Psychologists Use fMRI To Understand Ties Between Memories And The Imagination

ScienceDaily.com  —  Psychologists have found that thought patterns used to recall the past and imagine the future are strikingly similar. Using functional magnetic resonance imaging to show the brain at work, they have observed the same regions activated in a similar pattern whenever a person remembers an event from the past or imagines himself in a future situation. This challenges long-standing beliefs that thoughts about the future develop exclusively in the frontal lobe.

Remembering your past may go hand-in-hand with envisioning your future! It’s an important link researchers found using high-tech brain scans. It’s answering questions and may one day help those with memory loss.

For some, the best hope of ‘seeing’ the future leads them to seek guidance — perhaps from an astrologist. But it’s not very scientific. Now, psychologists at Washington University are finding that your ability to envision the future does in fact goes hand-in-hand with remembering the past. Both processes spark similar neural activity in the brain.

“You might look at it as mental time travel–the ability to take thoughts about ourselves and project them either into the past or into the future,” says Kathleen McDermott, Ph.D. and Washington University psychology professor. The team used “functional magnetic resonance imaging” — or fMRI — to “see” brain activity. They asked college students to recall past events and then envision themselves experiencing such an event in their future. The results? Similar areas of the brain “lit up” in both scenarios.

“We’re taking these images from our memories and projecting them into novel future scenarios,” says psychology professor Karl Szpunar.

Most scientists believed thinking about the future was a process occurring solely in the brain’s frontal lobe. But the fMRI data showed a variety of brain areas were activated when subjects dreamt of the future.

“All the regions that we know are important for memory are just as important when we imagine our future,” Szpunar says.

Researchers say besides furthering their understanding of the brain — the findings may help research into amnesia, a curious psychiatric phenomenon. In addition to not being able to remember the past, most people who suffer from amnesia cannot envision or visualize what they’ll be doing in the future — even

the next day.

An  MRI image depicts a scan of a normal human brain.  A new study has shown that a computer program can match scans of brain activity with visual images and even predict what people are seeing.      Image courtesy NIH/NIDA  

BACKGROUND: Researchers from Washington University in St. Louis have used advanced brain imaging techniques to show that remembering the past and envisioning the future may go hand-in-hand, with each process showing strikingly similar patterns of activity within precisely the same broad network of brain regions. This suggests that envisioning the future may be a critical prerequisite for many higher-level planning processes in the brain.

WHAT IS fMRI: Magnetic resonance imaging (MRI) uses radio waves and a strong magnetic field rather than X-rays to take clear and detailed pictures of internal organs and tissues. fMRI uses this technology to identify regions of the brain where blood vessels are expanding, chemical changes are taking place, or extra oxygen is being delivered. These are indications that a particular part of the brain is processing information and giving commands to the body. As a patient performs a particular task, the metabolism will increase in the brain area responsible for that task, changing the signal in the MRI image. So by performing specific tasks that correspond to different functions, scientists can locate the part of the brain that governs that function.

ABOUT THE STUDY: The researchers relied on fMRI to capture patterns of brain activation as college students were given 10 seconds to develop a vivid mental image of themselves or a famous celebrity participating in a range of common life experiences. Presented with a series of memory cues — such as getting lost, spending time with a friend, or attending a birthday party — participants were asked to recall a related event from their own past; to envision themselves experiencing such an event in their future life; or to picture a famous celebrity (specifically, former U.S. president Bill Clinton) participating in such an event.

WHAT THEY FOUND: Comparing images of brain activity in response to the ‘self-remember’ and ‘self future’ event cues, researchers found a surprisingly complete overlap among regions of the brain used for remembering the past and those used for envisioning the future. The study clearly demonstrates that the neural network underlying future thoughts is not only happening in the brain’s frontal cortex. Although the frontal lobes play an important role in carrying out future-oriented operations — such as anticipation, planning and monitoring — the spark for these activities may be the process of envisioning yourself in a specific future event. And that’s an activity based on the same brain network used to remember memories about our own lives. Also, patterns of activity suggest that the visual and spatial context for our imagined future is often pieced together using our past experiences, including memories of specific body movements: data our brain has stored as we navigated through similar settings in the past.

