The Brain Processes Complex Stimuli More Cumulatively Than We Thought

The finding represents a new view of how the brain creates internal representations of the visual world. "We are excited to see if this novel view will dominate the wider consensus" said senior author Dr. Miyashita, who is also Professor of Physiology at the University of Tokyo's School of Medicine, "and also about the potential impact of our new computational principle on a wide range of views on human cognitive abilities." The brain recalls the patterns and objects we observe by developing distinct neuronal representations that go along with them (this is the same way it recalls memories). Scientists have long hypothesized that these neuronal representations emerge in a hierarchical process limited to the same cortical region in which the representations are first processed. Because the brain perceives and recognizes the external world through these internal images, any new information about the process by which this takes place has the power to inform our understanding of related functions, including knowledge acquisition and memory. However, studies attempting to uncover the functional hierarchy involved in the cortical process of visual stimuli have tried to characterize this hierarchy by analyzing the activity of single nerve cells, which are not necessarily correlated with neurons nearby, thus leaving these analyses lacking. In a new study appearing in the 12 July issue of the journal Science, lead author Toshiyuki Hirabayashi and colleagues focus not on single neurons but instead on the relationship between neuron pairs, testing the possibility that the representation of an object in a single brain region emerges in a hierarchically lower brain area. "I became interested in this work," said Dr. Hirabayashi, "because I was impressed by the elaborate neuronal circuitry in the early visual system, which is well-studied, and I wanted to explore the circuitry underlying higher-order visual processing, which is not yet fully understood." Hirabayashi and colleagues analyzed nerve cell pairs in cortical areas TE and 36, the latter of which is hierarchically higher, in two adult macaques. After these animals looked at six sets of paired stimuli for several months to learn to associate related objects (a process that can lead to pair-coding neurons in the brain), the researchers recorded neuron responses in areas TE and 36 of both animals as they again performed this task. The neurons exhibited pair association, but not where the researchers would have thought. "The most surprising result," said senior author Dr. Yasushi Miyashita "was that the neuronal circuit that generated pair-association was found only in area TE, not in area 36." Indeed, based on previous studies, which indicated that the number of pair-coding neurons in area TE is much smaller, the researchers would have expected the opposite. During their study, Miyashita and other team members observed that in region TE of the macaque cortex, unit 1 neurons (or source neurons) provided input to unit 2 neurons (or target neurons), which -- unlike unit 1 neurons -- responded to both members of a stimulus pair. "The representations generated in area TE did not reflect a mere random fluctuation of response patterns," explained Dr. Miyashita, "but rather, they emerged as a result of circuit processing inherent to that area of the brain." In area 36, meanwhile, members of neuron pairs behaved differently; on average, unit 1 as well as unit 2 neurons responded to both members of a stimulus pair. Neurons in area 36 received input from area TE, but only from its unit 2 neurons. Taken together, these findings lead the authors to hypothesize the existence of a hierarchical relationship between regions TE and 36, in which paired associations first established in the former region are propagated to the latter one. Here, area 36 represents the next level of a so-called feed forward hierarchy. The work by Hirabayashi and colleagues suggests that the detailed representations of objects commonly observed in the brain are attained not by buildup of representations in a single area, but by emergence of these representations in a hierarchically prior area and their subsequent transfer to the brain region that follows. There, they become sufficiently prevalent for the brain to register. The work also reveals that the brain activity involved in recreating visual stimuli emerges in a hierarchically lower brain area than previously thought. Moving forward, the Japanese research team has plans to expand upon this research, thus continuing to contribute to studies worldwide that aim to give scientists the best possible tools with which to obtain a dynamic picture of the brain. As a next step, the team hopes to further elucidate interactions between the various cortical microcircuits that operate in memory encoding. Dr. Miyashita has conjectured that these microcircuits are manipulated by a global brain network. Using the results of this latest study, he and colleagues are poised to further evaluate this assumption. "It will also be important to weave the neuronal circuit mechanisms into a unified framework," said Dr. Hirabayashi," and to examine the effects of learning on these circuit organizations." Equipped with their new view of cortical processing, the team also hopes to trace the causal chain of memory retrieval across different areas of the cortex. "I am excited by the recent development of genetic tools that will allow us to do this," said Dr. Miyashita. A better understanding of object representations from one area of the brain to the next will shed even greater light on elusive aspects of this hierarchical organ

Brain Frontal Lobes Not Sole Center of Human Intelligence, Comparative Research Suggests

May 13, 2013 — Human intelligence cannot be explained by the size of the brain's frontal lobes, say researchers.  Research into the comparative size of the frontal lobes in humans and other species has determined that they are not -- as previously thought -- disproportionately enlarged relative to other areas of the brain, according to the most accurate and conclusive study of this area of the brain.

