Posts tagged brain activity
Articles and news from the latest research reports.
Brain’s dynamic duel underlies win-win choices
People choosing between two or more equally positive outcomes experience paradoxical feelings of pleasure and anxiety, feelings associated with activity in different regions of the brain, according to research led by Amitai Shenhav, an associate research scholar at the Princeton Neuroscience Institute at Princeton University.
In one experiment, 42 people rated the desirability of more than 300 products using an auction-like procedure. Then they looked at images of paired products with different or similar values and were asked to choose between them. Their brain activity was scanned using functional magnetic resonance imaging (fMRI). After the scan, participants reported their feelings before and during each choice. They received one of their choices at the end of the study.
Choices between two highly valued items (high-high), such as a digital camera and a camcorder, were associated with the most positive feelings and the greatest anxiety, compared with choices between items of low value (low-low), like a desk lamp and a water bottle, or between items of different values (low-high). Functional MRI scans showed activity in two regions of the brain, the striatum and the prefrontal cortex, both known to be involved in decision-making. Interestingly, lower parts of both regions were more active when subjects felt excited about being offered the choice, while activity in upper parts was strongly tied to feelings of anxiety.
This evidence that parallel brain circuits are associated with opposing emotional reactions helps to answer a puzzling question, according to Shenhav: “Why isn’t our positivity quelled by our anxiety, or our anxiety quelled by the fact that we’re getting this really good thing at the end? This suggests that it’s because these circuits evolved for two different reasons,” he said. “One of them is about evaluating the thing we’re going to get, and the other is about guiding our actions and working out how difficult the choice will be.”
The study, “Neural correlates of dueling affective reactions to win-win choices,” was published July 14 in the Proceedings of the National Academy of Sciences. Shenhav conducted the research as a graduate student at Harvard University, along with Professor of Psychology and Neuroscience Randy Buckner, the study’s senior author.
A second fMRI experiment showed that the same patterns of emotional reactions and brain activity persisted even when the participants were told before each choice how similarly they had valued the items. Their anxiety didn’t abate, despite knowing how little they stood to lose by making a “wrong” choice. In a third experiment, Shenhav and Buckner tested whether giving people more than two choices increased their levels of anxiety. Indeed, they found that providing six options led to higher levels of anxiety than two options, particularly when all six of the options were highly valued items. But positive feelings about being presented with the choice were similar for two or six options.
This suggests that the anxiety stems from the conflict of making the decision, rather than the opportunity cost of the choice — an economic concept that refers to the lost value of the second-best option. The opportunity cost should be the same, regardless of the number of choices. In addition, subjects in this final study were given an unlimited amount of time to make a decision, compared with 1.5 seconds in the first two studies. The results showed that time pressure was not the main source of anxiety during the choices.
At the end of each study, participants had a surprise opportunity to reverse their earlier choices. Higher activity in a part of the brain called the anterior cingulate cortex around the time of an initial choice predicted whether that decision would later be reversed. Previous work has shown that this brain region is involved in assessing how conflicted an individual feels over a particular choice; this result suggests that some choices may have continued to elicit conflict after the participant made a decision, Shenhav said. The researchers also found that people who reported more anxiety in their daily lives were more likely to change their minds.
This work could explain why ostensibly positive options can evoke a mixture of positive and negative responses, which are not explained by purely economic analyses of choice. “Rationally, there’s no reason why when you put one good thing with another good thing, you should feel worse about the situation,” said Brian Knutson, an associate professor of psychology and neuroscience at Stanford University, who is familiar with the work but was not involved in it. “The neuroimaging tells us that these different mechanisms are fighting with each other,” he said. “Understanding that dynamic can help us understand why decisions that we think should make us feel better can actually make us feel worse.”
According to Shenhav, this research could shed light on the neural processes that can make more momentous choices so paralyzing for some people — for instance, deciding where to go to college or which job offer to take. But he admits that even more trivial decisions can be tough for him. “I probably experience more win-win choice anxiety than the average person,” he said. “I’m even terrible at choosing where to eat dinner.”
