New insight into how our brain performs 'mental time travel'

In Proust's novel Recollection of Things Past, the distinctive smell of a lemon madeleine launches the narrator on a long, involved reminiscence of his past that fills seven chapters. It is an extreme example of what neuroscientists term "mental time travel" -- the recollection of memories so rich in detail regarding the time and place of an original experience that it is much like traveling through time. In a paper published Feb. 18 in the Journal of Neuroscience, a team of Vanderbilt scientists shed new light on how the brain processes these elaborate memories by analyzing the brain activity of individuals performing a simple memory recollection task. The researchers found that they can use the activity patterns in a specific region of the brain to substantially improve their ability to predict the order in which the participants recall information that they have recently studied. "It's extremely important that we understand what different brain regions are doing as we search through our memories," said Assistant Professor of Psychology Sean Polyn who headed the study. "Diseases like Alzheimer's and epilepsy are devastating to memory, and this information can help us develop treatments to preserve patients' memories, and identify adverse effects that new psychotropic drugs may have on people's memory." Scientists have known for some time that a portion of the brain called the medial temporal lobe plays a central role in memory because injuries to the MTL cause amnesia and other memory-related problems. However, they have not been able to answer the question: How does the brain control the fidelity of an individual memory? Of course, not all memories are recalled equally. High fidelity Proustian memories are at one end of the spectrum. At the other are bits of information that a person remembers clearly, but in complete isolation, without any accompanying details. Polyn, working with doctoral students James Kragel and Neal Morton (who is now at the University of Texas, Austin), has developed a model that accounts for how the structures in the MTL support memory retrieval. They have found that the anterior region of the MTL signals that a memory is being retrieved, but doesn't indicate how detailed it is. However, when the posterior region of the MTL becomes active it indicates that the person is experiencing a "time travel" memory accompanied by considerable detail. The researchers tested their model in an experiment with 20 participants (seven male and 13 female) between 18 and 35 years of age. They were put in an fMRI brain scanner and given a list of 24 names of common objects like horse, boat and window. Depending on the object they were asked to decide if it was big or small, animate or inanimate. (The purpose of the question was to make them concentrate on the words.) After a brief pause, they were asked to recall the words they had just studied in the order they occurred naturally. The researchers found that when a participant's brain scan indicated that they recalled an object with high fidelity, then their next response was likely to be the next item on the list. However, when the brain scan indicated that the object was an isolated recollection, then the next object the person recalled could come from anywhere on the list. For example, the participants might be asked to study the words "horse, window, robot and boat," in that order. An individual who experienced a time-travel experience when he or she recalled the word "horse," would be very likely to recall "window" immediately afterward. If, on the other hand, the person's memory of "horse" was low fidelity, his or her next response might instead be the more distant word, "boat." Polyn's group had previously developed a model of memory search that could be used to predict the order in which people would retrieve these items from memory. For example, the model predicts that people will tend to first recall the items from the end of the list, and if an item from the middle of the list is recalled, the next recollection is likely to come from a nearby list position. "This model was much better than chance at predicting what a person would recall next, but when we told the model what a person's brain activity was at the moment they recalled a particular item, the model became much better at predicting which item would be recalled next," Polyn said. "This demonstrates that the brain stamps memories with a temporal code. These time-travel recollections allow the brain to retrieve that temporal code, which makes memories for nearby things more accessible, in this case the next item in the list." The temporal code acts something like the time stamp that computers put on files. When you search for files stamped with a specific date and time, you retrieve all the files saved at the time you specify. Time-travel memory acts in much the same way, through a process psychologists call "reinstatement." This process is even more flexible than a computer, in that the temporal code can help you retrieve not just memories from the exact same time, but memories nearby in time, as well. When a strong memory is formed, it may include information about the sights, sounds, smells, emotions, and other information that was present at the time of the experience. All of this information becomes temporally linked, and time-travel memory allows a person to bring it back to mind, as when Proust smelled his famous madeleine cake. Polyn's memory model is an example of a new generation of brain simulations that are attempting to link brain activity with specific cognitive functions. The research was funded in part by National Science Foundation grant 1157432.