New research suggests that circuits in the adult brain are continually modified by experience. (Credit: iStockphoto/Mark Evans)

 

 

PLoS, July 29, 2010  —  The adult brain, long considered to be fixed in its wiring, is in fact remarkably dynamic. Neuroscientists once thought that the brain’s wiring was fixed early in life, during a critical period beyond which changes were impossible. Recent discoveries have challenged that view, and now, research by scientists at Rockefeller University suggests that circuits in the adult brain are continually modified by experience.

The researchers, led by Charles D. Gilbert, Arthur and Janet Ross Professor and head of the Laboratory of Neurobiology, observed how neurons responsible for receiving input from a mouse’s whiskers shift their relationships with one another after single whiskers are removed. The experiments explain how the circuitry of a region of the mouse brain called the somatosensory cortex, which processes input from the various systems in the body that respond to the sense of touch, can change.

The findings are published  in the online, open access journal PLoS Biology.

The Gilbert lab has been studying changing neuronal connections for several years. Their approach, in which the scientists use a viral labeling system to attach fluorescent proteins to individual neurons and then image individual synapses in an intact, living brain with a high-resolution two-photon microscope, has provided several important clues to understanding the dynamics of the brain’s wiring.

Students in the Gilbert lab, Dan Stettler and Homare (Matias) Yamahachi, in collaboration with Winfried Denk at the Max Planck Institute in Heidelberg, previously followed the same neurons week after week in the primary visual cortex of adult monkeys. They found that the circuits of the visual cortex are highly dynamic, turning over synapses at a rate of seven percent per week. These changes occurred without any learning regimen or physical manipulations to the neurons. Last year, Yamahachi, together with Sally Marik and Justin McManus, showed that when sensory experience is altered, even more dramatic changes in cortical circuits occur, with very rapid alterations in circuitry involving an exuberant growth of new connections paralleled by a pruning of old connections.

These studies and others by the Gilbert lab have begun to show that there are underlying dynamics in the sensory cortex and it’s not a fixed system, as has long been believed.

In the new study, Marik and other members of the Gilbert lab looked at excitatory and inhibitory neurons within the mouse cortex during periods of sensory deprivation to determine how experience shapes different components of cortical circuitry. For this study they used the whisker-barrel system in adult mice. The barrel cortex, part of the somatosensory cortex, receives sensory input from the animal’s whiskers. Scientists have shown that after a row of whiskers is removed, barrels shift their representation to adjacent intact whiskers.

Marik, together with Yamahachi and McManus, found that after a whisker was plucked excitatory connections projecting into the deprived barrels underwent exuberant and rapid axonal sprouting. This axonal restructuring occurred rapidly — within minutes or hours after whiskers were plucked — and continued over the course of several weeks. At the same time that excitatory connections were invading the deprived columns, there was a reciprocal outgrowth of the axons of inhibitory neurons from the deprived to the non-deprived barrels. This suggests that the process of reshaping cortical circuits maintains the balance between excitation and inhibition that exists in the normal cortex.

“Previously we showed changes only in excitatory connections,” Gilbert says. “We’ve now demonstrated a parallel involvement of inhibitory connections, and we think that inhibition may play a role equal in importance to excitation in inducing changes in cortical functional maps.”

The new study also showed that changes in the inhibitory circuits preceded those seen in the excitatory connections, suggesting that the inhibitory changes may mediate the excitatory ones. This process, Gilbert says, mimics what happens in the brain during early postnatal development.

“It’s surprising that the primary visual or somatosensory cortices are involved in plasticity and capable of establishing new memories, which previously had been considered to be a specialized function of higher brain centers,” Gilbert says. “We are just beginning to tease apart the mechanisms of adult cortical plasticity. We hope to determine whether the circuit changes associated with recovery of function following lesions to the central and peripheral nervous systems also occur under normal conditions of perceptual learning.”


