Phantom Penises In Transsexuals

In an article in the Journal of Consciousness Studies, Ramachandran and McGeoch offer evidence of an innate gender-specific body image in the brain:

How the brain constructs one’s inner sense of gender identity is poorly understood. On the other hand, the phenomenon of phantom sensations — the feeling of still having a body-part after amputation — has been much studied. Around 60% of men experience a phantom penis post-penectomy. As transsexuals report a mismatch between their inner gender identity and that of their body, we wondered what could be learned from this regarding innate gender-specific body image. We surveyed male-to-female transsexuals regarding the incidence of phantoms post-gender reassignment surgery. Additionally, we asked female-to-male transsexuals if they had ever had the sensation of having a penis when there was not one physically there. In post-operative male-to-female transsexuals the incidence of phantom penises was significantly reduced at 30%. Remarkably, over 60% of female-to-male transsexuals also reported phantom penises. We explain the absence/presence of phantoms here by postulating a mismatch between the brain’s hardwired gender-specific body image and the external somatic gender. Further studies along these lines may provide penetrating insights into the question of how nature and nurture interact to produce our brain-based body image.

Simon LeVay, an expert on human sexuality, does make the point that Ramachandran is comparing those who are extremely pleased with getting rid of their penis to others who are distressed and think about their penis all the time. It would appear that Ramachandran has largely left out emotions, and also the question of wishful thinking.

MindBlog's editorial assistant

It is very difficult to putter with this blog while lounging on my couch - one of my new Abyssianian kittens always helps out or wishes I would play with him instead.

A simple metric to infer personality from facial expression

Oosterhof and Todorov have devised a simple model that uses facial cues that have evolutionary significance to predict important social judgments as a function of two orthogonal dimensions of valence and dominance. Here is a graphic illustrating the essential facial features, followed by their abstract.

People automatically evaluate faces on multiple trait dimensions, and these evaluations predict important social outcomes, ranging from electoral success to sentencing decisions. Based on behavioral studies and computer modeling, we develop a 2D model of face evaluation. First, using a principal components analysis of trait judgments of emotionally neutral faces, we identify two orthogonal dimensions, valence and dominance, that are sufficient to describe face evaluation and show that these dimensions can be approximated by judgments of trustworthiness and dominance. Second, using a data-driven statistical model for face representation, we build and validate models for representing face trustworthiness and face dominance. Third, using these models, we show that, whereas valence evaluation is more sensitive to features resembling expressions signaling whether the person should be avoided or approached, dominance evaluation is more sensitive to features signaling physical strength/weakness. Fourth, we show that important social judgments, such as threat, can be reproduced as a function of the two orthogonal dimensions of valence and dominance. The findings suggest that face evaluation involves an overgeneralization of adaptive mechanisms for inferring harmful intentions and the ability to cause harm and can account for rapid, yet not necessarily accurate, judgments from faces.

Weekly musical offering - Stars & Stripes FOREVER!

Brain changes that correlate with successful dyslexia therapy

Meyler et al. have published an interesting study in Neuropsychologia showing brain plasticity during the remedial instruction of poor readers:

This study used fMRI to longitudinally assess the impact of intensive remedial instruction on cortical activation among 5th grade poor readers during a sentence comprehension task. The children were tested at three time points: prior to remediation, after 100 h of intensive instruction, and 1 year after the instruction had ended. Changes in brain activation were also measured among 5th grade good readers at the same time points for comparison. The central finding was that prior to instruction, the poor readers had significantly less activation than good readers bilaterally in the parietal cortex. Immediately after instruction, poor readers made substantial gains in reading ability, and demonstrated significantly increased activation in the left angular gyrus and the left superior parietal lobule. Activation in these regions continued to increase among poor readers 1 year post-remediation, resulting in a normalization of the activation. These results are interpreted as reflecting changes in the processes involved in word-level and sentence-level assembly. Areas of overactivation were also found among poor readers in the medial frontal cortex, possibly indicating a more effortful and attentionally guided reading strategy.