Brain cells' role in navigating environment

 

A new Dartmouth College study sheds light on the brain cells that function in establishing one's location and direction. The findings contribute to our understanding of the neural mechanisms underlying our abilities to successfully navigate our environment, which may be crucial to dealing with brain damage due to trauma or a stroke and the onset of diseases such as Alzheimer's. "Knowing what direction you are facing, where you are, how to navigate and your spatial orientation at a given moment are really fundamental to survival," says Professor Jeffrey Taube, the study's senior author. The study appears in the journal Science Express. The study's co-lead authors are Shawn Winter, a Dartmouth postdoctoral fellow in Psychological and Brain Sciences, and Benjamin Clark, an assistant professor at the University of New Mexico who received his PhD in Psychological and Brain Sciences from Dartmouth. The Dartmouth researchers study the neural mechanisms underlying our sense of location and directional heading, which forms the basis of our perceived spatial orientation in the environment. Knowing your spatial orientation is essential for being able to navigate to a goal. In the past few decades, researchers have discovered a number of cell types in the brain that respond in relation to where you are (so-called place cells) and your perceived directional heading (so-called head direction cells). More recently, a third cell type was discovered that is activated at multiple places in the environment: If you monitored the location of all these active places, you would find that they formed a repeating, grid-like pattern in a hexagonal array. These "grid cells" were identified in a different brain area, the entorhinal cortex. Researchers were excited about this discovery because theoretically these grid cells could account for how we can keep track of where we are at any given moment and how we update this perception as we move through our environment. Based on how these cells fire, they could also inform us of how far we have traveled and our precise path. The 2014 Nobel Prize in physiology/medicine was awarded to the two laboratories that discovered place cells and grid cells. Scientists have been investigating how the grid cell signal is generated. The Dartmouth experiments addressed what types of information go into forming this signal. They use microelectrodes to record the activity of cells in a rat's brain that make possible spatial navigation. They found that if they inactivate or turn off a key brain area that contains head direction cells, then the grid cell signal in the entorhinal cortex is disrupted, without affecting the place cell signal in the hippocampus. "These results indicate for the first time that although the grid cell signal is about places, the head direction cell information is critical for generating the grid signal," Taube says. "These findings contribute to our understanding of the neural mechanisms underlying our abilities to successfully navigate our environment." Story Source: The above story is based on materials provided by Dartmouth College. Note: Materials may be edited for content and length. Journal Reference: Shawn S. Winter, Benjamin J. Clark, and Jeffrey S. Taube. Disruption of the head direction cell network impairs the parahippocampal grid cell signal. Science, 5 February 2015 DOI: 10.1126/science.1259591

Copper on the brain at rest

 

