Frontal Cortex: unconscious inhibitory control

An interesting study from van Gaal et al. I give the abstract, followed by a figure describing the experimental procedure:

To further our understanding of the function of conscious experience we need to know which cognitive processes require awareness and which do not. Here, we show that an unconscious stimulus can trigger inhibitory control processes, commonly ascribed to conscious control mechanisms. We combined the metacontrast masking paradigm and the Go/No-Go paradigm to study whether unconscious No-Go signals can actively trigger high-level inhibitory control processes, strongly associated with the prefrontal cortex (PFC). Behaviorally, unconscious No-Go signals sometimes triggered response inhibition to the level of complete response termination and yielded a slow down in the speed of responses that were not inhibited. Electroencephalographic recordings showed that unconscious No-Go signals elicit two neural events: (1) an early occipital event and (2) a frontocentral event somewhat later in time. The first neural event represents the visual encoding of the unconscious No-Go stimulus, and is also present in a control experiment where the masked stimulus has no behavioral relevance. The second event is unique to the Go/No-Go experiment, and shows the subsequent implementation of inhibitory control in the PFC. The size of the frontal activity pattern correlated highly with the impact of unconscious No-Go signals on subsequent behavior. We conclude that unconscious stimuli can influence whether a task will be performed or interrupted, and thus exert a form of cognitive control. These findings challenge traditional views concerning the proposed relationship between awareness and cognitive control and stretch the alleged limits and depth of unconscious information processing.

Here is the procedure. SOA is the stimulus-onset asynchrony, the interval between the onsets of the two stimuli. (I wish these people would remind us what these jargon abbreviations mean, so I don't have go look them up to remind myself. )

Stimuli and trial timing of the masked Go/No-Go task and the control experiment. The gray circle and black cross duration was 16.7 ms. Go signal duration was 100 ms. In conscious No-Go trials, the SOA between the No-Go signal and the Go signal was 83 ms. Participants had to respond to the Go signal (black metacontrast mask) but were instructed to withhold their response when a No-Go signal preceded the Go signal. In the masked Go/No-Go task, a gray circle served as a No-Go signal, whereas in the control experiment, the No-Go signal was a black cross. Therefore, the masked gray circle was associated with inhibition in the masked Go/No-Go task and thus served as an unconscious No-Go signal. In the control experiment, the unconscious gray circle was not associated with inhibition (and was task irrelevant) because participants were instructed to inhibit their responses on a black cross. Comparing processing of unconscious gray circles between both experiments enabled us to test whether (1) high-level inhibitory control processes can be triggered unconsciously, (2) unconscious No-Go signals reach prefrontal areas, and (3) task relevance influences the depth of processing of unconscious stimuli.

Music for the week... Ode to Joy

My daughter sent me this gem...

MindBlog at the Chicago Art Institue

Lunch today in the Garden Restaurant at the Art Institute of Chicago, part of my annual summer ritual, which also includes the Halstead Street Days street fair in Boystown. (Click to enlarge picture).

Culture-sensitive neural substrates of human cognition.

Han and Northoff write a perspective piece in which they aim to show how the relatively novel approach of transcultural neuroimaging can bridge the gap between neuroscientific investigations of supposedly culture-invariant neural mechanisms and psychological evidence of culture-sensitive cognition. They collect and summarize a variety of neuroimaging data in summary figures. Below is the abstract, and PDF is here.

Our brains and minds are shaped by our experiences, which mainly occur in the context of the culture in which we develop and live. Although psychologists have provided abundant evidence for diversity of human cognition and behaviour across cultures, the question of whether the neural correlates of human cognition are also culture-dependent is often not considered by neuroscientists. However, recent transcultural neuroimaging studies have demonstrated that one's cultural background can influence the neural activity that underlies both high- and low-level cognitive functions. The findings provide a novel approach by which to distinguish culture-sensitive from culture-invariant neural mechanisms of human cognition.