Neymar’s brain on auto-pilot
Brazilian superstar Neymar’s brain activity while dancing past opponents is less than 10 per cent the level of amateur players, suggesting he plays as if on auto-pilot, according to Japanese neurologists.
Results of brain scans conducted on Neymar indicate minimal cerebral function when he rotates his ankle and point to the Barcelona striker’s wizardry being uncannily natural.
"From MRI images, we discovered Neymar’s brain activity to be less than 10 per cent of an amateur player," researcher Eiichi Naito said on Friday.
"It is possible genetics is a factor, aided by the type of training he does."
The findings were published in the Swiss journal Frontiers in Human Neuroscience following a series of motor skills tests carried out on the 22-year-old Neymar and several other athletes in Barcelona in February.
(Image: Sergio Moraes / REUTERS)
Brain imaging study examines second-language learning skills
With enough practice, some learners of a second language can process their new language as well as native speakers, research at the University of Kansas shows.
(Credit: bigstockphoto)
Using brain imaging, a trio of KU researchers was able to examine to the millisecond how the brain processes a second language. They then compared their findings with their previous results for native speakers and saw both followed similar patterns.
The research by Robert Fiorentino and Alison Gabriele, both associate professors in the linguistics department, and José Alemán Bañón, a former KU graduate student who is now a postdoctoral researcher at the University of Reading in the United Kingdom, was published this month in the journal Second Language Research.
For years, linguists have debated whether second-language learners would ever resemble native speakers in their ability to process language properties that differ between the first and second language, such as gender agreement, which is a property of Spanish but not English. In Spanish, all nouns are categorized as masculine or feminine, and various elements in the sentence, such as adjectives, need to carry the gender feature of the noun as well.
Some researchers argued that even those who spoke a second language with a high level of accuracy were using a qualitatively different mechanism than native speakers.
“We realized that these different theories proposing that either second-language learners use the same mechanism, or a different mechanism could actually be teased apart by using brain-imaging techniques,” Gabriele said.
The team studied 26 high-level Spanish speakers who hadn’t learned to speak Spanish until after age 11 and grew up with English as the majority language. The speakers used Spanish on a daily basis and had spent an average of a year and a half in a Spanish-speaking country.
They were compared with 24 native speakers, who were raised in Spanish-speaking countries and stayed in their home country until age 17.
To measure language processing as it happens, the team used a method known as electroencephalography (EEG), which uses an array of electrodes placed on the scalp to detect patterns of brain activity with high accuracy in timing.
Once hooked up to the EEG, the test subjects were asked to read sentences, some of which had grammatical errors in either number agreement or gender agreement.
The researchers then compared the results of the second-language learners to native speakers. They found that the highly proficient second-language speakers showed the same patterns of brain activity as native speakers when processing grammatical violations in sentences.
“We show that the learners’ brain activity looks qualitatively similar to that of native speakers, suggesting that they are using the same mechanisms,” Fiorentino said.
The study highlights the brain’s plasticity and its ability to acquire a new complex system even in adulthood.
“A lot of researchers have argued that there is some sort of language learning mechanism that might atrophy over the life span, particularly before puberty. And, we certainly have a lot of evidence that it is difficult to process your second language at nativelike levels and you have to go through quite a bit of effort to find people who can,” Gabriele said. “But I think what this paper shows is that it is possible.”
Gabriele and Fiorentino are working on a second phase of the research, studying how the brain processes a second language at the initial stages of exposure. Their preliminary results suggest that properties that are shared between the first and second language show patterns of brain activity that are very similar in learners and native speakers. This suggests that learners build on the representation for language that is already in place when learning a second language.