Mon, 12/01/2014 - 8:59am Lynn Yarris, Lawrence Berkeley National Laboratory Two-photon imaging of CF3 in cultured dissociated hippocampal neurons shows how the addition of the BCS chelator shrinks the presence of labile copper pools.In recent years it has been established that copper plays an essential role in the health of the human brain. Improper copper oxidation has been linked to several neurological disorders including Alzheimer’s, Parkinson’s, Menkes’ and Wilson’s. Copper has also been identified as a critical ingredient in the enzymes that activate the brain’s neurotransmitters in response to stimuli. Now a new study by researchers with the U.S. Dept. of Energy (DOE)’s Lawrence Berkeley National Laboratory (Berkeley Lab) has shown that proper copper levels are also essential to the health of the brain at rest. “Using new molecular imaging techniques, we’ve identified copper as a dynamic modulator of spontaneous activity of developing neural circuits, which is the baseline activity of neurons without active stimuli, kind of like when you sleep or daydream, that allows circuits to rest and adapt,” says Chris Chang, a faculty chemist with Berkeley Lab’s Chemical Sciences Div. who led this study. “Traditionally, copper has been regarded as a static metabolic cofactor that must be buried within enzymes to protect against the generation of reactive oxygen species and subsequent free radical damage. We’ve shown that dynamic and loosely bound pools of copper can also modulate neural activity and are essential for the normal development of synapses and circuits.” Chang, who also holds appointments with the Univ. of California (UC) Berkeley’s Chemistry Dept. and the Howard Hughes Medical Institute (HHMI), is the corresponding author of a paper that describes this study in the Proceedings of the National Academy of Sciences (PNAS). Co-authors are Sheel Dodani, Alana Firl, Jefferson Chan, Christine Nam, Allegra Aron, Carl Onak, Karla Ramos-Torres, Jaeho Paek, Corey Webster and Marla Feller. Although the human brain accounts for only two-percent of total body mass, it consumes 20% of the oxygen taken in through respiration. This high demand for oxygen and oxidative metabolism has resulted in the brain harboring the body’s highest levels of copper, as well as iron and zinc. Over the past few years, Chang and his research group at UC Berkeley have developed a series of fluorescent probes for molecular imaging of copper in the brain. “A lack of methods for monitoring dynamic changes in copper in whole living organisms has made it difficult to determine the complex relationships between copper status and various stages of health and disease,” Chang said. “We’ve been designing fluorescent probes that can map the movement of copper in live cells, tissue or even model organisms, such as mice and zebra fish.” For this latest study, Chang and his group developed a fluorescent probe called Copper Fluor-3 (CF3) that can be used for one- and two-photon imaging of copper ions. This new probe allowed them to explore the potential contributions to cell signaling of loosely bound forms of copper in hippocampal neurons and retinal tissue. “CF3 is a more hydrophilic probe compared to others we have made, so it gives more even staining and is suitable for both cells and tissue,” Chang says. “It allows us to utilize both confocal and two-photon imaging methods when we use it along with a matching control dye (Ctrl-CF3) that lacks sensitivity to copper.” With the combination of CF3 and Ctrl-CF3, Chang and his group showed that neurons and neural tissue maintain stores of loosely bound copper that can be attenuated by chelation to create what is called a “labile copper pool.” Targeted disruption of these labile copper pools by acute chelation or genetic knockdown of the copper ion channel known as CTR1 (for copper transporter 1) alters spontaneous neural activity in developing hippocampal and retinal circuits. “We demonstrated that the addition of the copper chelator bathocuproine disulfonate (BCS) modulates copper signaling which translates into modulation of neural activity,” Chang says. “Acute copper chelation as a result of additional BCS in dissociated hippocampal cultures and intact developing retinal tissue removed the copper which resulted in too much spontaneous activity.” The results of this study suggest that the mismanagement of copper in the brain that has been linked to Wilson’s, Alzheimer’s and other neurological disorders can also contribute to misregulation of signaling in cell−to-cell communications. “Our results hold therapeutic implications in that whether a patient needs copper supplements or copper chelators depends on how much copper is present and where in the brain it is located,” Chang says. “These findings also highlight the continuing need to develop molecular imaging probes as pilot screening tools to help uncover unique and unexplored metal biology in living systems.” Source: Lawrence Berkeley National Laboratory

How does the brain react to virtual reality? Completely different pattern of activity in brain

 

---

Illusions (stock image). UCLA neurophysicists have found that space-mapping neurons in the brain react differently to virtual reality than they do to real-world environments.

UCLA neurophysicists have found that space-mapping neurons in the brain react differently to virtual reality than they do to real-world environments. Their findings could be significant for people who use virtual reality for gaming, military, commercial, scientific or other purposes.

"The pattern of activity in a brain region involved in spatial learning in the virtual world is completely different than when it processes activity in the real world," said Mayank Mehta, a UCLA professor of physics, neurology and neurobiology in the UCLA College and the study's senior author. "Since so many people are using virtual reality, it is important to understand why there are such big differences."

The study was published today in the journal Nature Neuroscience.

The scientists were studying the hippocampus, a region of the brain involved in diseases such as Alzheimer's, stroke, depression, schizophrenia, epilepsy and post-traumatic stress disorder. The hippocampus also plays an important role in forming new memories and creating mental maps of space. For example, when a person explores a room, hippocampal neurons become selectively active, providing a "cognitive map" of the environment.

The mechanisms by which the brain makes those cognitive maps remains a mystery, but neuroscientists have surmised that the hippocampus computes distances between the subject and surrounding landmarks, such as buildings and mountains. But in a real maze, other cues, such as smells and sounds, can also help the brain determine spaces and distances.

To test whether the hippocampus could actually form spatial maps using only visual landmarks, Mehta's team devised a noninvasive virtual reality environment and studied how the hippocampal neurons in the brains of rats reacted in the virtual world without the ability to use smells and sounds as cues.

Researchers placed a small harness around rats and put them on a treadmill surrounded by a "virtual world" on large video screens -- a virtual environment they describe as even more immersive than IMAX -- in an otherwise dark, quiet room. The scientists measured the rats' behavior and the activity of hundreds of neurons in their hippocampi, said UCLA graduate student Lavanya Acharya, a lead author on the research.

The researchers also measured the rats' behavior and neural activity when they walked in a real room designed to look exactly like the virtual reality room.

