Posts tagged brain activity
Articles and news from the latest research reports.
Brain Benefits From Weight Loss Following Bariatric Surgery
Weight loss surgery can curb alterations in brain activity associated with obesity and improve cognitive function involved in planning, strategizing and organizing, according to a new study published in the Endocrine Society’s Journal of Clinical Endocrinology & Metabolism (JCEM).
Obesity can tax the brain as well as other organs. Obese individuals face a 35 percent higher risk of developing Alzheimer’s disease compared to normal weight people.
Bariatric surgery is used to help people who are dangerously obese lose weight. Bariatric surgery procedures are designed to restrict the amount of food you can eat before you feel full by reducing the stomach’s size or limit the absorption of nutrients by removing part of the small intestine from the path food takes through the digestive tract. Some procedures, such as Roux-en-Y gastric bypass (RYBG) surgery, use a combination of these methods. This study was the first to assess brain activity in women before and after bariatric surgery.
“When we studied obese women prior to bariatric surgery, we found some areas of their brains metabolized sugars at a higher rate than normal weight women,” said one of the study’s authors, Cintia Cercato, MD, PhD, of the University of São Paolo in São Paolo, Brazil. “In particular, obesity led to altered activity in a part of the brain linked to the development of Alzheimer’s disease – the posterior cingulate gyrus. Since bariatric surgery reversed this activity, we suspect the procedure may contribute to a reduced risk of Alzheimer’s disease and other forms of dementia.”
The longitudinal study examined the effect of RYBG surgery on the brain function of 17 obese women. Researchers used positron emission tomography (PET) scans and neuropsychological tests to assess brain function and activity in the participants prior to surgery and six months after the procedure. The same tests also were run once on a control group of 16 lean women.
Before they underwent surgery, the obese women had higher rates of metabolism in certain areas of the brain, including the posterior cingulate gyrus. Following surgery, there was no evidence of this exacerbated brain activity. Their brain metabolism rates were comparable to the activity seen in normal weight women.
After surgery, the obese women also performed better on a test measuring executive function – the brain’s ability to connect past experience and present action – than they did before the procedures. Executive function is used in planning, organizing and strategizing. Five other neuropsychological tests measuring various aspects of memory and cognitive function showed no change following the surgery.
“Our findings suggest the brain is another organ that benefits from weight loss induced by surgery,” Cercato said. “The increased brain activity the obese women exhibited before undergoing surgery did not result in improved cognitive performance, which suggests obesity may force the brain to work harder to achieve the same level of cognition.”
(Image: Getty)
'Haven't my neurons seen this before?'
The world grows increasingly more chaotic year after year, and our brains are constantly bombarded with images. A new study from Center for the Neural Basis of Cognition (CNBC), a joint project between Carnegie Mellon University and the University of Pittsburgh, reveals how neurons in the part of the brain responsible for recognizing objects respond to being shown a barrage of images. The study is published online by Nature Neuroscience.
The CNBC researchers showed animal subjects a rapid succession of images, some that were new, and some that the subjects had seen more than 100 times. The researchers measured the electrical response of individual neurons in the inferotemporal cortex, an essential part of the visual system and the part of the brain responsible for object recognition.
In previous studies, researchers found that when subjects were shown a single, familiar image, their neurons responded less strongly than when they were shown an unfamiliar image. However, in the current study, the CNBC researchers found that when subjects were exposed to familiar and unfamiliar images in a rapid succession, their neurons — especially the inhibitory neurons — fired much more strongly and selectively to images the subject had seen many times before.
"It was such a dramatic effect, it leapt out at us," said Carl Olson, a professor at Carnegie Mellon. "You wouldn’t expect there to be such deep changes in the brain from simply making things familiar. We think this may be a mechanism the brain uses to track a rapidly changing visual environment."
The researchers then ran a similar experiment in which they used themselves as subjects, recording their brain activity using EEG. They found that the humans’ brains responded similarly to the animal subjects’ brains when presented with familiar or unfamiliar images in rapid succession. In future studies, they hope to link these changes in the brain to improvements in perception and cognition.