Brain areas showing greater activation among good readers vs. poor readers at each phase of the study. The same data are presented overlaid on a surface rendering (right column) and overlaid on individual coronal slices (left column) of the normalized Montreal Neurological Institute canonical brain. Yellow ovals encircle parietal activation.

Cat Pols

My apologies, I can't help myself. Another cat video.. click on this link, not the picture below.

Oxytocin attenuates aversive reactions

Here is an interesting report from Dolan's laboratory, showing that oxytocin attenuates our emotional response and amygdala reactivity to faces that we have learned to dislike (enter oxytocin in the 'search MindBlog' box in the left column to note previous postings on oxytocin).

Social relations between humans critically depend on our affective experiences of others. Oxytocin enhances prosocial behavior, but its effect on humans' affective experience of others is not known. We tested whether oxytocin influences affective ratings, and underlying brain activity, of faces that have been aversively conditioned. Using a standard conditioning procedure, we induced differential negative affective ratings in faces exposed to an aversive conditioning compared with nonconditioning manipulation. This differential negative evaluative effect was abolished by treatment with oxytocin, an effect associated with an attenuation of activity in anterior medial temporal and anterior cingulate cortices. In amygdala and fusiform gyrus, this modulation was stronger for faces with direct gaze, relative to averted gaze, consistent with a relative specificity for socially relevant cues. The data suggest that oxytocin modulates the expression of evaluative conditioning for socially relevant faces via influences on amygdala and fusiform gyrus, an effect that may explain its prosocial effects.

Self interest versus the common good in economic policy design.

An essay by Bowles in Science points to a shortcoming in the conventional economic approach to policy design: It overlooks the possibility that economic incentives (i.e. those appealing to self-regarding preferences) may diminish ethical or other reasons for complying with social norms and contributing to the common good. Where this is the case, the kinds of incentives stressed by economists may have counterproductive effects.

Diego Rivera's mural of factory workers at Ford's River Rouge assembly plant (detail). Modern economies require cooperation toward common ends among countless individuals, often occurring as the result of both self-interested and ethical motives. Recent behavioral experiments show that organizational strategies may backfire if they rely solely on explicit economic incentives and seek to limit the options of group members.

One interesting real-life experiment:

In Haifa, at six day care centers, a fine was imposed on parents who were late picking up their children at the end of the day. Parents responded to the fine by doubling the fraction of time they arrived late. When after 12 weeks the fine was revoked, their enhanced tardiness persisted unabated. While other interpretations are possible, the counterproductive imposition of the fines illustrate a kind of negative synergy between economic incentives and moral behavior. The fine seems to have undermined the parents' sense of ethical obligation to avoid inconveniencing the teachers and led them to think of lateness as just another commodity they could purchase.

Here is the abstract of the article:

High-performance organizations and economies work on the basis not only of material interests but also of Adam Smith's "moral sentiments." Well-designed laws and public policies can harness self-interest for the common good. However, incentives that appeal to self-interest may fail when they undermine the moral values that lead people to act altruistically or in other public-spirited ways. Behavioral experiments reviewed here suggest that economic incentives may be counterproductive when they signal that selfishness is an appropriate response; constitute a learning environment through which over time people come to adopt more self-interested motivations; compromise the individual's sense of self-determination and thereby degrade intrinsic motivations; or convey a message of distrust, disrespect, and unfair intent. Many of these unintended effects of incentives occur because people act not only to acquire economic goods and services but also to constitute themselves as dignified, autonomous, and moral individuals. Good organizational and institutional design can channel the material interests for the achievement of social goals while also enhancing the contribution of the moral sentiments to the same ends.

And here is the PDF.

Cute Cat Overload on the Web

Several days ago my daughter sent me this link to a site of humorous cat pictures such as the following.













Now in today's New York Times I see an article by Dan Mitchell on other warm, cuddly, and fuzzy sites. An excerpt:

Meg Frost, a 36-year-old design manager at Apple, started cuteoverload.com three years ago to test Web software. Within months, it became an online institution, drawing about 88,000 unique visitors a day...viewing the site “is like taking a happy pill.”