The scientists were surprised to find that the results from the virtual and real environments were entirely different. In the virtual world, the rats' hippocampal neurons seemed to fire completely randomly, as if the neurons had no idea where the rat was -- even though the rats seemed to behave perfectly normally in the real and virtual worlds.

"The 'map' disappeared completely," said Mehta, director of a W.M. Keck Foundation Neurophysics center and a member of UCLA's Brain Research Institute. "Nobody expected this. The neuron activity was a random function of the rat's position in the virtual world."

Explained Zahra Aghajan, a UCLA graduate student and another of the study's lead authors: "In fact, careful mathematical analysis showed that neurons in the virtual world were calculating the amount of distance the rat had walked, regardless of where he was in the virtual space."

They also were shocked to find that although the rats' hippocampal neurons were highly active in the real-world environment, more than half of those neurons shut down in the virtual space.

The virtual world used in the study was very similar to virtual reality environments used by humans, and neurons in a rat's brain would be very hard to distinguish from neurons in the human brain, Mehta said.

His conclusion: "The neural pattern in virtual reality is substantially different from the activity pattern in the real world. We need to fully understand how virtual reality affects the brain."

Neurons Bach would appreciate

In addition to analyzing the activity of individual neurons, Mehta's team studied larger groups of the brain cells. Previous research, including studies by his group, have revealed that groups of neurons create a complex pattern using brain rhythms.

"These complex rhythms are crucial for learning and memory, but we can't hear or feel these rhythms in our brain. They are hidden under the hood from us," Mehta said. "The complex pattern they make defies human imagination. The neurons in this memory-making region talk to each other using two entirely different languages at the same time. One of those languages is based on rhythm; the other is based on intensity."

Every neuron in the hippocampus speaks the two languages simultaneously, Mehta said, comparing the phenomenon to the multiple concurrent melodies of a Bach fugue.

Mehta's group reports that in the virtual world, the language based on rhythm has a similar structure to that in the real world, even though it says something entirely different in the two worlds. The language based on intensity, however, is entirely disrupted.

When people walk or try to remember something, the activity in the hippocampus becomes very rhythmic and these complex, rhythmic patterns appear, Mehta said. Those rhythms facilitate the formation of memories and our ability to recall them. Mehta hypothesizes that in some people with learning and memory disorders, these rhythms are impaired.

"Neurons involved in memory interact with other parts of the hippocampus like an orchestra," Mehta said. "It's not enough for every violinist and every trumpet player to play their music flawlessly. They also have to be perfectly synchronized."

Mehta believes that by retuning and synchronizing these rhythms, doctors will be able to repair damaged memory, but said doing so remains a huge challenge.

"The need to repair memories is enormous," noted Mehta, who said neurons and synapses -- the connections between neurons -- are amazingly complex machines.

Previous research by Mehta showed that the hippocampal circuit rapidly evolves with learning and that brain rhythms are crucial for this process. Mehta conducts his research with rats because analyzing complex brain circuits and neural activity with high precision currently is not possible in humans.

Other co-authors of the study were Jason Moore, a UCLA graduate student; Cliff Vuong, a research assistant who conducted the research as a UCLA undergraduate; and UCLA postdoctoral scholar Jesse Cushman. The research was funded by the W.M. Keck Foundation and the National Institutes of Health.

Imagination, reality flow in opposite directions in the brain

 

---

Electrical and computer engineering Professor Barry Van Veen wears an electrode net used to monitor brain activity via EEG signals. His research could help untangle what happens in the brain during sleep and dreaming.

As real as that daydream may seem, its path through your brain runs opposite reality.

Aiming to discern discrete neural circuits, researchers at the University of Wisconsin-Madison have tracked electrical activity in the brains of people who alternately imagined scenes or watched videos.

"A really important problem in brain research is understanding how different parts of the brain are functionally connected. What areas are interacting? What is the direction of communication?" says Barry Van Veen, a UW-Madison professor of electrical and computer engineering. "We know that the brain does not function as a set of independent areas, but as a network of specialized areas that collaborate."

Van Veen, along with Giulio Tononi, a UW-Madison psychiatry professor and neuroscientist, Daniela Dentico, a scientist at UW-Madison's Waisman Center, and collaborators from the University of Liege in Belgium, published results recently in the journal NeuroImage. Their work could lead to the development of new tools to help Tononi untangle what happens in the brain during sleep and dreaming, while Van Veen hopes to apply the study's new methods to understand how the brain uses networks to encode short-term memory.

