Upstairs-Downstairs pathways regulating our cravings.

Kober et al. provide yet another "upstairs/downstairs" story of how it takes increased activity in our frontal cortex to override addictions and cravings fueled by the deeper structures in our old mammalian brain:

The ability to control craving for substances that offer immediate rewards but whose long-term consumption may pose serious risks lies at the root of substance use disorders and is critical for mental and physical health. Despite its importance, the neural systems supporting this ability remain unclear. Here, we investigated this issue using functional imaging to examine neural activity in cigarette smokers, the most prevalent substance-dependent population in the United States, as they used cognitive strategies to regulate craving for cigarettes and food. We found that the cognitive down-regulation of craving was associated with (i) activity in regions previously associated with regulating emotion in particular and cognitive control in general, including dorsomedial, dorsolateral, and ventrolateral prefrontal cortices, and (ii) decreased activity in regions previously associated with craving, including the ventral striatum, subgenual cingulate, amygdala, and ventral tegmental area. Decreases in craving correlated with decreases in ventral striatum activity and increases in dorsolateral prefrontal cortex activity, with ventral striatal activity fully mediating the relationship between lateral prefrontal cortex and reported craving. These results provide insight into the mechanisms that enable cognitive strategies to effectively regulate craving, suggesting that it involves neural dynamics parallel to those involved in regulating other emotions. In so doing, this study provides a methodological tool and conceptual foundation for studying this ability across substance using populations and developing more effective treatments for substance use disorders.

Figure - Regions active during or modulated by the cognitive regulation of craving. (A) Medial (Left) and lateral (Right) views of brain regions that showed greater activation when participants used a cognitive strategy to reduce their craving. Highlighted activations are shown in regions previously implicated in regulation of aversive emotion. (B) Medial (Left) and coronal (Right) views of brain regions that showed reduced activation. Highlighted reductions are shown in regions previously reported in studies of cue-induced craving or emotion. corr, Corrected for multiple comparisons; uncorr, uncorrected for multiple comparisons.

Delusions of Gender.

Katherine Bouton reviews what looks like a very interesting book by cognitive neuroscientist Cordelia Fine which has the title of this post. The book:

takes on that tricky question, Why exactly are men from Mars and women from Venus?, and eviscerates both the neuroscientists who claim to have found the answers and the popularizers who take their findings and run with them...Summarizing the research, she writes, “Nonexistent sex differences in language lateralization, mediated by nonexistent sex differences in corpus callosum structure, are widely believed to explain nonexistent sex differences in language skills.”...What all this adds up to, she says, is neurosexism. It’s all in the brain....But Dr. Fine persuasively argues that it is, in fact, all in the mind. Jan Morris, the historian, travel writer and male-to-female transsexual, saw this implicit stereotyping firsthand: “The more I was treated as a woman, the more woman I became. ”

Metacognitive deficits in public political discourse

Some interesting chunks from a recent David Brooks column in the NYTimes, on what he takes to be the underlying problem facing this country. He starts by describing the decay in the 19th and early 20th century emphasis on moral character,

...when people were more conscious of the fallen nature of men and women. People were held to be inherently sinful, and to be a decent person one had to struggle against one’s weakness...This emphasis on mental character lasted for a time, but it has abated. There’s less talk of sin and frailty these days...In the media competition for eyeballs, everyone is rewarded for producing enjoyable and affirming content. Output is measured by ratings and page views, so much of the media, and even the academy, is more geared toward pleasuring consumers, not putting them on some arduous character-building regime.

...we’re all less conscious of our severe mental shortcomings and less inclined to be skeptical of our own opinions...We have confirmation bias; we pick out evidence that supports our views. We are cognitive misers; we try to think as little as possible. We are herd thinkers and conform our perceptions to fit in with the group...The ensuing mental flabbiness is most evident in politics. Many conservatives declare that Barack Obama is a Muslim because it feels so good to say so...a seller’s market in ideologies...gives people a chance to feel victimized. There’s a rigidity to political debate. Issues like tax cuts and the size of government, which should be shaped by circumstances (often it’s good to cut taxes; sometimes it’s necessary to raise them), are now treated as inflexible tests of tribal purity.