And in that warm feeling lies the reason for its popularity. Given all the nastiness on the Internet — blog trolls, flame wars, vicious gossip, pornography, snark and spam — what better antidote is there than looking at pictures of tiny ducklings waddling in a line or kittens splayed on their backs, paw pads in the air?

The most famous cute-animal Web sites are presented with a touch of self-mockery. The site I Can Has Cheezburger? (icanhascheezburger.com) features cat pictures with ungrammatical captions, Stuff on My Cat (stuffonmycat.com) displays photos of objects stacked on sleeping cats, and Kittenwars.com pits pairs of cat photos in a cuteness showdown.

Brain Correlates of Borderline Personality Disorder

King-Casas et al. carry out interesting experiments in which they recruited 55 individuals afflicted with borderline personality disorder (BPD) to play a multiround economic exchange game with healthy partners. Imaging experiments were also performed that revealed different patterns of insula activation in BPD subjects. Here is the abstract, followed by a figure from an accompanying review by Meyer-Lindenberg.

To sustain or repair cooperation during a social exchange, adaptive creatures must understand social gestures and the consequences when shared expectations about fair exchange are violated by accident or intent. We recruited 55 individuals afflicted with borderline personality disorder (BPD) to play a multiround economic exchange game with healthy partners. Behaviorally, individuals with BPD showed a profound incapacity to maintain cooperation, and were impaired in their ability to repair broken cooperation on the basis of a quantitative measure of coaxing. Neurally, activity in the anterior insula, a region known to respond to norm violations across affective, interoceptive, economic, and social dimensions, strongly differentiated healthy participants from individuals with BPD. Healthy subjects showed a strong linear relation between anterior insula response and both magnitude of monetary offer received from their partner (input) and the amount of money repaid to their partner (output). In stark contrast, activity in the anterior insula of BPD participants was related only to the magnitude of repayment sent back to their partner (output), not to the magnitude of offers received (input). These neural and behavioral data suggest that norms used in perception of social gestures are pathologically perturbed or missing altogether among individuals with BPD. This game-theoretic approach to psychopathology may open doors to new ways of characterizing and studying a range of mental illnesses.


(Click to enlarge). Activation of the anterior insula is observed during an economic trust game in individuals with borderline personality disorder and healthy controls. Both groups show higher activation in response to stingy repayments they are about to make. However, only players with the disorder have no differential response to low offers from an investor (upper left graph), indicating that they lack the "gut feeling" that the relationship (cooperation) is in jeopardy.

Our expressions of fear and disgust serve specific adaptive purposes

Susskind et al. make some interesting observations that suggest that our facial expressions of fear or disgust are not set by arbitrary social conventions but rather have an evolved Darwinian basis. From Whalen and Kleck's review of this work of this work in the same issue of Nature Neuroscience:

...when subjects posed fearful faces, they were able to detect more flashes of light in the upper extent of their peripheral visual field, they were faster to move their eyes to targets in their visual field and they took in more air through the nose. In contrast, when they posed disgusted expressions, they detected fewer flashes of light in the upper extent of their visual field, they were slower to move their eyes to visual targets and they took in less air through the nose. Thus, the converse movements of the brows, eyelids and nose enacted in the formation of these expressions had opposite effects on sensory intake (see figure). This makes sense when one considers the situations where these expressions are encountered. Fearful expressions are observed at times when you would do well to learn more about your surroundings and disgusted expressions are observed at times when you feel you have learned quite enough.


Note how the various parts of the face move in opposite directions in the two expressions, and therefore have opposite effects on sensory intake.