During imagination, the researchers found an increase in the flow of information from the parietal lobe of the brain to the occipital lobe -- from a higher-order region that combines inputs from several of the senses out to a lower-order region.

In contrast, visual information taken in by the eyes tends to flow from the occipital lobe -- which makes up much of the brain's visual cortex -- "up" to the parietal lobe.

"There seems to be a lot in our brains and animal brains that is directional, that neural signals move in a particular direction, then stop, and start somewhere else," says. "I think this is really a new theme that had not been explored."

The researchers approached the study as an opportunity to test the power of electroencephalography (EEG) -- which uses sensors on the scalp to measure underlying electrical activity -- to discriminate between different parts of the brain's network.

Brains are rarely quiet, though, and EEG tends to record plenty of activity not necessarily related to a particular process researchers want to study.

To zero in on a set of target circuits, the researchers asked their subjects to watch short video clips before trying to replay the action from memory in their heads. Others were asked to imagine traveling on a magic bicycle -- focusing on the details of shapes, colors and textures -- before watching a short video of silent nature scenes.

Using an algorithm Van Veen developed to parse the detailed EEG data, the researchers were able to compile strong evidence of the directional flow of information.

"We were very interested in seeing if our signal-processing methods were sensitive enough to discriminate between these conditions," says Van Veen, whose work is supported by the National Institute of Biomedical Imaging and Bioengineering. "These types of demonstrations are important for gaining confidence in new tools."

The science behind total recall: New player in brain function and memory

 

---

Artist's abstraction (stock illustration).

Is it possible to change the amount of information the brain can store? Maybe, according to a new international study led by the Research Institute of the McGill University Health Centre (RI-MUHC). Their research has identified a molecule that puts a brake on brain processing and when removed, brain function and memory recall is improved. Published in the latest issue of Cell Reports, the study has implications for neurodevelopmental and neurodegenerative diseases, such as autism spectral disorders and Alzheimer's disease.

"Previous research has shown that production of new molecules is necessary for storing memories in the brain; if you block the production of these molecules, new memory formation does not take place," says RI-MUHC neuroscientist, Dr. Keith Murai, the study's senior author and Associate Professor in the Department of Neurology and Neurosurgery at McGill University. "Our findings show that the brain has a key protein that limits the production of molecules necessary for memory formation. When this brake-protein is suppressed, the brain is able to store more information."

FXR1P: a controller of certain forms of memory

Dr. Murai and his colleagues used a mouse model to study how changes in brain cell connections produce new memories. They demonstrated that a protein, FXR1P (Fragile X Related Protein 1), was responsible for suppressing the production of molecules required for building new memories. When FXR1P was selectively removed from certain parts of the brain, these new molecules were produced that strengthened connections between brain cells and this correlated with improved memory and recall in the mice.

Disease link

"The role of FXR1P was a surprising result," says Dr. Murai. "Previous to our work, no-one had identified a role for this regulator in the brain. Our findings have provided fundamental knowledge about how the brain processes information. We've identified a new pathway that directly regulates how information is handled and this could have relevance for understanding and treating brain diseases."

"Future research in this area could be very interesting," he adds. "If we can identify compounds that control the braking potential of FXR1P, we may be able to alter the amount of brain activity or plasticity. For example, in autism, one may want to decrease certain brain activity and in Alzheimer's disease, we may want to enhance the activity. By manipulating FXR1P, we may eventually be able to adjust memory formation and retrieval, thus improving the quality of life of people suffering from brain diseases."

---

Story Source:

The above story is based on materials provided by McGill University Health Centre. Note: Materials may be edited for content and length.

---

Journal Reference:

1. Denise Cook, Erin Nuro, Emma V. Jones, Haider F. Altimimi, W. Todd Farmer, Valentina Gandin, Edith Hanna, Ruiting Zong, Alessandro Barbon, David L. Nelson, Ivan Topisirovic, Joseph Rochford, David Stellwagen, Jean-Claude Béïque, Keith K. Murai. FXR1P Limits Long-Term Memory, Long-Lasting Synaptic Potentiation, and De Novo GluA2 Translation. Cell Reports, 2014 DOI: 10.1016/j.celrep.2014.10.028

---

 

Reminiscing can help boost mental performance

 

---

“The prevailing view is that activating brain regions referred to as the default network impairs performance on attention-demanding tasks because this network is associated with behaviors such as mind-wandering,” said Spreng. “Our study is the first to demonstrate the opposite – that engaging the default network can also improve performance.”

