Friday, May 30, 2008

Computer model knows what you're thinking

Published by Kerri Smith on Nature journal (29/05/08)

A computer model has been developed that can predict what word you are thinking of. The model may help to resolve questions about how the brain processes words and language, and might even lead to techniques for decoding people’s thoughts. Researchers led by Tom Mitchell of Carnegie Mellon University in Pittsburgh, Pennsylvania, 'trained' a computer model to recognize the patterns of brain activity associated with 60 images, each of which represented a different noun, such as 'celery' or 'aeroplane'. The team started with the assumption that the brain processes words in terms of how they relate to movement and sensory information. Words such as 'hammer', for example, are known to cause movement-related areas of the brain to light up; on the other hand, the word 'castle' triggers activity in regions that process spatial information. Click for more...

Thursday, May 29, 2008

Free choice activates a decision circuit between frontal and parietal cortex

Published by Bijan Pesaran, Matthew J. Nelson & Richard A. Andersen on Nature journal (16/04/08)

We often face alternatives that we are free to choose between. Planning movements to select an alternative involves several areas in frontal and parietal cortex that are anatomically connected into long-range circuits. These areas must coordinate their activity to select a common movement goal, but how neural circuits make decisions remains poorly understood. Here we simultaneously record from the dorsal premotor area (PMd) in frontal cortex and the parietal reach region (PRR) in parietal cortex to investigate neural circuit mechanisms for decision making. We find that correlations in spike and local field potential (LFP) activity between these areas are greater when monkeys are freely making choices than when they are following instructions. We propose that a decision circuit featuring a sub-population of cells in frontal and parietal cortex may exchange information to coordinate activity between these areas. Cells participating in this decision circuit may influence movement choices by providing a common bias to the selection of movement goals. Click for more...

Wednesday, May 28, 2008

Neuroscience: Brain control of a helping hand

Published by John F. Kalaska on Nature journal (28/05/08)
Paralysed patients would benefit if their thoughts could become everyday actions. The demonstration that monkeys can use brain activity for precise control of an arm-like robot is a step towards that end. Strokes, spinal-cord injuries and degenerative neuromuscular disease all cause damage that can severely compromise the ability of patients to use their muscles. The loss of mobility and independence that results from such motor deficits takes a devastating toll on their quality of life. Medical research is striving on many fronts to reverse the disease or injury state of such patients. Meanwhile, other approaches are needed to enhance their quality of life. Often, the patient's condition leaves intact parts of the cerebral cortex involved in voluntary motor control, including the primary motor cortex, premotor cortex and posterior parietal cortex. These patients are still able to produce the brain activity that would normally result in voluntary movements, but their condition prevents those signals from either getting to the muscles or activating them adequately. In such cases, one possible solution is to let the subjects think about what they would like to do as if they were mentally rehearsing the desired actions, record the resulting brain activity, and use those signals to control a robotic device. The development of such brain–machine interfaces (BMIs), or neuroprosthetic controllers, is being pursued in several laboratories. Click for more...