(Source: news.ku.edu)
Measuring Nurture: Study Shows How “Good Mothering” Hardwires Infant Brain
By carefully watching nearly a hundred hours of video showing mother rats protecting, warming, and feeding their young pups, and then matching up what they saw to real-time electrical readings from the pups’ brains, researchers at NYU Langone Medical Center have found that the mother’s presence and social interactions — her nurturing role — directly molds the early neural activity and growth of her offsprings’ brain.
Reporting in the July 21 edition of the journal Current Biology, the NYU Langone team showed that the mother’s presence in the nest regulated and controlled electrical signaling in the infant pup’s brain.
Although scientists have known for decades that maternal-infant bonding affects neural development, the NYU Langone team’s latest findings are believed to be the first to show — as it is happening — how such natural, early maternal attachment behaviors, including nesting, nursing, and grooming of pups, impact key stages in postnatal brain development.
Researchers say the so-called slow-wave, neural signaling patterns seen during the initial phases of mammalian brain development — between age 12 and 20 days in rats — closely resembled the electrical patterns seen in humans for meditation and conscious and unconscious sleep-wake cycles, and during highly focused attention. These early stages are when permanent neural communication pathways are known to form in the infant brain, and when increasing numbers of nerve axons become sheathed, or myelinated, to speed neural signaling.
According to senior study investigator and neurobiologist Regina Sullivan, PhD, whose previous research in animals showed how maternal interactions influenced gene activity in the infant brain, the latest study offers an even more profound perspective on maternal caregiving.
“Our research shows how in mammals the mother’s sensory stimulation helps sculpt and mold the infant’s growing brain and helps define the role played by ‘nurturing’ in healthy brain development, and offers overall greater insight into what constitutes good mothering,” says Sullivan, a professor at the NYU School of Medicine and its affiliated Nathan S. Kline Institute for Psychiatric Research. “The study also helps explain how differences in the way mothers nurture their young could account, in part, for the wide variation in infant behavior among animals, including people, with similar backgrounds, or in uniform, tightly knit cultures.”
“There are so many factors that go into rearing children,” says lead study investigator Emma Sarro, PhD, a postdoctoral research fellow at NYU Langone. “Our findings will help scientists and clinicians better understand the whole-brain implications of quality interactions and bonding between mothers and infants so closely after birth, and how these biological attachment behaviors frame the brain’s hard wiring.”
For the study, a half-dozen rat mothers and their litters, of usually a dozen pups, were watched and videotaped from infancy for preset times during the day as they naturally developed. One pup from each litter was outfitted with a miniature wireless transmitter, invisibly placed under the skin and next to the brain to record its electrical patterns.
Specifically, study results showed that when rat mothers left their pups alone in the nest, infant cortical brain electrical activity, measured as local field potentials, jumped 50 percent to 100 percent, and brain wave patterns became more erratic, or desynchronous. Researchers point out that such periodic desynchronization is key to healthy brain growth and communication across different brain regions.
During nursing, infant rat pups calmed down after attaching themselves to their mother’s nipple. Brain activity also slowed and became more synchronous, with clearly identifiable electrical patterns.
Slow-wave infant brain activity increased by 30 percent, while readings of higher brain-wave frequencies decreased by 30 percent. Milk delivery led to intermittent bursts of electrical brain activity that were double or five times higher than before.
Similar spikes in rat brain activity of more than 100 percent were observed when mothers naturally groomed their infant pups.
However, these brain surges progressively declined during weaning, as infant pups gained independence from their mothers, leaving the nest and seeking food on their own as they grew past two weeks of age.
Additional experiments with a neural-signaling blocking agent, propranolol, confirmed that maternal effects were controlled in part by secretion of norepinephrine, a key neurotransmitter and hormone involved in most basic brain and body functions, including regulation of heart rate and cognition. Noradrenergic blocking in infant rats mostly dampened all previously observed effects induced by their mothers.
Sullivan says her team next plans similar experiments to look at how behavioral variations by the mother affect infant rat brain development, with the added goal of mapping any differences in brain development.