Source:  Public Library of Science


Journal Reference:

  1. Marik SA, Yamahachi H, McManus JNJ, Szabo G, Gilbert CD. Axonal Dynamics of Excitatory and Inhibitory Neurons in Somatosensory Cortex. PLoS Biology, 2010; 8 (6): e1000395 DOI: 10.1371/journal.pbio.1000395

 

Public Library of Science (2010, June 16). Experience shapes the brain’s circuitry throughout adulthood.

Dendrites of a nerve cell in brain appear like branches of a tree. Left: A patch clamp pipette injects fluorescent dye into the cell. (Credit: Image courtesy of Technische Universitaet Muenchen)

ScienceDaily.com  —  Pioneering a novel microscopy method, neuroscientist Arthur Konnerth and colleagues from the Technische Universitaet Muenchen (TUM) have shown that individual neurons carry out significant aspects of sensory processing: specifically, in this case, determining which direction an object in the field of view is moving. Their method makes it possible for the first time to observe individual synapses, nerve contact sites that are just one micrometer in size, on a single neuron in a living mammalian brain.

Focusing on neurons known to play a role in processing visual signals related to movement, Konnerth’s team discovered that an individual neuron integrates inputs it receives via many synapses at once into a single output signal — a decision, in essence, made by a single nerve cell. The scientists report these results in the latest issue of the journal Nature. Looking ahead, they say their method opens a new avenue for exploration of how learning functions at the level of the individual neuron.

When light falls on the retina of the human eye, it hits 126 million sensory cells, which transform it into electrical signals. Even the smallest unit of light, a photon, can stimulate one of these sensory cells. As a result, enormous amounts of data have to be processed for us to be able to see. While the processing of visual data starts in the retina, the finished image only arises in the brain or, to be more precise, in the visual cortex at the back of the cerebrum. Scientists working with Arthur Konnerth — professor of neurophysiology at TUM and Carl von Linde Senior Fellow at the TUM Institute for Advanced Study — are interested in a certain kind of neuron in the visual cortex that fires electrical signals when an object moves in front of our eyes — or the eyes of a mouse.

When a mouse is shown a horizontal bar pattern in motion, specific neurons in its visual cortex consistently respond, depending on whether the movement is from bottom to top or from right to left. The impulse response pattern of these “orientation” neurons is already well known. What was not previously known, however, is what the input signal looks like in detail. This was not easy to establish, as each of the neurons has a whole tree of tiny, branched antennae, known as dendrites, at which hundreds of other neurons “dock” with their synapses.

To find out more about the input signal, Konnerth and his colleagues observed a mouse in the act of seeing, with resolution that goes beyond a single nerve cell to a single synapse. They refined a method called two-photon fluorescence microscopy, which makes it possible to look up to half a millimeter into brain tissue and view not only an individual cell, but even its fine dendrites. Together with this microscopic probe, they conducted electrical signals to individual dendrites of the same neuron using tiny glass pipettes (patch-clamp technique). “Up to now, similar experiments have only been carried out on cultured neurons in Petri dishes,” Konnerth says. “The intact brain is far more complex. Because it moves slightly all the time, resolving individual synaptic input sites on dendrites was extremely difficult.”

The effort has already rewarded the team with a discovery. They found that in response to differently oriented motions of a bar pattern in the mouse’s field of vision, an individual orientation neuron receives input signals from a number of differently oriented nerve cells in its network of connections but sends only one kind of output signal. “And this,” Konnerth says, “is where things get really exciting.” The orientation neuron only sends output signals when, for example, the bar pattern moves from bottom to top. Evidently the neuron weighs the various input signals against each other and thus reduces the glut of incoming data to the most essential information needed for clear perception of motion.

