all Department of Neurobiology stories

Transitivity, the orbitofrontal cortex, and neuroeconomics

404132862 — Mon, 10 Dec 2007 10:58:28 -0500

You study the menu at a restaurant and decide to order the steak rather than the salmon. But when the waiter tells you about the lobster special, you decide lobster trumps steak. Without reconsidering the salmon, you place your order — all because of a trait called "transitivity."

Human stem cells help monkeys recover from Parkinson's

404132862 — Thu, 16 Aug 2007 15:47:50 -0400

Monkeys with severe Parkinson's disease have recovered after human stem cells were transplanted into their brains. The successful experiment raises hopes that the treatment might work as well in humans. An injection of neural stem cells in their brains "led to dramatic functional recovery in severely Parkinsonian monkeys," notes Richard Sidman, Bullard Professor of Neuropathology Emeritus at Harvard Medical School (HMS). "They could stand, walk, feed themselves, and live independently."

Addiction illuminates concept of ‘free will’

50443248 — Tue, 02 Oct 2007 11:38:37 -0400

Whether humans possess free will or whether their actions are determined by something outside their conscious control is one of the most persistent problems in philosophy.

In a lecture May 9, Steven E. Hyman warned his audience that he would not attempt to resolve the issue of free will in an ultimate sense. He did, however, have some fascinating insights regarding a special instance of the free-will dilemma — namely, the neurochemical mechanisms that result in the loss of free will when a person becomes addicted to drugs.

“Drug addiction has been used as a yardstick for reward-based behavior,” said Hyman. “With addiction, there is a narrowing of life focus in that drug-seeking crowds out all other motivations and goals.”

Fruit fly bouts show gender-specific styles

Thu, 12 Jul 2007 09:17:52 -0400

Fighting like a girl or fighting like a boy is hardwired into fruit fly neurons, according to a study in the Nov. 19 Nature Neuroscience advance online publication by a research team from Harvard Medical School (HMS) and the Institute of Molecular Pathology in Vienna. The results confirm that a gene known as "fruitless" is a key factor underlying sexual differences in behavior. The findings mark a milestone in an unlikely new animal model for understanding the biology of aggression and how the nervous system gives rise to different behaviors.

Important signal uncovered in brain development

Thu, 12 Jul 2007 10:51:55 -0400

Nobody has counted them, but the best estimates put the number of human brain cells in the trillions. The best known among them, called neurons, do the heavy thinking and remembering. Each of these cells can connect to 10 or more others, forming a vast network of feelings, thoughts, memories, prejudices, and PINS.

But neurons don't do their jobs alone. They are supported and regulated by an immense system of star cells, called astrocytes, because of their shape. New research has discovered how these stars are born. The discovery also hints at how defective astrocytes may contribute to Alzheimer's disease.

It has been known for years that both neurons and astrocytes come from the same brain stem cells. But how do these cells know whether and when to make one or the other?

Attention shoppers: Researchers find neurons that encode the value of different goods

70652986 — Mon, 26 Mar 2007 06:26:35 -0400

Researchers at Harvard Medical School report in the April 23, 2006 issue of Nature that they have identified neurons that encode the values that subjects assign to different items. The activity of these neurons might facilitate the process of decision-making that occurs when someone chooses between different goods.

"We have long known that different neurons in various parts of the brain respond to separate attributes, such as quantity, color, and taste. But when we make a choice, for example, between different foods, we combine all these attributes -- we assign a value to each available item," says Camillo Padoa-Schioppa, PhD, HMS research fellow in neurobiology and lead author of the paper. "The neurons we have identified encode the value individuals assign to the available items when they make choices based on subjective preferences, a behavior called 'economic choice.'"

Everyday examples of economic choice include choosing between working and earning more or enjoying more leisure time, or choosing to invest in bonds or in stocks. Such choices have long been studied by economists and psychologists. In particular, research in behavioral economics shows that in numerous circumstances, peoples' choices violate the criteria of economic rationality. This motivates a currently growing interest for the neural bases of economic choice -- an emerging field called "neuroeconomics." In general, it is believed that economic choice involves assigning values to available options. However, the underlying brain mechanisms are not well understood.

In the study, Padoa-Schioppa and John Assad, PhD, HMS associate professor of neurobiology, found a population of neurons located in the orbitofrontal cortex (OFC) that assigns values to different goods on a common value scale. Assigning values on a common scale allows comparing goods, like apples and oranges, that otherwise lack a natural basis for comparison.