Are Three Brain Imaging Techniques Better than One?
Many recent imaging studies have shown that in children with autism, different parts of the brain do not connect with each other in typical ways. Initially, most researchers thought that the autistic brain has fewer connections between key regions. The most recent studies, however, point to an opposite conclusion: The brains of people with autism exhibit overconnectivity.
To date, almost all studies of autism in children have used a single imaging technique to explore connectivity. None has been able to capture a robust picture of the brain abnormalities associated with autism—until now.
Two new grants from the National Institute of Mental Health (NIMH) will allow San Diego State University Psychology Professor Ralph-Axel Müller to combine three imaging techniques and harness the best of each one in his study of autism.
Techniques in tandem
Although the term “brain imaging” gets thrown around a lot when describing the latest advances in neuroscience and psychology, there are dozens of different brain imaging techniques. Each gives scientists a different view of the inner workings of the brain, and each comes with its own strengths and limitations.
For example, the frequently cited technique of fMRI, or functional magnetic resonance imaging, measures blood flow in different areas of the brain at specific snapshots in time, based on the knowledge that increased blood flow indicates increased activity of nerve cells in that area of the brain. The technique is powerful, but has limitations when it comes to detecting dynamic changes in brain activity that occur very fast, within milliseconds.
EEG (electroencephalography), a much older technique, is actually better at detecting such dynamic changes, although it cannot pinpoint exactly where in the brain the activity occurs. A powerful and more recent technique is MEG, or magnetoencephalography, which can detect dynamic changes in brain activity that happen within a few milliseconds.
Müller looks for disorganized patterns of brain activity that could be responsible for some of the telltale characteristics of autism spectrum disorder, such as inattention to social cues and repetitive and obsessive behaviors. For example, last year, Müller and his colleagues discovered that in children with autism, connectivity was impaired between the cerebral cortex and the thalamus, a deep brain structure that is important for sensorimotor functions and attention.
With $4.2 million in new funding from NIH, Müller—together with collaborators Ksenija Marinkovic at SDSU and Thomas Liu at the University of California, San Diego—will apply fMRI, EEG, and MEG to study both autistic and non-autistic, or typically-developing, children and adolescents during a variety of tests, including language tests designed to tease out activity in various parts of the brain.
Defining the differences
One component of the project will concern the visual system. Previous research has shown that people with autism rely on their visual cortex more than typically- developing people during thought processes, for example, when making a semantic distinction, such as deciding whether a truck is a vehicle. Using the one-two punch of fMRI and MEG together, Müller and his team will be able to determine the dynamic processes in how brain regions work together to come up with a response, and how these processes differ in autism.
The study will also examine brain function during its resting state in order to identify abnormalities in brain network organization. The combined use of EEG and MEG, together with fMRI techniques that reveal brain anatomy, will produce a much more complete picture of abnormal brain organization in autism.
Ultimately, Müller and his colleagues hope to identify biomarkers in the brain that can reliably indicate whether the participant falls on the autism spectrum.
“Autism is a brain-based disorder, but its diagnosis is still based entirely on behavioral observation,” Müller said. “This is inadequate. We need to find brain biomarkers for autism.”
Another goal of the researchers is to find brain biomarkers that can distinguish different subtypes of autism. It is generally suspected that the term “autism” actually covers several different disorders, each of which may be caused by different genetic and environmental risk factors. Eventually, brain biomarkers might be tied to genetic data, giving scientists a better understanding of the origins of autism, as well as new leads for treatment.
“For decades, research teams studying autism have specialized in one or another scientific technique, often without understanding well what other techniques can reveal. Our study combining several of the major imaging techniques will be one step toward a more comprehensive account of how the autistic brain differs from the typically developing one – and what may be done about it,” Müller said.
