Primary Visual Cortex Size Highly Variable


[T]he primary visual cortex – the area at the back of the brain responsible for processing what we see in the world around us – is known to differ in size by up to three times from one individual to the next.

Now, researchers at the Wellcome Trust Centre for Neuroimaging at UCL (University College London) have shown for the first time that the size of this area affects how we perceive our environment. [...]

Dr D Samuel Schwarzkopf, Chen Song and Professor Geraint Rees showed a series of optical illusions to thirty healthy volunteers. These included the Ebbinghaus illusion, a well-known illusion in which two circles of the same size are each surrounded by circular ‘petals’; one of the circles is surrounded by larger petals, the other by smaller petals. Most people will see the first circle as smaller than the second one

In a second optical illusion, the Ponzo illusion, the volunteers were shown two identically sized circles superimposed onto the image of a tunnel. In this illusion, the circle placed further back in the tunnel appears larger than that placed near the front.

By adapting these illusions, the researchers were able to show that individual volunteers saw the illusions differently. For example, some people saw a big (although illusory) difference in size between the two circles, but others barely saw any difference in apparent size. [...]

[T]here was a strong link between its size and the extent to which volunteers perceived the size illusion – the smaller the area, the more pronounced the visual illusion. [...] “We have shown that precisely how big something appears to you depends on the size of a brain area that is necessary for vision. How much your brain tricks you depends on how much ‘real estate’ your brain has put aside for visual processing.” (via.)


Anterior cingulate cortex, religion, atheism, and more.


With two experiments, the researchers showed that when people think about religion and God, their brains respond differently—in a way that lets them take setbacks in stride and react with less distress to anxiety-provoking mistakes. Participants either wrote about religion or did a scrambled word task that included religion and God-related words. Then the researchers recorded their brain activity as they completed a computerized task—one that was chosen because it has a high rate of errors. The results showed that when people were primed to think about religion and God, either consciously or unconsciously, brain activity decreases in areas consistent with the anterior cingulate cortex (ACC), an area associated with a number of things, including regulating bodily states of arousal and serving an alerting function when things are going wrong, including when we make mistakes.

Interestingly, atheists reacted differently; when they were unconsciously primed with God-related ideas, their ACC increased its activity. The researchers suggest that for religious people, thinking about God may provide a way of ordering the world and explaining apparently random events and thus reduce their feelings of distress. In contrast, for atheists, thoughts of God may contradict the meaning systems they embrace and thus cause them more distress. (via.)

More on the anterior cingulate cortex, and in this case, specifically religious extremism:

Across all studies, anxious conditions caused participants to become more eagerly engaged in their ideals and extreme in their religious convictions. In one study, mulling over a personal dilemma caused a general surge toward more idealistic personal goals. In another, struggling with a confusing mathematical passage caused a spike in radical religious extremes. In yet another, reflecting on relationship uncertainties caused the same religious zeal reaction.

Researchers found that religious zeal reactions were most pronounced among participants with bold personalities (defined as having high self-esteem and being action-oriented, eager and tenacious), who were already vulnerable to anxiety, and felt most hopeless about their daily goals in life.

A basic motivational process called Reactive Approach Motivation (RAM) is responsible, according to lead researcher Ian McGregor, Associate Professor in York’s Department of Psychology, Faculty of Health. “Approach motivation is a tenacious state in which people become ‘locked and loaded’ on whatever goal or ideal they are promoting. They feel powerful, and thoughts and feelings related to other issues recede,” he says.

“RAM is usually an adaptive goal regulation process that can re-orient people toward alternative avenues for effective goal pursuit when they hit a snag. Our research shows that humans can sometimes co-opt RAM for short term relief from anxiety, however. By simply promoting ideals and convictions in their own minds, people can activate approach motivation, narrow their motivational focus away from anxious problems, and feel serene as a result,” says McGregor. [...]

Findings published last year in the journal Psychological Science by the same authors and collaborators at the University of Toronto found that strong religious beliefs are associated with low activity in the anterior cingulate cortex, the part of the brain that becomes active in anxious predicaments.