To use a fancy word, there’s a metacognition deficit. Very few in public life habitually step back and think about the weakness in their own thinking and what they should do to compensate.

Inflammatory and neural responses to social rejection.

Slavich et al. measure changes in both brain activity and inflammatory chemical activity in response to social rejection:

Although stress-induced increases in inflammation have been implicated in several major disorders, including cardiovascular disease and depression, the neurocognitive pathways that underlie inflammatory responses to stress remain largely unknown. To examine these processes, we recruited 124 healthy young adult participants to complete a laboratory-based social stressor while markers of inflammatory activity were obtained from oral fluids. A subset of participants (n = 31) later completed an fMRI session in which their neural responses to social rejection were assessed. As predicted, exposure to the laboratory-based social stressor was associated with significant increases in two markers of inflammatory activity, namely a soluble receptor for tumor necrosis factor-α (sTNFαRII) and interleukin-6 (IL-6). In the neuroimaging subsample, greater increases in sTNFαRII (but not IL-6) were associated with greater activity in the dorsal anterior cingulate cortex and anterior insula, brain regions that have previously been associated with processing rejection-related distress and negative affect. These data thus elucidate a neurocognitive pathway that may be involved in potentiated inflammatory responses to acute social stress. As such, they have implications for understanding how social stressors may promote susceptibility to diseases with an inflammatory component.

The psychology of possibility.

An interesting article in the Harvard Magazine describes the life work of Ellen Langer, her demonstrations that our social self image (old versus young, for example) strongly patterns our actual vitality and physiology, her work on Mindfulness, unconscious processing, etc. I recommend that you read the article. Here are some clips from its beginning that hooked me (I actually did my own mini-repeat of the experiment described, a simple self-experiment of pretending that I had been transported back in time to 40 years ago, and convinced myself I was experiencing some of the effects described)...

In 1981, early in her career at Harvard, Ellen Langer and her colleagues piled two groups of men in their seventies and eighties into vans, drove them two hours north to a sprawling old monastery in New Hampshire, and dropped them off 22 years earlier, in 1959. The group who went first stayed for one week and were asked to pretend they were young men, once again living in the 1950s. The second group, who arrived the week afterward, were told to stay in the present and simply reminisce about that era. Both groups were surrounded by mid-century mementos—1950s issues of Life magazine and the Saturday Evening Post, a black-and-white television, a vintage radio—and they discussed the events of the time: the launch of the first U.S. satellite, Castro’s victory ride into Havana, Nikita Khrushchev and the need for bomb shelters.

...Before and after the experiment, both groups of men took a battery of cognitive and physical tests, and after just one week, there were dramatic positive changes across the board. Both groups were stronger and more flexible. Height, weight, gait, posture, hearing, vision—even their performance on intelligence tests had improved. Their joints were more flexible, their shoulders wider, their fingers not only more agile, but longer and less gnarled by arthritis. But the men who had acted as if they were actually back in 1959 showed significantly more improvement. Those who had impersonated younger men seemed to have bodies that actually were younger.

Delaying age-related damange to nerves and muscle

Both exercise and drastic dieting have been shown to have anti-ageing effects in the brain. Studies on mice now suggest that such lifestyle changes preserve communication between nerves and muscles:

The cellular basis of age-related behavioral decline remains obscure but alterations in synapses are likely candidates. Accordingly, the beneficial effects on neural function of caloric restriction and exercise, which are among the most effective anti-aging treatments known, might also be mediated by synapses. As a starting point in testing these ideas, we studied the skeletal neuromuscular junction (NMJ), a large, accessible peripheral synapse. Comparison of NMJs in young adult and aged mice revealed a variety of age-related structural alterations, including axonal swellings, sprouting, synaptic detachment, partial or complete withdrawal of axons from some postsynaptic sites, and fragmentation of the postsynaptic specialization. Alterations were significant by 18 mo of age and severe by 24 mo. A life-long calorie-restricted diet significantly decreased the incidence of pre- and postsynaptic abnormalities in 24-mo-old mice and attenuated age-related loss of motor neurons and turnover of muscle fibers. One month of exercise (wheel running) in 22-mo-old mice also reduced age-related synaptic changes but had no effect on motor neuron number or muscle fiber turnover. Time-lapse imaging in vivo revealed that exercise partially reversed synaptic alterations that had already occurred. These results demonstrate a critical effect of aging on synaptic structure and provide evidence that interventions capable of extending health span and lifespan can partially reverse these age-related synaptic changes.