To solve a mental puzzle, the brain’s executive control network for externally focused, goal-oriented thinking must activate, while the network for internally directed thinking like daydreaming must be turned down to avoid interference – or so we thought.

New research led by Cornell University neuroscientist Nathan Spreng shows for the first time that engaging brain areas linked to so-called “off-task” mental activities (such as mind-wandering and reminiscing) can actually boost performance on some challenging mental tasks. The results advance our understanding of how externally and internally focused neural networks interact to facilitate complex thought, the authors say.

“The prevailing view is that activating brain regions referred to as the default network impairs performance on attention-demanding tasks because this network is associated with behaviors such as mind-wandering,” said Spreng. “Our study is the first to demonstrate the opposite – that engaging the default network can also improve performance.”

There are plenty of neuroimaging studies showing that default network activation interferes with complex mental tasks – but in most, Spreng explained, the mental processes associated with default network conflict with task goals. If you start thinking about what you did last weekend while taking notes during a lecture, for example, your note-taking and ability to keep up will suffer.

Spreng and his team developed a new approach in which off-task processes such as reminiscing can support rather than conflict with the aims of the experimental task. Their novel task, “famous faces n-back,” tests whether accessing long-term memory about famous people, which typically engages default network brain regions, can support short-term memory performance, which typically engages executive control regions.

While undergoing brain scanning, 36 young adults viewed sets of famous and anonymous faces in sequence and were asked to identify whether the current face matched the one presented two faces back. The team found participants were faster and more accurate when matching famous faces than when matching anonymous faces and that this better short-term memory performance was associated with greater activity in the default network. The results show that activity in the default brain regions can support performance on goal-directed tasks when task demands align with processes supported by the default network, the authors say.

“Outside the laboratory, pursuing goals involves processing information filled with personal meaning – knowledge about past experiences, motivations, future plans and social context,” Spreng said. “Our study suggests that the default network and executive control networks dynamically interact to facilitate an ongoing dialogue between the pursuit of external goals and internal meaning.”

The study, “Goal-congruent default network activity facilitates cognitive control,” published in October in the Journal of Neuroscience, was funded in part by the National Institutes of Health and the Natural Sciences and Engineering Research Council of Canada.

---

Story Source:

The above story is based on materials provided by Cornell University. The original article was written by Melissa Osgood. Note: Materials may be edited for content and length.

---

Journal Reference:

1. R. N. Spreng, E. DuPre, D. Selarka, J. Garcia, S. Gojkovic, J. Mildner, W.-M. Luh, G. R. Turner. Goal-Congruent Default Network Activity Facilitates Cognitive Control. Journal of Neuroscience, 2014; 34 (42): 14108 DOI: 10.1523/JNEUROSCI.2815-14.2014

---

 

See-through sensors open new window into the brain

 

---

A blue light shines through a clear implantable medical sensor onto a brain model. See-through sensors, which have been developed by a team of UW-Madison engineers, should help neural researchers better view brain activity.

Developing invisible implantable medical sensor arrays, a team of University of Wisconsin-Madison engineers has overcome a major technological hurdle in researchers' efforts to understand the brain.

The team described its technology, which has applications in fields ranging from neuroscience to cardiac care and even contact lenses, in the Oct. 20 issue of the online journal Nature Communications.

Neural researchers study, monitor or stimulate the brain using imaging techniques in conjunction with implantable sensors that allow them to continuously capture and associate fleeting brain signals with the brain activity they can see. However, it's difficult to see brain activity when there are sensors blocking the view.

"One of the holy grails of neural implant technology is that we'd really like to have an implant device that doesn't interfere with any of the traditional imaging diagnostics," says Justin Williams, a professor of biomedical engineering and neurological surgery at UW-Madison. "A traditional implant looks like a square of dots, and you can't see anything under it. We wanted to make a transparent electronic device."

The researchers chose graphene, a material gaining wider use in everything from solar cells to electronics, because of its versatility and biocompatibility. And in fact, they can make their sensors incredibly flexible and transparent because the electronic circuit elements are only 4 atoms thick -- an astounding thinness made possible by graphene's excellent conductive properties. "It's got to be very thin and robust to survive in the body," says Zhenqiang (Jack) Ma, a professor of electrical and computer engineering at UW-Madison. "It is soft and flexible, and a good tradeoff between transparency, strength and conductivity."