Long term, they say, they hope to develop diagnostic tools and therapies for people whose brains may have been impaired or simply underdeveloped during infancy.
Sarro says more research is also under way to investigate what other, nonadrenergic biological mechanisms might also be involved in controlling maternal sensory stimulation of the infant brain.
(Image caption: Whole brain functional connectivity between the nucleus accumbens (NAc) and other brain areas in response to cannabis cues (vs. neutral cues) in all participants)
Dependence Alters the Brain’s Response to Pot Paraphernalia
New research from The University of Texas at Dallas demonstrates that drug paraphernalia triggers the reward areas of the brain differently in dependent and non-dependent marijuana users.
The study, published July 1 in Drug and Alcohol Dependence, demonstrated that different areas of the brain activated when dependent and non-dependent users were exposed to drug-related cues.
The 2012 National Survey on Drug Use and Health shows marijuana is the most widely used illicit drug in the United States. According to a 2013 survey from the Pew Research Center, 48 percent of Americans ages 18 and older have tried marijuana. The National Institute on Drug Abuse says that 9 percent of daily users will become dependent on marijuana.
“We know that people have a hard time staying abstinent because seeing cues for the drug use triggers this intense desire to seek out the drugs,” said Dr. Francesca Filbey, lead author of the study and professor at the Center for BrainHealth in the School of Behavioral and Brain Sciences. “That’s a clinically validated phenomenon and behavioral studies have also shown this to be the case. What we didn’t know was what was driving those effects in the brain.”
To find this effect, Filbey and colleagues conducted brain-imaging scans, called functional magnetic resonance imaging (fMRI), on 71 participants who regularly used marijuana. Just more than half of those were classified as dependent users. While being scanned, the participants were given either a used marijuana pipe or a pencil of approximately the same size that they could see and feel.
A comparison of the images revealed that the nucleus accumbens, the reward region in the brain, was activated in all users in response to the pipe. However, the strengths of the connections with other areas differed between dependent and non-dependent users.
“We found that the reward network is actually being driven by other areas unrelated to reward, like the areas in memory and attention or emotion,” Filbey said.
Non-dependent users showed greater activations in the orbital frontal cortex and hippocampus, suggesting that memory and attention were connected to the activation of the reward network. Dependent users had greater activations in the amygdala and anterior cingulate gyrus, suggesting a more emotional connection.
Additionally, the areas of the brain activated resemble areas activated for other addictions, such as nicotine or cocaine, lending greater support to the addictiveness of marijuana.
These findings suggest that marijuana abuse intervention needs to cater more specifically to a user’s level of addiction.
"Clinicians treating people with problems with marijuana dependence should consider the different processes that trigger the reward response when determining possible pharmacological or behavioral interventions,” Filbey said.
Brain responses to emotional images predict PTSD symptoms after Boston Marathon bombing
The area of the brain that plays a primary role in emotional learning and the acquisition of fear – the amygdala – may hold the key to who is most vulnerable to post-traumatic stress disorder.
Researchers at the University of Washington, Boston Children’s Hospital, Harvard Medical School and Boston University collaborated on a unique opportunity to study whether patterns of brain activity predict teenagers’ response to a terrorist attack.
The team had already performed brain scans on Boston-area adolescents for a study on childhood trauma. Then in April 2013 two bombs went off at the finish line of the Boston Marathon, killing three people and injuring hundreds more. Even people who were nowhere near the bombing reported distress about the attack and the days-long manhunt for the suspects.
So, one month after the attack, Katie McLaughlin, then at Boston Children’s Hospital and Harvard Medical School and now an assistant professor of psychology at the UW; co-author Margaret Sheridan, of Boston Children’s Hospital and Harvard Medical School; and their fellow researchers sent online surveys to teenagers who had previously participated in studies to assess PTSD symptoms related to the attack.