Predicting inherited risk for anxiety

Ned Kalin and his colleagues here at the University of Wisconsin have made the interesting observation that increased brain activity in the amygdala (not inheritable) and anterior hippocampus (inheritable) of young monkeys can predict anxious temperament in young monkeys, leading Kalin to suggest that "that young children who have higher activity in these brain regions are more likely to develop anxiety and depression as adolescents and adults, and are also more likely to develop drug and alcohol problems in an attempt to treat their distress." The study looked at 238 young rhesus monkeys from a family of more than 1500 lab-raised monkeys with well-documented pedigrees. By analyzing the family connections among the young monkeys, which ranged from siblings to distant cousins, the finding was that an anxious temperament was partly heritable, accounting for about 36% of the variability in individual monkeys' responses on a human intruder test (as measured by the reduction in movement and vocalization and increase in stress hormone levels). Elevated responses in the hippocampus were heritable (accounting for about half of individual variability), whereas the elevated responses in the amygdala were not.

Figure from paper - Anxious monkeys show elevated activity in the amygdala (left) and anterior hippocampus (right), but the effects of heredity seem to act more on the hippocampus.

Oxytocin makes people trusting, but not gullible.

Mikolajczak et al. demonstrate that oxytocin (OT) is not the magical “trust elixir” described in the news, on the Internet, or even by some influential researchers. They design experiments to show that it does not make people indiscriminately prosocial (trusting to a fault). They used a customized version of the trust game that manipulated partners’ trustworthiness and measured participants’ investment in each partner. They found higher investment by participants who received a nasal OT spray than by control participants, unless there were cues that a partner might not be trustworthy. They also observed a significant effect of OT when the partner was a computer suggesting that OT’s effect may be primarily moderated not by the human versus nonhuman nature of the partner, but rather by the perceived risk inherent to the interaction. In case you are interested, here is their description of the setup:

Each participant assumed the role of investor and could transfer money to a “trustee,” in whose hands the funds would triple. The trustee would then transfer all the money, part of it, or none of it back to the investor. If the investor entrusted the trustee with all of his money, he could maximize his profits if the trustee was reliable and fair. Conversely, he could lose everything if the trustee was not fair. The trust game is perfectly suited to establish the investor’s level of trust (i.e., the higher the trust, the higher the transfer). Each participant played with three different types of trustees: seemingly reliable humans, seemingly unreliable humans, and the computer (i.e., a fully neutral device). By manipulating the partners’ trustworthiness, we sought to determine the extent to which OT impairs sensitivity to potential signs of dishonesty.

In one part of the game, participants were told that they would play 10 rounds with the computer, which would randomly determine the back transfers; in another part, participants were told that they would play online with real people. We gave participants a brief description of their partner before each round. Based on a pretest, these descriptions were manipulated to induce high or low trust: We combined trustworthy academic fields (e.g., philosophy) and activities (e.g., practicing first aid) to make some partners seem reliable, and untrustworthy academic fields (e.g., marketing) and activities (e.g., playing violent sports) to make other partners seem unreliable. The main effect of partner type  confirms that these descriptions were effective in inducing trust or mistrust in this study. Each participant played 10 rounds with 10 different partners (5 trustworthy, 5 untrustworthy). No back-transfers feedback was provided during the experiment, and presentation order was randomized. Before leaving the laboratory, participants were asked to guess the group (OT or control) to which they had been assigned.

Coping with stress stimulates new brain cell growth.