In the future, Konnerth would like to extend this research approach to observation of the learning process in an individual neuron. Neuroscientists speculate that a neuron might be caught in the act of learning a new orientation. Many nerve endings practically never send signals to the dendritic tree of an orientation neuron. Presented with visual input signals that represent an unfamiliar kind of movement, formerly silent nerve endings may become active. This might alter the way the neuron weighs and processes inputs, in such a way that it would change its preferred orientation; and the mouse might learn to discern certain movements better or more rapidly. “Because our method enables us to observe, down to the level of a single synapse, how an individual neuron in the living brain is networked with others and how it behaves, we should be able to make a fundamental contribution to understanding the learning process,” Konnerth asserts. “Furthermore, because here at TUM we work closely with physicists and engineers, we have the best possible prospects for improving the spatial and temporal resolution of the images.”

This work was supported by grants from Deutsche Forschungsgemeinschaft (DFG) and Friedrich-Schiedel-Stiftung.

Journal Reference: Hongbo Jia, Nathalie L. Rochefort, Xiaowei Chen, Arthur Konnerth. Dendritic organization of sensory input to cortical neurons in vivo. Nature, 2010; 464 (7293): 1307 DOI: 10.1038/nature08947

Technische Universitaet Muenchen (2010, April 30). Watching a living brain in the act of seeing — with single-synapse resolution.

 

GoogleNews.com, July 29, 2010, by Nicole Aber  —  Working in sales means dealing face-to-face with clients. So when Larry Webb looked in the mirror and noticed he looked “gaunt” due to aging, he began to feel inhibited in his career.

“I didn’t want people looking at my cheeks, but to look at my eyes,” Webb, 65, said.

So in an effort to gain a more youthful appearance, the Dallas man underwent Cell Enriched Cosmetic Surgery, an experimental procedure that transfers a combination of fat cells containing stem cells to other areas of the body .

The procedure was performed by Dr. Jeffrey Caruth, medical director of Plano Aesthetics in Plano, Texas, about three months ago, and it gave Webb more volume in his face to reverse the “aging and deterioration of muscle tissue in the cheeks,” Webb said.

The procedure is not yet approved by the Food and Drug Administration, but Caruth estimates it will be within six months. Stem cell fat transfers have been approved and performed in Europe for years, he said.

Cell Enriched Cosmetic Surgery, which Caruth began performing in March, involves removing fat cells from one or multiple parts of the body, treating the fat cells to multiply the amount of stem cells within them, and then transferring those stem cell-rich fat cells to the breasts, face, or other areas of the body to provide more volume and a longer-lasting result, Caruth told FoxNews.com.

Multiplying the stem cells by thousands, Caruth said, allows for a better survival rate of the transported fat cells in addition to helping “in the anti-aging process because the stem cells will promote better tissue regeneration and tissue healing.”

But some plastic surgeons are wary of the effectiveness of stem cells in these procedures and say not enough research has been done to prove their benefit in cosmetic surgery.

Dr. William Adams Jr., who practices in Dallas, said there is a lack of research in this area to prove that stem cells add any benefit to the regular fat transfer procedures, which plastic surgeons have been using for years.

“Although stem cell things is the sexy thing to talk about right now … the reality is that the science right now hasn’t necessarily shown that it’s any better than the standard technique,” Adams said.

In Webb’s case, Caruth removed fat cells from the abdomen and transferred them to his face. Webb said that appealed to him because it used something natural from his own body.

He said he has had no complications and would recommend the procedure “definitely for people that need it not only for their job, maybe possibly if they’re in sales, or for themselves and want to look the best they can.”

Advantages of the stem cell fat transfer procedure over other types of cosmetic surgeries on the market are the ability to use more volume of the fat cells than the popular, more expensive synthetic fillers like Resilin, and the longevity of the procedure – about five to 10 years, according to Caruth, who has performed about 20 to 25 of these autologous stem cell fat transfers.

And compared to other plastic surgeries, Caruth said, the stem cell fat transfers are much less invasive, as they are done using local anesthesia either through an outpatient procedure or right in the office.

But for a procedure that hasn’t been fully proven to be effective, Adams said the cost of these stem cell fat transfers is relatively expensive – about $3,000 more than standard fat transfer procedures. A face lift that uses the stem cell fat transfer costs about $6,500, while breast augmentation costs an average of $15,000, Caruth said.