The many maps of the brain

Your brain has at least four different senses of location – and perhaps as many as 10. And each is different, according to new research from the Kavli Institute for Systems Neuroscience, at the Norwegian University of Science and Technology.

The findings, published in the 6 December 2012 issue of Nature, show that rather than just a single sense of location, the brain has a number of “modules” dedicated to self-location. Each module contains its own internal GPS-like mapping system that keeps track of movement, and has other characteristics that also distinguishes one from another.

"We have at least four senses of location," says Edvard Moser, director of the Kavli Institute. "Each has its own scale for representing the external environment, ranging from very fine to very coarse. The different modules react differently to changes in the environment. Some may scale the brain’s inner map to the surroundings, others do not. And they operate independently of each other in several ways."

This is also the first time that researchers have been able to show that a part of the brain that does not directly respond to sensory input, called the association cortex, is organized into modules. The research was conducted using rats.

Johns Hopkins Surgeons Implant First Brain ‘Pacemaker’ for Alzheimer’s Disease in United States as Part of a Clinical Trial Designed to Slow Memory Loss

Researchers at Johns Hopkins Medicine in November surgically implanted a pacemaker-like device into the brain of a patient in the early stages of Alzheimer’s disease, the first such operation in the United States. The device, which provides deep brain stimulation and has been used in thousands of people with Parkinson’s disease, is seen as a possible means of boosting memory and reversing cognitive decline.

The surgery is part of a federally funded, multicenter clinical trial marking a new direction in clinical research designed to slow or halt the ravages of the disease, which slowly robs its mostly elderly victims of a lifetime of memories and the ability to perform the simplest of daily tasks, researchers at Johns Hopkins say. Instead of focusing on drug treatments, many of which have failed in recent clinical trials, the research focuses on the use of the low-voltage electrical charges delivered directly to the brain. There is no cure for Alzheimer’s disease.

As part of a preliminary safety study in 2010, the devices were implanted in six Alzheimer’s disease patients in Canada. Researchers found that patients with mild forms of the disorder showed sustained increases in glucose metabolism, an indicator of neuronal activity, over a 13-month period. Most Alzheimer’s disease patients show decreases in glucose metabolism over the same period.

The first U.S. patient in the new trial underwent surgery at The Johns Hopkins Hospital, and a second patient is scheduled for the same procedure in December. The surgeries at Johns Hopkins are being performed by neurosurgeon William S. Anderson, M.D.

The surgery involves drilling holes into the skull to implant wires into the fornix on either side of the brain. The fornix is a brain pathway instrumental in bringing information to the hippocampus, the portion of the brain where learning begins and memories are made, and where the earliest symptoms of Alzheimer’s appear to arise. The wires are attached to a pacemaker-like device, the “stimulator,” which generates tiny electrical impulses into the brain 130 times a second. The patients don’t feel the current, says Paul B. Rosenberg, M.D., an associate professor of psychiatry and behavioral sciences at the Johns Hopkins University School of Medicine, and site director of the trial’s Johns Hopkins location. 

Mammalian brain knows where it’s at

A new study in the journal Neuron suggests that the brain uses a different region than neuroscientists had thought to associate objects and locations in the space around an individual. Knowing where this fundamental process occurs could help treat disease and brain injury as well as inform basic understanding of how the brain supports memory and guides behavior.

“Understanding how and where context is represented in the brain is important,” said study senior author Rebecca Burwell, professor of psychology and neuroscience at Brown University. “Context, or the place in which events occur, is the hallmark of episodic memory, but context is more than a place or a location. This room, for example, has a window, furniture, and other objects. You walk into a room and all that information helps you remember what happened there.”

Pinpointing where the brain puts together objects and places to form a context could also matter for treating traumatic brain injuries or neuropsychiatric diseases, such as schizophrenia and depression, that involve that part of the brain, said Burwell, who is also affiliated with the Brown Institute for Brain Science.

“We know that contextual representations are disrupted in mental disorders, particularly schizophrenia and depression,” Burwell said. “Individuals with these disorders have trouble using context to plan actions or choose appropriate behaviors.”

After 100 Years, Understanding the Electrical Role of Dendritic Spines

It’s the least understood organ in the human body: the brain, a massive network of electrically excitable neurons, all communicating with one another via receptors on their tree-like dendrites. Somehow these cells work together to enable great feats of human learning and memory. But how?

Researchers know dendritic spines play a vital role. These tiny membranous structures protrude from dendrites’ branches; spread across the entire dendritic tree, the spines on one neuron collect signals from an average of 1,000 others. But more than a century after they were discovered, their function still remains only partially understood.

A Northwestern University researcher, working in collaboration with scientists at the Howard Hughes Medical Institute (HHMI) Janelia Farm Research Campus, has recently added an important piece of the puzzle of how neurons “talk” to one another. The researchers have demonstrated that spines serve as electrical compartments in the neuron, isolating and amplifying electrical signals received at the synapses, the sites at which neurons connect to one another.

The key to this discovery is the result of innovative experiments at the Janelia Farm Research Campus and computer simulations performed at Northwestern University that can measure electrical responses on spines throughout the dendrites.

A paper about the findings, “Synaptic Amplification by Dendritic Spines Enhances Input Cooperatively,” was published November 22 in the journal Nature.

