Semantic memory pinpointed in the brain

日期:2019-03-02 06:19:08 作者:夹谷盲颅 阅读:

By Helen Thomson The part of the brain responsible for the way we understand words, meanings and concepts has been revealed as the anterior temporal lobe – a region just in front of the ears. In a novel experiment, neuroscientists pinpointed the exact region of the brain that is responsible for encoding semantic memory, which is disrupted in certain forms of dementia. Semantic dementia is the second most common form of dementia in under-65s and is associated with significant loss of brain tissue in the temporal lobe. Patients are able to generate speech fluently but lose their knowledge of objects, people and abstract concepts. For example, when shown a picture of a camel, they may understand that it is an animal but will not be able to give its name, and they lose the idea of associated concepts, such as deserts and palm trees. Matthew Lambon-Ralph and colleagues at the University of Manchester in the UK used transcranial magnetic stimulation (TMS) on 12 healthy volunteers in an attempt to detect which area of the brain is responsible for encoding this type of memory. In some positions, TMS caused the participants to experience a temporary version of the same type of memory loss seen in patients with semantic dementia, he found. TMS uses a figure-of-eight coil to send a magnetic pulse to stimulate and temporarily “tire out” neurons in specific areas of the brain. When TMS was performed over the temporal lobe, volunteers were unable to associate conceptual ideas to objects: and effect similar to semantic dementia. Within 5 to 10 minutes, brain function returned to normal. The data allowed Lambon-Ralph and his team to locate semantic memory specifically to the frontal pole of the temporal lobe, an area just in front of the ear. “Conventional neurology thought this memory was associated with Wernick’s area, further back in the temporal lobe. Our new TMS data allows us to provide confirmation that the temporal pole gets involved in encoding a conceptual database,” says Lambon-Ralph. The findings may one day help researchers treat dementia by targeting gene therapy or administering drugs directly into the brain region responsible for specific types of memory loss, says Clea Warburton, a neuroscientist at the University of Bristol, UK. The research was announced at the British Association for the Advancement of Science Festival in Norwich,