Drawing on his expertise in developing revolutionary flexible electronics, he, Williams and their students designed and fabricated the microelectrode arrays, which -- unlike existing devices -- work in tandem with a range of imaging technologies. "Other implantable microdevices might be transparent at one wavelength, but not at others, or they lose their properties," says Ma. "Our devices are transparent across a large spectrum -- all the way from ultraviolet to deep infrared. We've even implanted them and you cannot find them in an MR scan."

The transparent sensors could be a boon to neuromodulation therapies, which physicians increasingly are using to control symptoms, restore function, and relieve pain in patients with diseases or disorders such as hypertension, epilepsy, Parkinson's disease, or others, says Kip Ludwig, a program director for the National Institutes of Health neural engineering research efforts. "Despite remarkable improvements seen in neuromodulation clinical trials for such diseases, our understanding of how these therapies work -- and therefore our ability to improve existing or identify new therapies -- is rudimentary."

Currently, he says, researchers are limited in their ability to directly observe how the body generates electrical signals, as well as how it reacts to externally generated electrical signals. "Clear electrodes in combination with recent technological advances in optogenetics and optical voltage probes will enable researchers to isolate those biological mechanisms. This fundamental knowledge could be catalytic in dramatically improving existing neuromodulation therapies and identifying new therapies."

The advance aligns with bold goals set forth in President Barack Obama's BRAIN (Brain Research through Advancing Innovative Neurotechnologies) Initiative. Obama announced the initiative in April 2013 as an effort to spur innovations that can revolutionize understanding of the brain and unlock ways to prevent, treat or cure such disorders as Alzheimer's and Parkinson's disease, post-traumatic stress disorder, epilepsy, traumatic brain injury, and others.

While the team centered its efforts on neural research, they already have started to explore other medical device applications. For example, working with researchers at the University of Illinois-Chicago, they prototyped a contact lens instrumented with dozens of invisible sensors to detect injury to the retina; the UIC team is exploring applications such as early diagnosis of glaucoma.

Additional authors on the Nature Communications paper include UW-Madison electrical and computer engineering graduate students Dong-Wook Park and Solomon Mikael, materials science graduate student Amelia A. Schendel, biomedical engineering research specialist Sarah K. Brodnick; biomedical engineering graduate students Thomas J. Richner, Jared P. Ness and Mohammed R. Hayat; collaborators Farid Atry, Seth T. Frye and Ramin Pashaie of the University of Wisconsin-Milwaukee; and Sanitta Thongpang of Mahidol University in Bangkok, Thailand.

The researchers are patenting their technology through the Wisconsin Alumni Research Foundation. Funding for the research came from the U.S. Defense Advanced Research Projects Agency, the National Institutes of Health, and the U.S. Office of Naval Research.

---

Story Source:

The above story is based on materials provided by University of Wisconsin-Madison. The original article was written by Renee Meiller. Note: Materials may be edited for content and length.

---

Journal Reference:

1. Dong-Wook Park, Amelia A. Schendel, Solomon Mikael, Sarah K. Brodnick, Thomas J. Richner, Jared P. Ness, Mohammed R. Hayat, Farid Atry, Seth T. Frye, Ramin Pashaie, Sanitta Thongpang, Zhenqiang Ma, Justin C. Williams. Graphene-based carbon-layered electrode array technology for neural imaging and optogenetic applications. Nature Communications, 2014; 5: 5258 DOI: 10.1038/ncomms6258

---

 

University of Wisconsin-Madison. "See-through sensors open new window into the brain." ScienceDaily. ScienceDaily, 20 October 2014. <www.sciencedaily.com/releases/2014/10/141020212345.htm>.

 

How the brain leads us to believe we have sharp vision

 

---

The thumbnail at the end of an outstretched arm: This is the area that the eye actually can see in sharp detail. Researchers have investigated why the rest of the world also appears to be uniformly detailed.

We assume that we can see the world around us in sharp detail. In fact, our eyes can only process a fraction of our surroundings precisely. In a series of experiments, psychologists at Bielefeld University have been investigating how the brain fools us into believing that we see in sharp detail. The results have been published in the scientific magazine Journal of Experimental Psychology: General. Its central finding is that our nervous system uses past visual experiences to predict how blurred objects would look in sharp detail.

"In our study we are dealing with the question of why we believe that we see the world uniformly detailed," says Dr. Arvid Herwig from the Neuro-Cognitive Psychology research group of the Faculty of Psychology and Sports Science. The group is also affiliated to the Cluster of Excellence Cognitive Interaction Technology (CITEC) of Bielefeld University and is led by Professor Dr. Werner X. Schneider.

