Posts tagged neuroscience

March 26, 2012 By Angela Herring

All human languages contain two levels of structure, said Iris Berent, a psychology professor in Northeastern’s College of Science. One is syntax, or the ordering of words in a sentence. The other is phonology, or the sound structure of individual words.

Berent — whose research focuses on the phonological structure of language — examines the nature of linguistic competence, its origins and its interaction with reading. While previous studies have all centered on adult language acquisition, she is now working with infants to address two core questions.

“First,” she said, “do infants have the capacity to encode phonological rules? And, second, are some phonological rules innate?”

To address the first issue, Berent collaborated with neuroscientists Janet Werker, of the University of British Columbia, and Judit Gervain, of the Paris-based Centre National de la Recherche Scientifique.

By utilizing an optical brain imaging technique called near-infrared spectroscopy, or NIRS, the researchers found that newborns have the capacity to learn linguistic rules. This finding — published this month in the Journal of Cognitive Neuroscience — suggests that the neural foundations of language acquisition are present at birth.

Armed with this knowledge, Berent has begun conducting behavioral studies on more than two-dozen infants to explore whether linguistic rules are innate or entirely learned.

“We want to see whether infants prefer certain sound patterns to others even if neither occurs in their language,” Berent explained. “For instance, we know that human languages prefer sequences such as bnog over bdog. Would six-month-old infants show this preference even if their language (English) does not include either sequence?”

For the study, each child is placed in front of a video screen that displays an image pulsing in coordination with rotating sounds, such as “bnog” and “bdog.” Berent hypothesized that infants would look longer at the video screen when they hear sounds to which they are innately biased.

Preliminary results have upheld the hypothesis, but Berent is still accepting new subjects for the study. Her entire research program forms part of a new book called “The Phonological Mind,” which will be published by Cambridge University Press this year.

Provided by Northeastern University

Source: medicalxpress.com

March 26, 2012

(Medical Xpress) — Storytelling is a skill not everyone can master, but even the most crashing bore gets help from their audience’s brain which ‘talks over’ their monotonous quotes, according to scientists.

Researchers from the University of Glasgow’s Institute of Neuroscience and Psychology investigated the ‘voice-selective’ areas of the brain and revealed that when listening to someone monotonously repeating direct speech quotations, the brain will ‘talk over’ the speaker to make the quotes more vivid.

Previously, the researchers had shown the brain ‘talks’ when silently reading direct quotations.

Dr Bo Yao, the principal investigator of the study, said: “You may think the brain need not produce its own speech while listening to one that is already available.

“But, apparently, the brain is very picky on the speech it hears. When the brain hears monotonously-spoken direct speech quotations which it expects to be more vivid, the brain simply ‘talks over’ the speech it hears with more vivid speech utterances of its own.”

Dr Bo Yao explains why the brain ‘talks over’ boring speech: 

[Audio]

The research was conducted by Dr Yao and colleagues Professor Pascal Belin and Professor Christoph Scheepers within the Institute’s Centre for Cognitive Neuroimaging.

The team enlisted 18 participants in the study and scanned their brains using functional magnetic resonance imaging (fMRI) while they listened to audio clips of short stories containing direct or indirect speech quotations. The direct speech quotations — e.g., Mary said excitedly: “The latest Sherlock Holmes film is fantastic!” – were either spoken ‘vividly’ or ‘monotonously’ (i.e., with or without much variation in speech melody).

The results showed that listening to monotonously spoken direct speech quotations increased brain activity in the ‘voice-selective areas’ of the brain. These voice-selective areas – originally discovered by Prof Belin – are certain areas of the auditory cortex which are particularly interested in human voices when stimulated by actual speech sounds perceived by the ears.

However, the present and previous studies also reveal that these areas can be activated by different linguistic reporting styles – such as direct versus indirect speech.

Prof Scheepers said: “Direct speech quotations are generally assumed to be more vivid and perceptually engaging than indirect speech quotations as they are more frequently associated with depictions of voices, facial expressions and co-speech gestures.