By using functional Magnetic Resonance Imaging scans from before the attack and survey data from after, the researchers found that heightened amygdala reaction to negative emotional stimuli was a risk factor for later developing symptoms of PTSD.
The research study was published July 3 in the journal Depression and Anxiety.
“The amygdala responds to both negative and positive stimuli, but it’s particularly attuned to identifying potential threats in the environment,” said McLaughlin, the study’s first author. “In the current study of adolescents the more their amygdala responded to negative images, the more likely they were to have symptoms of PTSD following the terrorist attacks.”
The brain scans were conducted during the year prior to the bombing. At that time, the teens were evaluated for their responses to emotional stimuli by viewing neutral and negative images. Neutral images included items such as a chair or button. Negative images showed people who were sad, fighting or threatening someone else. Participants rated the degree of emotion they felt while looking at each image. The MRIs measured whether blood flow increased to the amygdala and the hippocampus when viewing negative images as compared to neutral images.
In the follow-up survey the teens were asked whether they were at the finish line during the bombing, how much media exposure they had after the attack, whether they were part of the lockdown at home or school while authorities searched for the suspects, and how their parents responded to the incident. They also were asked about specific PTSD symptoms, such as how often they had trouble concentrating and whether they kept thinking about the bombing when they tried not to.
Researchers found a significant association between amygdala activation while viewing negative images and whether the teens developed PTSD symptoms after the bombing.
McLaughlin said a number of previous studies have shown that people with PTSD had heightened amygdala responses to negative emotions, but researchers didn’t know whether that came before or after the trauma.
“It’s often really difficult to collect neurobiological markers before a traumatic event has occurred,” she said. By scanning the adolescents’ brains before the bombing, she and her fellow researchers were able to show that “amygdala reactivity before a traumatic event predicts your response to that traumatic event.”
While two-thirds of Americans will be exposed to some kind of traumatic event during their lifetime, most, fortunately, will not develop PTSD.
“The more we understand the underlying neurobiological systems that shape reactions to traumatic events, the closer we move to understanding a person’s increased vulnerability to them,” McLaughlin said. “That could help us develop early interventions to help people who might develop PTSD later.”
(Source: washington.edu)
Transplantation of healthy new brain cells reverses learning and memory loss in Alzheimer’s disease model
A new study from the Gladstone Institutes has revealed a way to alleviate the learning and memory deficits caused by apoE4, the most important genetic risk factor for Alzheimer’s disease, improving cognition to normal levels in aged mice.
In the study, which was conducted in collaboration with researchers at UC San Francisco and published today in the Journal of Neuroscience, scientists transplanted inhibitory neuron progenitors—early-stage brain cells that have the capacity to develop into mature inhibitory neurons—into two mouse models of Alzheimer’s disease, apoE4 or apoE4 with accumulation of amyloid beta, another major contributor to Alzheimer’s. The transplants helped to replenish the brain by replacing cells lost due to apoE4, regulating brain activity and improving learning and memory abilities.
“This is the first time transplantation of inhibitory neuron progenitors has been used in aged Alzheimer’s disease models,” said first author Leslie Tong, a graduate student at the Gladstone Institutes and UCSF. “Working with older animals can be challenging from a technical standpoint, and it was amazing to see that the cells not only survived but affected activity and behavior.”
The success of the treatment in older mice, which corresponded to late adulthood in humans, is particularly important, as this would be the age that would be targeted were this method ever to be used therapeutically in people.
“This is a very important proof of concept study,” said senior author Yadong Huang, MD, PhD, an associate investigator at Gladstone Institutes and associate professor of neurology and pathology at UCSF. “The fact that we see a functional integration of these cells into the hippocampal circuitry and a complete rescue of learning and memory deficits in an aged model of Alzheimer’s disease is very exciting.”
