Bronnen bij Neurologie beslissingen: beslissingsneuronen

Het onderstaande stuk gaat over een onderzoek dat laat zien op welke manier de neuronen de beslissingsfuncties vervullen (New Scientist, 22-06-2005, door Anna Gosline)
  Why your brain has a ‘Jennifer Aniston cell'

Obsessed with reruns of the TV sitcom Friends? Well then you probably have at least one "Jennifer Aniston cell" in your brain, suggests research on the activity patterns of single neurons in memory-linked areas of the brain. The results point to a decades-old and dismissed theory tying single neurons to individual concepts and could help neuroscientists understand the elusive human memory.
    "For things that you see over and over again, your family, your boyfriend, or celebrities, your brain wires up and fires very specifically to them. These neurons are very, very specific, much more than people think," says Christof Koch at the California Institute of Technology in Pasadena, US, one of the researchers.
    In the 1960s, neuroscientist Jerry Lettvin suggested that people have neurons that respond to a single concept such as, for example, their grandmother. The notion of these hyper-specific neurons, coined "grandmother cells" was quickly rejected by psychologists as laughably simplistic.
    But Rodrigo Quiroga, at the University of Leicester, UK, who led the new study, and his colleagues have found some very grandmother-like cells. ...
    To investigate further, the team turned to eight patients currently undergoing treatment for epilepsy. In an attempt to locate the brain areas responsible for their seizures, each patient had around 100 tiny electrodes implanted in their brain. Many of the wires were placed in the hippocampus - an area of the brain vital to long-term memory formation.
    They first gave each subject a screening test, showing them between 71 and 114 images of famous people, places, and even food items. For each subject, the researchers measured the electrical activity or "firing" of the neurons connected to the electrodes. Of the 993 neurons sampled, 132 fired to at least one image.
    The team then went back for a testing phase, this time showing participants three to seven different pictures of the initial 132 photo subjects that hit. For example, one woman saw seven different photos of the Jennifer Aniston alongside 80 other photos of animals, buildings or additional famous people such as Julia Roberts. The neuron almost ignored all other photos, but fired steadily each time Aniston appeared on screen.
    The team found similar results with another woman who had a neuron for pictures of Halle Berry, including a drawing of her face and an image of just the words of her name. "This neuron is responding to the concept, the abstract entity, of Halle Berry," says Quiroga. "If you show a line drawing or a profile, it's the same response. We also showed pictures of her as Catwoman, and you can hardly see her because of the mask. But if you know it is Halle Berry then the neurons still fire."    ...
    These object-specific neurons may be at the core of how we make memories, say Connor. ...

De formulering dat het enkele neuron de "Jennifer Aniston"-geheugenfunctie vervult, is op zijn minst onzorgvuldig. Wat ze waargenomen hebben, is dat dan een enkel neuron vuurt, maar dat is ongetwijfeld onder invloed van talloze andere, tezamen een netwerk, die een beeltenis of iets dergelijks analyseren, en het analyse-apparaat zeeft daar het "Jennifer Aniston" aspect uit. Wat het doorgeeft aan dat ene neuron. Het beslissingsneuron: "Dit is of gaat over Jennifer Aniston".


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7 jun.2009