“When the brain does not receive actual stimulation of auditory speech during silent reading, it tends to produce its own to enliven written direct speech quotations – a phenomenon commonly referred to as the ‘inner voice’ during silent reading. Now it appears the brain does the same even when listening to monotonously-spoken direct speech quotations.”

Dr Yao added: “This research demonstrates that human speech processing is an active process in which the brain generates models for the incoming speech utterances in order to predict actual auditory input.

“By doing so, the brain attempts to optimise the processing of the incoming speech, ensuring more speedy and accurate responses.

“These predictions are probably grounded in our past experiences in which direct speech is frequently associated with vivid depictions of the reported speaker’s voice whereas indirect speech is usually stated in a more flat and steady tone.

“The brain’s ‘talking over’ monotonously spoken direct quotes seems to reflect that it tries to bridge the incongruence between the expected speech utterances (vivid) and the actually perceived speech (monotonous) by simulating or imagining the expected vivid vocal depictions.

“We believe that such a simulation mechanism is an integral part of language comprehension — we naturally recruit our sensory and motor systems to interpret the language input. Language processing, in this sense, is embodied.”

The research paper ‘Brain “talks over” boring quotes: Top-down activation of voice-selective areas while listening to monotonous direct speech quotations’ is published in NeuroImage.

Provided by University of Glasgow

Source: medicalxpress.com 

March 24, 2012

(HealthDay) — Neurodegenerative diseases may be characterized by specific regions of the brain that are critical network epicenters, with disease-related vulnerability associated with shorter paths to the epicenter and greater total connectional flow, according to a study published in the March 22 issue of Neuron.

Neurodegenerative diseases may be characterized by specific regions of the brain that are critical network epicenters, with disease-related vulnerability associated with shorter paths to the epicenter and greater total connectional flow, according to a study published in the March 22 issue of Neuron.

To investigate how intrinsic connectivity in health predicts regional vulnerability to neurodegenerative disease, Juan Zhou, Ph.D., from the University of California in San Francisco, and colleagues used task-free functional magnetic resonance imaging to identify the healthy intrinsic connectivity patterns seeded by brain regions vulnerable to five neurodegenerative diseases (Alzheimer’s disease, behavioral variant frontotemporal dementia, semantic dementia, progressive nonfluent aphasia, and corticobasal syndrome).

The investigators found that, for each neurodegenerative disease, specific regions emerged as critical network epicenters, and their normal connectivity profile was most similar to the disease-linked pattern of atrophy. In healthy subjects, greater disease-related vulnerability was consistently associated with regions with shorter functional paths to the epicenters and also with higher total connectional flow.

"These findings best fit a transneuronal spread model of network-based vulnerability. Molecular pathological approaches may help clarify what makes each epicenter vulnerable to its targeting disease and how toxic protein species travel between networked brain structures," the authors write.

More information: Abstract

Source: medicalxpress.com

ScienceDaily (Mar. 24, 2012) — Researchers are suggesting that there is a link between the number of friends you have and the size of the region of the brain — known as the orbital prefrontal cortex — that is found just above the eyes. A new study shows that this brain region is bigger in people who have a larger number of friendships.

Friends. Researchers are suggesting that there is a link between the number of friends you have and the size of the region of the brain — known as the orbital prefrontal cortex — that is found just above the eyes. (Credit: © Rido / Fotolia)

Their study is published on 1 February 2012 in the journal, Proceedings of the Royal Society B.

The research was carried out as part of the British Academy Centenary ‘Lucy to Language’ project, led by Professor Robin Dunbar of the University of Oxford in a collaboration with Dr Joanne Powell and Dr Marta Garcia-Finana at Liverpool University, Dr Penny Lewis at Manchester University and Professor Neil Roberts at Edinburgh University.

The study suggests that we need to employ a set of cognitive skills to maintain a number of friends (and the keyword is ‘friends’ as opposed to just the total number of people we know). These skills are described by social scientists as ‘mentalising’ or ‘mind-reading’- a capacity to understand what another person is thinking, which is crucial to our ability to handle our complex social world, including the ability to hold conversations with one another. This study, for the first time, suggests that our competency in these skills is determined by the size of key regions of our brains (in particular, the frontal lobe).

