3 posts tagged plasticity
Neurons that can multitask greatly enhance the brain’s computational power, study finds.
Over the past few decades, neuroscientists have made much progress in mapping the brain by deciphering the functions of individual neurons that perform very specific tasks, such as recognizing the location or color of an object.
However, there are many neurons, especially in brain regions that perform sophisticated functions such as thinking and planning, that don’t fit into this pattern. Instead of responding exclusively to one stimulus or task, these neurons react in different ways to a wide variety of things. MIT neuroscientist Earl Miller first noticed these unusual activity patterns about 20 years ago, while recording the electrical activity of neurons in animals that were trained to perform complex tasks.
"We started noticing early on that there are a whole bunch of neurons in the prefrontal cortex that can’t be classified in the traditional way of one message per neuron," recalls Miller, the Picower Professor of Neuroscience at MIT and a member of MIT’s Picower Institute for Learning and Memory.
In a paper appearing in Nature on May 19, Miller and colleagues at Columbia University report that these neurons are essential for complex cognitive tasks, such as learning new behavior. The Columbia team, led by the study’s senior author, Stefano Fusi, developed a computer model showing that without these neurons, the brain can learn only a handful of behavioral tasks.
"You need a significant proportion of these neurons," says Fusi, an associate professor of neuroscience at Columbia. "That gives the brain a huge computational advantage."
Lead author of the paper is Mattia Rigotti, a former grad student in Fusi’s lab.
Neurons in the brain switch identity and re-route fibres
New findings could one day lead to gene therapies for stroke and spinal cord injuries
These drawings by Santiago Ramón y Cajal show the cellular structure of three different areas of the human cerebral cortex. The cortex is the seat of higher mental functions such as language and decision-making, and contains dozens of distinct, specialised areas. As Cajal’s drawings show, it has a characteristic layered structure, which differs somewhat from one area to the next, so that the layers vary in thickness according to the number of cells they contain. Cells throughout the cortex are arranged in a highly ordered manner. Those in layers 2 and 3, for example, send fibres to the other side of the brain, whereas those in layers 5 and 6 send theirs straight downwards. This organization is under genetic control and, once established, was thought to be fixed. Now, though, researchers at Harvard University report that fully matured neurons in the intact brain can be made to switch identity and re-route their fibres to acquire the characteristics of cells in other layers. (via Neurons in the brain switch identity and re-route fibres | Mo Costandi | Science | guardian.co.uk)