It concludes that the size of our frontal lobes cannot solely account for humans' superior cognitive abilities.

The study by Durham and Reading universities suggests that supposedly more 'primitive' areas, such as the cerebellum, were equally important in the expansion of the human brain. These areas may therefore play unexpectedly important roles in human cognition and its disorders, such as autism and dyslexia, say the researchers.

The study is published in the Proceedings of the National Academy of Sciences (PNAS) today.

The frontal lobes are an area in the brain of mammals located at the front of each cerebral hemisphere, and are thought to be critical for advanced intelligence.

Lead author Professor Robert Barton from the Department of Anthropology at Durham University, said: "Probably the most widespread assumption about how the human brain evolved is that size increase was concentrated in the frontal lobes.
"It has been thought that frontal lobe expansion was particularly crucial to the development of modern human behaviour, thought and language, and that it is our bulging frontal lobes that truly make us human. We show that this is untrue: human frontal lobes are exactly the size expected for a non-human brain scaled up to human size.

"This means that areas traditionally considered to be more primitive were just as important during our evolution. These other areas should now get more attention. In fact there is already some evidence that damage to the cerebellum, for example, is a factor in disorders such as autism and dyslexia."

The scientists argue that many of our high-level abilities are carried out by more extensive brain networks linking many different areas of the brain. They suggest it may be the structure of these extended networks more than the size of any isolated brain region that is critical for cognitive functioning.

Previously, various studies have been conducted to try and establish whether humans' frontal lobes are disproportionately enlarged compared to their size in other primates such as apes and monkeys. They have resulted in a confused picture with use of different methods and measurements leading to inconsistent findings

Using Anticholinergics for as Few as 60 Days Causes Memory Problems in Older Adults

May 7, 2013 — Research from the Regenstrief Institute, the Indiana University Center for Aging Research and Wishard-Eskenazi Health on medications commonly taken by older adults has found that drugs with strong anticholinergic effects cause cognitive impairment when taken continuously for as few as 60 days. A similar impact can be seen with 90 days of continuous use when taking multiple drugs with weak anticholinergic effect.

The study of 3,690 older adults is among the first to explore how length of use of this group of drugs affects the brain. The study is available online in advance of publication in a print issue of Alzheimer's & Dementia, the journal of the Alzheimer's Association. The research was funded by a grant (R24MH080827) from the National Institute on Aging.

Anticholinergic drugs block acetylcholine, a nervous system neurotransmitter. Drugs with anticholinergic effects are sold over the counter and by prescription. Older adults commonly use over-the-counter drugs with anticholinergic effects as sleep aids and to relieve bladder leakage. Drugs with anticholinergic effects are frequently prescribed for many chronic diseases including hypertension, cardiovascular disease and chronic obstructive pulmonary disease.

A list of drugs noting their anticholinergic burden can be found on the Aging Brain Care website.

The Regenstrief Institute, IU Center for Aging Research and Wishard-Eskenazi Health researchers reported that continuously taking strong anticholinergics, like many sleeping pills or antihistamines, for only 60 days caused memory problems and other indicators of mild cognitive impairment. Taking multiple drugs with weaker anticholinergic effects, such as many common over-the-counter digestive aids, had a negative impact on cognition in 90 days.

"We found that a high anticholinergic burden -- either from one or multiple drugs -- plus two to three months of continuous exposure to that high burden approximately doubled the risk of developing cognitive impairment," said Noll Campbell, Pharm.D., study co-author and Regenstrief Institute investigator. "Millions of older adults are taking sleeping pills or prescription drugs year after year that may be impacting their organizational abilities and memory."

Dr. Campbell is also an IU Center for Aging Research scientist, a research assistant professor in the Department of Pharmacy Practice, Purdue University College of Pharmacy, and a clinical pharmacy specialist in geriatrics with Wishard-Eskenazi Health Services.