ADHD children make poor decisions due to less differentiated learning processes
Which shirt do we put on in the morning? Do we drive to work or take the train? From which takeaway joint do we want to buy lunch? We make hundreds of different decisions every day. Even if these often only have a minimal impact, it is extremely important for our long-term personal development to make decisions that are as optimal as possible. People with ADHD often find this difficult, however. They are known to make impulsive decisions, often choosing options which bring a prompt but smaller reward instead of making a choice that yields a greater reward later on down the line. Researchers from the University Clinics for Child and Adolescent Psychiatry, University of Zurich, now reveal that different decision-making processes are responsible for such suboptimal choices and that these take place in the middle of the frontal lobe.
Mathematical models help to understand the decision-making processes
In the study, the decision-making processes in 40 young people with and without ADHD were examined. Lying in a functional magnetic resonance imaging scanner to record the brain activity, the participants played a game where they had to learn which of two images carried more frequent rewards. In order to understand the impaired mechanisms of participants with ADHD better, learning algorithms which originally stemmed from the field of artificial intelligence were used to evaluate the data. These mathematical models help to understand the precise learning and decision-making mechanisms better. “We were able to demonstrate that young people with ADHD do not inherently have difficulties in learning new information; instead, they evidently use less differentiated learning patterns, which is presumably why sub-optimal decisions are often made”, says first author Tobias Hauser.
Multimodal imaging affords glimpses inside the brain
In order to study the brain processes that triggered these impairments, the authors used multimodal imaging methods, where the participants were examined using a combined measurement of functional magnetic resonance imaging (fMRI) and electroencephalography (EEG) to record the electrical activity and the blood flow in the brain. It became apparent that participants with ADHD exhibit an altered functioning in the medial prefrontal cortex – a region in the middle of the frontal lobe. This part of the brain is heavily involved in decision-making processes, especially if you have to choose between several options, and in learning from errors. Although a change in activity in this region was already discovered in other contexts for ADHD, the Zurich researchers were now also able to pinpoint the precise moment of this impairment, which already occurred less than half a second after a feedback, i.e. at a very early stage.
Psychologist Tobias Hauser, who is now researching at the Wellcome Trust Centre for Neuroimaging, University College London, is convinced that the results fundamentally improve our understanding of the mechanisms of impaired decision-making behavior in people with ADHD. The next step will be to study the brain messenger substances. “If our findings are confirmed, they will provide key clues as to how we might be able to design therapeutic interventions in future,” explains Hauser.
Literature:
Tobias U. Hauser, Reto Iannaccone, Juliane Ball, Christoph Mathys, Daniel Brandeis, Susanne Walitza & Silvia Brem: Role of Medial Prefrontal Cortex in Impaired Decision Making in Juvenile Attention-Deficit/Hyperactivity Disorder, in: JAMA Psychiatry
Stuck in neutral: brain defect traps schizophrenics in twilight zone
People with schizophrenia struggle to turn goals into actions because brain structures governing desire and emotion are less active and fail to pass goal-directed messages to cortical regions affecting human decision-making, new research reveals.
Published in Biological Psychiatry, the finding by a University of Sydney research team is the first to illustrate the inability to initiate goal-directed behaviour common in people with schizophrenia.
The finding may explain why people with schizophrenia have difficulty achieving real-world goals such as making friends, completing education and finding employment.
"The apparent lack of motivation in schizophrenic patients isn’t because they lack goals or don’t enjoy rewards and pleasure," says the University of Sydney’s Dr Richard Morris, the study’s lead author.
"They enjoy as many experiences as other people, including food, movies and scenes of natural beauty.
"What appears to block them are specific brain deficits that prevent them from converting their desires and goals into choices and behaviour."
Using a control group research design, the researchers used a two-prong approach to reveal how and why schizophrenics fail to convert their preferences into congruent choices.
First, using a series of experiments involving choosing between different snack food rewards, experimenters revealed that:
- schizophrenic subjects had a liking for snack foods equivalent to healthy adults
- when researchers reduced the value of one of the snacks, both subjects and healthy adults subsequently preferred different snacks, as expected
- surprisingly, schizophrenic subjects had major difficulty choosing their preferred snack when provided with a choice between their preferred snack and the devalued snack.