How a sperm wags its tail

70652986 — Mon, 26 Mar 2007 06:24:46 -0400

The electric activity that spurs sperm to make a final dash to, then into, a female egg has been measured for the first time. To produce this all-important fertility sprint, sperm tails must switch from an easy, symmetrical beating to a frenetic whiplike lashing. This switching slows down sperm cells but gives them the extra force they need to penetrate an egg's protective coating.

Dendritic spines don't go with the flow

70652986 — Mon, 26 Mar 2007 06:23:26 -0400

Neurons receive incoming signals through synapses at hundreds of dendritic spines, the lollipop-shaped structures with thin necks and bubblelike heads that stud the surface of dendrites. Each spine serves as an antenna relaying the chemical and electrical signals at the synapse to the cell body. If the din is loud enough, the entire cell will rouse itself to fire an action potential.

Synapses hold the key to understanding how the brain perceives, records, and responds to incoming information. With the right stimulation, some of the synaptic signals grow stronger, like soloists in a chorus. And this regulation of synaptic strength allows the brain to change in response to experience.

Many studies have looked at the complex molecular changes that influence synaptic strength. But a study led by Bernardo Sabatini, Harvard Medical School assistant professor of neurobiology, suggests that part of the control may lie in the shape of the spines themselves. He and graduate student Brenda Bloodgood found that the necks of dendritic spines constrict or widen in response to different inputs, regulating the ability of molecules to flow from the spine into the cell body. This action, detailed in the Nov. 4, 2005 Science, could be a way that the spines control synaptic strength and give synapses some independence from the cell.

"One of the big questions in neuroscience is, how do neurons integrate all the synaptic inputs they get?" said Bloodgood. "Not all synapses on a neuron are equal." The structure of dendritic spines keeps each synapse separate, marooned on its own peninsula at the cell surface. It is thought that this physical separation helps regulate the synapses, allowing each one to keep its own pool of molecular signals. But until now, it was difficult to study whether their isolation was a regulated property.

Vaccine may clear Alzheimer's brain plaques

70652986 — Mon, 26 Mar 2007 05:41:07 -0400

While there is still no consensus about the role of waxy amyloid plaques that fill the brains of Alzheimer's patients, many in the field believe they are a root cause of neurodegeneration and that clearing them may improve the cognitive function of patients. A major strategy has been to remove amyloid-beta by creating antibodies against it. But trials for an amyloid-beta vaccine were halted in 2003 when 6 percent of the patients developed life- threatening encephalitis. Since then, two follow-up studies provided some evidence that patients did benefit, raising hopes that a vaccine may work if side effects are limited. Another trial is under way to see if delivering amyloid-beta antibodies, rather than the peptide itself, can be effective and safer.

In the September 2005 Journal of Clinical Investigation, a team led by Howard Weiner, the Robert L. Kroc professor of neurology at Harvard Medical School and Brigham and Women's Hospital, unveiled another vaccine strategy for Alzheimer's disease that clears the build-up of amyloid plaques in a mouse model. The new strategy triggers cells of the immune system to gobble up amyloid-beta, sidestepping antibodies completely. It is delivered as a simple nasal spray, and consists of two FDA-approved drugs already in use for other conditions.

The vaccine emerged from a fortuitous discovery during an investigation of the role of the immune system in Alzheimer's. After the problems with the amyloid-beta vaccine, Weiner worked with postdoctoral fellow Dan Frenkel and Ruth Maron, assistant professor of neurology at BWH, to investigate the relationship between Alzheimer's and an overactive immune system that would produce encephalitis.

T cell misfits may spell autoimmunity

70652986 — Mon, 26 Mar 2007 06:18:08 -0400

For a would-be T cell, the journey from cradle to grave is likely to be brief. After leaving the bone marrow, the immature immune cell travels directly to the thymus, where it undergoes a winnowing process. To become a mature T cell, it must learn to attack alien proteins and not those peptides produced by the body. Precursors that fail this task -- because they have a strong affinity for self-peptides -- are eliminated. But occasionally an autoreactive T cell will slip by and travel to the periphery, where it can cause disease. In multiple sclerosis, for example, T cells leave the thymus, travel to the brain, and attack a protein in the myelin sheath surrounding nerve fibers. Researchers have wondered how the rogue T cells are able to avoid elimination. It now appears that autoreactive T cells can disguise their presence by altering the way their receptors interact with their target. Kai Wucherpfennig, a Harvard Medical School associate professor of neurology at the Dana Farber Cancer Institute, and colleagues revealed the trick by capturing and crystallizing a T cell receptor. Taken from a patient with multiple sclerosis, the receptor was caught in the act of binding. This is the first time a human autoreactive T cell receptor has been crystallized and imaged. The findings appear in the April 10, 2005, Nature Immunology.