Interesting stuff from Lyons et al., experiments on monkeys which look like they would extrapolate to us humans:

Coping with intermittent social stress is an essential aspect of living in complex social environments. Coping tends to counteract the deleterious effects of stress and is thought to induce neuroadaptations in corticolimbic brain systems. Here we test this hypothesis in adult squirrel monkey males exposed to intermittent social separations and new pair formations. These manipulations simulate conditions that typically occur in male social associations because of competition for limited access to residency in mixed-sex groups. As evidence of coping, we previously confirmed that cortisol levels initially increase and then are restored to prestress levels within several days of each separation and new pair formation. Follow-up studies with exogenous cortisol further established that feedback regulation of the hypothalamic-pituitary-adrenal axis is not impaired. Now we report that exposure to intermittent social separations and new pair formations increased hippocampal neurogenesis in squirrel monkey males. Hippocampal neurogenesis in rodents contributes to spatial learning performance, and in monkeys we found that spatial learning was enhanced in conditions that increased hippocampal neurogenesis. Corresponding changes were discerned in the expression of genes involved in survival and integration of adult-born granule cells into hippocampal neural circuits. These findings support recent indications that stress coping stimulates hippocampal neurogenesis in adult rodents. Psychotherapies designed to promote stress coping potentially have similar effects in humans with major depression.

Solving protein folding - humans outperform computers

I remember from my graduate student days in the 1960's attending biochemistry lectures in which the professors expressed confidence that we would soon know the algorithms for predicting from the linear sequence of amino acids in a protein the three dimensional shape into which it would fold. That goal has seemed to recede from view despite increasing effort with sophisticated supercomputers. (The problem is that even a moderately sized protein can theoretically fold into more possible shapes than there are particles in the universe.) It turns out that Foldit, a multiplayer online game that engages non-scientists, is now yielding more accurate predictions of correct protein folding than one of the best known computer folding programs, Rosetta@home, which was created by molecular biologist David Baker at Univ. Washington, Seattle. (The program distributes its calculations to thousands of home computers around the world, automatically sending the results back to Baker's lab.) From the abstract of the Cooper et al. paper on their Foldit game:

...top-ranked Foldit players excel at solving challenging structure refinement problems in which substantial backbone rearrangements are necessary to achieve the burial of hydrophobic residues. Players working collaboratively develop a rich assortment of new strategies and algorithms; unlike computational approaches, they explore not only the conformational space but also the space of possible search strategies. The integration of human visual problem-solving and strategy development capabilities with traditional computational algorithms through interactive multiplayer games is a powerful new approach to solving computationally-limited scientific problems.

Two useful reviews summarize this work, one in the NYTimes, the other in Science Now.

A Brahms Capriccio as a TGIF offering...

I've been lazy about playing and recording lately, and so have decided to spend a bit more time with my piano. This Brahms Capriccio has one randomly occurring error, which happens with any piece I play regardless of how well I know the notes. (I don't do the cut and paste editing of the good parts. Whatever happens on one complete play through is what you get.) See if you can find the stumble.

Watching our brains perceive the intentions of others.

Two interesting papers on  people playing economic or cooperation games during MRI imaging that reveals activations flitting about different areas of the frontal cortex as different inferences and judgments about other game participants are made:

First, from Dolan's group, on inference of belief:

Humans have the arguably unique ability to understand the mental representations of others. For success in both competitive and cooperative interactions, however, this ability must be extended to include representations of others' belief about our intentions, their model about our belief about their intentions, and so on. We developed a "stag hunt" game in which human subjects interacted with a computerized agent using different degrees of sophistication (recursive inferences) and applied an ecologically valid computational model of dynamic belief inference. We show that rostral medial prefrontal (paracingulate) cortex, a brain region consistently identified in psychological tasks requiring mentalizing, has a specific role in encoding the uncertainty of inference about the other's strategy. In contrast, dorsolateral prefrontal cortex encodes the depth of recursion of the strategy being used, an index of executive sophistication. These findings reveal putative computational representations within prefrontal cortex regions, supporting the maintenance of cooperation in complex social decision making.