"While the link between anticholinergics and cognitive impairment has been reported by our group and others, the cumulative burden of anticholinergics was rather unexpected, as was the lack of a clear association between anticholinergic burden and dementia," said Regenstrief Institute investigator Malaz Boustani, M.D., MPH. Dr. Boustani, the senior author of the study, who is also associate director of the IU Center for Aging Research and an associate professor of medicine at IU School of Medicine. He sees patients at the Healthy Aging Brain Center at Wishard-Eskenazi Health.

"The fact that taking anticholinergics is linked with mild cognitive impairment, involving memory loss without functional disability, but not with Alzheimer's disease and other dementing disorders, gives hope. Our research efforts will now focus on whether anticholinergic-induced cognitive impairment may be reversible," Dr. Boustani said.

Alzheimer's Fuzzy Signals Into High Definition

 May 7, 2013 — Scientists at the Virginia Tech Carilion Research Institute have discovered how the predominant class of Alzheimer's pharmaceuticals might sharpen the brain's performance

17One factor even more important than the size of a television screen is the quality of the signal it displays. Having a life-sized projection of Harry Potter dodging a Bludger in a Quidditch match is of little use if the details are lost to pixilation.

The importance of transmitting clear signals, however, is not relegated to the airwaves. The same creed applies to the electrical impulses navigating a human brain. Now, new research has shown that one of the few drugs approved for the treatment of Alzheimer's disease helps patients by clearing up the signals coming in from the outside world.

The discovery was made by a team of researchers led by Rosalyn Moran, an assistant professor at the Virginia Tech Carilion Research Institute. Her study indicates that cholinesterase inhibitors -- a class of drugs that stop the breakdown of the neurotransmitter acetylcholine -- allow signals to enter the brain with more precision and less background noise.

"Increasing the levels of acetylcholine appears to turn your fuzzy, old analog TV signal into a shiny, new, high-definition one," said Moran, who holds an appointment as an assistant professor in the Virginia Tech College of Engineering. "And the drug does this in the sensory cortices. These are the workhorses of the brain, the gatekeepers, not the more sophisticated processing regions -- such as the prefrontal cortex -- where one may have expected the drugs to have their most prominent effect."

Alzheimer's disease affects more than 35 million people worldwide -- a number expected to double every 20 years, leading to more than 115 million cases by 2050. Of the five pharmaceuticals approved to treat the disease by the U.S. Food and Drug Administration, four are cholinesterase inhibitors. Although it is clear that the drugs increase the amount of acetylcholine in the brain, why this improves Alzheimer's symptoms has been unknown. If scientists understood the mechanisms and pathways responsible for improvement, they might be able to tailor better drugs to combat the disease, which costs more than $200 billion annually in the United States alone.

In the new study, Moran recruited 13 healthy young adults and gave them doses of galantamine, one of the cholinesterase inhibitors commonly prescribed to Alzheimer's patients. Two electroencephalographs were taken -- one with the drugs and one without -- as the participants listened to a series of modulating tones while focusing on a simple concentration task.

The researchers were looking for differences in neural activity between the two drug states in response to surprising changes in the sound patterns that the participants were hearing.

The scientists compared the results with computer models built on a Bayesian brain theory, known as the Free Energy Principle, which is a leading theory that describes the basic rules of neuronal communication and explains the creation of complex networks.

The theory hypothesizes that neurons seek to reduce uncertainty, which can be modeled and calculated using free energy molecular dynamics. Connecting tens of thousands of neurons behaving in this manner produces the probability machine that we call a brain.

Moran and her colleagues compiled 10 computer simulations based on the different effects that the drugs could have on the brain. The model that best fit the results revealed that the low-level wheels of the brain early on in the neural networking process were the ones benefitting from the drugs and creating clearer, more precise signals.

"When people take these drugs you can imagine the brain bathed in them," Moran said. "But what we found is that the drugs don't have broad-stroke impacts on brain activity. Instead, they are working very specifically at the cortex's entry points, gating the signals coming into the network in the first place."

Distorted Thinking in Gambling Addiction: What Are the Cognitive and Neural Mechanisms?

Apr. 8, 2013 — Fascinating new studies into brain activity and behavioural responses have highlighted the overlap between pathological gambling and drug addiction. The research, which is presented at the British Neuroscience Association Festival of Neuroscience (BNA2013) has implications for both the treatment and prevention of problem gambling.