Second, researchers used functional magnetic resonance imaging (fMRI) to measures brain activity while study subjects performed learning tasks involving snack foods.
This technique relies on the fact that cerebral blood flow and neuronal activity are coupled. When an area of the brain is in use, bloodflow to that region increases, thereby indicating neural activity. This neural activity can be presented graphically by colour-coding the strength of activation across the brain or in specific brain regions. The technique can localise neural activity to within millimetres.
Functional MRI results revealed the following:
- schizophrenic subjects had normal neural activity in the brain region responsible for decision-making (prefrontal cortex)
- among schizophrenic subjects, brain regions responsible, in part, for controlling actions and choice (the caudate) had far lower neural activity than in healthy subjects
- lower neural activity in the caudate regions was correlated with the difficulty that schizophrenic subjects’ had applying their food preferences to obtain future snack foods.
"Pathology in the caudate and associated brain regions may prevent schizophrenic subjects from properly evaluating their desires then transmitting that information to guide their behavior," says Dr Morris.
"This means that desires and goals are intact in people with schizophrenia, however they have difficulty choosing the right course of action to achieve those goals.
"This failure to integrate desire with action means people with schizophrenia are stuck in limbo, wanting a normal life but unable to take the necessary steps to achieve it."
Schizophrenia affects one per cent of people worldwide, including in Australia.
However so-called “poor motivation” in schizophrenia is a major economic concern because it is not treated by current medicines, and often means patients fail to finish their education or hold a full-time job.
(Source: sydney.edu.au)
Scientists use lasers to control mouse brain switchboard
Ever wonder why it’s hard to focus after a bad night’s sleep? Using mice and flashes of light, scientists show that just a few nerve cells in the brain may control the switch between internal thoughts and external distractions. The study, partly funded by the National Institutes of Health, may be a breakthrough in understanding how a critical part of the brain, called the thalamic reticular nucleus (TRN), influences consciousness.
“Now we may have a handle on how this tiny part of the brain exerts tremendous control over our thoughts and perceptions,” said Michael Halassa, M.D., Ph.D., assistant professor at New York University’s Langone Medical Center and a lead investigator of the study. “These results may be a gateway into understanding the circuitry that underlies neuropsychiatric disorders.”
The TRN is a thin layer of nerve cells on the surface of the thalamus, a center located deep inside the brain that relays information from the body to the cerebral cortex. The cortex is the outer, multi-folded layer of the brain that controls numerous functions, including one’s thoughts, movements, language, emotions, memories, and visual perceptions. TRN cells are thought to act as switchboard operators that control the flow of information relayed from the thalamus to the cortex.
“The future of brain research is in studying circuits that are critical for brain health and these results may take us a step further,” said James Gnadt, Ph.D., program director at NIH’s National Institute Neurological Disorders and Stroke (NINDS), which helped fund the study. “Understanding brain circuits at the level of detail attained in this study is a goal of the President’s Brain Research through Advancing Innovative Neurotechnologies (BRAIN) Initiative.”
To study the circuits, the researchers identified TRN cells that send inhibitory signals to parts of the thalamus known to relay visual information to the cortex. Using a technique known as multi-electrode recordings, they showed that sleep and concentration affected these cells in opposite ways.
They fired often when the mice were asleep, especially during short bursts of simultaneous brain cell activity called sleep spindles. These activity bursts briefly widen electrical brain wave traces making them look like spindles, the straight spikes with rounded bottoms used to make yarn. In contrast, the cells fired infrequently when the mice were tasked with using visual cues to find food. The results suggested that these cells blocked visual information from reaching the cortex during sleep and allowed its transmission when the mice were awake and attentive.