Behavioral therapy can reverse chronic fatigue syndrome and increase prefrontal volume

Another example of a therapy that induces brain plasticity, this work from de Lange et al. , carried out with women, since chronic fatigue syndrome predominantly affects women. Here is a clip describing the therapy, followed by the abstract of the paper.

During cognitive behavioral therapy (CBT), fatigue-related cognitions were challenged to diminish somatic attributions, to improve sense of control over symptoms and to facilitate behavioral changes. In parallel, a structured physical activity program was implemented. Furthermore, a work rehabilitation schedule was drawn up in order to realize a gradual work reentry. Final sessions of CBT dealt with relapse prevention and further improvement of self-control.

Chronic fatigue syndrome (CFS) is a disabling disorder, characterized by persistent or relapsing fatigue. Recent studies have detected a decrease in cortical grey matter volume in patients with CFS, but it is unclear whether this cerebral atrophy constitutes a cause or a consequence of the disease. Cognitive behavioural therapy (CBT) is an effective behavioural intervention for CFS, which combines a rehabilitative approach of a graded increase in physical activity with a psychological approach that addresses thoughts and beliefs about CFS which may impair recovery. Here, we test the hypothesis that cerebral atrophy may be a reversible state that can ameliorate with successful CBT. We have quantified cerebral structural changes in 22 CFS patients that underwent CBT and 22 healthy control participants. At baseline, CFS patients had significantly lower grey matter volume than healthy control participants. CBT intervention led to a significant improvement in health status, physical activity and cognitive performance. Crucially, CFS patients showed a significant increase in grey matter volume, localized in the lateral prefrontal cortex. This change in cerebral volume was related to improvements in cognitive speed in the CFS patients. Our findings indicate that the cerebral atrophy associated with CFS is partially reversed after effective CBT. This result provides an example of macroscopic cortical plasticity in the adult human brain, demonstrating a surprisingly dynamic relation between behavioural state and cerebral anatomy. Furthermore, our results reveal a possible neurobiological substrate of psychotherapeutic treatment.

Mental imagergy induces cortical reorganization that reduces phantom limb pain

The journal Brain offers an interesting open access article by MacIver et al. on the use of mental imagery to reduce phantom limb pain. They used a mindfulness-based ‘body-scan’ meditation technique as a means of achieving a relaxed state, based on a pain management technique developed by Kabat-Zinn et al. This remarkably simple technique of imagining movement and sensation in the missing limb resulted in significant pain relief. All subjects found learning the body scan useful as a means of relaxation, regardless of whether their pain lessened, and they all felt that the body scan was a useful facilitator to imagining the return of the phantom limb. I give the abstract here, with apologies for not taking the time to translate it into more friendly prose.

Using functional MRI (fMRI) we investigated 13 upper limb amputees with phantom limb pain (PLP) during hand and lip movement, before and after intensive 6-week training in mental imagery. Prior to training, activation elicited during lip purse showed evidence of cortical reorganization of motor (M1) and somatosensory (S1) cortices, expanding from lip area to hand area, which correlated with pain scores. In addition, during imagined movement of the phantom hand, and executed movement of the intact hand, group maps demonstrated activation not only in bilateral M1 and S1 hand area, but also lip area, showing a two-way process of reorganization. In healthy participants, activation during lip purse and imagined and executed movement of the non-dominant hand was confined to the respective cortical representation areas only. Following training, patients reported a significant reduction in intensity and unpleasantness of constant pain and exacerbations, with a corresponding elimination of cortical reorganization. Post hoc analyses showed that intensity of constant pain, but not exacerbations, correlated with reduction in cortical reorganization. The results of this study add to our current understanding of the pathophysiology of PLP, underlining the reversibility of neuroplastic changes in this patient population while offering a novel, simple method of pain relief.

Sexual orientation - basis in brain structure and function

Swaab offers a useful brief review of this topic (PDF here) with a complete list of references.