The second, from Cooper et al., on judging the intentions of others:

In social decision-making, people care both about others' outcomes and their intentions to help or harm. How the brain integrates representations of others' intentions with their outcomes, however, is unknown. In this study, participants inferred others' decisions in an economic game during functional magnetic resonance imaging. When the game was described in terms of donations, ventromedial prefrontal cortex (VMPFC) activation increased for inferring generous play and decreased for inferring selfish play. When the game was described in terms of individual savings, however, VMPFC activation did not distinguish between strategies. Distinct medial prefrontal regions also encoded consistency with situational norms. A separate network, including right temporoparietal junction and parahippocampal gyrus, was more activated for inferential errors in the donation than in the savings condition. These results demonstrate that neural responses to others' generosity or selfishness depend not only on their actions but also on their perceived intentions.

Summary highlights of Cooper et al.:
- Response to others in identical economic games depends on game description
- Liking, VMPFC distinguish generous from selfish play in “group donation” game only
- Distinct MPFC regions encode consistency with norms regardless of outcome
- Right TPJ and MTL are more activated by learning errors in donation game

My hero questioned...

In this field of studying human and animal minds, I've long been in awe of the intelligence and originality of Mark Hauser. (If you enter the name Hauser in the search box in the left column of this blog you will find no fewer than 20 previous posts on his work!)  He has published crucial experiments on morality in animals, leading him to suggest a universal moral grammar analogous to Chomsky' universal language grammar, and has also reported mirror self recognition and inferring intentions of others in monkeys. His 2002 paper with Chomsky and Fitch on language evolution is a classic.

It appears now that his ambition may have outstripped his intellect. I was saddened to read this recent article in the NYTimes saying that Hauser has gone on academic leave from Harvard after an investigation by the university found problems with his research.

... his undoing seems to have been his experiments, many of which depended on videotaping cotton-topped tamarin monkeys and noting their responses. It is easy for human observers to see the response they want and so to be fooled by the monkeys.

The papers on mirror self recognition and inferring intention are particularly in question. A psychology colleague at Columbia University noted:

First there was arbitrary interpretation of the videotapes to suit the hypothesis...The other was whether the data was real. There have been a number of papers using videotape, and all of them have to be reviewed to see if the data holds up.

Paradigm change in the practice of science?

John Markoff writes an interesting article on how fundamentally critical discourse in mathematics and physics is being transformed by the web. The case in point was the claim by a researcher that he had demonstrated that P (the set of problems that can be easily solved) does not equal NP (those problems that are difficult to solve, but easy to verify once a solution is found). This inequality is fundamental to the modern cryptography required for electronic commerce and digital privacy. The proposed proof was found to have significant shortcomings within weeks, instead of the months to years required by exchanges of written papers and debate at scientific meetings, because discussion and analysis was carried out in real time on blogs and a wiki that had been quickly set up for the purpose of collectively analyzing the paper. Clay Shirky, author of “Cognitive Surplus: Creativity and Generosity in a Connected Age” argues:

....that the emergence of these new collaborative tools is paving the way for a second scientific revolution in the same way the printing press created a demarcation between the age of alchemy and the age of chemistry...a new set of norms is emerging about what it means to do mathematics, assuming coordinated participation.

Stereotypes can prevent perceptual learning.

Some interesting observations from Rydell et al, who find that simply reminding women about the negative stereotype about women's math and visual processing performance inhibits their performance on a visual search task...

Stereotype threat (ST) refers to a situation in which a member of a group fears that her or his performance will validate an existing negative performance stereotype, causing a decrease in performance. For example, reminding women of the stereotype “women are bad at math” causes them to perform more poorly on math questions from the SAT and GRE. Performance deficits can be of several types and be produced by several mechanisms. We show that ST prevents perceptual learning, defined in our task as an increasing rate of search for a target Chinese character in a display of such characters. Displays contained two or four characters and half of these contained a target. Search rate increased across a session of training for a control group of women, but not women under ST. Speeding of search is typically explained in terms of learned “popout” (automatic attraction of attention to a target). Did women under ST learn popout but fail to express it? Following training, the women were shown two colored squares and asked to choose the one with the greater color saturation. Superimposed on the squares were task-irrelevant Chinese characters. For women not trained under ST, the presence of a trained target on one square slowed responding, indicating that training had caused the learning of an attention response to targets. Women trained under ST showed no slowing, indicating that they had not learned such an attention response.

