an intrinsic reward signal that serves to reinforce avoidance behavior. Activity in the medial OFC not only increased after avoiding an aversive outcome or receiving reward, but also decreased after failing to obtain a reward or receiving an aversive outcome. Consequently, this region shows a fully opponent response profile to rewarding and aversive outcomes and their omission.

Making faces in the brain

Some regions of the inferior temporal cortex (IT) respond with high selectivity to faces. Afraz et al. have shown a causal link between activity of these region and actual face perception measured behaviorally. Artificially activating the right neurons at the right time causes visual perception of a face. This new result shows that such neurons directly underlie the recognition of complex objects. Their abstract:

"The inferior temporal cortex (IT) of primates is thought to be the final visual area in the ventral stream of cortical areas responsible for object recognition. Consistent with this hypothesis, single IT neurons respond selectively to highly complex visual stimuli such as faces. However, a direct causal link between the activity of face-selective neurons and face perception has not been demonstrated. In the present study of macaque monkeys, we artificially activated small clusters of IT neurons by means of electrical microstimulation while the monkeys performed a categorization task, judging whether noisy visual images belonged to 'face' or 'non-face' categories. Here we show that microstimulation of face-selective sites, but not other sites, strongly biased the monkeys' decisions towards the face category. The magnitude of the effect depended upon the degree of face selectivity of the stimulation site, the size of the stimulated cluster of face-selective neurons, and the exact timing of microstimulation. Our results establish a causal relationship between the activity of face-selective neurons and face perception."

Evidence for stroke-induced neurogenesis in the human brain

The Work of Bhardwaj et. al. mentioned in the Aug. 22 blog posting has made the point that under normal conditions new neurons are not born at detectable levels in the adult human brain. These measurements had a detection limit of ~ 1%, however, and would not have been expected to note small amounts of nerve cell proliferation occurring near areas damaged by stroke. Jin et al. now report in PNAS that in patients with stroke, cells that express markers associated with newborn neurons are present in the ischemic penumbra surrounding cerebral cortical infarcts, where these cells are preferentially localized in the vicinity of blood vessels. These findings suggest that stroke-induced compensatory neurogenesis may occur in the human brain, where it could contribute to postischemic recovery and represent a target for stroke therapy.