Genetics of political behaviors - molecular level

I wanted to bring into a separate post the comment by James Fowler on the post below mentioning his work. "We do have some papers that go to the molecular level, associating drd2, drd4, maoa, and 5htt with various political behaviors. One of these papers has just been published in Journal of Politics, and all of these papers are all available at my website
http://jhfowler.ucsd.edu."

Your nose, and your bored brain...

From today's Science NYTimes: An article by Natalie Angier on the emotional clout of smells and the curious fact that smell cues most frequently evoke thoughts of early childhood, under the age of 10 (this certainly has been my experience.) Also, an article by Benedict Carey on the creative aspects of boredome.

A new perspective on the genetic basis of brain diseases

An article by Nicholas Wade notes the emergence of a new view on the genetic basis of brain diseases like schizophrenia (see also article by Sands in Nature). There has been a presumption that we looked hard enough, we would find an ensemble of genes whose mutations typically correlated with a disease. The search for common variants in schizophrenia has largely drawn a blank, suggesting that natural selection has done its job in keeping them at bay (after all, reproductive success is compromised in schizophrenics). A view is emerging that the genetic component of the disease may be due to a large number of variants, each of which is very rare (mainly deletions of DNA segments), rather than to a handful of common variants. According to this new idea, schizophrenia continues to appear because it is driven by a spate of new mutations that occur all the time in the population. The new landscape might complicate development of genetic diagnostics for schizophrenia, but not necessarily of therapies based on understanding the underlying mechanisms of the disease.

Gender differences in math performance...

... don't exist for children in grades 2 to 11, according according to a massive statistical analysis carried out by Hyde et al. on data provided through school reporting on the No Child Left Behind federal program (PDF here) - although there is slightly more male variability in scores.

The theologians, the neurologists, and God

Here is the PDF of a review by Alasdair Coles in a recent issue of Brain of a series of recent books that evaluate contributions of neurobiology to the understanding of the relationships between brain, psyche and God. He reviews the history of such efforts starting with Pascal, William James, and others.

Mendelssohn, conclusion

Here is the posting of the final piece done at the house concert at Twin Valley on 6/29/08 the final movement, allegro appasionata, of Mendelssohn's 2nd piano trio. A notable feature of this finale is its inclusion of the melody of a chorale taken from the sixteenth-century Genevan psalter ''Vor deinen Thron tret ich hiermit.'

Lifespan Mental Activity Predicts Diminished Rate of Hippocampal Atrophy

Valenzuela et al. offer further confirmation of the 'use it or lose it' perspective by showing that lifetime mental activity correlates with a diminished rate of hippocampal atrophy with aging. They suggest that neuroprotection in medial temporal lobe may be one mechanism underlying the link between mental activity and lower rates of dementia observed in population-based studies.

We learn abstract categories unconsciously.

Brady and Oliva report interesting experiments in Psychological Science. Below I pass on their abstract, and also their presentation of the first experiment mentioned:

Recent work has shown that observers can parse streams of syllables, tones, or visual shapes and learn statistical regularities in them without conscious intent (e.g., learn that A is always followed by B). Here, we demonstrate that these statistical-learning mechanisms can operate at an abstract, conceptual level. In Experiments 1 and 2, observers incidentally learned which semantic categories of natural scenes covaried (e.g., kitchen scenes were always followed by forest scenes). Stimuli: In Experiments 3 and 4, category learning with images of scenes transferred to words that represented the categories. In each experiment, the category of the scenes was irrelevant to the task. Together, these results suggest that statistical-learning mechanisms can operate at a categorical level, enabling generalization of learned regularities using existing conceptual knowledge. Such mechanisms may guide learning in domains as disparate as the acquisition of causal knowledge and the development of cognitive maps from environmental exploration.

From their description of the first experiment:

Stimuli: Twelve scene categories were used (see figure): bathroom, bedroom, bridge, building, coast, field, forest, kitchen, living room, mountain, street, and waterfall.