A balance of excitatory and inhibitory activity in the brain is essential for normal function. However, in the apoE4 model of Alzheimer’s disease—a genetic risk factor that is carried by approximately 25% of the population and is involved in 60-75% of all Alzheimer’s cases—this balance gets disrupted due to a decline in inhibitory regulator cells that are essential in maintaining normal brain activity. The hippocampus, an important memory center in the brain, is particularly affected by this loss of inhibitory neurons, resulting in an increase in network activation that is thought to contribute to the learning and memory deficits characteristic of Alzheimer’s disease. The accumulation of amyloid beta in the brain has also been linked to this imbalance between excitatory and inhibitory activity in the brain.
In the current study, the researchers hoped that by grafting inhibitory neuron progenitors into the hippocampus of aged apoE4 mice, they would be able to combat these effects, replacing the lost cells and restoring normal function to the area. Remarkably, these new inhibitory neurons survived in the hippocampus, enhancing inhibitory signaling and rescuing impairments in learning and memory.
In addition, when these inhibitory progenitor cells were transplanted into apoE4 mice with an accumulation of amyloid beta, prior deficits were alleviated. However, the new inhibitory neurons did not affect amyloid beta levels, suggesting that the cognitive enhancement did not occur as a result of amyloid clearance, and amyloid did not impair the integration of the transplant.
According to Dr. Huang, the potential implications for these findings extend beyond the current methods used. “Stem cell therapy in humans is still a long way off. However, this study tells us that if there is any way we can enhance inhibitory neuron function in the hippocampus, like through the development of small molecule compounds, it may be beneficial for Alzheimer disease patients.”
(Source: gladstoneinstitutes.org)
Months before their first words, babies’ brains rehearse speech mechanics
Infants can tell the difference between sounds of all languages until about 8 months of age when their brains start to focus only on the sounds they hear around them. It’s been unclear how this transition occurs, but social interactions and caregivers’ use of exaggerated “parentese” style of speech seem to help.
University of Washington research in 7- and 11-month-old infants shows that speech sounds stimulate areas of the brain that coordinate and plan motor movements for speech.
The study, published July 14 in the Proceedings of the National Academy of Sciences, suggests that baby brains start laying down the groundwork of how to form words long before they actually begin to speak, and this may affect the developmental transition.
“Most babies babble by 7 months, but don’t utter their first words until after their first birthdays,” said lead author Patricia Kuhl, who is the co-director of the UW’s Institute for Learning and Brain Sciences. “Finding activation in motor areas of the brain when infants are simply listening is significant, because it means the baby brain is engaged in trying to talk back right from the start and suggests that 7-month-olds’ brains are already trying to figure out how to make the right movements that will produce words.”
Kuhl and her research team believe this practice at motor planning contributes to the transition when infants become more sensitive to their native language.
The results emphasize the importance of talking to kids during social interactions even if they aren’t talking back yet.
“Hearing us talk exercises the action areas of infants’ brains, going beyond what we thought happens when we talk to them,” Kuhl said. “Infants’ brains are preparing them to act on the world by practicing how to speak before they actually say a word.”
In the experiment, infants sat in a brain scanner that measures brain activation through a noninvasive technique called magnetoencephalography. Nicknamed MEG, the brain scanner resembles an egg-shaped vintage hair dryer and is completely safe for infants. The Institute for Learning and Brain Sciences was the first in the world to use such a tool to study babies while they engaged in a task.
The babies, 57 7- and 11- or 12-month-olds, each listened to a series of native and foreign language syllables such as “da” and “ta” as researchers recorded brain responses. They listened to sounds in English and in Spanish.
The researchers observed brain activity in an auditory area of the brain called the superior temporal gyrus, as well as in Broca’s area and the cerebellum, cortical regions responsible for planning the motor movements required for producing speech.
This pattern of brain activation occurred for sounds in the 7-month-olds’ native language (English) as well as in a non-native language (Spanish), showing that at this early age infants are responding to all speech sounds, whether or not they have heard the sounds before.