“Taken together, the results of this research program suggest that bold but vulnerable people gravitate to idealistic and religious extremes for relief from anxiety,” McGregor says. (via.)

Interestingly, according to Wikipedia (egads! check your sources, man!) the ACC also plays a role in empathy:

A large number of experiments using functional MRI, electroencephalography (EEG) and magnetoencephalography (MEG) have shown that certain brain regions (in particular the anterior insula, anterior cingulate cortex, and inferior frontal cortex) are active when a person experiences an emotion (disgust, happiness, pain, etc.) and when he or she sees another person experiencing an emotion.

There’s also this…

At the functional level, roles played by this region in communication include social bonding in mammals, control of vocalization in humans, semantic and syntactic processing, and initiation of speech. The involvement of the anterior cingulate cortex in social cognition is suggested where, for infants, joint attention skills are considered both prerequisites of social cognition and prelinguistic communication acts.

A few more tidbits on the ACC from Wikipedia:

The anterior cingulate cortex can be divided anatomically based on cognitive (dorsal), and emotional (ventral) components. The dorsal part of the ACC is connected with the prefrontal cortex and parietal cortex as well as the motor system and the frontal eye fields making it a central station for processing top-down and bottom-up stimuli and assigning appropriate control to other areas in the brain. By contrast, the ventral part of the ACC is connected with amygdala, nucleus accumbens, hypothalamus, and anterior insula, and is involved in assessing the salience of emotion and motivational information. The ACC seems to be especially involved when effort is needed to carry out a task such as in early learning and problem-solving. Many studies attribute functions such as error detection, anticipation of tasks, motivation, and modulation of emotional responses to the ACC. Rehearsing a task that originally produced spontaneous, novel responses to the point of producing rigid, stereotypic responses results in a diminished ACC response. [...]

Because the ACC is intricately involved with error detection and affective responses, it may very well be that this area forms the bases of self-confidence. [..] Whenever the dorsal area was active, fewer errors were committed providing more evidence that the ACC is involved with effortful performance. The second finding showed that, during error trials, the ACC activated later than for correct responses, clearly indicating a kind of evaluative function.[...]

There is evidence that damage to ACC is present in patients with schizophrenia, where studies have shown patients have difficulty in dealing with conflicting spatial locations in a Stroop-like task and having abnormal ERNs. Participants with ADHD were found to have reduced activation in the dorsal area of the ACC when performing the Stroop task. [...] There is evidence that this area may have a role in obsessive–compulsive disorder due to the fact that what appears to be an unnaturally low level of glutamate activity in this region has been observed in patients with the disorder, in strange contrast to many other brain regions that are thought to have excessive glutamate activity in OCD. Recent meta-analyses of voxel-based morphometry studies comparing people with OCD and healthy controls has found people with OCD to have [...] decreased grey matter volumes in bilateral dorsal medial frontal/anterior cingulate cortex.

Helen S. Mayberg and two collaborators described how they cured 4 of 6 depressed people — individuals virtually catatonic with depression despite years of talk therapy, drugs, even shock therapy — with pacemakerlike electrodes in area 25 (the anterior cingulate cortex). A decade earlier, Mayberg had identified area 25 as a key conduit of neural traffic between the “thinking” frontal cortex and the phylogenetically older central limbic region that gives rise to emotion. She subsequently found that area 25 appeared overactive in these depressed people — “like a gate left open,” as she puts it — allowing negative emotions to overwhelm thinking and mood. Inserting the electrodes closed this gate and rapidly alleviated the depression of two-thirds of the trial’s patients.[...]

Greater ACC activation levels were present in more emotionally-aware female participants when shown short ‘emotional’ video clips. Better emotional awareness is associated with improved recognition of emotional cues or targets, which is reflected by ACC activation.

From the Brodmann Area 25 (ventral ACC) Wikipedia article which should probably be merged into the “anterior cingulate cortex” page:

This region is extremely rich in serotonin transporters and is considered as a governor for a vast network involving areas like hypothalamus and brain stem, which influences changes in appetite and sleep; the amygdala and insula, which affect the mood and anxiety; the hippocampus, which plays an important role in memory formation; and some parts of the frontal cortex responsible for self-esteem.