Each category contained 120 different full-color images. For each observer, 1 picture was drawn from each of the 12 categories at random, resulting in a set of 12 different images...Each of the 12 selected images was randomly assigned a position in one of four triplets (e.g., ABC)—sequences of three images that always appeared in the same order. Then a sequence of images was generated by randomly interleaving 75 repetitions of each triplet, with the constraints that the same triplet could never appear twice in a row and the same set of two triplets could never appear twice in a row (e.g., ABCGHIABCGHI was disallowed). In addition, 100 repeat images were inserted into the stream such that sometimes either the first or third image in a triplet repeated immediately (e.g., ABCCGHI or ABCGGHI). Allowing only the first or third image in a triplet to repeat served to keep the triplet structure intact, yet prevented the repeat images from being informative for delineating triplets from one another.

Procedure: Observers watched a 20-min sequence of 1,000 images, presented one at a time for 300 ms each with a 700-ms interstimulus interval (ISI). During this sequence, the task was to detect back-to-back repeats of the same image and to indicate repeats as quickly as possible by hitting the space bar. This cover task was intended to help prevent observers from becoming explicitly aware of the structure in the stream (Turk-Browne et al., 2005), and also avoided having observers simply view the stream passively (which would make it unclear what they were processing). Note that they were never informed that there was any structure in the stream of images...Following this study period, observers were asked if they had recognized any structure in the stream and then were given a surprise forced-choice familiarity test. On each test trial, observers viewed two 3-image test sequences, presented sequentially at the center of the screen with the same ISI as during the study phase and segmented from each other by an additional 1,000-ms pause. One of these test sequences was always a triplet of images that had been seen in the stream (e.g., ABC), and another was a foil constructed from images from three different triplets (e.g., AEI). After the presentation of the two test sequences, observers were told to press either the "1" or the "2" key to indicate whether the first or second test sequence seemed more familiar from the initial study period. Each of the four triplets was tested eight times, paired twice with each of four different foil sequences (AEI, DHL, GKC, JBF), for a total of 32 test trials. Observers' ability to discriminate triplet sequences from foil sequences was used as a measure of statistical learning.

Results and Discussion: All 10 of the observers completed the repeat-detection task during the study period with few errors, detecting an average of 91% of the repetitions (SD= 5%) and committing between one and five false alarms. These results demonstrate that observers were attending to the sequence of images. However, when asked, no observers reported explicitly noticing that the study stream had any structure.1 Nonetheless, performance on the familiarity test indicated very robust statistical learning, with triplets being successfully discriminated from foils (86.6% of the test sequences chosen were triplets, and 13.4% were foils), t(9) = 8.72, p= .00001.

These results extend previous demonstrations of visual statistical learning in two ways. First, they demonstrate visual statistical learning for scene stimuli, which are more complicated and information rich than the stimuli for which statistical learning has been demonstrated previously. Second, choosing the correct triplets at test in this experiment required not just forming episodic associations between the correct pictures, but also overcoming prior knowledge about how the scenes represented are associated in the world (e.g., bridges are rarely associated with living rooms).

In this experiment, learning likely occurred at the image level, because identical stimuli were repeated throughout the learning and test phases (and statistical learning has been previously demonstrated for shape and color.

To examine the role of category-level semantics in statistical learning, the authors then moved on to experiments in which the same string of images was never presented twice, but a pattern occurred at the categorical level.

Would I pull that switch?

I recommend this NYTimes piece by Benedict Carey on recent experiments that give more nuance to the classic Stanley Milgram obedience studies of the early 1960s,

...that together form one of the darkest mirrors the field has held up to the human face. In a series of about 20 experiments, hundreds of decent, well-intentioned people agreed to deliver what appeared to be increasingly painful electric shocks to another person, as part of what they thought was a learning experiment. The “learner” was in fact an actor, usually seated out of sight in an adjacent room, pretending to be zapped.

The more recent work looks at conditions under which which participants were most likely to disobey the experimenter and quit delivering shocks. The participants' perception of the human rights of the learner as well as whether they felt themselves or the experiments actually responsible for delivering the shocks influenced the threshold beyond which they would no longer obey the experimenter.