“This research conclusively shows that dendritic spines respond to and process synaptic inputs not just chemically, but also electrically,” said William Kath, professor of engineering sciences and applied mathematics at Northwestern’s McCormick School of Engineering, professor of neurobiology at the Weinberg College of Arts and Sciences, and one of the paper’s authors.

Infants learn to look and look to learn

Researchers at the University of Iowa have documented an activity by infants that begins nearly from birth: They learn by taking inventory of the things they see.

In a new paper, the psychologists contend that infants create knowledge by looking at and learning about their surroundings. The activities should be viewed as intertwined, rather than considered separately, to fully appreciate how infants gain knowledge and how that knowledge is seared into memory.

“The link between looking and learning is much more intricate than what people have assumed,” says John Spencer, a psychology professor at the UI and a co-author on the paper published in the journal Cognitive Science.

The researchers created a mathematical model that mimics, in real time and through months of child development, how infants use looking to understand their environment. Such a model is important because it validates the importance of looking to learning and to forming memories. It also can be adapted by child development specialists to help special-needs children and infants born prematurely to combine looking and learning more effectively.

“The model can look, like infants, at a world that includes dynamic, stimulating events that influence where it looks. We contend (the model) provides a critical link to studying how social partners influence how infants distribute their looks, learn, and develop,” the authors write.

Four is the “magic” number

According to psychological lore, when it comes to items of information the mind can cope with before confusion sets in, the “magic” number is seven. But a new analysis by a leading Australian psychiatrist challenges this long-held view, suggesting the number might actually be four.

In 1956, American psychologist George Miller published a paper in the influential journal Psychological Review arguing the mind could cope with a maximum of only seven chunks of information. The paper, “The Magical Number Seven, Plus or Minus Two. Some Limits on Our Capacity for Processing Information”, has since become one of the most highly cited psychology articles and has been judged by the Psychological Review as its most influential paper of all time.

But UNSW professor of psychiatry Gordon Parker says a re-analysis of the experiments used by Miller shows he missed the correct number by a wide mark. Writing in the journal Acta Psychiatrica Scandinavica, Scientia Professor Parker says a closer look at the evidence shows the human mind copes with a maximum of four ‘chunks’ of information, not seven.

“So to remember a seven numeral phone number, say 6458937, we need to break it into four chunks: 64. 58. 93. 7.   Basically four is the limit to our perception.

“That’s a big difference for a paper that is one of the most highly referenced psychology articles ever – nearly a 100 percent discrepancy,” he suggests.

Professor Parker says the success of the original paper lies “more in its multilayered title and Miller’s evocative use of the word ‘magic’,” than in the science.

Professor Parker says 50 years after Miller there is still uncertainty about the nature of the brain’s storage capacity limits: “There may be no limit in storage capacity per se but only a limit to the duration in which items can remain active in short-term memory”. “Regardless, the consensus now is that humans can best store only four chunks in short-term memory tasks,” he says.

Re-learning words lost to dementia

A simple word-training program has been found to restore key words in people with a type of dementia that attacks language and our memory for words.

This ability to relearn vocabulary indicates that even in brains affected by dementia, some recovery of function is possible.

The study, led by Ms Sharon Savage at NeuRA (Neuroscience Research Australia), utilised a simple computer training-program that paired images of household objects such as food, appliances, utensils, tools and clothing, with their names.

“People with this type of dementia lose semantic memory, the memory system we use to store and remember words and their meanings,” says Ms Savage.

“Even the simplest words around the house can be difficult to recall. For example, a person with this type of dementia usually knows what a kettle does, but they may not know what to call it and may not recognize the word ‘kettle’ when they hear it,” she says.

Ms Savage found that after just 3 weeks of training for 30–60 min each day, patients’ ability to recall the name of the items improved, even for patients with more advanced forms of the dementia.

“Semantic dementia is a younger-onset dementia and because sufferers lose everyday words life can be very frustrating for them and their families. By relearning some of these everyday words, day to day conversations around the house may become less frustrating, improving patient well-being,” Ms Savage concludes.

This paper is published in the journal Cortex.

Smoking ‘rots’ brain, says King’s College study

Smoking “rots” the brain by damaging memory, learning and reasoning, according to researchers at King’s College London. A study of 8,800 people over 50 showed high blood pressure and being overweight also seemed to affect the brain, but to a lesser extent.

Scientists involved said people needed to be aware that lifestyles could damage the mind as well as the body. Their study was published in the journal Age and Ageing.

Researchers at King’s were investigating links between the likelihood of a heart attack or stroke and the state of the brain. Data about the health and lifestyle of a group of over-50s was collected and brain tests, such as making participants learn new words or name as many animals as they could in a minute, were also performed.

They were all tested again after four and then eight years. The results showed that the overall risk of a heart attack or stroke was “significantly associated with cognitive decline” with those at the highest risk showing the greatest decline.

It also said there was a “consistent association” between smoking and lower scores in the tests. One of the researchers, Dr Alex Dregan, said: “Cognitive decline becomes more common with ageing and for an increasing number of people interferes with daily functioning and well-being.

"We have identified a number of risk factors which could be associated with accelerated cognitive decline, all of which, could be modifiable." He added: "We need to make people aware of the need to do some lifestyle changes because of the risk of cognitive decline."

The researchers do not know how such a decline could affect people going about their daily life. They are also unsure whether the early drop in brain function could lead to conditions such as dementia.

(Image: Alamy)