Exercise moderates anger

Tara Parker-Pope does a summary of several studies on psychological effects of exercise, which numerous studies have shown to make people (and laboratory mice) more relaxed, confident, and happy. She describes a Univ. of Georgia study showing that students with short fuses are less likely to feel anger at a provocative stimulus after exercise.

Effect of wilderness vs. tech-world on the brain

Matt Richtel describes the efforts of a group of five neuroscientists to guage the brain effects of their multitasking high tech world by taking themselves on a 5-day rafting wilderness region of the San Juan river in the Glen Canyon preserve - no email, no cell phones, no laptops, etc.

...to understand how heavy use of digital devices and other technology changes how we think and behave, and how a retreat into nature might reverse those effects.

The group contained believers (who believe in damaging psychological effects of too much digital stimulation) and skeptics (who don't). They discussed (the following is a cut/paste/edit gemash):

...a debate that has become increasingly common as technology has redefined the notion of what is “urgent.” How soon do people need to get information and respond to it? The believers in the group say the drumbeat of incoming data has created a false sense of urgency that can affect people’s ability to focus.
...a seminal study from the University of Michigan that showed people can better learn after walking in the woods than after walking a busy street...The study indicates that learning centers in the brain become taxed when asked to process information, even during the relatively passive experience of taking in an urban setting. By extension, some scientists believe heavy multitasking fatigues the brain, draining it of the ability to focus.
...Why don’t brains adapt to the heavy stimulation, turning us into ever-stronger multitaskers?..Why wouldn’t the circuits be exercised, in a sense, and we’d get stronger?
...Behavioral studies have shown that performance suffers when people multitask... researchers are wondering whether attention and focus can take a hit when people merely anticipate the arrival of more digital stimulation...The expectation of e-mail seems to be taking up our working memory...To the extent you have less working memory, you have less space for storing and integrating ideas and therefore less to do the reasoning you need to do...Working memory is a precious resource in the brain...might they be able to prove it using imaging?
...On the trip time slows down, there are periods of silence and awed looks at surroundings...The group becomes more reflective, quieter, more focused on the surroundings...even the more skeptical of the scientists say something is happening to their brains that reinforces their scientific discussions — something that could be important to helping people cope in a world of constant electronic noise...If we can find out that people are walking around fatigued and not realizing their cognitive potential...What can we do to get us back to our full potential?

"The Law of Emotional Balance?"

I thought I would pass on to readers an example of the sort of stuff that I, retired professor and minor blog writer that I am - get sent several times a weeks to "please support or link to," presumably because internet scanning algorithms point to the MindBlog site. I got hooked into spending more time on this one than I should have because the cover email was from Stephen Takowsky, publisher of The Beverly Hills Times, who had:

...come across a book about which we are considering running an article.... Your assistance would be greatly appreciated. Our main goal at this point is to determine whether there is any established scientific evidence that tends either to support or invalidate the theory presented in the book. We want to find out if there is any scientific research that is relevant to the premise of the book.

So....   I take the bait and click on http://www.ofgrandeur.com/ , find a slightly horrific graphic and an introduction on "The Law of Emotional Balance" that raises multiple red flags.   I can't get the better of my curiosity, so I click on, find "comments from active scientist in associated field" which appear to vague clips mentioning general ideas, but which do not reference this book's specific contents.  The brief introduction/preface pretty well finally cashes it in for me, and then I find the text, whose author is one Stephen Takowsky, owner and publisher of The Beverly Hills Times ("who had come across a book..", see above....must be his evil twin). He  has solicited the opinion of hundreds or academics and reports thus far that the professors' votes are 381 nay, and 253 yea...

Still, having taken as much of my time (and yours).... I click through the book and realize that any attempt to make detailed comments would be a promethean and futile task.