Professor Dunbar, from the Institute of Cognitive and Evolutionary Anthropology, explained: ‘“Mentalising” is where one individual is able to follow a natural hierarchy involving other individuals’ mind states. For example, in the play ‘Othello’, Shakespeare manages to keep track of five separate mental states: he intended that his audience believes that Iago wants Othello to suppose that Desdemona loves Cassio [the italics signify the different mind states]. Being able to maintain five separate individuals’ mental states is the natural upper limit for most adults.’

The researchers took anatomical MR images of the brains of 40 volunteers at the Magnetic Resonance and Image Analysis Research Centre at the University of Liverpool to measure the size of the prefrontal cortex, the part of the brain used in high-level thinking. Participants were asked to make a list of everyone they had had social, as opposed to professional, contact with over the previous seven days. They also took a test to determine their competency in mentalising.

Professor Robin Dunbar, said: ‘We found that individuals who had more friends did better on mentalising tasks and had more neural volume in the orbital frontal cortex, the part of the forebrain immediately above the eyes. Understanding this link between an individual’s brain size and the number of friends they have helps us understand the mechanisms that have led to humans developing bigger brains than other primate species. The frontal lobes of the brain, in particular, have enlarged dramatically in humans over the last half million years.’

Dr Joanne Powell, from the Department of Psychology, University of Liverpool, said: ‘Perhaps the most important finding of our study is that we have been able to show that the relationship between brain size and social network size is mediated by mentalising skills. What this tells us is that the size of your brain determines your social skills, and it is these that allow you have many friends.’

Professor Dunbar said: ‘All the volunteers in this sample were postgraduate students of broadly similar ages with potentially similar opportunities for social activities. Of course, the amount of spare time for socialising, geography, personality and gender all influence friendship size, but we also know that at least some of these factors, notably gender, also correlate with mentalising skills. Our study finds there is a link between the ability to read how other people think and social network size.’

Professor Dunbar’s research was funded by the British Academy Centenary Research Project and by the British Academy Research Professorship. His research has already examined the different brain sizes of different species, but this study looks at the differences within species. Professor Dunbar published a paper last year, which found that people living near to the Poles needed larger brains for visual processing because of the dimmer light conditions.

Source: Science Daily

ScienceDaily (Mar. 23, 2012) — Nodding off in class may not be such a bad idea after all. New research from the University of Notre Dame shows that going to sleep shortly after learning new material is most beneficial for recall.

New research shows that going to sleep shortly after learning new material is most beneficial for recall. (Credit: © Claudia Nagel / Fotolia)

Notre Dame psychologist Jessica Payne and colleagues studied 207 students who habitually slept for at least six hours per night. Participants were randomly assigned to study declarative, semantically related or unrelated word pairs at 9 a.m. or 9 p.m., and returned for testing 30 minutes, 12 hours or 24 hours later. Declarative memory refers to the ability to consciously remember facts and events, and can be broken down into episodic memory (memory for events) and semantic memory (memory for facts about the world). People routinely use both types of memory every day — recalling where we parked today or learning how a colleague prefers to be addressed.

At the 12-hour retest, memory overall was superior following a night of sleep compared to a day of wakefulness. However, this performance difference was a result of a pronounced deterioration in memory for unrelated word pairs; there was no sleep-wake difference for related word pairs. At the 24-hour retest, with all subjects having received both a full night of sleep and a full day of wakefulness, subjects’ memories were superior when sleep occurred shortly after learning, rather than following a full day of wakefulness.

"Our study confirms that sleeping directly after learning something new is beneficial for memory. What’s novel about this study is that we tried to shine light on sleep’s influence on both types of declarative memory by studying semantically unrelated and related word pairs," Payne says.

"Since we found that sleeping soon after learning benefited both types of memory, this means that it would be a good thing to rehearse any information you need to remember just prior to going to bed. In some sense, you may be ‘telling’ the sleeping brain what to consolidate."

Source: Science Daily

March 23, 2012 by Cathryn Delude

Our fond or fearful memories — that first kiss or a bump in the night — leave memory traces that we may conjure up in the remembrance of things past, complete with time, place and all the sensations of the experience. Neuroscientists call these traces memory engrams.

