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 advanceand that the part they
zapped constantly updates these plans. Evidence from stroke
victims and brain imaging experiments suggests that three
separate areas of the brainthe parietal cortex, the premotor
cortex and the cerebellumsomehow work together to plan and
execute movements. However, their precise roles are
controversial ("The hand in your head", 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 ...
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