Dr Luke Clark, a senior lecturer at the University of Cambridge (UK), told the meeting that neurocognitive tests of impulsivity and compulsivity, and also positron emission tomography (PET) imaging of the brain have started to show how gambling becomes addictive in pathological gamblers -- people whose gambling habit has spiralled out of control and become a problem.

"Around 70% of the British population will gamble occasionally, but for some of these people, it will become a problem," he said. "Our work has been seeking to understand the changes in decision-making that happen in people with gambling problems. It represents the first large scale study of individuals seeking treatment for gambling problems in the UK, at a time when this disorder is being re-classified alongside drug addiction as the first 'behavioural addiction'. Given the unique legislation around gambling from country to country, it is vital that we understand gambling at a national level. For example, 40% of the problem gamblers at the National Problem Gambling Clinic report that the game they have a problem with is roulette on Fixed Odds Betting Terminals; this kind of gambling machine is peculiar to the British gambling landscape."

In collaboration between the University of Cambridge and Dr Henrietta Bowden-Jones, director of the UK's only specialist gambling clinic in the Central and North West London NHS Trust, Dr Clark and his colleagues compared the brains and behaviours of 86 male, pathological gamblers with those of 45 healthy men without a gambling problem.

"We approach gambling within the framework of addiction, where we think that problematic gambling arises from a combination of individual risk factors, such as genetics, and features of the games themselves. To study individual factors, we have been testing gamblers at the National Problem Gambling Clinic on neurocognitive tests of impulsivity and compulsivity, and we have also measured their dopamine levels using PET imaging," said Dr Clark.

The tests showed that problem gamblers had increased impulsivity, similar to people with alcohol and drug addictions, but there was less evidence of compulsivity. Levels of dopamine -- a neurotransmitter involved in signalling between nerve cells and which is implicated in drug addiction -- showed differences in the more impulsive gamblers.

"Previous PET research has shown that people with drug addiction have reduced dopamine receptors. We predicted the same effect in pathological gamblers, but we did not see any group differences between the pathological gamblers and healthy men. Nevertheless, the problem gamblers do show some individual differences in their dopamine function, related to their levels of impulsivity: more impulsive gamblers showed fewer dopamine receptors," said Dr Clark. "These studies highlight the overlap between pathological gambling and drug addiction.

"To study the properties of the games themselves and how they relate to problem gambling, we have focussed on two psychological distortions that occur across many forms of gambling: 'near-miss' outcomes (where a loss looks similar or 'close' to a jackpot win) and the 'gambler's fallacy' (for example, believing that a run of heads means that a tail is 'due', in a game of chance). In one important discovery, we were the first lab to show that gambling 'near-misses' recruit brain regions that overlap with those recruited in gambling 'wins'. These responses may cause 'near-misses' to maintain gambling play despite their objective status as losses."

Dr Clark said that these findings had implications for both prevention and treatment. "Gambling distortions like the 'near-miss' effect may be amenable to both psychological therapies for problem gambling, and also by drug treatments that may act on the underlying brain systems. By understanding the styles of thinking that characterise the problem gambler, we may also be able to improve education about gambling in teenagers and young adults, to reduce the number of people developing a gambling problem."

The researchers also found a striking demonstration of the underlying brain regions that are involved in gambling when they studied the gambling behaviour of patients who had experienced brain injury due to a tumour or stroke.

"We have seen that two gambling distortions -- the 'gambler's fallacy' and the 'near-miss' effect -- that are evident in the general population, and which appear to be increased in problem gamblers, are actually abolished in patients with damage to the insula region of the brain," he said. "This suggests that in the healthy brain, the insula may be a critical area in generating these distorted expectancies during gambling play, and that interventions to reduce insula activity may have treatment potential.

"The insula is quite a mysterious part of the brain, tucked deep inside the lateral fissure. It is important in processing pain and, more broadly, in representing the state of the body in the brain, and it is striking that gambling is a very visceral, exciting activity. Our ongoing neuroimaging work will look at the relationship between responses in the insula and the body during our gambling tests."

Future work will investigate the styles of thinking that are in evidence when the problem gamblers at the National Problem Gambling Clinic play the simplified games the researchers have developed. "This is the first study to directly look at whether these biases are more pronounced in problem gamblers. We are also starting to recruit the siblings of problem gamblers (those who do not have a gambling problem themselves) in order to look at underlying vulnerability factors," concluded Dr Clark.

This research is funded by grants from the UK's Medical Research Council, and involves further collaboration with researchers at Imperial College London and the University of Oxford.