In the older infants, brain activation was different. By 11-12 months, infants’ brains increase motor activation to the non-native speech sounds relative to native speech, which the researchers interpret as showing that it takes more effort for the baby brain to predict which movements create non-native speech. This reflects an effect of experience between 7 and 11 months, and suggests that activation in motor brain areas is contributing to the transition in early speech perception.
The study has social implications, suggesting that the slow and exaggerated parentese speech – “Hiiiii! How are youuuuu?” – may actually prompt infants to try to synthesize utterances themselves and imitate what they heard, uttering something like “Ahhh bah bah baaah.”
“Parentese is very exaggerated, and when infants hear it, their brains may find it easier to model the motor movements necessary to speak,” Kuhl said.
Brain activity in sex addiction mirrors that of drug addiction
Pornography triggers brain activity in people with compulsive sexual behaviour – known commonly as sex addiction – similar to that triggered by drugs in the brains of drug addicts, according to a University of Cambridge study published in the journal PLOS ONE. However, the researchers caution that this does not necessarily mean that pornography itself is addictive.
Although precise estimates are unknown, previous studies have suggested that as many as one in 25 adults is affected by compulsive sexual behaviour, an obsession with sexual thoughts, feelings or behaviour which they are unable to control. This can have an impact on a person’s personal life and work, leading to significant distress and feelings of shame. Excessive use of pornography is one of the main features identified in many people with compulsive sexual behaviour. However, there is currently no formally accepted definition of diagnosing the condition.
In a study funded by the Wellcome Trust, researchers from the Department of Psychiatry at the University of Cambridge looked at brain activity in nineteen male patients affected by compulsive sexual behaviour and compared them to the same number of healthy volunteers. The patients started watching pornography at earlier ages and in higher proportions relative to the healthy volunteers.
“The patients in our trial were all people who had substantial difficulties controlling their sexual behaviour and this was having significant consequences for them, affecting their lives and relationships,” explains Dr Valerie Voon, a Wellcome Trust Intermediate Clinical Fellow at the University of Cambridge. “In many ways, they show similarities in their behaviour to patients with drug addictions. We wanted to see if these similarities were reflected in brain activity, too.”
The study participants were shown a series of short videos featuring either sexually explicit content or sports whilst their brain activity was monitored using functional magnetic resonance imaging (fMRI), which uses a blood oxygen level dependent (BOLD) signal to measure brain activity.
The researchers found that three regions in particular were more active in the brains of the people with compulsive sexual behaviour compared with the healthy volunteers. Significantly, these regions – the ventral striatum, dorsal anterior cingulate and amygdala – were regions that are also particularly activated in drug addicts when shown drug stimuli. The ventral striatum is involved in processing reward and motivation, whilst the dorsal anterior cingulate is implicated in anticipating rewards and drug craving. The amygdala is involved in processing the significance of events and emotions.
The researchers also asked the participants to rate the level of sexual desire that they felt whilst watching the videos, and how much they liked the videos. Drug addicts are thought to be driven to seek their drug because they want – rather than enjoy – it. This abnormal process is known as incentive motivation, a compelling theory in addiction disorders.
As anticipated, patients with compulsive sexual behaviour showed higher levels of desire towards the sexually explicit videos, but did not necessarily rate them higher on liking scores. In the patients, desire was also correlated with higher interactions between regions within the network identified – with greater cross-talk between the dorsal cingulate, ventral striatum and amygdala – for explicit compared to sports videos.
Dr Voon and colleagues also found a correlation between brain activity and age – the younger the patient, the greater the level of activity in the ventral striatum in response to pornography. Importantly, this association was strongest in individuals with compulsive sexual behaviour. The frontal control regions of the brain – essentially, the ‘brakes’ on our compulsivity – continue to develop into the mid-twenties and this imbalance may account for greater impulsivity and risk taking behaviours in younger people. The age-related findings in individuals with compulsive sexual behaviours suggest that the ventral striatum may be important in developmental aspects of compulsive sexual behaviours in a similar fashion as it is in drug addictions, although direct testing of this possibility is needed.