Only the fovea, the central area of the retina, can process objects precisely. We should therefore only be able to see a small area of our environment in sharp detail. This area is about the size of a thumb nail at the end of an outstretched arm. In contrast, all visual impressions which occur outside the fovea on the retina become progressively coarse. Nevertheless, we commonly have the impression that we see large parts of our environment in sharp detail.

Herwig and Schneider have been getting to the bottom of this phenomenon with a series of experiments. Their approach presumes that people learn through countless eye movements over a lifetime to connect the coarse impressions of objects outside the fovea to the detailed visual impressions after the eye has moved to the object of interest. For example, the coarse visual impression of a football (blurred image of a football) is connected to the detailed visual impression after the eye has moved. If a person sees a football out of the corner of her eye, her brain will compare this current blurred picture with memorised images of blurred objects. If the brain finds an image that fits, it will replace the coarse image with a precise image from memory. This blurred visual impression is replaced before the eye moves. The person thus thinks that she already sees the ball clearly, although this is not the case.

The psychologists have been using eye-tracking experiments to test their approach. Using the eye-tracking technique, eye movements are measured accurately with a specific camera which records 1000 images per second. In their experiments, the scientists have recorded fast balistic eye movements (saccades) of test persons. Though most of the participants did not realise it, certain objects were changed during eye movement. The aim was that the test persons learn new connections between visual stimuli from inside and outside the fovea, in other words from detailed and coarse impressions. Afterwards, the participants were asked to judge visual characteristics of objects outside the area of the fovea. The result showed that the connection between a coarse and detailed visual impression occurred after just a few minutes. The coarse visual impressions became similar to the newly learnt detailed visual impressions.

"The experiments show that our perception depends in large measure on stored visual experiences in our memory," says Arvid Herwig. According to Herwig and Schneider, these experiences serve to predict the effect of future actions ("What would the world look like after a further eye movement"). In other words: "We do not see the actual world, but our predictions."

---

Story Source:

The above story is based on materials provided by Bielefeld University. Note: Materials may be edited for content and length.

---

Journal Reference:

1. Arvid Herwig, Werner X. Schneider. Predicting object features across saccades: Evidence from object recognition and visual search. Journal of Experimental Psychology: General, 2014; 143 (5): 1903 DOI: 10.1037/a0036781

---

Bielefeld University. "How the brain leads us to believe we have sharp vision." ScienceDaily. ScienceDaily, 17 October 2014. <www.sciencedaily.com/releases/2014/10/141017101339.htm>.

 

Make tough tasks seem easier by zapping the brain

 

My, what big eyes you have – you must be trying really hard. A study of how pupils dilate with physical effort could allow us to make strenuous tasks seem easier by zapping specific areas of the brain.

We know pupils dilate with mental effort, when we think about a difficult maths problem, for example. To see if this was also true of physical exertion, Alexandre Zenon at the Catholic University of Louvain in Belgium, measured the pupils of 18 volunteers as they squeezed a device which reads grip strength. Sure enough, the more force they exerted, the larger their pupils.

To see whether pupil size was related to actual or perceived effort, the volunteers were asked to squeeze the device with four different grip strengths. Various tests enabled the researchers to tell how much effort participants felt they used, from none at all to the most effort possible.

Comparing the results from both sets of experiments suggested that pupil dilation correlated more closely with perceived effort than actual effort.

Mind over matter

The fact that both mental effort and perceived physical effort are reflected in pupil size suggests there is a common representation of effort in the brain, says Zenon.

To see where in the brain this might be, the team looked at which areas were active while similar grip tasks were being performed. Zenon says they were able to identify areas within the supplementary motor cortex – which plays a role in movement – associated with how effortful a task is perceived to be.

Next, they used a non-invasive method called transcranial magnetic stimulation to block activity in that area as people repeated the task. "When we disrupted this area, there was a clear drop in the perception of effort," says Zenon. In other words, the participants made the same actual effort but to them, it seemed significantly easier.

The implications are really interesting, says Zenon. "I don't know how practical it would be to use stimulation to make some activity seem less effortful, but in theory it's possible. For now, we are just trying to understand what mental effort actually is."

Journal reference: Frontiers in Behavioral Neuroscience, DOI: 10.3389/fnbeh.2014.00286