For Dr. Halassa, a practicing psychiatrist who treats schizophrenia, these surprising results may provide fundamental insights into how the brain controls information transmission, a process that is disrupted in patients with neuropsychiatric disorders. Previous studies suggested that people who experienced more spindles while sleeping were less susceptible to being disturbed by outside noises. Moreover, people with schizophrenia and autism spectrum disorder may experience fewer spindles.
“Spindles may be peepholes into the mysteries of these disorders,” said Dr. Halassa.
To test this idea, the researchers used optogenetics, a technique that introduces light-sensitive molecules into nerve cells. This allowed them to precisely control the firing patterns of visual TRN cells with flashes of laser light. The experiments were performed in well-rested as well as sleep-deprived mice. Similar to what is seen in humans, sleep deprivation can disrupt the ability of mice to focus and block out external distractions.
Well-rested mice needed just a second or two to find the food whereas sleep-deprived mice took longer, suggesting that lack of sleep had detrimental effects on their ability to focus. When the researchers used flashes of laser light to inhibit the firing of optogenetically engineered visual TRN cells in sleep-deprived mice, the mice found the food faster. In contrast, if they used optogenetics to induce sleep-like firing patterns in well-rested mice, then the mice took longer to find food.
“It’s as if with a flick of a switch we could alter the mental states of the mice and either mimic or cure their drowsiness,” said Dr. Halassa.
In a parallel set of experiments the researchers found neighbors of the visual TRN cells had very different characteristics. These neighboring cells control the flow of information to the cortex from limbic brain regions, which are involved with memory formation, emotions and arousal. The cells fired very little during sleep and instead were active when the mice were awake. Dr. Halassa thinks that their firing pattern may be important for the strengthening of new memories that often occurs during sleep. Combined, the results suggest that the TRN is divided into sub-networks that oversee discrete mental states. The researchers think understanding the sub-networks is an initial step in thoroughly exploring the role of the TRN in brain disorders.
Overhaul of our understanding of why autism potentially occurs
An analysis of autism research covering genetics, brain imaging, and cognition led by Laurent Mottron of the University of Montreal has overhauled our understanding of why autism potentially occurs, develops and results in a diversity of symptoms. The team of senior academics involved in the project calls it the “Trigger-Threshold-Target” model. Brain plasticity refers to the brain’s ability to respond and remodel itself, and this model is based on the idea that autism is a genetically induced plastic reaction. The trigger is multiple brain plasticity-enhancing genetic mutations that may or may not combine with a lowered genetic threshold for brain plasticity to produce either intellectual disability alone, autism, or autism without intellectual disability. The model confirms that the autistic brain develops with enhanced processing of certain types of information, which results in the brain searching for materials that possess the qualities it prefers and neglecting materials that don’t. “One of the consequences of our new model will be to focus early childhood intervention on developing the particular strengths of the child’s brain, rather than exclusively trying to correct missing behaviors, a practice that may be a waste of a once in a lifetime opportunity,” Mottron said.
Mottron and his colleagues developed the model by examining the effect of mutations involved in autism together with the brain activity of autistic people as they undertake perceptual tasks. “Geneticists, using animals implanted with the mutations involved in autism, have found that most of them enhance synaptic plasticity – the capacity of brain cells to create connections when new information is encountered. In parallel, our group and others have established that autism represents an altered balance between the processing of social and non-social information, i.e. the interest, performance and brain activity, in favor of non-social information,” Mottron explained. “The Trigger-Threshold-Target model builds a bridge between these two series of facts, using the neuro cognitive effects of sensory deprivation to resolve the missing link between them.”