“There are clear differences in brain activity between patients who have compulsive sexual behaviour and healthy volunteers. These differences mirror those of drug addicts,” adds Dr Voon. “Whilst these findings are interesting, it’s important to note, however, that they could not be used to diagnose the condition. Nor does our research necessarily provide evidence that these individuals are addicted to porn – or that porn is inherently addictive. Much more research is required to understand this relationship between compulsive sexual behaviour and drug addiction.”
Dr John Williams, Head of Neuroscience and Mental Health at the Wellcome Trust, says: “Compulsive behaviours, including watching porn to excess, over-eating and gambling, are increasingly common. This study takes us a step further to finding out why we carry on repeating behaviours that we know are potentially damaging to us. Whether we are tackling sex addiction, substance abuse or eating disorders, knowing how best, and when, to intervene in order to break the cycle is an important goal of this research.”
Why does a relentless stream of subjective experiences normally fill your mind? Maybe that’s just one of those mysteries that will always elude us.
Yet, research from Northwestern University suggests that consciousness lies well within the realm of scientific inquiry — as impossible as that may currently seem. Although scientists have yet to agree on an objective measure to index consciousness, progress has been made with this agenda in several labs around the world.
“The debate about the neural basis of consciousness rages because there is no widely accepted theory about what happens in the brain to make consciousness possible,” said Ken Paller, professor of psychology in the Weinberg College of Arts and Sciences and director of the Cognitive Neuroscience Program at Northwestern.
“Scientists and others acknowledge that damage to the brain can lead to systematic changes in consciousness. Yet, we don’t know exactly what differentiates brain activity associated with conscious experience from brain activity that is instead associated with mental activity that remains unconscious,” he said.
In a new article, Paller and Satoru Suzuki, also professor of psychology at Northwestern, point out flawed assumptions about consciousness to suggest that a wide range of scientific perspectives can offer useful clues about consciousness.
“It’s normal to think that if you attentively inspect something you must be aware of it and that analyzing it to a high level would necessitate consciousness,” Suzuki noted. “Results from experiments on perception belie these assumptions.
“Likewise, it feels like we can freely decide at a precise moment, when actually the process of deciding begins earlier, via neurocognitive processing that does not enter awareness,” he said.
The authors write that unconscious processing can influence our conscious decisions in ways we never suspect.
If these and other similar assumptions are incorrect, the researchers state in their article, then mistaken reasoning might be behind arguments for taking the science of consciousness off the table.
“Neuroscientists sometimes argue that we must focus on understanding other aspects of brain function, because consciousness is never going to be understood,” Paller said. “On the other hand, many neuroscientists are actively engaged in probing the neural basis of consciousness, and, in many ways, this is less of a taboo area of research than it used to be.”
Experimental evidence has supported some theories about consciousness that appeal to specific types of neural communication, which can be described in neural terms or more abstractly in computational terms. Further theoretical advances can be expected if specific measures of neural activity can be brought to bear on these ideas.
Paller and Suzuki both conduct research that touches on consciousness. Suzuki studies perception, and Paller studies memory. They said it was important for them to write the article to counter the view that it is hopeless to ever make progress through scientific research on this topic.
They outlined recent advances that provide reason to be optimistic about future scientific inquiries into consciousness and about the benefits that this knowledge could bring for society.
“For example, continuing research on the brain basis of consciousness could inform our concerns about human rights, help us explain and treat diseases that impinge on consciousness, and help us perpetuate environments and technologies that optimally contribute to the well being of individuals and of our society,” the authors wrote.
They conclude that research on human consciousness belongs within the purview of science, despite philosophical or religious arguments to the contrary.
Their paper, “The Source of Consciousness,” has been published online in the journal Trends in Cognitive Sciences.
(Image: Shutterstock)