That eye widening should facilitate environmental monitoring is consistent with other data showing that the amygdala has a unique relationship with fearful facial expressions. Indeed, the amygdala uses the widened eyes in fearful expressions as a proxy for the presence of fearful faces, and lesions of the human amygdala result in an inability to properly scan the eye whites in fearful faces. Further, electrical stimulation of the human amygdala results in eye widening and heightened visual scanning of the environment and produces nonspecific arousal responses such as pupil dilation. Neuroimaging studies have shown that the amygdala is sensitive to the pupil size of others. Taken together, these findings support the hypothesized role of the amygdala in potentiating sensory information processing to facilitate learning about the predi. More generally, these results suggest that your amygdala is sensitive to the very facial responses in others that it controls in you.

If the amygdala has shown an affinity for the facial expression of fear, then the analogous brain region for disgusted expressions would be the insular cortex. Neuroimaging, as well as depth electrode recording studies, show that human insular cortex responds to disgusted faces, and damage to the insula produces deficits in the recognition of disgusted faces11. Furthermore, insular pathology in Huntington's disorder is associated with a decreased disgust response and a similar recognition deficit of disgust. Although it is tempting to divide duties for the amygdala and insular cortex between fear and disgust and to suggest that they represent unique neural substrates for their processing, other work suggests that these reciprocally connected regions will interact along dimensions such as arousal, valence and/or attention, dimensions that cross the stark boundary between these two expression categories.

Mindblog does an experiment with resveratrol, the anti-aging compound.

I have done a number of posts on resveratrol (to have a look at them, enter 'resveratrol' in the search box in the left column). This compound appears to mimic the effects of caloric restriction in some animals, and in some cases extends lifespans. It has effects on enzyme profiles that resemble those caused by exercise. With some hesitation, I decided to do a self-experiment, taking the compound for several weeks to see if I noted any steady state changes in physiology, energy, temperament, etc. and then stopping the supplement to observe whether any changes I noted went away. (Goggling away on the web, you find a large number of sites, having almost the aura of cults, claiming wondrous properties of this new magic molecule.)

If you don't feel like reading through the whole account below, the bottom line is that after noting some positive, but transient, positive changes in energy and temperament, the appearance of arthritic symptoms led me to terminate the self-experiment. The arthritic symptoms then disappeared. (Added note, in response to immediate input from a reader of this post: Resveratrol is an anti-TNF (tumor necrosis factor) agent and in some instances this may trigger autoimmune symptoms.)

The hesitation to start this experiment derived from my experience when I tried this in 2004. Then, as now, I used resveratrol obtained from Now Foods, pills containing 400 mg of a root extract that claims to contain 200 mg resveratrol. After a few weeks I noted that my hands were becoming stiff, finger joints were starting to 'click' , i.e. arthritic symptoms. I freaked out, stopped the resveratrol, and started taking glucose amine, chondroitin sulfate, MSM, Calcium, Magnesium. The arthritis went away over the next week or two, but of course I didn't know whether to attribute that to stopping the resveratrol, starting the latter supplements, or placebo effect.

So, this time I started 200 mg with breakfast, tried to stay very flat and objective in my observations, especially attentive to any negative effects. (I tried in vain to find in the literature, on the web, any reported negative side effects reported by people taking resveratrol.) On day 11, I started another 200 mg with dinner.

On day 13, I decided to write down a number of effects, fairly subtle, but quite clear. (I had been looking mainly for negative symptoms, and so required the following observations to be clear and sustained, noticed as facts, not goals, with changes clearly different from the previous period in a sustained way. My food intake and level of formal exercise (gym) activity had not changed significantly.)

-more constant energy in just moving through a day, from one activity to another… (While running at gym, I didn't begin to slow down after the first mile).
-an absence of mildly negative, curmudgeonly, temperament, the temperament being now more flat to positive.
-more sexual energy (I check the web: resveratrol inhibitis the esterase that breaks down testosterone)
-a bit more spontaneous emotional reactivity, to memories, things in the environment,
-the daily weight range (lowest on waking in the a.m. then plus a few pounds by gym weighing) may have shifted down 1-2 pounds

By day 15 I'm deciding I don’t think the weight range has changed significantly. Further, over a period of just a few days, everything seems to return to where it was, as if physiological and temperamental homeostatic mechanisms had noted a 'perturbation' and so were returning the body to its normal set-points. On day 16 I sign off on thinking that the positive effects reported above are long term. I also realize that hand stiffness has been increasing over the past few days, finger joints have started clicking. (These observations seem to be contrary to several reports that resveratrol inhibits enzymes (COX-1 and COX-2) involved in inflammatory arthritic responses.)