One study has noted that BA25 is metabolically overactive in treatment-resistant depression and has found that chronic deep brain stimulation in the white matter adjacent to the area is a successful treatment for some patients. A different study found that metabolic hyperactivity in this area is associated with poor therapeutic response of persons with Major Depressive Disorder to cognitive-behavioral therapy and venlafaxine.


Heightened immune response in socially anxious


Everyone experiences social stress, whether it is nervousness over a job interview, difficulty meeting people at parties, or angst over giving a speech. In a new report, UCLA researchers have discovered that how your brain responds to social stressors can influence the body’s immune system in ways that may negatively affect health.

Lead author George Slavich, a postdoctoral fellow at the UCLA Cousins Center for Psychoneuroimmunology, and senior author Shelley Taylor, a UCLA professor of psychology, show that individuals who exhibit greater neural sensitivity to social rejection also exhibit greater increases in inflammatory activity to social stress. [...]

The researchers recruited 124 individuals — 54 men and 70 women — and put them into two awkward social situations. First, in the lab, the volunteers completed the Trier Social Stress Test (TSST), which involves preparing and delivering an impromptu speech and performing difficult mental arithmetic, both in front of a socially rejecting panel of raters wearing white lab coats. Mouth swabs were taken before and after the public-speaking tasks to test for changes in two key biomarkers of inflammatory activity — a receptor for tumor necrosis factor-? (sTNF?RII) and interleukin-6 (IL-6).

In a second session, 31 of the participants received an MRI brain scan while playing a computerized game of catch with what they believed were two other real people. The researchers focused on two areas of the brain known to respond to social stress — the dorsal anterior cingulate cortex (dACC) and the anterior insula.

At first, the game was between all three “players.” Halfway through the game, however, the research subject was excluded, leading to an experience of social rejection. The researchers then examined how differences in neural activity during social rejection correlated with differences in inflammatory responses to the TSST.

Their results showed that individuals who exhibited greater neural activity in the dorsal anterior cingulate cortex and anterior insula during social rejection in the brain scanner also exhibited greater increases in inflammatory activity when exposed to acute social stress in the lab.

“This is further evidence of how closely our mind and body are connected,” Slavich said. “We have known for a long time that social stress can ‘get under the skin’ to increase risk for disease, but it’s been unclear exactly how these effects occur. To our knowledge, this study is the first to identify the neurocognitive pathways that might be involved in inflammatory responses to acute social stress.” [...]

One critical question raised by the present findings is why neural sensitivity to social rejection would cause an increase in inflammation. There are several possible reasons, the authors note. For one, since physical threats have historically gone hand in hand with social threat or rejection, inflammation may be triggered in anticipation of a physical injury. Inflammatory cytokines — proteins that regulate the immune system — are released in response to impending (or actual) physical assault because they accelerate wound-healing and reduce the risk of infection.

via.

This may also be of interest: Tylenol (acetaminophen) eases social anxiety.


Brain abnormalities in adolescents with substance abuse & conduct disorders


The scientists, including collaborators at the University of Colorado at Boulder and the University of Maryland, studied 20 adolescent boys. On average they had been on probation 139 of the last 180 days; 19 of the 20 had the psychiatric diagnosis of conduct disorder, and all had diagnoses of substance use disorder. They had been abstinent, however, an average of about five weeks when studied. They were compared with 20 other boys who did not have serious antisocial or drug problems, but who were of similar age, ethnicity, and home neighborhoods.

All played a computerized risk-taking game that repeatedly presented a choice between a cautious and a risky behavior: press the left button and always win one cent, or press the right button and either win five cents or lose ten cents. The scientists examined brain activation with functional magnetic resonance imaging (fMRI) as the boys decided to press right or left, and then as they experienced wins or losses after right presses.

Brain activation differed dramatically in the two groups. The anterior cingulate cortex monitors changing rewards and punishments, and then sends that information to another brain region (dorsolateral prefrontal cortex), which regulates one’s choices among possible behaviors. During decision-making, antisocial boys had significantly less brain activity than normals in both of those regions, and also in other decision-making areas (orbitofrontal cortex, amygdala, insula).

via.