The various superiorities that subgroups of autistic people present in perception or in language indicates that an autistic infant’s brain adapts to the information it is given in a strikingly similar way to sensory-deprived people. A blind infant’s brain compensate the lack of visual input by developing enhanced auditory processing abilities for example, and a deaf infant readapts to process visual inputs in a more refined fashion. Similarly, cognitive and brain imaging studies of autistic people work reveal enhanced activity, connectivity and structural modifications in the perceptive areas of the brain. Differences in the domain of information “targeted” by these plastic processes are associated with the particular pattern of strengths and weaknesses of each autistic individual. “Speech and social impairment in some autistic toddlers may not be the result of a primary brain dysfunction of the mechanisms related to these abilities, but the result of their early neglect,” Mottron said. “Our model suggests that the autistic superior perceptual processing compete with speech learning because neural resources are oriented towards the perceptual dimensions of language, neglecting its linguistic dimensions. Alternatively, for other subgroups of autistic people, known as Asperger, it’s speech that’s overdeveloped. In both cases, the overdeveloped function outcompetes social cognition for brain resources, resulting in a late development of social skills.”
The model provides insight into the presence or absence of intellectual disability, which when causative mutation alter the function of brain cell networking. Rather than simply triggering a normal but enhanced plastic reaction, these mutations cause neurons to connect in a way that does not exist in non-autistic people. When brain cell networking functions normally, only the allocation of brain resources is changed.
As is the case with all children, environment and stimulation have an effect on the development and organization of an autistic child’s brain. “Most early intervention programs adopt a restorative approach by working on aspects like social interest. However this focus may monopolize resources in favor of material that the child process with more difficulties, Mottron said. “We believe that early intervention for autistic children should take inspiration from the experience of congenitally deaf children, whose early exposure to sign language has a hugely positive effect on their language abilities. Interventions should therefore focus on identifying and harnessing the autistic child’s strengths, like written language.” By indicating that autistic ‘’restricted interests” result from cerebral plasticity, this model suggest that they have an adaptive value and should therefore be the focus of intervention strategies for autism.
(Source: nouvelles.umontreal.ca)
Testosterone in Healthy Men Increases Their Brains’ Response to Threat
Testosterone, a steroid hormone, is well known to contribute to aggressive behavior in males, but the neural circuits through which testosterone exerts these effects have not been clear.
Prior studies found that the administration of a single dose of testosterone influenced brain circuit function. Surprisingly, however, these studies were conducted exclusively in women.
Researchers, led by Dr. Justin Carré, sought to rectify this gap by conducting a study of the effects of testosterone on the brain’s response to threat cues in healthy men.
They focused their attention on brain structures that mediate threat processing and aggressive behavior, including the amygdala, hypothalamus, and periaqueductal gray.
The researchers recruited 16 healthy young male volunteers, who completed two test days on which they received either testosterone or placebo. On both testing days, the men first received a drug that suppressed their testosterone. This step ensured that testosterone levels were similar among all study participants. The amount of testosterone administered in this study only returned testosterone levels to the normal range. Subjects then completed a face-matching task while undergoing a functional magnetic resonance imaging scan.
Data analyses revealed that, compared with placebo, testosterone increased reactivity of the amygdala, hypothalamus and periaqueductal grey when viewing angry facial expressions.
"We were able to show for the first time that increasing levels of testosterone within the normal physiological range can have a profound effect on brain circuits that are involved in threat-processing and human aggression," said Carré, Assistant Professor at Nipissing University.
"Understanding testosterone effects on the brain activity patterns associated with threat and aggression may help us to better understand the ‘fight or flight’ response in males that may be relevant to aggression and anxiety," commented Dr. John Krystal, Editor of Biological Psychiatry.
Expanding our knowledge of exactly how testosterone affects the male brain is particularly important, as testosterone augmentation has become increasingly promoted and aggressively marketed as a solution to reduced virility in aging men. Further work is indeed continuing, Carré said. “Our current work is examining the extent to which a single administration of testosterone influences aggressive and competitive behavior in men.”
(Source: elsevier.com)
Study captures brain activity in children suffering emergence delirium
In a world-first, a newly published study has captured in detail the brain electrical activity in children as they emerge from anaesthesia, shedding light on why some are distressed and agitated when they wake up.
Researchers from Swinburne University of Technology together with colleagues from the Murdoch Childrens Research Institute (MCRI) were able to collect electroencephalography (EEG) data on children who exhibited emergence delirium.