I continue to take the 400 mg of daily resveratrol for two more days, note increasing arthritic symptoms, and discontinue on day. 19. Over the next week, the stiffness and clicking joints disappear, and hand movements become supple again.

So, that is it. Deric's experiment was finished. Don't think I'm going to go there again.

The Mind Does the Tricks for a Magician

Benedict Carey does a fascinating article on how short cuts that our brains make to assemble our perceptions are exploited by magicians. He describes collaboration between magicians and neuroscientists which have generated a paper in Nature Review Neuroscience. One example:

The visual cortex is attentive to sudden changes in the environment, both when something new appears and when something disappears...A sudden disappearance causes an after-discharge: a ghostly image of the object lingers for a moment...This illusion is behind a spectacular trick by the Great Tomsoni. The magician has an assistant appear on stage in a white dress and tells the audience he will magically change the color of her dress to red. He first does this by shining a red light on her, an obvious ploy that he turns into a joke. Then the red light flicks off, the house lights go on and the now the woman is unmistakably dressed in red. The secret: In the split-second after the red light goes off, the red image lingers in the audience’s brains for about 100 milliseconds, covering the image of the woman. It’s just enough time for the woman’s white dress to be stripped away, revealing a red one underneath.

Anticipation of movement suppresses sensory awareness.

Here is an interesting tidbit...Voss et al. show that the mere expectation of moving a part of our body suppresses that body part's openness to sensory input. Here is the abstract:

When a part of the body moves, the sensation evoked by a probe stimulus to that body part is attenuated. Two mechanisms have been proposed to explain this robust and general effect. First, feedforward motor signals may modulate activity evoked by incoming sensory signals. Second, reafferent sensation from body movements may mask the stimulus. Here we delivered probe stimuli to the right index finger just before a cue which instructed subjects to make left or right index finger movements. When left and right cues were equiprobable, we found attenuation for stimuli to the right index finger just before this finger was cued (and subsequently moved). However, there was no attenuation in the right finger just before the left finger was cued. This result suggests that the movement made in response to the cue caused ‘postdictive’ attenuation of a sensation occurring prior to the cue. In a second experiment, the right cue was more frequent than the left. We now found attenuation in the right index finger even when the left finger was cued and moved. This attenuation linked to a movement that was likely but did not in fact occur, suggests a new expectation-based mechanism, distinct from both feedforward motor signals and postdiction. Our results suggest a new mechanism in motor-sensory interactions in which the motor system tunes the sensory inputs based on expectations about future possible actions that may not, in fact, be implemented.

Brooks on status rules and collectivism

Two recent Op-Ed columns by David Brooks are worth a glance. In the first he argues (one has to admit in a rather superficial and facile manner) that the advent of the iPhone signaled the start of a new era in which the means of transmission has replaced the content of culture as the center of historical excitement and as the marker of social status. He cites this as the third of three epochs of intellectual affectation.

The first, lasting from approximately 1400 to 1965, was the great age of snobbery. Cultural artifacts existed in a hierarchy, with opera and fine art at the top, and stripping at the bottom... This code died sometime in the late 1960s and was replaced by the code of the Higher Eclectica. The old hierarchy of the arts was dismissed as hopelessly reactionary...During this period, status rewards went to the ostentatious cultural omnivores — those who could publicly savor an infinite range of historically hegemonized cultural products.

In his third iPhone era:

...prestige has shifted from the producer of art to the aggregator and the appraiser. Inventors, artists and writers come and go, but buzz is forever. Maximum status goes to the Gladwellian heroes who occupy the convergence points of the Internet infosystem — Web sites like Pitchfork for music, Gizmodo for gadgets, Bookforum for ideas, etc.