Lazy eyes aid artists, biologist says

50443248 — Tue, 24 Jul 2007 14:56:00 -0400

Margaret Livingstone found herself in a small room at the Louvre museum in Paris with four self-portraits by Rembrandt. She noticed something strange. The eyes of the great 17th century artist are crooked. The eye on the right side of the painting looks straight at the viewer, but the other eye looks off to the side. Because these are self-portraits, Rembrandt did them by looking in the mirror, so his left eye would be the one looking off to the side.
This view led the Harvard Medical School professor of neurobiology to the conclusion that Rembrandt was stereoblind, he could not see three dimensions well. His world was flat. She and her colleague, Bevil Conway, subsequently checked a total of 24 self-portraits and confirmed that conclusion.

First view of many neurons processing information in living brain

70652986 — Mon, 26 Mar 2007 05:36:18 -0400

A Harvard Medical School (HMS) research team used a new technique to obtain the first close-up look at the neural circuits that produce vision in cats and rats. "Put simply, this technique allows us to see the brain seeing," said R. Clay Reid, HMS professor of neurobiology, a member of the HMS Systems Neuroscience initiative, and principal investigator on the project. "It's an entirely new way of looking at brain function." The method, the first to track the responses of all the neurons in a visual circuit simultaneously, promises to rapidly advance our understanding of how the brain is wired for complex image processing. Lessons learned by studying the visual system may eventually apply to other brain functions like movement, thinking, and learning, as well as neurodegenerative diseases. The results were reported in the Jan. 19, 2005 issue of the journal Nature.

Why the brains of humans are bigger

70652986 — Mon, 26 Mar 2007 05:23:14 -0400

The largest structure in the brain, the cerebral cortex is the headquarters of our intellect -- often referred to as "gray matter." The large surface area of the cortex houses two-thirds of the brain's 100 billion neurons in a thin layer, only slightly thicker than the peel of an orange. In order for this expanded surface area to fit within the confines of the human skull, the cortex folds in on itself, resulting in a series of ridges and grooves that give the brain its "wrinkled" appearance. This characteristic is unique to humans. "This study looked at how the cerebral cortex develops and the role of the beta catenin protein in cortical growth," explains senior author Christopher A. Walsh, a neurogeneticist at Beth Israel Deaconess Medical Center who has been studying cortical development and its role in mental retardation and epilepsy for nearly 10 years. Walsh, who is also the Bullard Professor of Neurology at the Medical School, and Anjen Chenn, a research fellow in Walsh's laboratory and a pathologist at Brigham and Women's Hospital, worked together on the investigation into how and why the human cortex grows so large.

New online approach builds community around medical cases

70652986 — Mon, 26 Mar 2007 05:22:01 -0400

A new suite of Internet tools is boosting student-faculty interaction in an engrossing twist on traditional case-based teaching at Harvard Medical School. Called ICON, for "interactive case-based online network," the cases are run by a faculty-student-IT specialist trio at Harvard Medical School, backed by extensive cross-faculty collaboration. ICON is revamping neuroscience case-based learning by engrossing both students and faculty in the plight of virtual patients struggling with real-world diseases. Assistant Professor of Neuroscience at the Medical School James Quattrochi, the program's director and ICON's developer and driving force, said ICON's online case-based learning modules allow a greater level of student and faculty participation than possible in traditional, paper-based case learning. ICON was designed and developed by the Harvard Interfaculty Neuroscience Program, a year-old program that includes faculty from the Medical School, the Faculty of Arts and Sciences, the Business School, the Derek Bok Center for Teaching and Learning, Beth Israel Deaconess Medical Center, Brigham and Women's Hospital, Massachusetts General Hospital, and the Massachusetts Mental Health Center. ICON was developed with support from the Harvard Provost's Funds for Interfaculty Collaboration and Innovations in Instructional Technology.

Link found between body rhythms and circadian clock, light

70652986 — Mon, 26 Mar 2007 05:17:45 -0400

The brain's circadian clock is a tiny cluster of neurons behind the eyes. This cluster of cells sends out signals that control the body's daily rhythms. New research from Harvard Medical School has started us on the path to understanding better how this process works. The possible implications of understanding how the circadian clock works are obvious. "If you could figure out the factors that promote wakefulness and sleep, that could in principle be turned into better drugs for particular sleep disorders," said Charles Weitz, Harvard Medical School professor of neurobiology. So his research team began investigating the molecular pathway that transmits sleep and wakefulness signals. His team's findings appeared in the Dec. 21, 2001, Science.