But are engrams conceptual, or are they a physical network of neurons in the brain? In a new MIT study, researchers used optogenetics to show that memories really do reside in very specific brain cells, and that simply activating a tiny fraction of brain cells can recall an entire memory — explaining, for example, how Marcel Proust could recapitulate his childhood from the aroma of a once-beloved madeleine cookie.

“We demonstrate that behavior based on high-level cognition, such as the expression of a specific memory, can be generated in a mammal by highly specific physical activation of a specific small subpopulation of brain cells, in this case by light,” says Susumu Tonegawa, the Picower Professor of Biology and Neuroscience at MIT and lead author of the study reported online today in the journal Nature. “This is the rigorously designed 21st-century test of Canadian neurosurgeon Wilder Penfield’s early-1900s accidental observation suggesting that mind is based on matter.”

In that famous surgery, Penfield treated epilepsy patients by scooping out parts of the brain where seizures originated. To ensure that he destroyed only the problematic neurons, Penfield stimulated the brain with tiny jolts of electricity while patients, who were under local anesthesia, reported what they were experiencing. Remarkably, some vividly recalled entire complex events when Penfield stimulated just a few neurons in the hippocampus, a region now considered essential to the formation and recall of episodic memories.

Scientists have continued to explore that phenomenon but, until now, it has never been proven that the direct reactivation of the hippocampus was sufficient to cause memory recall.

Shedding light on the matter

Fast forward to the introduction, seven years ago, of optogenetics, which can stimulate neurons that are genetically modified to express light-activated proteins. “We thought we could use this new technology to directly test the hypothesis about memory encoding and storage in a mimicry experiment,” says co-author Xu Liu, a postdoc in Tonegawa’s lab. 

Read more …

ScienceDaily (Mar. 23, 2012) — Insulin resistance in the brain precedes and contributes to cognitive decline above and beyond other known causes of Alzheimer’s disease, according to a new study by researchers from the Perelman School of Medicine at the University of Pennsylvania. Insulin is an important hormone in many bodily functions, including the health of brain cells. The team identified extensive abnormalities in the activity of two major signaling pathways for insulin and insulin-like growth factor in non-diabetic people with Alzheimer’s disease. These pathways could be targeted with new or existing medicines to potentially help resensitize the brain to insulin and possibly slow down or even improve cognitive decline.

This is the first study to directly demonstrate that insulin resistance occurs in the brains of people with Alzheimer’s disease. The study is now online in the Journal of Clinical Investigation.

"Our research clearly shows that the brain’s ability to respond to insulin, which is important for normal brain function, is going offline at some point. Insulin in the brain not only modulates glucose uptake, but also promotes the health of brain cells — their growth, survival, remodeling, and normal functioning. We believe that brain insulin resistance may be an important contributor to the cognitive decline associated with Alzheimer’s disease," said senior author, Steven E. Arnold, MD, professor of Psychiatry and Neurology. Arnold is also the director of the Penn Memory Center, a National Institute on Aging-designated Alzheimer’s Disease Core Center. "If we can prevent brain insulin resistance from occurring, or re-sensitize brain cells to insulin with any of the currently available insulin-sensitizing diabetes medicines, we may be able to slow down, prevent, or perhaps even improve cognitive decline.

The risk of developing Alzheimer’s disease is increased by 50 percent in people with diabetes. Type 2 diabetes is due to insulin resistance and accounts for 90 percent of all diabetes. The defining clinical feature of Type 2 diabetes (and Type 1 “juvenile” diabetes) is hyperglycemia — high levels of sugar in the blood — but there is no evidence that the brain in Alzheimer’s is hyperglycemic. Insulin acts differently in the brain than in the rest of the body. Researchers found that insulin resistance of the brain occurs in Alzheimer’s disease independent of whether someone has diabetes, by excluding people with a history of diabetes from this study.