The second Brooks essay, which probes the different cognitive styles of Eastern and Western socities, is inspired by the opening ceremony of the Beijing Olympics:

The ceremony drew from China’s long history, but surely the most striking features were the images of thousands of Chinese moving as one — drumming as one, dancing as one, sprinting on precise formations without ever stumbling or colliding. We’ve seen displays of mass conformity before, but this was collectivism of the present — a high-tech vision of the harmonious society performed in the context of China’s miraculous growth...If Asia’s success reopens the debate between individualism and collectivism (which seemed closed after the cold war), then it’s unlikely that the forces of individualism will sweep the field or even gain an edge...For one thing, there are relatively few individualistic societies on earth. For another, the essence of a lot of the latest scientific research is that the Western idea of individual choice is an illusion and the Chinese are right to put first emphasis on social contexts.

Different social attachment styles - different brain structures.

Here is an interesting article arguing that three classic prototypes of attachment style (secure, avoidant, anxious) appear to be regulated by two separate affective dimensions centered on ventral striatum and amygdala circuits, respectively. Here is the abstract, to see the fMRI data showing the relevant structures, follow the link to the article.

Adult attachment style refers to individual personality traits that strongly influence emotional bonds and reactions to social partners. Behavioral research has shown that adult attachment style reflects profound differences in sensitivity to social signals of support or conflict, but the neural substrates underlying such differences remain unsettled. Using functional magnetic resonance imaging (fMRI), we examined how the three classic prototypes of attachment style (secure, avoidant, anxious) modulate brain responses to facial expressions conveying either positive or negative feedback about task performance (either supportive or hostile) in a social game context. Activation of striatum and ventral tegmental area was enhanced to positive feedback signaled by a smiling face, but this was reduced in participants with avoidant attachment, indicating relative impassiveness to social reward. Conversely, a left amygdala response was evoked by angry faces associated with negative feedback, and correlated positively with anxious attachment, suggesting an increased sensitivity to social punishment. Secure attachment showed mirror effects in striatum and amygdala, but no other specific correlate. These results reveal a critical role for brain systems implicated in reward and threat processing in the biological underpinnings of adult attachment style, and provide new support to psychological models that have postulated two separate affective dimensions to explain these individual differences, centered on the ventral striatum and amygdala circuits, respectively. These findings also demonstrate that brain responses to face expressions are not driven by facial features alone but determined by the personal significance of expressions in current social context. By linking fundamental psychosocial dimensions of adult attachment with brain function, our results do not only corroborate their biological bases but also help understand their impact on behavior.

The emerging web Leviathan - paranoia over search and content

I thought I would pass on this interesting piece in the New York Times business section on yet more controversy surrounding Google, this time over its emergence as a company that provides not only search results but also original content. I use its two main content subsidiaries: Blogger (to host this blog) and YouTube (the top video site). Now Knol comes along,a potential competitor with Wikipedia, a place where experts can share their knowledge on a variety of topics. The article points out: "Google’s growing reach into the content business could create conflicts similar to those faced by Microsoft in its dual role as a provider of an operating system that others run their software applications on and a maker of applications."

Right hemisphere more involved in self recognition of body parts.

Hemispheric asymmetries in self and other body parts recognition is examined by Frassinetti et al., by comparing how healthy patients, and patients with left and right hemisphere brain damage perform in visual matching experiments involving body parts. Their abstract:

