Two brain areas fail to connect when children with attention deficit hyperactivity disorder attempt a task that measures attention, according to researchers at the UC Davis Center for Mind and Brain and M.I.N.D. Institute.

"This is the first time that we have direct evidence that this connectivity is missing in ADHD," said Ali Mazaheri, postdoctoral researcher at the Center for Mind and Brain. Mazaheri and his colleagues made the discovery by analyzing the brain activity in children with ADHD. The paper appears in the current online issue of the journal Biological Psychiatry.

Activating a small fraction of neurons triggers complete memory.

By Lizzie Buchen

Just as a whiff of pumpkin pie can unleash powerful memories of holiday dinners, the stimulation of a tiny number of neurons can evoke entire memories, new research in mice suggests.

Memories are stored in neurons distributed across a host of brain regions. When something triggers a memory, that diffuse information is immediately and cohesively reactivated, but it's unclear how the circuit gets kicked into full gear. Over the past few years, a handful of studies have suggested that a small number of neurons — perhaps even single neurons — can trigger sensations. But this idea remains controversial and has never been demonstrated with memory.

ANN ARBOR, Mich.—University of Michigan mathematicians and their British colleagues say they have identified the signal that the brain sends to the rest of the body to control biological rhythms, a finding that overturns a long-held theory about our internal clock.

Understanding how the human biological clock works is an essential step toward correcting sleep problems like insomnia and jet lag. New insights about the body's central pacemaker might also, someday, advance efforts to treat diseases influenced by the internal clock, including cancer, Alzheimer's disease and mood disorders, said University of Michigan mathematician Daniel Forger.

best in science, biology, brain researchby Cathryn M. Delude, McGovern Institute

The human brain can adapt to changing demands even in adulthood, but MIT neuroscientists have now found evidence of it changing with unsuspected speed. Their findings suggest that the brain has a network of silent connections that underlie its plasticity.

by Monya Baker

Three recent papers and questions for clinical translation

It's not easy to assess the quality of science from press releases, three of which caught my eye this month. All of them described the use of stem cells for neurodegenerative applications. All of them looked interesting, but I wanted to be particularly careful because of their potential for translation to human patients as well as their company connections. I asked Phil Schwartz, a neural stem cell expert at Children's Hospital of Orange County, California, to help me understand the gaps between study and therapy, and then I asked authors from each paper to respond. The papers were published in Biomaterials1, The Journal of Comparative Neurology2 and Cell Transplantation3.

john dick, science, biologyby Monya Baker

The University of Toronto scientist calls for more controversy

John Dick identified the first cancer stem cell, in leukaemia. The widely used xenotransplantation assay that he developed can confirm the identity of prospective haematopoietic stem cells by demonstrating their ability to re-establish a human blood system in the mouse. He is a professor at the University of Toronto and its affiliated Princess Margaret Hospital and Director of the Program in Cancer Stem Cells at the Ontario Institute for Cancer Research. 

Tell me about the xenotransplantation assay.

Lucky for us that there is enough complementarity between what human stem cells need and what the mouse can provide so you can get human repopulation of the mouse's blood system.

In the blood system, there are a lot of steps that a cell has to go through to read out as a stem cell. You take a source of stem cells, you put it in a syringe and you squirt them into the blood stream. Essentially you are taking advantage of a beautiful property of these cells, which is [their ability] to find their way to the bone marrow.

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