快猫短视频

ZAP the back of the head with an electromagnet and people reach for the place
where something was, rather than where it has moved to, say a team of
neurologists. They say this shows that the brain plans movements in
advance鈥攁nd that the part they zapped constantly updates these plans.

Evidence from stroke victims and brain imaging experiments suggests that
three separate areas of the brain鈥攖he parietal cortex, the premotor cortex
and the cerebellum鈥攕omehow work together to plan and execute movements.
However, their precise roles are controversial (鈥淭he hand in your head鈥�, New
快猫短视频, 8 May, p 42).

Scott Grafton and his colleagues at Emory University School of Medicine in
Atlanta looked at the role of the posterior parietal cortex. They asked
volunteers to point to a light hovering in darkness. As they reached out, the
researchers moved the target slightly, causing the volunteers to compensate
subconsciously, so their hands pointed at the light鈥檚 new position.

The researchers then used transcranial magnetic stimulation to disrupt
electrical activity in the posterior parietal cortex just as the volunteers鈥�
hands began to move. When this happened, they pointed to the light鈥檚 original
position rather than to its new one. The magnetic stimulation had no effect on
their ability to touch stationary targets. (Nature Neuroscience, vol 2,
p 563).

鈥淚t really provides strong evidence that we plan in advance,鈥� says Grafton,
鈥渁nd that you use the parietal cortex to revise these plans.鈥