The investigators used samples of postmortem brain tissue from non-diabetics who had died with Alzheimer’s disease, stimulated the tissue with insulin, and measured how much the insulin activated various proteins in the insulin-signaling pathways. There was less insulin activation in Alzheimer’s cases than in tissue from people who had died without brain disease. Other proteins linked to insulin action in the brain were abnormal in Alzheimer’s disease samples. These abnormalities were highly correlated with episodic memory and other cognitive disabilities in the Alzheimer’s disease patients.

In tissue from people with Alzheimer’s disease and mild cognitive impairment (MCI), researchers found that changes to a protein called insulin receptor substrate-1 (IRS-1 pS636/639 and pS616) in brain cells were linked to the severity of memory impairments regardless of age, sex, diabetes history, or apolipoprotein E (APOE) gene status. Levels of IRS-1 were also significantly associated with, but not likely to affect, the presence of amyloid beta plaques and neurofibrillary tangles, the signature markers of Alzheimer’s disease. This suggests that insulin resistance contributes to cognitive decline independent of the classical pathology of Alzheimer’s disease.

Researchers noted that three insulin-sensitizing medicines are already approved by the FDA for treatment of diabetes. These drugs readily cross the blood-brain barrier and may have therapeutic potential to correct insulin resistance in Alzheimer’s disease and MCI. “Clinical trials would need to be conducted to determine the impact the drugs have on Alzheimer’s disease and MCI in non-diabetic patients,” said Dr. Arnold.

Source: Science Daily

March 23, 2012

One cup or two faces? What we believe we see in one of the most famous optical illusions changes in a split second; and so does the path that the information takes in the brain. In a new theoretical study, scientists of the Max Planck Institute for Dynamics and Self-Organization, the Bernstein Center Göttingen and the German Primate Center now show how this is possible without changing the cellular links of the network. The direction of information flow changes, depending on the time pattern of communication between brain areas. This reorganisation can be triggered even by a slight stimulus, such as a scent or sound, at the right time.

The way how the different regions of the brain are connected with each other plays a significant role for information processing. This processing can be changed by the assembling and disassembling of nerve fibres joining distant brain circuits. But such events are much too slow to explain rapid changes in perception. From experimental studies it was known that the responsible actions must be at least two orders of magnitude faster. The Göttingen scientists now show for the first time that it is possible to change the information flow in a tightly interconnected network in a simple manner.

Many areas of the brain display a rhythmic nerve cell activity. “The interacting brain areas are like metronomes that tick at the same speed and in a distinct temporal pattern,” says the physicist and principal investigator Demian Battaglia. The researchers were now able to demonstrate that this temporal pattern determines the information flow. “If one of the metronomes is affected, e.g. through an external stimulus, then it changes beat, ticking in an altered temporal pattern compared to the others. The other areas adapt to this new situation through self-organisation and start playing a different drum beat as well. It is therefore sufficient to impact one of the areas in the network to completely reorganize its functioning, as we have shown in our model,” explains Battaglia.

The applied perturbation does not have to be particularly strong. “It is more important that the ‘kick’ occurs at exactly the right time of the rhythm,” says Battaglia. This might play a significant role for perception processes: “When viewing a picture, we are trained to recognize faces as quickly as possible – even if there aren’t any,” points out the Göttingen researcher. “But if we smell a fragrance reminiscent of wine, we immediately see the cup in the picture. This allows us to quickly adjust to things that we did not expect, changing the focus of our attention.”

Next, the scientists want to test the model on networks with a more realistic anatomy. They also hope that the findings inspire future experimental studies, as Battaglia says: “It would be fantastic if, in some years, certain brain areas could be stimulated so finely and precisely that the theoretically predicted effects can be measured through imaging methods.”

Provided by Max-Planck-Gesellschaft

Source: medicalxpress.com

ScienceDaily (Mar. 22, 2012) — Anxious people have a heightened sense of smell when it comes to sniffing out a threat, according to a new study by Elizabeth Krusemark and Wen Li from the University of Wisconsin-Madison in the US.

In animals, the sense of smell is an essential tool to detect, locate and identify predators in the surrounding environment. In fact, the olfactory-mediated defense system is so prominent in animals, that the mere presence of predator odors can evoke potent fear and anxiety responses.