Seeking immortality in words, not religion

Christopher Hitchens, atheist author of "God is Not Great: How Religion Poisons Everything," is most likely dying of esophageal cancer. Liesl Schillinger writes on how his writing of an essay on his experience of illness has

...elicited hundreds of responses from well-wishers (and some foes), who urge Mr. Hitchens in online comments (and in their prayers, many write) to accept salvation...When asked, “Do you find it insulting for people to pray for you?” Mr. Hitchens responded: “No, no. I take it kindly, under the assumption that they are praying for my recovery.”..All the same, Mr. Hitchens dismissed both the notion that his cancer would lead him to make a tardy profession of faith and the idea that, if it did, such a profession would be valid...“The entity making such a remark might be a raving, terrified person whose cancer has spread to the brain,” he said. “I can’t guarantee that such an entity wouldn’t make such a ridiculous remark, but no one recognizable as myself would ever make such a remark.”

Hitchens' friend, novelist Martin Amis,

...said his friend, like other writers, surely believed that after death, “not all of you will die,” because the printed words they leave behind constitute a kind of immortality. He added, “The desire for immortality ... explains all the extraordinary achievements, both good and bad.”

Another British-born intellectual's faith in articulacy caught the public eye this summer. On Aug. 6, Tony Judt died of amyotrophic lateral sclerosis. He had told a former student

...that he wanted his epitaph to read, “I did words.”

A custody battle for the mind - brain genes from different parents

Relatively few genes (∼100) have previously been shown to be imprinted such that their expression in progeny derives from either the maternal or paternal copy. Two papers by Gregg et al. now expand this number by an order of magnitude, and reveal complex patterns of parent-of-origin bias in gene expression in the brain that are developmentally and regionally restricted, and in many cases, sexually dimorphic. They uncovered over 1300 loci with maternal or paternal allelic bias. Comparison of the parent-of-origin allelic expression bias in the adult hypothalamus and cortex, and in the developing brain, revealed spatiotemporal and sex-specific regulation. Here are a few clips from the first and the second articles:

...Many imprinted genes are expressed in neural systems associated with feeding and motivated behaviors, and parental biases preferentially target genetic pathways governing metabolism and cell adhesion. We observed a preferential maternal contribution to gene expression in the developing brain and a major paternal contribution in the adult brain. Thus, parental expression bias emerges as a major mode of epigenetic regulation in the brain.
...Our study identified preferential selection of the maternally inherited X chromosome in glutamatergic neurons of the female cortex. Moreover, analysis of the cortex and hypothalamus identified 347 autosomal genes with sex-specific imprinting features. In the hypothalamus, sex-specific imprinted genes were mostly found in females, which suggests parental influence over the hypothalamic function of daughters. We show that interleukin-18, a gene linked to diseases with sex-specific prevalence, is subject to complex, regional, and sex-specific parental effects in the brain. Parent-of-origin effects thus provide new avenues for investigation of sexual dimorphism in brain function and disease.

I found some background given in a review of this work by Tollkuhn et. al. to be useful. Some clips:

Genomic imprinting is a phenomenon in which either the maternal or paternal copy of a gene is expressed preferentially in all progeny. This curious phenomenon, which violates classical Mendelian genetics, appears to occur only in mammals among vertebrates....An imprinted gene renders the organism functionally haploid at that locus, and permits the expression of phenotypes from mutations that would normally be recessive. In other words, imprinting precludes the protection of a back-up copy afforded by a diploid genome. It has been postulated therefore that the existence of imprinting in mammals must confer a selective advantage. What this selective pressure might be remains to be settled, but the most widely accepted explanation is that imprinting is a consequence of parental conflict over resource allocation to the progeny. Briefly, it is in the father's interest to maximize maternal resources devoted to his progeny, whereas the mother might wish to allocate resources more equitably to current and future progeny, who might conceivably result from matings with other males. This conflict is particularly acute in placental mammals, in whom the progeny develop in utero and often for prolonged gestational periods, requiring greater maternal investment. As applied to imprinting, the conflict theory predicts that paternally expressed genes should increase the use of maternal resources to produce more fit offspring. By contrast, maternally expressed genes should quell the effects of such paternally expressed genes.