Emergence delirium is a major risk associated with anaesthesia in children and occurs when patients wake up from anaesthesia in a delirious and disassociated state.
Swinburne Professor David Liley said PhD student Jessica Martin and staff at MCRI were able to record, with unprecedented fidelity, brain electrical activity from 60 children aged 5-15 years who emerged from anaesthesia some of whom went on to exhibit emergence delirium.
“This clinical phenomenon is prevalent in children aged six and under, with an estimated 10-30% exhibiting emergence delirium,” said Professor Liley.
Researchers found that the brain activity recorded just after stopping sevoflurane (a form of gas anaesthesia) in children exhibiting emergence delirium was substantially different to those children who woke up peacefully.
Associate Professor Andrew Davidson from MCRI said they discovered that children who wake up suddenly from a deeper plane of anaesthetic are more likely to develop the delirium.
“In contrast, the children who develop sleep like patterns on their EEG before they wake up are more likely to wake up peacefully.”
“Intriguingly, emergence delirium looks very much like the more severe form of night terror, which occurs when some pre-school children are disturbed during deep sleep.
“Our study suggests the EEG signatures and the mechanisms may indeed be similar between night terror and emergence delirium.
“Allowing children to wake up in a quiet and undisturbed environment should increase the likelihood that they go into a light sleep-like state after the anaesthetic and then wake up peacefully,” said Associate Professor Davidson.
The findings will have significant implications in both predicting those children who will go on to develop emergence delirium, as well as helping medical professionals better understand its causes in both children and adults.
The study, Alterations in the Functional Connectivity of Frontal Lobe Networks Preceding Emergence Delirium in Children, will appear in the October issue of the high profile clinical journal, Anesthesiology and is electronically available ahead of print.
(Source: swinburne.edu.au)
Important advance in brain mapping and memory
“When a tiger starts to move towards you, you need to know whether it is something you are actually seeing or whether it’s just something that you remember or have imagined,” says Prof. Julio Martinez-Trujillo of McGill’s Department of Physiology. The researcher and his team have discovered that there is a clear frontier in the brain between the area that encodes information about what is immediately before the eyes and the area that encodes the abstract representations that are the product of our short-term memory or imagination. It is an important advance in brain mapping and opens the doors to further research in the area of short-term memory.
These finding, which are described in an article just published in Nature Neuroscience, resolve a question that has occupied neuroscientists for years. Namely that of how and where exactly in the brain the visual information coming from our eyes is first transformed into short-term memories. “We found that while one area in the brain processes information about what we are currently seeing, an area right beside it stores the information in short-term memory,” says McGill PhD student Diego Mendoza-Halliday, first author of the article. “What is so exciting about this finding is that until now, no one knew the place where visual information first gets transformed into short-term memory.”
The researchers arrived at this conclusion by measuring the neuronal activity in these two areas in the brains of macaques as they first looked at, and then after a short time (1.2 - 2 seconds) remembered, a random sequence of dots moving across a computer screen like rainfall. What surprised Martinez-Trujillo and his team was how clearly demarcated the divide was between the activities and functions of the two brain areas, and this despite the fact that they lie side-by-side.
“It is rare to find this kind of sharp boundary in biological systems of any kind,” says Martinez-Trujillo. “Most of the time, when you look at the function of different brain areas, there is more of a transitional zone, more grey and not such a clear border between black and white. I think the evolutionary reason for this clear frontier is that it helped us to survive in dangerous situations.”
The discovery comes after five years spent by Martinez-Trujillo and his team doing research in the area. Despite this fact, he acknowledges that there was a certain amount of serendipity, and a lot of technological help involved in being able to capture a signal that travels for 3 milliseconds and fires synapses in neurons that lie right beside one another.
Martinez-Trujillo and his team continue to work on mapping the receptors and connectivity between these two areas of the brain. But what is most important for him is to try and relate this discovery to schizophrenia and other diseases that involve hallucinations, and in order to do so he is working with a psychiatrist at Montreal’s Douglas Hospital.
(Image: Bigstock)