Smells also evoke powerful emotional responses in humans. Krusemark and Li hypothesized that in humans, detection of a particular bad smell may signal danger of a noxious airborne substance, or a decaying object that carries disease.

Their work is published online in Springer’s journal Chemosensory Perception. The study is part of a special issue of this journal on neuroimaging the chemical senses.

The researchers exposed 14 young adult participants to three types of odors: neutral pure odor, neutral odor mixture, and negative odor mixture. They asked them to detect the presence or absence of an odor in an MRI scanner. During scanning, the researchers also measured the skin’s ability to conduct electricity (a measure of arousal level) and monitored the subjects’ breathing patterns. Once the odor detection task was over, and the subjects were still in the scanner, they were asked to rate their current level of anxiety. The authors then analyzed the brain images obtained.

They found that as anxiety levels rose, so did the subjects’ ability to discriminate negative odors accurately — suggesting a ‘remarkable’ olfactory acuity to threat in anxious subjects. The skin conductance results showed that anxiety also heightened emotional arousal to smell-induced threats.

The authors uncovered amplified communication between the sensory and emotional areas of the brain in response to negative odors, particularly in anxiety. This increased connectivity could be responsible for the heightened arousal to threats.

Krusemark and Li conclude: “This enhanced sensory-emotional coupling could serve as a critical mechanism to arouse adequate physiological alertness to potential insults.”

Source: Science Daily

March 22, 2012

Scripps Research Institute scientists and their colleagues have successfully harnessed neurons in mouse brains, allowing them to at least partially control a specific memory. Though just an initial step, the researchers hope such work will eventually lead to better understanding of how memories form in the brain, and possibly even to ways to weaken harmful thoughts for those with conditions such as schizophrenia and post traumatic stress disorder.

The results are reported in the March 23, 2012 issue of the journal Science.

Researchers have known for decades that stimulating various regions of the brain can trigger behaviors and even memories. But understanding the way these brain functions develop and occur normally—effectively how we become who we are—has been a much more complex goal.

"The question we’re ultimately interested in is: How does the activity of the brain represent the world?" said Scripps Research neuroscientist Mark Mayford, who led the new study. "Understanding all this will help us understand what goes wrong in situations where you have inappropriate perceptions. It can also tell us where the brain changes with learning."

On-Off Switches and a Hybrid Memory

As a first step toward that end, the team set out to manipulate specific memories by inserting two genes into mice. One gene produces receptors that researchers can chemically trigger to activate a neuron. They tied this gene to a natural gene that turns on only in active neurons, such as those involved in a particular memory as it forms, or as the memory is recalled. In other words, this technique allows the researchers to install on-off switches on only the neurons involved in the formation of specific memories.

For the study’s main experiment, the team triggered the “on” switch in neurons active as mice were learning about a new environment, Box A, with distinct colors, smells and textures.

Next the team placed the mice in a second distinct environment—Box B—after giving them the chemical that would turn on the neurons associated with the memory for Box A. The researchers found the mice behaved as if they were forming a sort of hybrid memory that was part Box A and part Box B. The chemical switch needed to be turned on while the mice were in Box B for them to demonstrate signs of recognition. Alone neither being in Box B nor the chemical switch was effective in producing memory recall.

"We know from studies in both animals and humans that memories are not formed in isolation but are built up over years incorporating previously learned information," Mayford said. "This study suggests that one way the brain performs this feat is to use the activity pattern of nerve cells from old memories and merge this with the activity produced during a new learning session."

Future Manipulation of the Past

The team is now making progress toward more precise control that will allow the scientists to turn one memory on and off at will so effectively that a mouse will in fact perceive itself to be in Box A when it’s in Box B.

Once the processes are better understood, Mayford has ideas about how researchers might eventually target the perception process through drug treatment to deal with certain mental diseases such as schizophrenia and post traumatic stress disorder. With such problems, patients’ brains are producing false perceptions or disabling fears. But drug treatments might target the neurons involved when a patient thinks about such fear, to turn off the neurons involved and interfere with the disruptive thought patterns.

Provided by The Scripps Research Institute

Source: medicalxpress.com