Your genes and your politics.

Here are some clips from a piece by Constance Holden reporting on presentations at the recent annual Behavior Genetics Association meeting.

Numerous studies over the past 2 decades...have indicated that genes have a significant influence over whether you're "liberal" or "conservative" on various political and social issues. Some heritability estimates have been as high as 50%. That's roughly the heritability found for many personality traits such as "extraversion" or "agreeableness," and it implies that, in a given population, about half of the variation in a particular trait is attributable to genetic differences.

Now James Fowler, UCSD, and grad student Christopher Dawes say they've produced fresh evidence that DNA also has a hand in the intensity of someone's partisan attachment and even in whether someone bothers to vote...they did that by crunching data from twin registries and the government's long-running National Longitudinal Study of Adolescent Health (NLSAH)...they matched data on voting by 396 Los Angeles-area twins, including identical (who share 100% of their genes) and fraternal (who average 50% genetic overlap) twins, obtained from Los Angeles voter-turnout records. All twins were same-sex pairs to avoid confounding results with sex differences. The researchers corrected for environmental factors such as whether more of the identical than fraternal twins were living together, which might inflate their degree of similarity. They concluded that the correlation for voting was much higher between pairs of identical (.71) than fraternal (.50) twins. From this they estimated the heritability of voting behavior--that is, whether people eligible to vote actually do so--at 53%, suggesting that at least half the individual variation can be traced to genetic influences. They found an even higher heritability--72%--when they replicated the study with data on 806 twins from NLSAH, they reported in the May issue of the American Political Science Review.

Several groups are now trying to correlate personality data with DNA markers from studies such as NLSAH, which contains DNA as well as behavioral data from many subjects, in hope of identifying specific genes that feed into underlying traits, such as "desire for cooperation," that Fowler, for one, believes have been selected for throughout human evolution. Studies so far have focused on the same genes that are of interest in psychiatric genetics--in particular those involved with neurotransmitters such as dopamine and serotonin that are known to be important in regulating higher brain activities.

We are talking here about the fact that genetics are important, not really going after a complex behavior like political leanings at the molecular level. What is important is that:

social scientists are plunging into biological and evolutionary issues. At least some are starting to acknowledge that humans are genetically unique individuals and not just cloned pawns of their environment. And that suggests that prophets and pundits, however prescient, are probably never going to get much better at predictions than they are now.

A Twin Valley collage

A few pics I made last Saturday in the yard of our Twin Valley home in Middleton, WI (click to enlarge).

Moral Hypocrisy

John Tierney has a nice piece in the NYTimes on studies that probe moral flip-flops of the sort evidenced in the current presidential campaign. Does the hypocrite really believe in his heart what he is saying? Clips:

In voting against the Bush tax cut in 2001, Senator John McCain said he “cannot in good conscience support a tax cut in which so many of the benefits go to the most fortunate.” Today he campaigns in favor of extending that same tax cut beyond its expiration date...Senator Barack Obama last year called himself a “longtime advocate” of public financing of election campaigns. This month, he reiterated his “support” for such financing while becoming the first major party presidential nominee ever to reject it for his own campaign...Do you think either of these men is a hypocrite?

Moral hypocrisy allows us to gain the social benefits of appearing virtuous without incurring the personal costs of virtuous behavior. If you can deceive even yourself into believing that you’re acting for the common good, you’ll have more energy and confidence to further your own interests — and your self-halo can persuade others to help you along.

But as useful as hypocrisy can be, it’s apparently not quite as basic as the human instinct to do unto others as you would have them do unto you. Your mind can justify double standards, it seems, but in your heart you know you’re wrong.

The Curious Parallel of Language and Species Evolution

An article in PLoS Biology with the title of this post with worth a look. It describes recent work that has it origins in Charles Darwin's passage in The Descent of Man: “The formation of different languages and of distinct species, and the proofs that both have been developed through a gradual process, are curiously parallel.”