The aim of this study was to investigate whether the recognition of "self body parts" is independent from the recognition of other people's body parts. If this is the case, the ability to recognize "self body parts" should be selectively impaired after lesion involving specific brain areas. To verify this hypothesis, patients with lesion of the right (right brain-damaged [RBD]) or left (left brain-damaged [LBD]) hemisphere and healthy subjects were submitted to a visual matching-to-sample task in two experiments. In the first experiment, stimuli depicted their own body parts or other people's body parts. In the second experiment, stimuli depicted parts of three categories: objects, bodies, and faces. In both experiments, participants were required to decide which of two vertically aligned images (the upper or the lower one) matched the central target stimulus. The results showed that the task indirectly tapped into bodily self-processing mechanisms, in that both LBD patients and normal subjects performed the task better when they visually matched their own, as compared to others', body parts. In contrast, RBD patients did not show such an advantage for self body parts. Moreover, they were more impaired than LBD patients and normal subjects when visually matching their own body parts, whereas this difference was not evident in performing the task with other people's body parts. RBD patients' performance for the other stimulus categories (face, body, object), although worse than LBD patients' and normal subjects' performance, was comparable across categories. These findings suggest that the right hemisphere may be involved in the recognition of self body parts, through a fronto-parietal network.

Circuits that switch fear ON and OFF

Sah and Westbrook write a brief review of work by Herry et al. and Likhtik et al. Here are some mixed and edited clips:

The work pinpoints the neural circuits that mediate the bidirectional transition between a defensive behaviour — fear — and the default exploratory behaviour. These functions are evolutionarily old, and their dysfunction is thought to underlie a host of anxiety disorders in humans, including post-traumatic stress and panic disorder

To study the neural mechanisms that mediate fear responses, fear conditioning is widely used. In a typical procedure, animals are exposed to a normally harmless stimulus (such as a sound or light) before a brief exposure to an aversive stimulus — typically a foot shock. A few such rounds of pairing the harmless (conditioned) stimulus with the aversive (unconditioned) stimulus create an association between them in the animals' minds...It is important to study how fear is first learned. However, the pertinent question for clinicians is how fear can be eliminated or reduced. Extinction of fear occurs when the association between the conditioned and the unconditioned stimuli is broken by repeated presentations of the conditioned stimulus only. But does the association get completely erased from the memory? The answer is no. Although the conditioned stimulus eventually fails to elicit fear responses, much, if not all, of the original learned fear survives extinction. So when the extinguished conditioned stimulus is tested either during, or shortly after, exposure to a dangerous context again, the conditioned fear is renewed spontaneously. Extinction therefore involves new learning, and its activation by situational cues inhibits the expression of fear responses to the conditioned stimulus.

During fear conditioning, convergence of inputs from the conditioned stimulus (CS) and unconditioned stimulus (US) to fear neurons in the basolateral amygdala (BLA) leads to potentiation of the conditioned input and activation by the CS of neurons in the central nucleus (CEA) that initiates physiological and behavioural responses characteristic of fear. b, During extinction, inputs from the medial prefrontal cortex (PFC) activate neurons in the intercalated cell masses (ICMs) — either directly or through activation of extinction neurons in the basolateral amygdala — which then inhibit the activity of fear output neurons in the CEA. c, During fear renewal, inputs from the hippocampus, which evaluates the current context, activate inhibitory interneurons in the basolateral amygdala that silence extinction neurons, thus restoring fear responses.

Noninvasive Brain Stimulation Improves Language Learning

Here are some interesting results from Flöel et al. :

Anodal transcranial direct current stimulation (tDCS) is a reliable technique to improve motor learning. We here wanted to test its potential to enhance associative verbal learning, a skill crucial for both acquiring new languages in healthy individuals and for language reacquisition after stroke-induced aphasia. We applied tDCS (20 min, 1 mA) over the posterior part of the left peri-sylvian area of 19 young right-handed individuals while subjects acquired a miniature lexicon of 30 novel object names. Every subject participated in one session of anodal tDCS, one session of cathodal tDCS, and one sham session in a randomized and double-blinded design with three parallel versions of the miniature lexicon. Outcome measures were learning speed and learning success at the end of each session, and the transfer to the subjects' native language after the respective stimulation. With anodal stimulation, subjects showed faster and better associative learning as compared to sham stimulation. Mood ratings, reaction times, and response styles were comparable between stimulation conditions. Our results demonstrate that anodal tDCS is a promising technique to enhance language learning in healthy adults and may also have the potential to improve language reacquisition after stroke.